Geological Survey of Israel
Ministry of National infrastructures
Energy and Water Resources
Silicate sediments dissolution
during interaction with seawater
Daniel Winkler
This work was submitted as a thesis for the degree of Master of Science to the Department of
Geological and Environmental Sciences, Faculty of Natural Sciences, Ben- Gurion University of the
Negev.
The study was carried out under the supervision of:
Prof. Jiwchar Ganor, Ben Gurion University of the Negev.
Dr. Yehudit Harlavan, Geological Survey of Israel, Jerusalem.
Report GSI/01/2015
Jerusalem, January 2015
‫המסת סדימנטים סיליקטיים באינטראקציה עם מי ים‬
Silicate sediments dissolution during interaction with seawater
Abstract
Throughout geological history, the isotopic composition of Sr (87Sr/86Sr) in the oceans has
changed due to riverine influx of Sr from weathered rocks and from hydrothermal exchange
in mid-ocean ridges.
The residence time of Sr in the oceans (4*106years) is short compared to the long geological
time-scale, and this allows the documentation of
87
Sr/86Sr variation as recorded in ocean
floor carbonates. 87Sr/86Sr is often used an indirect proxy of the geochemical, tectonic and
climate changes occurred on earth. The factors that control the isotopic composition of the
oceans are mainly riverine input and hydrothermal exchange in mid-ocean ridges.
Nevertheless, sediments lying in the ocean's bottom may also, in principle, release Sr to
oceans water. This research examined the dissolution rate of sediments and their Sr release
due to interaction with seawater.
Previous studies focused on the dissolution kinetics and Sr release rate of specific silicate
minerals, such as labradorite, mica and plagioclase, but limited research was done on silicate
rocks which are poly-mineral by nature. In addition, most of the studies used pure samples
which were often separated from pegmatites, hydrothermal veins and even on synthetic
minerals. In nature, however, mineral samples are not pure and often contain inclusions of
other minerals or are coated due to diagenetic alteration. Moreover, previous experiments
were usually conducted under very acidic conditions (pH=1-3) and not in seawater
(pH=8.2).It is known that the pH has as a direct effect on the activities of the different ions in
the solution and thus affects the solubility of different minerals and their dissolution rate.
In the present study 7 closed batch experiments were conducted, during which different
parameters, including Al, Si, Sr concentrations were measured. Two types of synthetic
solutions were used: (1) seawater solution with low Sr background (17 ppb) and (2) borax
solution. Both solutions had the same pH (8.2) but the ionic strength was different (0.7 in
sweater and 0.015mol/kg in the borax solution). Riverine sediments (fluvial alluvium) were
sampled from homogenous drainage basins (Roded quartz-diorite, Yehoshafat granite, Eilat
granite and Amram rhyolite) and two minerals (albite from Ontario, Canada and K-feldspar
from Eilat pegmatite) were used in the dissolution experiments. The dissolution rates were
calculated by the Si change with time. In addition, Sr concentration and 87Sr/86Sr ratio were
tracked throughout the experiments.
In this research, changes in Si and Al concentrations were observed during time-scale of
several days, which confirms the basic assumption that indeed a substantial interaction of
Report GSI/01/2015
Silicate sediments dissolution during interaction with seawater
‫המסת סדימנטים סיליקטיים באינטראקציה עם מי ים‬
seawater with sediments and minerals takes place. It was found out that replacement of
solution with a new one prior to the long-term experiment allows the dissolution of the
most fine and most reactive particles (high surface area in comparison to their volume). This
initial dissolution and solution replacement lowers the dissolution rate during the post-wash
period, compared with similar experiments which did not undergo such treatment
(extinction of the reactive particles). The reactivity is decreasing with time, until a steadystate is reached, in which no change in Al or Si with time is observed.
This study showed that the albite sample was incongruently dissolved in seawater, and the
isotopic composition of Sr is decreasing in a hyperbolic-shape manner with time. The ratio
87
Sr/86Sr versus 1/Sr in the experiment suggests mixture of two end-member components in
the sample (two minerals having different 87Sr/86Sr value and concentration). Probably, the
albite sample contains also trace amount of biotite and apatite, as SEM analysis shows.
During the K-feldspar experiment it was found out that this mineral was congruently
dissolving (stoichiometric dissolution) in seawater (Al: Si ration of 1:3). This mineral contains
only trace amounts of Sr (0.2 ppm) and therefore it did not contributed Sr to the solution.
Comparison of seawater and borax solution reveals that: (1) the dissolution rate in the borax
solution is faster, although both have the same pH (8.2). In the borax experiments the
solution is more under-saturated than in the sea water solution (Thereby the higher rate).
(2) 87Sr/86Sr variation with time is similar, though not identical in the two albite experiments.
It is suggested that in the borax experiment the solution is more undersaturated with
respect to biotite, which causes a sharp decrease in the isotopic composition at the
beginning of the experiment, which is different from the composition of the bulk albite
(similar phenomenon of shift of 87Sr/86Sr values during the experiment appears also in the
Roded quartz-diorite experiment).
In conclusion, silicate sediments indeed dissolve during interaction with seawater, and we
have the ability to track the changes in the solution's chemistry following the dissolution.
Keywords: Water Geochemistry, dissolution rate in seawater, Silicate sediments from Eilat
region, isotopic composition of Strontium.
Report GSI/01/2015
Silicate sediments dissolution during interaction with seawater
‫המסת סדימנטים סיליקטיים באינטראקציה עם מי ים‬
Acknowledgment
I would like to thank my advisors Jiwchar Ganor and Yehudit Harlavan for their
professional assistance and support.
I would like to thank my friends from the Water-Rock-Interactions research
group in the Geological and Environmental Sciences department in BenGurion University: Chen Gruber, Peter Rendel, Rotem Golan and Amit Reiss for
their assistance along the way.
I would like to thank Nataliya Teplyakov, Olga Yoffe and Dina Stiber from the
Geological Survey in Jerusalem for the various chemical analyses conducted
professionally by them and Raanan Bodzin who was on control on the SEM.
I thank Ester Shani, Rivka Eini and Zahala Sharabi from the administration of
the Geological and Environmental Sciences department in Ben-Gurion
University, on the procedural issues behind the scenes.
I would like to thank my friends from the Hebrew University in Jerusalem:
Yoav ben Dor and Keren Sarussi-Weiss for their assistance on the SEM and Sr
separation process (respectively.)
I thank my darling Noy Shpatz for her support.
This research was partly funded by the ministry of national infrastructures,
research and development department, the chief scientist office.
Report GSI/01/2015
Silicate sediments dissolution during interaction with seawater
‫המסת סדימנטים סיליקטיים באינטראקציה עם מי ים‬
Table of Contents
1. Introduction ..................................................................... 1
1.1 The main motivation
1
1.2 Geochemistry of Sr
1
1.3 The Strontium Budget of the Ocean
2
1.4 Previous Studies of rock/mineral Dissolution
6
1.5 Goal of the Present Study
7
2 Materials and Methods ..................................................... 8
2.1 Geological Setting
8
2.1.1 Amram rhyolite
8
2.1.2 Yehoshafat granite
8
2.1.3 Roded quartz-diorite
8
2.1.4 Eilat granite
9
2.2 Samples preparation
9
2.3 Solutions
12
2.3.1 Seawater Solution
12
2.3.2 Borax Solution
12
2.4 Experimental Setting
13
2.5 Analyses
16
2.5.1 SEM
16
2.5.2 Major element Analysis
16
2.5.3 Sr isotopic composition analysis
17
2.5.4 pH and density of solute ions
17
2.5.5 Saturation index
17
2.6 Calculations
17
3 Results ..........................................................................20
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Silicate sediments dissolution during interaction with seawater
‫המסת סדימנטים סיליקטיים באינטראקציה עם מי ים‬
3.1 Albite dissolution experiments
20
3.1.1 Albite dissolution experiment in Sea-Water
22
3.1.2 Albite dissolution experiment with borax solution
23
3.2.1 K-Feldspar dissolution experiment with Sea-Water
27
3.2.2 K-Feldspar dissolution experiment in borax-solution
29
3.3 Amram rhyolite dissolution experiments in Sea-Water
30
3.4 Yehoshafat granite dissolution experiment in Seawater
32
3.5 Roded quartz-diorite dissolution experiments
34
3.5.1 Roded quartz-diorite dissolution experiments with Sea-Water
34
3.5.2 Roded quartz-diorite dissolution experiment in borax solution
36
3.6 Eilat granite dissolution experiments
38
3.6.1 Eilat granite dissolution experiment with sea-water
38
3.6.2 Eilat granite dissolution experiment in borax solution
40
4. Discussion .......................................................................43
4.1 Effect of solution replacement (prewashing)
43
4.2 Comparison of dissolution rate in Seawater versus Borax solution
44
4.3 Albite and K-feldspar dissolution experiments
45
Albite
45
K-feldspar
46
4.4 Sr release during dissolution
46
4.5 The dissolution experiments of various siliciclastic sediments
50
4.6 Mineral dissolution rates
53
4.7 Si release rates in the various experiments:
53
5 Summary and Conclusions ...............................................55
6 References ......................................................................56
7 Appendix........................................................................ A1
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Silicate sediments dissolution during interaction with seawater
‫המסת סדימנטים סיליקטיים באינטראקציה עם מי ים‬
7.1 Albite Sea-Water Experiment
7.1.1 Albite-Seawater Experiment: Ion activities estimations
A1
A2
7.2 Albite Borax-Solution Experiment
A3
7.2.1 Two-weeks washing period
A3
7.2.2 Long-term (after-washing period) experiment
A5
7.3 K-Feldspar Sea-Water Experiment
A6
7.3.1 Pre-washing period [41days]
A6
7.3.2 Long-term experiment
A7
7.3.3 K-feldsparexperiment in seawater: ion activity products
A8
7.4 K-Feldspar Borax Experiment
A9
7.4.1 Two weeks washing period
A9
7.4.2 K-feldspar in Borax solution: long-term experiment
A11
7.4.3 K-feldspar in Borax solution: ion activities estimations
A12
7.5 Amram rhyolite dissolution experiments in Seawater
A13
7.6 Yehoshafat granite dissolution experiment in Seawater
A14
8.7 Roded quartz-diorite dissolution experiments
A15
8.7.1Roded quartz-diorite in Seawater (without pre-wash treatment)
A15
8.7.2Roded Quartz-diorite in Seawater after washing period
A16
8.7.3Roded quartz-diorite in seawater: washing period
A16
8.7.4Roded quartz-diorite in Borax solution: washing period
A18
8.7.5Roded quartz-diorite d in Borax solution: long-term experiment
A20
8.8 Eilat granite dissolution experiments
A21
8.8.1Eilat granite dissolution in Seawater: two times washing period
A21
8.8.2Eilat granite dissolution in Seawater: Long term period
A23
8.8.3Eilat granite in Borax solution: two times washing period
A24
8.9 Eilat granite inBorax solution: long term experiment
A26
8.10 Bulk Sediment Analysis
A27
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Silicate sediments dissolution during interaction with seawater
‫המסת סדימנטים סיליקטיים באינטראקציה עם מי ים‬
List of Tables
Table 1: Rock/Mineral Samples........................................................................................ 10
Table 2: Chemical and physical properties of experiments solutions .................................. 13
Table 3:Basic experiments settings .................................................................................. 15
Table 4: Dissolution equations of four main minerals ........................................................ 19
Table 5: Comparison of dissolution rates of albite and K-feldspar ...................................... 53
Table 6 :Comparison of Si release rates ............................................................................ 54
List of figures
Figure 1: Isotopic composition of Sr in the oceans over time .............................................. 3
Figure 2: Sr budget of the oceans ...................................................................................... 6
Figure 3:Sampling area.................................................................................................... 11
Figure4: Sample preparation flow-chart ........................................................................... 12
Figure 5: SEM images of albite sample used in the experiment.. ........................................ 20
Figure 6: SEM images and elemental distributionof minerals found in the 'Alb' sample ....... 21
Figure 7: albite dissolution experiment in Seawater .......................................................... 23
Figure 8: Prewashing period of albitein Borax solution ..................................................... 24
Figure 9:albite in Borax dissolution experiment ................................................................ 26
Figure 10: SEM photographs of K-feldspar sample. ........................................................... 27
Figure 11: K-feldspar dissolution experiment in Seawater. ................................................ 28
Figure 12: K-feldspar dissolution in Borax solution.. .......................................................... 30
Figure 13:Amram rhyolite dissolution experiments. .......................................................... 32
Figure 14: Yehoshafat granite dissolution experiment in Seawater .................................... 33
Figure 15: Roded quartz-diorite dissolution in Seawater. .................................................. 36
Figure 16: Roded quartz-diorite dissolution in Borax solution ............................................ 38
Figure 17: Eilat-granite dissolution experiment in Sea-Water ............................................ 40
Figure 18: Eilat-granite dissolution experiment in Borax solution ....................................... 42
Figure 19: Comparison of the effect of solution replacement on dissolution rate. ............... 44
Figure 20: Comparison of two albite experiments. ............................................................ 49
Figure 21: Comparison between the dissolution rates of various siliciclastic sediments ....... 52
Report GSI/01/2015
Chapter 1
Introduction
1. Introduction
1.1 The main motivation
The isotopic composition of Sr (87Sr/86Sr) in the oceans is fluctuating at least since
the beginning of the Phanerozoic eon, mainly as a result of mixture between riverine
input of weathered rocks and hydrothermal exchange in mid-ocean ridges (e.g. Faure
G. , 1986).Theoretically, additional sources for Sr in seawater may result from
interaction of seawater with sediments at the ocean floor, hence altering its Sr
isotopic composition. Though numerous laboratory based experiments used many
different types of solution to study the dissolution of various rocks and minerals,
only a few have used seawater as the interacting solution (Lerman & Mackenzie
1975, Berger et al. 1988).In the present study, the dissolution of feldspars and
alluvial sediment of silicate origin during interaction with synthetic seawater is
studied by tracking the changes in water chemistry and in 87Sr/86Sr ratio.
1.2 Geochemistry of Sr
Strontium (atomic number 38) is an alkaline-earth metal which has four naturally
occurring stable isotopes: 88Sr which is the most abundant (82.58%), 87Sr (7.0%), 86Sr
(9.86%), and 84Sr (0.56%). Among these isotopes, only 87Sr is radiogenic (a product of
first-order 87Rb beta-decay).
Rubidium (atomic number 37) has 2 naturally occurring isotopes: the stable
the most abundant (72.2%) and the radioactive
87
85
Rb is
Rb (27.8%) which decays to
87
Sr
(t1/2=4.92*1010years). The87Sr/86Sr ratio in minerals changes through time as a result
of87Rb to 87Sr decay. The 87Sr/86Sr ratio in a mineral depends therefore on its age and
its initial Rb/Sr ratio.
Sr is the major cation in strontium-carbonate (SrCO3, strontianite) and in strontiumsulfate (SrSO4, celestite). However, these minerals are not common and are found
only in certain low-temperature hydrothermal and evaporate deposits, respectively.
Nevertheless, Sr2+ is an accessory cation in Ca2+-forming minerals, such as anorthite
(CaAl2Si2O8), apatite (Ca5(PO4)3(OH,F,Cl), and calcite (CaCO3) which are common in
nature. Due to their similar charge and ionic radius (1.13Å in Sr2+ compared to
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
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Chapter 1
Introduction
0.99Åfor Ca2+), Sr2+ may replace Ca2+ in these minerals. In addition, Sr2+ may also
replace K+ in K-feldspar but this substitution must be coupled by replacement of Si 4+
by Al3+ to maintain electrical neutrality(Faure, 1986).
The charge and ionic radius of Rb+ (1.48 Å) are similar to that of K+ (1.33 Å). This
allows substitution of K+ with Rb+ in all K-bearing minerals. Such minerals are micas
(e.g., muscovite KAl2(AlSi3O10)(F,OH)2 and biotite K(Mg,Fe)3AlSi3O10(F,OH)2), and Kfeldspar (KAlSi3O8) which are very common in mafic silicate rocks.
The Rb/Sr ratios in igneous rocks have a wide range from 0.06 in basaltic rocks
(basic) to 1.7 (or more) in highly-differentiated granitic rocks (felsic). This is a result
of the behavior of Sr during fractional crystallization in which Sr tends to concentrate
in plagioclase (NaAlSi3O8 to CaAl2Si2O8), whereas Rb initially remains in the liquid
phase or concentrates, by a minor extent, in potassium feldspar. Consequently, the
Rb/Sr ratio of the residual magma increases during the course of progressive
crystallization. The highest Rb/Sr ratios (~10 or higher) are found in late-stage
differentiated magmas, like pegmatites (Faure, 2005, p.76)
In general, basic rocks have lower Rb/Sr ratios and consequently tend to have
lower87Sr/86Sr ratio than felsic rocks, given that they crystallized at the same time.
This concept is observed geochemically: a worldwide-systematic collection of basalt
and granite isotopic composition data shows that the
87
Sr/86Sr ratio in granites is
higher and has a wider range (0.705-0.850) than basalts (0.702-0.707). The 87Sr/86Sr
ratio in oceanic basalts has a particular narrow range (0.7022-0.7045, (Allègre, 2008).
1.3 The Strontium Budget of the Ocean
Strontium is homogeneously distributed in the oceans due to its long residence time
(4*106yr,Holland, 1978) relative to the short mixing rate of the oceans (less than 103
years, Broecker, 1963). The isotopic homogeneity in the oceans in a given time,
together with the observed sharp changes in the isotopic ratio over time (on a
geological time scale) allows the documentation of global changes in the
ratio of the oceans over time. The
87
87
Sr/86Sr
Sr/86Sr ratio changes as recorded in marine
carbonates with time are commonly used as an indirect indicator of continental
rocks weathering during the time of deposition. Hence the
87
Sr/86Sr as recorded in
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
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Chapter 1
Introduction
the oceans is also used as a proxy for global tectonic and climatic changes in earth
geological history.
Measurementsofthe87Sr/86Sr ratios in the ocean by numerous studies were
integrated to plot the change of this ratio with time. Biogenic carbonates are fairly
resistant to diagentic alteration (Dickin, 2005 ) and are easy to date, hence are often
used as indicators to the marine 87Sr/86Sr ratio at time of deposition. Pioneering work
of this kind was conducted by Peterman et al. (1970) who revealed that the isotopic
composition of Sr in the oceans fluctuated repeatedly, which was in contrast to
Wickman's proposal (1948) that this ratio should only increase gradually over time as
a result of 87Rb decay to 87Sr.
Major improvement of this plot was made by Burke et al. (1982) who compiled 785
samples of marine carbonates, evaporates and phosphate sediments of known age.
His plot reveals that there were distinct periods of change in the 87Sr/86Sr ratio in the
oceans (Figure 1).
Today
Figure 1: Isotopic composition of Sr in the oceans over time (Faure and Mensing,
2005,p.440).
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
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Chapter 1
Introduction
Although the geochemistry of Sr in the oceans is fairly understood, the causes for the
fluctuations remain in debate. In general, Sr in the ocean is derived from chemical
weathering of continental rocks via riverine input, and from diagenetic alteration at
mid ocean ridge basalts. In addition, since Sr2+ may replace Ca2+it can also be
incorporated in marine biogenic carbonates by organisms that secrete strontium
directly from sea-water. Faure et al. (1965) suggested that Sr in the oceans is mainly
derived from 3 types of sources:
(1) Seawater interaction with young volcanic rocks.
(2)Weathering of old aluminosillicates (sialic) rocks.
(3) Weathering of marine carbonates.
Using a model in which each of the 3 fractions is given a representative value of
87
Sr/86Sr ratio (0.704, 0.720, and 0.708, respectively) allowed examining the effect of
each of the 3 contributors on the overall isotopic composition of Sr in the oceans.
This model concluded that because marine carbonates have on one hand high Sr
concentration and on the other hand low 87Sr/86Sr ratio (i.e. less radiogenic) they act
as a buffer which tends to diminish sharp changes over short periods of time caused
by intensive old-rock weathering. The basic assumption of this model is that marine
carbonates are highly soluble and widespread and therefore are the main donors
(60-80%) of Sr into the oceans (Faure, 1986).
The isotopic ratio of Sr in marine carbonates during the whole Paleozoic era
remained fairly close to the value of 0.708 (reviewed Faure, 1986) and therefore
diagenetic re-crystallization of marine carbonates only recycles old sea-water Sr and
thus diminishes sharp fluctuations of 87Sr/86Sr over time (Elderfield & Gieskes, 1982).
It is thus reasonable to assume that the variations in the isotopic ratio were mainly
caused due to changes in the supply of non-marine sediments such as interaction
with non-radiogenic young volcanic rocks and weathering of radiogenic old crustal
rocks (Brass, 1976).
Armstrong (1971) suggested that 87Sr/86Sr ratio of seawater increased during periods
of continental glaciations which exposed and thus accelerated the weathering of old
granitic rocks (having high
87
Sr/86Sr ratio) of the Precambrian shields. This idea was
later investigated by Blum & Erel (1995) who showed that the87Sr/86Sr ratio released
by silicates weathering is affected by glaciation. They concluded that accelerated
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
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Chapter 1
Introduction
biotite weathering in younger soils is responsible for the high radiogenic
87
Sr/86Sr
ratio contribution to the ocean following deglaciation.
The effect of hydrothermal exchange at mid ocean ridge basalts was proposed by
Spooner (1976) who noticed that the
87
Sr/86Sr ratio delivered to the oceans by
continental run-off is much higher (~0.716) than the current Seawater ratio (0.7091).
He proposed that the 87Sr/86Sr ratio in the oceans is balanced by isotopic exchange at
oceanic crust during hydrothermal convection, which has a much lower ratio
(0.7035). Based on sea-floor spreading rates data, Spooner argued that the increase
of
87
Sr/86Sr ratio since the cretaceous from 0.707 to 0.709 (see Figure 1, page 3) is
due to an increase of the exposed land area. Higher land area exposed (low sealevel) allowed intense weathering of continental rocks which caused higher riverine
Sr flux with higher than ocean 87Sr/86Sr ratio throughout earth history.
The contribution of the riverine influx of Sr into the oceans was investigated by
Palmer & Edmond (1989) who compiled a database of the major rivers of the world
with their discharge, isotopic composition and Sr concentration. Plotting
87
Sr/86Sr
ratio versus 1/Sr of the world's major rivers revealed a straight line, which is
attributed to mixing between radiogenic Sr (derived from silicate weathering) and
less radiogenic Sr (derived from carbonate weathering).The Ganges- Brahmaputra
basin which drains the Himalayas, falls above the mixing line, contributing high
concentration of highly radiogenic Sr. These rivers receive a highly radiogenic Sr
probably from weathering of exposed limestones that underwent regional
metamorphism which led to an enrichment of radiogenic Sr derived from coexisting
silicate rocks. Palmer & Edmond (1989) concluded that the annual fluvial (i.e.
riverine) contribution is 3.3*1010molSr/year with 87Sr/86Sr ratio of 0.7119, while the flux
of Sr from hydrothermal flux is one half this magnitude and with a much lower
87
Sr/86Sr ratio (0.7035).
The best opportunity to study the interaction of competing Sr fluxes (riverine versus
hydrothermal flux) is during periods of rapid changes in
87
Sr/86Sr with time, such as
the last increase that happened since the beginning of the Tertiary. Increased rates
of uplift in the Himalayas and the Andes 20My ago could plausibly be explained by
substantial increase in the supply of radiogenic Sr to the oceans. The rivers that drain
these regions supply 20% of the total solid load into the oceans, and therefore play a
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
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Chapter 1
Introduction
major role in the increase of the 87Sr/86Sr variations during that period of time. The
average
87
Sr/86Sr in the modern oceans is 0.70918±0.00001(±2σ) with respect to
NBS987 standard (0.71025, Faure & Mensing, 2005).
A comprehensive review on the issue of 87Sr/86Sr variations in the oceans is given in
Dickin (2005).See Figure 2for an illustrated summary
Interaction
with sea-floor
sediments
(Unknown)
Figure 2: Sr budget of the oceans (modified after Dickin, 2005)
1.4 Previous Studies of rock/mineral Dissolution
Previous studies examined mainly the dissolution kinetics and Sr-release from
specific silicate minerals, such as labradorite, micas and plagioclase (Taylor et al.,
2000, Brantley et al., 1998), but little work has been done on poly-mineral silicate
rocks. Most of the studies dealt with pure samples that were separated from
pegmatites, hydrothermal veins and even synthetic minerals. In nature, however,
rock samples are not pure and often include inclusions within minerals or coatings
due to diagenetic alteration. In addition, in most cases, dissolution experiments were
conducted under very acidic conditions (pH=1-3) and not in natural water or
seawater (pH=5-8.2). The pH has as a direct effect on the activities of different ions
in the solution and thus affects the solubility of different minerals.
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
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Chapter 1
Introduction
1.5 Goal of the Present Study
The present study aims to test the dissolution rate of fine particles of silicate
alluvium in seawater solution, by tracking water chemistry and
87
Sr/86Sr ratio over
time.
The vast majorty of studiesfocused mainly on interaction of river water with silicate
rocks of different origin along the river drainage system and their Sr release (e.g.
Galy et al., 1999, Krishnaswami et al., 1992, Oliver et al., 2003).Only a few fieldbased studies on Sr release from silicates during interaction with seawater weredone
due to the inherent difficutly in noticing minute changes in water chemistry (due to
the high ionic background).
The purpose of this work is to shed light on silicates interaction with seawater by
means of experimental study of the interaction between silicates alluvium from Eilat
region and synthetic seawater. The Eilat region is a good study area, since within a
small area, old (the Precambrian Arabian-Nubian shield) and diverse silicates of
different origin can be conveniently sampled.
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Chapter 2
Materials and Methods
2 Materials and Methods
2.1 Geological Setting
The study area for sample collection is the Eilat Region where the northern tip of the
Arabian-Nubian Shield is located. This area reveals a large variety of magmatic and
metamorphic rocks, over a relatively small area (ca.60km2). In this study, various
magmatic silicates of different composition were sampled: felsic granites and quartzdiorites (Eilat granite and Roded quartz-diorite) and volcanic rocks (Amram
rhyolite).Within this area, small watersheds which drain a single homogenous rock
and stream sediments were located (Figure 3) and sampled as described below and
listed in section‎2.2along with relevant data.
2.1.1 Amram rhyolite
Amram rhyolite, which is extensively exposed in the southern part of Amram massif,
consists of up to 30% phenocrysts of alkali feldspar and quartz in a microcrystalline
groundmass of similar mineralogy. Kaolinitization and sericitization of feldspars, as
well as chloritization of mafic minerals are common. The aphanitic texture implies
that it crystallized at shallow depths (Mushkin et al., 2002).
2.1.2 Yehoshafat granite
Yehoshafat granite is a small alkaline pluton that intrudes Eilat granite and consists
of 50% alkali-feldspar, 35% quartz, and 15% plagioclase (Steinitz at al., 2009).
2.1.3 Roded quartz-diorite
Roded quartz-diorite is an I-type granitoid. It consists mostly of oligoclase to
andesine plagioclase (50-60%), and quartz (15-20%). In addition, it contains biotite
(5-10%), hornblende (4-10%) and k-feldspar (1-3%). Biotite usually dominates over
hornblende. Accessory minerals are titanite (up to several percent), zircon,
magnetite, and apatite. Minor alteration products are sericite, chlorite and calcite
(Bogoch et al., 2002).
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2.1.4 Eilat granite
Eilat granite from the wadi Shelomo pluton is leucocratic pinkish to light gray
monzogranite. The plagioclase grains (oligoclase: An12–15) are mostly unzoned. The
alkali feldspar has a perthitic texture with about 20-30 vol% of albite phase. The
plagioclase is partially resorbed by alkali feldspar, commonly with myrmekitic
intergrowths. Biotite occurs in euhedral flakes and elongated aggregates. Muscovite
is practically absent.
According to Eyal et al. (2004) the average composition of this rock ( 1 standard
deviation) is as follow: quartz 36.6(1.5)%, plagioclase 25.0(2.7)%, alkali feldspar
32.7(1.9)%, biotite 4.5(0.7)%.
2.2 Samples preparation
Alluvial sediments from streams that mostly drain single homogenous silicate-rock
unit from Eilat region were sampled and dry-sieved via nylon mesh to isolate a
narrow range of grain-size fractions. The sediment was not crushed, in order to
preserve its original surface area. Later on, in order to eliminate fine particles, the
sediment was ultrasonically shaken in ethanol solution and the suspended fine
particles were decanted. The residue was then dried in a 60°C-oven overnight. After
examining the silicate sediments by SEM it was clear that in some samples some
amount of dust still adhered to the surface of the larger mineral grains. In order to
remove some of the dust, mainly carbonate, the Eilat granite and Roded quartzdiorite samples were immersed in 0.5M acetic acid for one hour. The samples were
subsequently rinsed with double-deionized water and the suspended fine-particles
were immediately decanted. This process was carried out 3 times. The other rock
samples (Amram rhyolite, Yehoshafat granite and Roded quartz-diorite), though
were also ultrasonically pretreated. However, they were not rinsed in acetic Acid.
In addition to the various felsic silicate rocks, two pure minerals which comprise a
major component of felsic rocks were chosen; albite and k-feldspar. Albite
(Na0.98Ca0.02AlSi3O8), from Bancroft Ontario Canada was purchased from Ward's
Science [no.460233], and K-feldspar (K0.91Na0.09AlSi3O8) was sampled from Eilat
Pegmatite. These samples were crushed with agate mortar and pestle and later were
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
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Materials and Methods
dry-sieved to isolate the desired size fraction. Rock samples are listed in Table 1below
along with relevant data.
Table 1: Rock/Mineral Samples
Sampl
Type
e
Rock Age* Sampling
[Myr]
Coordinates**
87Sr/86Sr
Sr [ppm]
Name
Alb
Albite
N/A
[Purchased]
0.707470
37.2
KSP
K-Feldspar
N/A
193,540/386,890
N.D.
0.2
YJ6
Amram
625±2
196,830/397,255
0.710737
10.0
526±2
196,830/397,255
0.707294
10.0
605±4
190,080/384,839
0.710498
8.8
634±5
192,300/390,400
0.706402
8.7
634±5
192,300/390,400
0.706402
8.5
636±8
189,928/385,528
0.71199
N/A
Rhyolite
Rhy
Amram
Rhyolite
Yt
Yehoshafat
granite
Rd
Roded
quartz-diorite
QDR
Roded
quartz-diorite
(pretreated
with Acetate)
GE
Eilat granite
(pretreated
with Acetate)
*after Morag et al. (2011) and references therin.**coordinates of Israel New-Grid
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Amram rhyolite
Roded quartz-diorite
Eilat granite
Yehoshafatgranite
Figure 3: Sampling area(Geological map 1:50,000 of Eilat, Beyth et al. 2011)
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
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Sampling
Sieving to 60-90µm
Ultrasonic Shaking in ethanol
and in 60C-oven overnight
drying
Immersion in 0.5M Acetic acid for 1hr
and DDW rinsing (3 times)
Figure4: Sample preparation flow-chart
2.3 Solutions
2.3.1 Seawater Solution
Due to the relatively high concentration of Sr in seawater, it was decided to use
synthetic sea-water with Sr concentration as low as possible. The synthetic sea-water
solution was prepared at the Geological Survey of Israel, by dissolving the following
ultra-pure salts: NaCl, KCl, MgCl2x6H2O, KBr, MgSO4x7H2O and CaCl2x2H2O. All salts
were examined separately for their Sr content, after dissolving each one of them in
separate reactors with DDW. Most of the salts contributed trace amount of Sr
(below detection limit).The major contributor of Sr to the synthetic sea-water
solution is calcium chloride which contributes 17ppb [µgr/kg], MgCl2x6H2O and
MgSO4x7H2O each contributed only 0.5ppb of Sr.
In addition, in order to reach a pH value of ~8.2, NaHCO3 was added to the solution
until the desired pH value was attained.
2.3.2 Borax Solution
A solution of a similar pH to that of natural sea-water was prepared by mixing 100mL
of 0.025M sodium tetraborate (Borax:Na2B4O7x10H2O) with 37.6mL 0.1M HCl in
200mL DDW. This solution (denoted as 'Borax') was used to test the dissolution rates
under the same pH conditions as in the sea-water solution. However, the much
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
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12
Chapter 2
Materials and Methods
lower ionic strength and background, allows tracking minute changes in the water
chemistry.
The chemical composition of the initial seawater and borax solutions is shown in
Table 2.
Table 2: Chemical and physical properties of experiments solutions
Synthetic
Water
SeaSolution
Natural Seawater
Borax
[after
Solution
Wilson,
(this study)
1975]
8.13
8.13
8.25
1.025
0.997
0.7
0.015
Activity of water (aH2O) 0.98
0.98
1
Cl- [mg/L]
19300
19354
394
Na+ [mg/L]
10750
10770
340
Mg2+ [mg/L]
1300
1290
0.1
SO42- [mg/L]
2760
2712
2
Ca2+ [mg/L]
385
412
0.6
K+ [mg/L]
402
399
2.1
Si [µM]
1.629
7.779†
0.832
Al [µM]
1.447
0.035†
1.618
Sr [µM]
0.274
90‡
0.022
pH
Density
at
25ºc 1.024
[gr/cm3]
Ionic
Strength 0.658
[mol/kg]
†after Hem (1985, see Langmuir, 1997). ‡ after Palmer & Edmond(1989)
2.4 Experimental Setting
The experiments were conducted in closed (batch) tubes. The setting that was used
is 'single-point' experiment, in which every point refers to a different independent
tube. The advantage in this technique is that every tube can be analyzed repeatedly
to ensure precise measurements.
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The experiments were conducted in 60mL Corning™ tubes, fully immersed in
thermostatic rocking water-bath, held at a constant temperature of 25.0±0.1˚C. The
ratio of sediment/solution in all the experiments was 0.4(±0.0001) gr sediment in
40(±0.005) gr solution (±σ, n=109). Periodically, on a logarithmic scale, the solution
was separated from the sediment, via Millipore™ Durapore 0.22µm PVDF filter-disk
using a vacuum pump. The purpose behind logarithmic scale sampling stems from
the notion that initially the dissolution rate is faster than afterwards so that there
needs to be short-time intervals sampling at the beginning of the experiment.
The sediments were kept in desiccators for later SEM analysis and the solution was
kept in a new tube for various chemical analyses.
Two types of experiments were conducted; one without solution replacement
(referred to as 'pre-wash') and in the other experiment the solution of the first and
second week were replaced. The reason behind the 'pre-washing' procedure is to
eliminate the effect of the fine particles, which are the most reactive.
1. Unwashed sample– in 25C bath: The solution was kept in the tubes until the full
separation of solution from the sediment. Samples: Alb-SW (albite), YJ6 (Amram
rhyolite), Rd (Roded quartz-diorite) and Yt (Yehoshafat granite).One experiment,
the Amram rhyolite(Rhy) was conducted on a rolling-cylinders device kept in an
ambient room temperature and by which the experiment tubes are situated
horizontally.
2. Pre-Washed - in 25C bath: All tubes had 40gr of solution such as in the other
experiments. On a logarithmic scale (i.e, after 0.5,1,2 and 4 days), 15mL of
solution was withdrawn from one of the tubes with a clean syringe and was kept
in a new tube (two different tubes undergone separation on each sampling time).
The rest of the solution (~25mL) remained in the original tubes until a week is
over. After one week, all tubes were centrifuged (4000RPM) for 5 minutes and
the solution was separated from the sediment. The experiment continued with
new 40gr of solution. This process was repeated for one more week and after a
second replacement of solution, the solutions were then separated from the
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sediment on a logarithmic-scale exactly as described above (referred as 'longterm' experiment). Sample 'KSP-SW' was washed only once after 41days, as
opposed to the other experiments which underwent twice replacement of
solution.
Table 3 describes the different experiments.
Table 3:Basic experiments settings
or
Size
Sample
Mineral
Name
Rock
Alb-SW
Albite
67-75
Seawater
Alb-Bx
Albite
67-75
KSP-SW
K-feldspar
KSP-Bx
K-feldspar
YJ6-SW
rhyolite
fraction
Solution
Duration
No. of Prewashing
tubes
period
172
7
No
Borax Solution
152
7
Yes
60-90
Seawater
152
7
Yes
60-90
Borax Solution
152
7
Yes
0-63
Seawater
172
7
No
0-63
Seawater
174
7
No
60-90
Seawater
140
7
No
60-90
Seawater
140
7
No
60-90
Seawater
152
7
Yes
60-90
Borax Solution
152
7
Yes
60-90
Seawater
162
7
Yes
60-90
Borax Solution
152
7
Yes
[µm]
[days]
(Amram)
Rhy-SW
Yt-SW
Rd-SW
QDR-SW
QDR-Bx
GE-SW
GE-Bx
rhyolite
(Amram)
granite
(Yehoshafat)
quartz-diorite
(Roded)
quartz-diorite
(Roded)
quartz-diorite
(Roded)
granite
(Roded)
granite
(Roded)
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2.5 Analyses
2.5.1 SEM
The sediments were examined under a Scanning Electron Microscope (SEM, FEI
Quanta 450) in the Geological Survey of Israel (GSI) for their grain morphology and
for elements analysis using the combined electron microscope energy dispersive
spectrometry (EDS).
2.5.2 Major element Analysis
Total Si and Al concentrations were analyzed colorimetrically with UV-Visible
spectrophotometer, using the catechol violet method (Koroleff, 1976) and the
molybdate blue method (Dougan & Wilson, 1974). Five standards of Si (4-40µM) and
7 standards of Al (0.5-16µM) were measured before and after the experimental
solutions. The uncertainty in the measured Si and Al was better than ±5%. The Al
precision dropped to ±7% for measurements at low concentrations of 0.6μM-2μM.
Internal standards for Si and Al analyses were prepared from the original synthetic
sea-water solution in order to ensure that there is no continuous instrumental drift.
The internal standards had concentrations that fall approximately in the middle of
the Si and Al calibration curve (19.47µM and 12.00µM respectively).
The concentrations of Ca2+,Mg2+,Fe2+,K+,Na+ and Sr2+ were measured using
Inductively Coupled Plasma Optical Emission Spectrometer (Perkin–Elmer Optima
3300V) at the GSI (low concentrations were measured with the Perkin Elmer SCIEX
ELAN ICP-MS).
All solid samples were also analyzed for their bulk chemical composition as follows:
0.25gr of a well-dried (1hr in 106˚c oven) powder was fused on a 1000˚Cflame for
20min with 1.25gr lithium meta-borate (LiB4O7). The molten alloy was then cooled
and the resulting glass was dissolved in a mixture of 150mL double-distilled water
with 8mL concentrated (65%) and pure (AnalaR Normapur™) HNO3. The solution was
stirred for 3 hours until complete dissolution was achieved and was later analyzed by
inductively coupled plasma – optical emission spectrometry (ICP-OES). This
procedure is discussed in Weissman (2010).
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2.5.3 Sr isotopic composition analysis
In order to remove the Sr from the sample matrix, Sr was separated by cationexchange column separation procedure using Eichrom Sr Spec 50-100µm resin,
following the routine procedure at the GSI(Ehrlich et al., 2001). Some 0.4-8 mL of
solution was evaporated to dryness in Teflon beakers on a 215˚C hotplate depending
upon their Sr concentration to reach 125 ng Sr. Samples were subsequently dissolved
by 200µL 3.5N nitric acid. The residue was then loaded to the columns and the resin
was washed 4 times with HNO3, first with 3.5N (1mL, 1mL, 0.5mL) and then with 1mL
0.1N. The Sr-fraction was then eluted into tube in three steps with 0.1N HNO 3 (1mL,
1mL, 0.5mL). The Sr yield was ca. 95%. The
87
Sr/86Sr ratio was measured with the
'Nu-Instruments' Multi Collector ICP-MS using NIST 987-SRM strontium standard
(87Sr/86Sr=0.71024). The internal and external precisions (2σ) are ±0.002% and
±0.001% respectively.
2.5.4 pH and density of solute ions
The pH was measured at room temperature on an unstirred aliquot of solution, using
a semimicro 83-01 Orion 720A Ross combination electrode. The reported accuracy is
±0.02pH units (±4.5% in H+activities).
The density of the initial solutions was measured with KEM TYOTO DA-130N density
meter. The uncertainty in the density measurement is ±0.0005gr/cm 3.
2.5.5 Saturation index
The saturation indexes of the different minerals were calculated with phreeqC v.3
computer program (Parkhurst & Appelo, 2013), using the 'specific ion theory' (SIT) of
Brønsted-Guggenheim. This equation calculates the activities of different species in
solutions which have high ionic strength, such as seawater (I=0.7mol/kg).
2.6 Calculations
The dissolution rate [mol*gr-1 sec-1] of a mineral in a closed-batch experiment is
described by the following equation:
(2.6.1) Rate 
dC j V 1
 
dt m  j
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Chapter 2
Materials and Methods
where dCj/dt is the concentration derivative of species j [mol/L] with time [sec-1 or
day-1], V is the volume of solution [L], m is the mass of the sample [g] and ν is the
stoichiometric coefficient of j in the mineral formula. Note that in this formalism, the
rate is defined as positive for dissolution.
The uncertainty in the calculated rate is estimated using the Gaussian error
propagation method (Barrante, 1974)using the equation:
(2.6.2) Rate  (
1 V 2
dC
1 dC
V dC
 )  [ ]2  (  dt ) 2  V 2  ( 2  dt ) 2  m 2
m j
dt
m j
m j
The variables with the delta prefix (ΔdC/dt) denote the uncertainty in determining
the value (±dC/dt). The uncertainty in the calculated ratesis8% for Al and Si (for Sr
the uncertainty increases to 14%)
For the general reaction:
(2.6.3) aA  bB  cC  dD
The activity product (AP) is:
(2.6.4) AP 
(aC )c (aD ) d
( a A ) a ( a B )b
.
For a dissolution reaction, that is written as mineral --> dissolved product, the degree
of saturation (Ω) with respect to the mineral is calculated by:
(2.6.5)  
AP
K eq
where Keq is the equilibrium constant of the dissolution reaction at a given
temperature. When Ω<1 the solution is under saturated with respect to the mineral
(hence it may dissolve) and when Ω>1 the solution is super saturated with respect to
that mineral (hence it may precipitate).
The degree of saturation can be described in terms of the Gibbs free energy of
reaction (ΔGr):
(2.6.6) G r  RT ln()
where R is the gas constant (8.314 J/K*mol or 1.987cal/K*mol) and T is the
temperature in Kelvin.
The activity of a dissolved species in solution is defined as:
(2.6.7) ai   i Ci .
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Chapter 2
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where Ci is the concentration and γi is the activity coefficient of i.
The activity coefficient (αi) is calculated in the present study using the BrønstedGuggenheim-Scatchard specific ion interaction theory (SIT):
(2.6.8) log(  i )   z 2 D    (i, j, I )m( j )
k
where I is the ionic strength (2.6.9) I 
(2.6.10) D 
1
2
 (C Z
i
2
i
) ]), D, is the Debye-Hückel term
0.5901 I
), z is the charge of ion i, m(j) is the molality of major
1  1.5 I
electrolyte ion j which is of opposite charge to ion i.
The interaction parameters ε(i,j,I) refer to interaction between ion i and major
electrolyte ion j. Computer program phreeqC v.3.0 holds a database which contains a
list of the different ions parameters.
The dissolution equations for the four main minerals which will be discussed later
appear in the table below with their respective equilibrium constants (at 25°C):
Table 4: Dissolution equations of four main minerals
Mineral
Equation
Keq*
Albite
NaAlSi 3O8  4H 2O  4H   Na   Al 3  3H 4 SiO4
102.74
K-feldspar
KAlSi 3O8  8H 2O  K   Al (OH ) 4  3H 4 SiO4
10-20.573
Gibbsite
Al (OH )3  3H   Al 3  3H 2O
107.74
Kaolinite
Al 2 Si2O5 (OH ) 4  6H   2 Al 3  2H 4 SiO4  H 2O
106.48

* The Keq values are taken from phreeqC standard database.
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Chapter 3
Results
3 Results
3.1 Albite dissolution experiments
As stated above, albite sub-samples used in the dissolution experiments were sieved
and ultrasonically cleansed in order to achieve homogenization of grain size and to
eliminate small particles and dust which adhered to the mineral grains surfaces
(Figure 5a). These small particles are expected to be highly reactive and the
ultrasonic-cleansing appeared to successfully clean the grains surface and achieve
size unity (Figure 5b). As can be seen in Figure 5c, the result is a clean and
homogenous fraction. Nevertheless, particles which are not albite can be also
observed (Figure 5c, brighter particles).
Elemental mapping shows that indeed the sample is composed of albite grains, with
minute amounts of biotite and apatite (Figure 6).
In addition, EDS analysis of the grains reveals that the albite sample is close to the
pure end-member (Na0.98Ca0.02AlSi3O8).
a
b
c
Figure 5: SEM images of albite sample used in the experiment. (a) albite surface
before ultrasonic cleansing; (b) after ultrasonic cleansing; and (c) an overall look at
the sample.
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Results
A
albite
biotite
B
apatite
albite
Figure 6: SEM images and elemental distributionof 3 types of minerals found in the 'Alb'
sample: spots A and D are albite, spot C is biotite and spot B is apatite.
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
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3.1.1 Albite dissolution experiment in Sea-Water
This experiment lasted ca.180 days, during which the Si concentration increased
while the Al concentration and pH remained relatively constant (Figure 7a).Two
stages of Si release rate can be identified: On the initial stage (3-20days) the Si
concentration change is 0.37±0.03µM/day (0.036±0.003µmolSi/gralbite*day) and on
the subsequent stage (20-172days) the rate decreases by a factor of 7.2, to
0.05±0.004µM/day (0.005±0.0004µmolSi/gralbite*day).
The isotopic composition of Sr decreases with time in a hyperbolic-shape manner
(Figure 7b) and the
87
Sr/86Sr versus the reciprocal of Sr concentration (Figure 7c)
shows a straight line. The degree of saturation with respect to albite and two main
Concentration [µmol/L]
25
14
13
12
11
10
9
8
7
6
5
4
3
2
1
20
15
10
Si
Al
pH
5
0
0
20
40
60
80
pH
secondary phases (gibbsite and kaolinite) over time is plotted on Figure 7d.
100 120 140 160 180
Time [days]
a
0.7090
Seawater
0.7085
87Sr/86Sr
0.7080
Bulk Sample
0.7075
0.7070
87Sr/86Sr
= 0.7073t-4E-04
R² = 0.98
0.7065
0.7060
0.7055
0
b
20
40
60
80
100
120
140
160
180
Time [days]
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87Sr/86Sr
Chapter 3
Results
0.70720
0.70700
0.70680
0.70660
0.70640
0.70620
0.70600
0.70580
0.70560
(Time)0.3
0.4
0.5
0.6
0.7
0.8
1/Sr [1/µM]
c
Degree of Saturation Ω [IAP/Keq]
1000
100
10
time [days]
1
0
20
40
60
80
100
120
140
160
180
0.1
0.01
Albite
0.001
Kaolinite
0.0001
Gibbsite
0.00001
d
Figure 7: albite dissolution experiment in Seawater. (a) Si,Al and pH variations over time; (b)
87
Sr/86Sr variations over time; (c)
87
Sr/86Sr versus the reciprocal of Sr concentration
throughout the experiment; (d) Degree of saturation with respect to albite and secondary
phases during the experiment.
3.1.2 Albite dissolution experiment with borax solution
In contrast to the Seawater dissolution experiment, in the Borax solution experiment
the sediment was first subjected to a pre-experiment wash, in order to dissolve fine
grains and highly reactive sites. Results show that the initial dissolution rate
(0.90±0.07µM/day) is slightly higher than the rate after replacement of solution
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
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Chapter 3
Results
(0.68±0.05µM/day, Figure 8a). The Al release rate is also affected in a similar
extent;0.73±0.06µM-Al/day on the pre-washing period and 0.43±0.03µM-Al/day
after replacement of solution with a new one (Figure 8b).
Si [uM]
a
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Pre-wash: dSi/dt= 0.90µM/day
R² = 0.95
postwash: dSi/dt= 0.68µM/day
R² = 0.91
pre-wash
post wash
0.0
1.0
2.0
3.0
4.0
5.0
time [days]
6
5
Al [µM]
4
3
2
pre-wash
1
post wash
0
0.0
1.0
b
2.0
3.0
4.0
5.0
time [days]
Figure 8: Prewashing period of albite in Borax solution (a) Si; (b) Al in the pre-wash and postwash (after replacement of solution).
After replacement of the solution for a second time, the long-term experiment
started. Opposed to the albite-Seawater experiment in which the Al concentration
remained constant over time (Figure 7a) the Al concentration increased with time
(Figure 9a).
In both experiments (seawater and borax solution) pH remains constant due to
buffer reaction. In the seawater experiment the buffer is bicarbonate and in the
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Chapter 3
Results
Borax solution it is the borate. The Si release rate is 0.26±0.02µM/day during the first
84 days (R2=0.95) and later is approaching a constant value 24µM. The Al release
rate is 0.13±0.01µM/day (R2=0.98) during the whole 152days of the experiment. It
can also be noticed that the Al increases more sharply compared to Si during the
initial 3days (2.0±0.16µM-Al/day compared to 0.6±0.05µM-Si/day)
(Figure 9a, page 26).
The Sr release rate is 0.05±0.004µM/day (R2=0.98) during the first 40days, in which
the 87Sr/86Sr ratio changes in a logarithmic shape. After 40days, the Sr release rate is
reaching steady-state condition and so the
87
Sr/86Sr ratio does not change
significantly (Figure 9b). Like as in the sea-water experiment, the
87
Sr/86Sr ratio is
decreasing logarithmically over time, but the 87Sr/86Sr ratio is shifted to lower values.
The isotopic composition during the experiment is far below the initial value of the
solution which occurred also in the Seawater experiment.
As can be seen in Figure 9c, there is a correlation between Ca2+ and Sr2+
concentration during the experiment.
Conentration [µmol/L]
30
14
13
12
11
10
9
8
7
6
5
4
3
2
1
25
20
15
Si
Al
pH
10
5
0
0
50
Time [days]
100
150
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
25
pH
a
GSI/01/2015
Chapter 3
Results
0.70900
Initial Borax solution
0.70850
87Sr/86Sr
0.70800
Bulk Sediment
0.70750
0.70700
y = 0.7065x-3E-04
R² = 0.93
0.70650
0.70600
0.70550
0.70500
0
50
Time [days]
b
100
150
600
500
Ca = 171.5Sr
R² = 0.98
Ca [µM]
400
300
200
100
0
0.0
0.5
1.0
1.5
2.0
2.5
Sr [µM]
c
3.0
3.5
1000
Degree of Saturation Ω [IAP/Keq]
100
d
10
time [days]
1
0.1 0
20
40
60
80
100
120
140
160
0.01
0.001
0.0001
Albite
1E-05
Kaolinite
1E-06
Gibbite
1E-07
1E-08
Figure 9: albite in Borax dissolution experiment (a) Si,Al and pH variations throughout the
experiment (b)
87
Sr/86Sr versus time (c) Ca versus Sr (d) Saturation degree evolution with
respect to albite and secondary phases.
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
26
GSI/01/2015
Chapter 3
Results
3.2.1 K-Feldspar dissolution experiment with Sea-Water
In these experiments, K-feldspar separated from Eilat pegmatite, was used with both
types of solutions: Seawater and borax. The K-feldspar is a perthite
(K0.91Na0.09AlSi3O8) with grains which are homogenous in size (Figure 10a). Elemental
mapping on the EDS-SEM shows that in accordance with its formula, most of the
sample is K-Si-Al oxide and minor parts are Na-Si-Al oxide (Figure 10b).
Early on, in the first stages of the experiment it was observed that the K-feldspar
does not contribute Sr above the solution background. Indeed the Sr concentration
of the whole sample is 0.2ppm. Thus the 87Sr/86Sr ratio was not measured.
b
a
Figure 10: SEM photographs of K-feldspar sample. (a) General overview, (b) colored mapping
of K-rich (red) and Na-rich phases (blue).
In this experiment, K-feldspar was subjected to a pre-washing period, in which 15mL
of solution was withdrawn from the tubes and taken to Si and Al analysis. The rest of
the solution (~25mL) remained in the tubes until 41 days were over, after which the
whole solution was replaced with a new one.
In the initial stage (first two weeks) the Si release rate is ~3 times faster than Al
release rate (0.31±0.02µM-Si/day compared with 0.09±0.01µM-Al/day). In the later
stage (26-41days) the release rate decreases by a factor of ~2 (0.09±0.01µM/day for
Si and 0.03±0.002µM/day for Al).
During the long-term experiment (after 41days of initial dissolution and replacement
of solution with a new one), Si concentration continues to increase but in a lower
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
27
GSI/01/2015
Chapter 3
Results
rate (0.02±0.002µM/day) and Al concentration increases only during the first 10days
(0.26±0.02µM/day), and later on remains constant over time (Figure 11b).
Concentration [μM]
10
8
6
4
2
Si
Al
0
0
2
4
6
8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40
time [days]
a
Concentration [µM]
10
8
6
4
Si
2
Al
0
0
20
40
60
b
80
100
Time [days]
120
140
160
180
Degree of Saturation [Ω=IAP/Keq]
1.E+02
c
1.E+01
Time [days]
1.E+00
1.E-01
0
50
100
150
200
1.E-02
1.E-03
Albite
1.E-04
K-feldspar
1.E-05
Gibbsite
1.E-06
Kaolinite
1.E-07
Figure 11: K-feldspar dissolution experiment in Seawater (a) Pre-wash period (b) The
concentration in the residual tubes until 41days were over (c) The long-term experiment (d)
Degree of saturation over time with respect to specific minerals.
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
28
GSI/01/2015
Chapter 3
Results
Figure 11c shows the change with time of the degree of saturation with respect to the
dissolved minerals. The solution is under-saturated with respect to both K-feldspar
and albite during the whole experiment and continues to dissolve and release Si and
Al.
3.2.2 K-Feldspar dissolution experiment in borax-solution
In this experiment, the initial Si release rate is 0.32±0.03µM/day and the
replacement of solution does not affect the dissolution rate ( Figure 12a). The Al
concentration during that time remains constant: 2.5(±0.2)µM (±σ).
On longer time scale (Figure 12b) Si release rate reduces by half (0.16±0.01µM/day)
during the first 40 days (R2=0.99) and decreases to 0.05±0.004µMSi/day for the next
time period (40-152days, R2=0.95).
Al release rate in the first 3 days is high (1.98±0.16µM/day, Figure 12b) but then
decreases substantially to 0.08±0.006µM/day during the second stage (3-20days).
Later on (40-152days) Al release rate reduces by a factor of 4 to 0.02±0.002µM/day
(R2=0.99). In addition there is an exponential decrease with time in potassium
concentration (Figure 12b).
The solution is undersaturated (Ω<1) with respect to both K-feldspar and albite
(Figure 12c).
concentration [µM]
7
Si [prewash]
dSi/dt= 0.32µM/day
R² = 0.94
6
Si [post-wash]
Al [pre-wash]
5
Al [post-wash]
4
3
2
1
0
0
2
4
time [days]
6
8
a
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
29
GSI/01/2015
Chapter 3
Results
Concentration
16
14
Si [uM]
12
Al [uM]
K [ppm]
10
8
6
4
2
0
0
20
40
60
b
80
100
Time [days]
120
140
160
1000
Degree of Saturation Ω [IAP/Keq]
100
10
Time [days]
1
0.1 0
20
40
60
80
100
120
140
160
0.01
0.001
0.0001
0.00001
0.000001
0.0000001
K-feldspar
Gibbsite
Kaolinite
Albite
1E-08
c
Figure 12: K-feldspar dissolution in Borax solution. (a) The pre-wash time-period (b) longterm period experiment (c) Degree of saturation over time.
3.3 Amram rhyolite dissolution experiments in Sea-Water
The Amram rhyolite dissolution experiment in Seawater was conducted on two
independent devices: one was a thermostatic shaking bath, on which the tubes are
placed vertically, and the other was on a rolling-cylinders device, on which the tubes
are situated horizontally. The thermostatic bath was programmed to remain on
25◦Cwhile the rolling device was kept in ambient room temperature which varies
with time around this temperature.
In spite of the differences, there was a similarity between the results of the two
experiments (Figure 13a). Si concentration increases gradually during the first 40days
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
30
GSI/01/2015
Chapter 3
Results
(0.85µM/day, R2=0.95), thereafter becomes constant (days 40-54) and then
decreases by a rate of 0.30±0.02µM/day during ~68 to 80days, and thereafter
increases again. The observation that this trend is apparent in two independent
experiments indicates that the decline in Si concentration is real.
Al also behaves in the same manner in the two experiments. There is a notable
'peak' in Al concentration after 2-6days with a later decrease in Al concentration
(Figure 13b). After that period, steady-state conditions for the Al concentration
appear.
The Sr concentration during the experiment remained constant with an average
value of 3.00(±0.09) µM (±σ, Figure 13c), though the 87Sr/86Sr ratio varies substantially
Si [µM]
(Figure 13d).
100
90
80
70
60
50
40
30
20
10
0
shaking bath
0
20
40
60
a
80
100
Time [days]
120
rolling device
140
160
180
3.0
2.5
Al [µM]
2.0
1.5
1.0
0.5
shaking bath
rolling device
0.0
0
20
40
60
80
100
120
140
160
180
Time [days]
b
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
31
GSI/01/2015
Chapter 3
Results
c
4
Sr [µM]
3
2
1
shaking bath
rolling device
0
0
20
40
60
80
100
Time [days]
120
140
160
180
d
0.70855
shaking bath
rolling device
87Sr/86Sr
0.70850
0.70845
0.70840
0.70835
0
20
40
60
80
100
120
140
160
180
Time [days]
Figure 13: Amram rhyolite dissolution experiments (a) Si; (b) Al; (c) Sr concentrations over
time; (d) Variations in 87Sr/86Sr ratio throughout the experiment.
3.4 Yehoshafat granite dissolution experiment in Seawater
In this experiment Si concentration increases gradually and reaches a constant value
after 80 days (Figure 14a). Al concentration and pH remain constant over time:
2.51(±0.47)µM and 8.09(±0.10), respectively (±σ).
Sr concentration and87Sr/86Sr variation with time is plotted in Figure 14c and Figure
14d, respectively.
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
32
GSI/01/2015
Results
Concentration [µM]
60
14
13
12
11
10
9
8
7
6
5
4
3
2
1
50
40
30
Si
20
Al
10
pH
0
0
20
40
60
80
100
120
140
pH
Chapter 3
160
time [days]
a
0.70
0.60
Sr [µM]
0.50
0.40
0.30
0.20
0.10
0.00
0
50
100
150
time [days]
b
0.708550
0.708500
87Sr/86Sr
0.708450
0.708400
0.708350
0.708300
0.708250
0.708200
0.708150
0
50
100
150
Time [days]
c
Figure 14: Yehoshafat granite dissolution experiment in Seawater (a) Si,Al and pH; (b) Sr
concentration; (c) 87Sr/86Sr over time.
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
33
GSI/01/2015
Chapter 3
Results
3.5 Roded quartz-diorite dissolution experiments
3.5.1 Roded quartz-diorite dissolution experiments with Sea-Water
In this experiment, Roded quartz-diorite sediment was subjected to seawater in two
independent experiments. One without washing treatment, in which the sediment is
taken 'as is' and placed in the tubes, and the other (Figure 15b) has gone a preexperiment treatment (replacement of solution two times once a week prior the
long term experiment). In addition, the sediment in the 'with washing treatment'
was leached in 0.5M acetic acid for one hour prior the experiment in order to
dissolve carbonate dust.
During the first two days, the Si concentration in solution increases rapidly in a rate
of 6.6±0.5 µM-Si/day (pre-wash) and after replacement of solution the rate
decreases by a factor of ~1.8 to 3.7±0.3µM-Si/day (R2=0.96, for 12 independent
points, Figure 15a). Al concentration remains constant (~2(±0.5)µM (±σ) ,Figure 15a).
A noticeable increase in Si concentration during days 2 and 4 is observed for both
post-wash time-period in the sea-water and in the Borax solution (described in the
next section, Figure 15a). An apparent enhancement in Si release rate is observed
during days 2-4.
After the washing period, Si concentration increases gradually (Figure 15b). In
addition, in the 'without pre-wash' the Si release rate is ~3 times higher
(3.24±0.26µM/day compared to 1.12±0.09µM/day (R2=0.98) than in the 'after
washing period' experiment (slope taken from the first 20days).
After 40 days of experiment, the dissolution rate becomes slower in both
experiments and Si concentration is approaching a constant value.
Sr concentration in the 'without pre-wash' experiment increases from day 6 to day
20 whereas in the 'after washing period' Sr concentration does not vary much, and
remains on a value of 0.56(±0.02) (±1σ) (Figure 15c).
The87Sr/86Sr variations of the two independent experiments ('without wash'
experiment and 'after washing period' experiment) are is shown Figure 15d.
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
34
GSI/01/2015
Concentration [µM]
Chapter 3
Results
45
Si [pre-wash]
40
Si [post-wash]
35
30
Al [pre-wash]
25
Al [post-wash]
20
15
10
5
0
0
1
1
2
2
3
3
4
4
5
Time [days]
a
140
120
Si [µM]
100
80
60
without pre-wash
40
after washing period
20
0
0
20
40
60
Sr [µM]
b
100
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
120
140
160
without pre-wash
after washing period
0
c
80
Time [days]
20
40
60
80
100
120
140
160
Time [days]
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
35
GSI/01/2015
Chapter 3
Results
0.70870
0.70860
87Sr/86Sr
0.70850
0.70840
0.70830
0.70820
0.70810
0.70800
without pre-wash
0.70790
after washing period
0.70780
0
d
20
40
60
80
100
Time [days]
120
140
160
Figure 15: Roded quartz-diorite dissolution in Seawater. (a) Si and Al concentration during
the pre-wash and after a replacement of solution, i.e 'post-wash'; (b) and (c) Comparison of
Si and Sr concentration (respectively) in the 'without wash' experiment and in the
experiment in which the solution was replaced two times, i.e "after washing period"; (d) The
isotopic composition of Sr throughout these experiments.
3.5.2 Roded quartz-diorite dissolution experiment in borax solution
In this experiment the Si release rate during the pre-wash period is higher than after
replacement of solution (compare pre-wash to post-wash, in Figure 16a). For time
interval 1-2 days, the Si release rate is 6.38±0.51µM/day for the pre-wash period,
and it reduces to 2.67±0.21µM/day after replacement of solution. An enhancement
in the Si release rate can be observed, between 2-4 days, as is also apparent in the
Seawater experiment. Al concentration is constant with time(2.56±0.62µM
;±1σ,n=15).
In the long term experiment, Si concentration continues to increase but with a lower
rate. The initial (3-20 days) Si release rate is 1.40±0.11µM/day (R2=0.96) and it seems
as though Si approaches a constant concentration, but after 40 days Si concentration
continues to increase by a rate of 0.39±0.03µM/day (R2=0.88) during time period 40152days.
Al concentration is decreasing by a minor extent (rate of 0.03±0.002µM/day,
R2=0.87) and the pH stays constant on the value of the buffer solution (8.25).
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
36
GSI/01/2015
Chapter 3
Results
Sr concentration and 87Sr/86Sr variations over time are shown in Figure 16c and Figure
16d respectively. It can be noticed that values reach maximum after 7days of
dissolution (both in Sr concentration and isotopic composition), after which the Sr
concentration increases by a rate of 0.0007±0.0001µM/day, while the isotopic
composition decreases until day-20 when it starts to increase until day-84 and then
decreases again.
50
Concentration [µM]
45
40
35
30
25
Si [pre-wash]
Si [post-wash]
Al [pre-wash]
Al [post-wash]
20
15
10
5
0
0
a
1
2 Time [days] 3
4
5
100
14
13
12
11
10
9
8
7
6
5
4
3
2
1
80
70
60
pH
Concentration [µM]
90
50
40
Si
30
Al
20
pH
10
0
0
b
20
40
60
80
100
120
140
160
Time [days]
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
37
GSI/01/2015
Chapter 3
Results
0.35
0.30
Sr [µM]
0.25
0.20
0.15
0.10
0.05
0.00
0
20
40
60
80
100
120
140
160
140
160
Time [days]
c
0.70844
0.70842
87Sr/86Sr
0.7084
0.70838
0.70836
0.70834
0.70832
0.7083
0.70828
0
20
40
60
80
100
120
Time [days]
d
Figure 16: Roded quartz-diorite dissolution in Borax solution. (a) Si and Al concentrations
variations in the pre-wash and post-wash time-periods (b); Si, Al and pH throughout the
long-term experiment; (c) Sr concentration and (d) Sr isotopic composition during the longterm experiment.
3.6 Eilat granite dissolution experiments
3.6.1 Eilat granite dissolution experiment with sea-water
In this experiment, Si and Al concentrations during the washing period varies as
shown in Figure 17a (page 40). Si release rate is 5.77±0.46µM/day during the prewash and reduces to 2.89±0.23µM/day in post-wash period (slope taken from points
of first two days). The general slope of the two lines remains, however, similar on a
value of ~2±0.2µM/day and no significant decrease in the Si release rate can be
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
38
GSI/01/2015
Chapter 3
Results
observed during 8 days-time. The Al concentration does not vary much during the
washing period and stays on a value of 4.96±0.86µM (±1σ).
After replacement of solution for the second time, the long-term experiment started
and the Si, Al, and pH variations can be seen in Figure 17b. There is a linear Si release
rate during days 3-80 (0.25±0.02µM/day, R2=0.98) and then a constant value is
approached. The Al concentration initially increases during the first 3 days
(0.18±0.01µM/day,
R2=0.92)
and
then
decreases
by
a
minor
rate
of
0.01±0.001µM/day.
During the initial stage (3-21days) the Sr concentration stays constant (within
precision boundaries, Figure 17c), though the isotopic composition (Figure 17d)
increases. Afterwards (21-80 days) the Sr concentration increases while the isotopic
composition decreases, and at the end (80-150 days) both of them decrease
simultaneously.
Concentration [µM]
30
25
20
15
Si [pre-wash]
Si [post-wash]
Al [pre-wash]
Al [post-wash]
10
5
0
Concentration [µM]
4 Time [days] 6
35
30
25
20
15
10
5
0
8
Si
Al
pH
0
b
2
50
100
Time [days]
14
13
12
11
10
9
8
7
6
5
4
3
2
1
150
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
39
10
pH
0
a
GSI/01/2015
Chapter 3
Results
0.4
Sr [µM]
0.3
0.2
0.1
0
0
20
40
60
80
100
120
140
160
180
160
180
Time [days]
c
87Sr/86Sr
0.7088
0.7086
0.7084
0.7082
0.708
0
20
40
60
80
100
120
140
Time [days]
d
Figure 17: Eilat-granite dissolution experiment in Sea-Water: (a) Si and Al variations in the
pre-wash and post-wash periods prior the long term experiment; (b)Si,Al and pH variations
in the long term experiment; (c) Sr concentration versus time; (d) Variations in the 87Sr/86Sr
ratio.
3.6.2 Eilat granite dissolution experiment in borax solution
The changes in Si and Al concentrations with time for the pre-wash and post-wash
period are shown in Figure 18a (page 42). The Si release rate is higher in the pre-wash
period
than
in
the
post-wash
period
(4.18±0.33µM/day
compared
to
2.31±0.18µM/day, R2=0.95 and R2=0.88, respectively). The pre-wash Si release rate is
two
times
higher
than
that
obtained
with
the
seawater
experiment
(4.18±0.33µM/day compared to 2.05±0.16µM/day). The Al concentration remains
constant (6.27(0.93)µM and 4.54(0.57)µM (±σ) for the pre-wash and the post-wash,
respectively).
Si and Al variations for the long-term experiment are plotted in Figure 18b. Si is
increasing on a logarithmic manner, while pH and Al remain constant, on value of
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
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GSI/01/2015
Chapter 3
Results
5.27±0.9µM and 4.64±0.6 µM (±1σ) for the pre-wash and post-wash periods,
respectively.
In this experiment a logarithmic decrease in potassium concentration, together with
a simultaneous logarithmic increase in Sr concentration is observed (Figure 18c). The
Sr release rate is higher during the initial stage (during days 2-40 the rate is
0.01±0.001 µM/day, R2=0.85) and then remains constant over time period 40-84
days, with a small increase after 152 days.
After an initial decrease in 87Sr/86Sr (7-10days, Figure 18d), there is a gradual increase
in the isotopic composition up until day-84 when it drops dramatically to a value of
0.70833 after 152days.
50
45
Concentration [µM]
40
35
30
Si [pre-wash]
25
Si [post-wash]
20
Al [pre-wash]
15
Al [post-wash]
10
5
0
2
4 Time [days] 6
8
10
70
Si= 12.631ln(t) - 8.4864
R² = 0.97
60
Concentration [µM]
14
13
12
11
10
9
8
7
6
5
4
3
2
1
50
40
30
Si
20
Al
pH
10
0
0
b
20
40
60
80
100
120
140
pH
0
a
160
Time [days]
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
41
GSI/01/2015
Chapter 3
Results
0.60
160
140
0.50
120
100
0.30
80
K [µM]
Sr [µM]
0.40
60
0.20
40
Sr
0.10
K
20
0.00
0
0
20
40
60
c
80
100
Time [days]
120
140
160
0.708900
87Sr/86Sr
0.708800
0.708700
0.708600
0.708500
0.708400
0.708300
0
20
40
60
80
100
120
140
160
Time [days]
d
Figure 18: Eilat-granite dissolution experiment in Borax solution: (a) Si and Al concentration
in the pre and post wash periods; (b) Changes in Si,Al and pH throughout the long term
experiment; (c) Sr and K versus time; (d) Variations in 87Sr/86Sr throughout the experiment.
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
42
GSI/01/2015
Chapter 4
Discussion
4. Discussion
4.1 Effect of solution replacement (prewashing)
In seven of the experiments, the solution was replaced for two times during two
weeks prior to the long-term experiment. This was done in order to eliminate the
effect of small particles which have a relatively high surface area compared to their
volume. In the first week of prior replacement ('pre-wash') the dissolution rate was 5
to 7 times faster than the long-term experiment (in the Roded quartz diorite and
Eilat granite experiments in seawater, respectively). For K-feldspar, however, no
change was observed. For Borax solution the dissolution rate for Roded quartzdiorite and Eilat granite was 4 and 3 times faster, while for K-feldspar and albite no
significant change was observed (1.5 to 2 times faster).
In addition, there appears to be a major increase in Si release rate in both Roded
quartz-diorite experiments (seawater and in borax solutions, Figure 15a on page 36)
during the time interval of 2 to 4 days in the second week of the pre-wash (after
replacement of solution for the first time). One suggestion for the enhanced Si
release rate during this time period is the removal of iron oxide coating that exposes
new surface area, as was shown by Ganor et al. (2005)in their study of Eilat granite.
The first week of dissolution (pre-wash) appeared to affect the reactivity of the
sediment-sample and to lower the Si release rate in the post-wash period (Figure 19).
The decrease in the reactivity (which lowers the slope of Si concentration over time)
is more pronounced in the Eilat granite in borax solution experiments, as Figure 19b
shows. The decrease in the reactivity is also apparent in the Roded quartz-diorite
experiment (Figure 15b, page 36).The effect of removal of some of the fine particles
prior the long-term experiment ("pre-washing") can be observed: during the time
interval of 0-40 days the Si release rate in the 'after-washing period' sample is much
lower than in the experiment in which no washing period was conducted. The
decrease in the reactivity is only apparent at the beginning of the experiment (040days) and later on, the two experiments continue to dissolve in a similar rate.
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
43
GSI/01/2015
Chapter 4
QDR-SW [pre-wash]
QDR-SW [post-wash]
QDR-Bx [pre-wash]
QDR-Bx [post-wash]
50
40
Si [µM]
Discussion
30
20
10
0
0
a
50
2 Time [days] 3
GE-SW [post-wash]
40
5
GE-Bx [pre-wash]
35
GE-SW [pre wash] dSi/dt= 2.05uM/day
R² = 0.97
GE-Bx [post-wash]
30
25
20
15
GE-Bx [post-wash] dSi/dt= 2.31uM/day
R² = 0.88
GE-SW [post wash] dSi/dt = 2.04uM/day
R² = 0.94
10
5
0
0
b
4
GE-Bx [pre wash] dSi/dt = 4.17uM/day
R² = 0.95
GE-SW [pre-wash]
45
Si [µM]
1
1
2
3
4
5
Time [days]
6
7
8
9
Figure 19: Comparison of the effect of solution replacement on dissolution rate.
Si
concentration changes in both solutions before and after washing (a) QDR= Roded quartzdiorite (b) GE= Eilat granite. SW= Seawater and Bx = borax solutions
4.2
Comparison of dissolution rate in Seawater versus Borax solution
Though the pH was similar, (~8.2) there appeared to be higher dissolution rate in the
borax solution compared to that in the seawater experiments. The major difference
between the two solutions is the ionic strength, 0.7 in seawater compared to
0.015mol/L in the borax solution. In high ionic strength, silicate minerals become less
soluble (Langmuir, 1997) and thus the dissolution rate decreases. The high
concentration of Na+ and Cl- in seawater reduces the free water molecules in
solution by forming hydration spheres around them.
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
44
GSI/01/2015
Chapter 4
Discussion
Similar to the pre-wash experiments, on the long-term period (40-170days) an
enhanced dissolution rate in the borax experiments was observed (for K-feldspar,
Roded quartz-diorite and Eilat granite experiments).
In Eilat granite in borax solution experiment, the dissolution rate within the first prewash week is two times faster than the dissolution rate after replacement of solution
(4.17±0.33and 2.31±0.18µM/day, respectively). In contrast, in the seawater
experiment, the Si release rate did not change (2.05±0.16µM/day, Figure 19b). After
initial dissolution, the Si release rate becomes similar in the two experiments
(~2µM/day).
4.3 Albite and K-feldspar dissolution experiments
Albite: The dSi/dAl ratio during the dissolution of albite in seawater, with respect to
the initial concentration, gradually increases in the course of the experiment from
0.9 to congruent dissolution of 3.1 at day 172. The variations in the dSi/dAl ratio can
be explained by simultaneous precipitation of supersaturated alumino-sillicates such
as kaolinite and gibbsite as suggested by Holdren & Berner (1979) who conducted an
albite dissolution experiment at the same pH. They argued that silicate mineral
dissolution is usually incongruent, with precipitation of relatively amorphous
metastable products that may crystallize with time, to form minerals such as gibbsite
and kaolinite (Helgeson et al., 1984).
Indeed, phreeqC (Parkhurst & Appelo, 2013)simulation (Figure 7d, page 23) shows
that in the beginning of the experiment (0-10days),gibbsite (Al(OH)3) is more supersaturated (Ω=11-40) than kaoliniteSi2Al2O5(OH)4 (Ω =0.16-38.9). However, after
10days kaolinite becomes far more super-saturated than gibbsite reaching value of
Ω=534 after 172days. Hence, it is suggested that the dSi/dAl ratio during the
experiment reflects the incongruent dissolution of albite and/or precipitation of
gibbsite and kaolinite. Since the kinetics of these processes for these types of
solutions are unknown, further investigation on this is needed.
The dissolution rate that was achieved after 10days is 1.48±0.12*10-13molAb/sec*gr.
This is ~1.5fasterthan the value by Knauss & Wolery (1986) obtained under the same
pH and temperautre for unwashed albite in boric acid+sodium hydroxide
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
45
GSI/01/2015
Chapter 4
Discussion
solution(7.74*10-14molAb/sec*gr). The difference may lay in the actual surface area,
though calculated for gram mineral. Knauss & Wolery used 75-125μm while in this
experiment 63-75μm was used.
In the albite-borax experiment (Figure 9d, page 26), gibbsite is oversaturated during
the initial 10days, during which the dSi/dAl ratio is ~4compared to 3 for
stoichiometric dissolution. This may result from rapid precipitation of gibbsite which
consumes only Al. The dSi/dAl ratio during days 10 to 83 interval is ~2 which suggests
precipitation of kaolinite.
K-feldspar: In the K-feldspar experiment in Seawater, a stoichiometric release of Si
and Al was observed (congruent dissolution, Si:Al ratio of 3:1). The release rate of Si
in the K-feldspar-seawater experiment is by a factor of ~44 lower than that obtained
by Wollast(1967) who conducted K-feldspar dissolution experiment under similar
conditions (pH=8, Temp=26˚C): 14.07µM-Si/day compared to 0.32µM-Si/day in the
current experiment.
The Al concentration in the experiment (Figure 11b, page 28) does not increase from
day 11. It is suggested that Al is consumed by precipitation of a secondary mineral,
either gibbsite Al(OH)3 which is more readily precipitated thermodynamically, or
kaolinite.
In the experiment with borax solution the solution is initially highly under saturated
with respect to K-feldspar (Figure 12c, page 30) and therefore the dissolution rate is
faster than in later stages. Gibbsite is more oversaturated than kaolinite and the
ratio between the release rates of Si to that of Al is ~2.3, lower than expected for
stoichiometric dissolution (~3). The most plausible explanation for the observed Si
concentration change over time is Si uptake by kaolinite precipitation.
The exponential decrease of K+ over time (Figure 12b) in the K-feldspar-Borax
experiment is rather an unexpected phenomenon. K+ normally increases as a result
of K-feldspar dissolution unless it is absorbed on the surface of the grains (electrical
attraction) or by precipitation of K-bearing clay.
4.4 Sr release during dissolution
Sr release during albite experiment: In the albite-Borax experiment, in which Ca2+
concentration was measured, a coupling between Ca2+ and Sr2+concentrations over
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
46
GSI/01/2015
Chapter 4
Discussion
time can be observed (Figure 9c, page 26). This indicates that Sr is derived from the
same sites in the crystal lattice as Ca2+.
The
87
Sr/86Sr ratio in both experiments (seawater and borax) decreases in a
hyperbolic manner (Figure 20c, page 49). Faure (1986) suggests that this hyperbolic
shape may be due to the presence of two minerals, each contributing a different
87
Sr/86Sr ratio and Sr concentrations. The initial seawater solution ratio is far more
radiogenic (0.70849) than the value reached after 3 days of dissolution (0.70696).
This value is also lower than the value that was obtained for the bulk whole-rock
analysis (0.70747). The sea-water initial ratio was omitted from the
87
Sr/86Sr versus
1/Sr plot (Figure 7c, page 23) because it appears on the graph off the line (appears on
the extreme upper-right corner), which indicates that there is no 'mixing' between
the Sea-Water end-member and the albite. The straight line on Figure 7c implies the
presence of two end-members in the 'Alb' sample which contribute two distinct
isotopic ratios. The high ratio obtained during the initial stage of the experiment is
contributed by a highly reactive mineral while the lower values by albite. It is
suspected that the highly-reactive mineral is biotite and/or apatite. SEM
backscattered-electrons (BSE) image (Figure 6a, page 21) shows the lamellar shape of
biotite, which appears to be in trace amount (see brighter particles in Figure 6a). EDS
analysis on this spot labeled 'C' reveals that it is indeed a Si-Al-K-Mg-Fe mineral
(biotite). Combined SEM and EDS allowed automated scanning of the sample that
revealed that biotite is present in minor amounts (3.03%) by area. In addition, it is
suspected that apatite is also present in trace amounts as shown in Figure 6 on page
21 (Ca-P-F mineral). Chemical Analysis of the bulk sample, together with the notion
that
phosphorus
comes
predominantly
from
apatite
dissolution
allows
approximation of the amount of apatite (0.23-0.66%). The premise that biotite is
indeed a notable contributor of Sr is in accordance with Brantley et al.(1998) who
examined Sr release rate and isotopic ratios of dissolving feldspars. As Blum & Erel
(1995) noted, biotite is a potentially a large source of radiogenic Sr, especially from
fine material, such as in our case. At the initial stages of the experiment the most
fine particles and reactive minerals dissolve. As Brantley et al. (1998) noted, rocks
weather to yield Sr ratio which is not consistent with the bulk ratio, but with the
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
47
GSI/01/2015
Chapter 4
Discussion
ratio of the most quickly-dissolving phases. The higher ratio appears at the beginning
of this experiment (0-20days) when biotite is probably dissolving. Another
mechanism that is suggested is the openings of etch pits and the removal of coatings
which allows inclusions found within the biotite particles to dissolve. Figure 6a (page
21) shows that indeed part of the biotite grains contain inclusions of another mineral
(EDS analysis could not reveal what this mineral is because of its tiny size).
In both albite experiments there is a similar logarithmic decrease in the
87
Sr/86Sr
ratio over time (Figure 20b, page 49), but in the borax-solution experiment, at each
stage87Sr/86Sr values are lower. The reason might be the rapid dissolution of biotite
at the beginning of the borax experiment, which lowers the 87Sr/86Sr value sharply at
the beginning. Later on, the
87
Sr/86Sr on both experiments varies in the same
manner, but with a shift of values due to the contribution of biotite in the beginning
of the experiment. In general, the average difference between the two experiments
is 0.0006(±0.0003,±σ).
On a87Sr/86Sr versus 1/Sr plot (Figure 20c, page49) two linear mixing lines are
observed each for experiment type. However both mixing lines converge to a low
end-member (0.705533).
K-feldspar: The K-feldspar does not contribute Sr and therefore does not affect the
87
Sr/86Sr in the solution. The bulk analysis reveals that indeed it contains only trace
amounts of Sr (0.2ppm).
30
25
Si [µM]
20
15
10
Albite [seawater]
5
Albite [borax solution]
0
0
a
50
100
Time [days]
150
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
48
200
GSI/01/2015
Chapter 4
Discussion
0.70900
0.70850
albite in seawater
87Sr/86Sr
0.70800
albite in borax-solution
0.70750
0.70700
0.70650
0.70600
0.70550
0.70500
0
50
100
150
200
Time [days]
b
0.70720
0.70700
Albite [seawater]
0.70680
albite [borax]
87Sr/86Sr
0.70660
0.70640
0.70620
0.70600
0.70580
0.70560
0.70540
0.00
0.50
1.00
1.50
2.00
1/Sr [1/uM]
c
Figure 20: Comparison of two albite experiments: (a) Si and (b)
87
Sr/86Sr variations
throughout the experiment; (c) 87Sr/86Sr versus the reciprocal of Sr concentration.
Sr release during dissolution of various alluvial sediments:
In general no systematic trend of
87
87
Sr/86Sr ratio with time is observed. On a plot of
Sr/86Sr versus 1/Sr (Figure 21b, page 52) it can be noticed that Amram rhyolite
contributes relatively high concentration of Sr with a narrow range of
87
Sr/86Sr(0.70838-0.70851), whereas the other silicates contribute less Sr but with a
broader
87
Sr/86Srrange (0.70831-0.70860 in Roded quartz-diorite experiment,
0.70819-0.70846 in Yehoshafat granite experiment, i.e. broader range by a factor of
2).
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
49
GSI/01/2015
Chapter 4
Discussion
The narrow range in the Amram rhyolite suggests that the Sr may come from
dissolution of one mineral or, more likely, from dissolution of a homogenous
groundmass, over the whole course of the experiment. The broader range in
Yehoshafat granite and Roded quartz diorite comes probably from dissolution of few
minerals (i.e. plagioclase, alkali feldspar, biotite and others), each having a different
and distinct isotopic ratio and dissolves at a different stage.
The
87
Sr/86Sr in all of the silicates experiments ranged around ~0.708. This value is
lower than what is usually found in granitic rocks (0.718-0.720, Faure G., 1986), and
closer to the current average seawater value (~0.709). It is suggested that the lower
value that was observed in the experiments is related to the weathering and
extinction of the most radiogenic minerals (such as biotite) in the alluvium that was
used in the experiments.
On a plot of
87
Sr/86Sr versus time in both Roded quartz-diorite experiments (Figure
21c, page 52) a similar trend is observed for both seawater and borax solutions.
However, in this case the
87
Sr/86Sr values in the borax solution are higher(more
radiogenic) than that in seawater. This could result from the degree of under
saturation with respect to radiogenic minerals (such as biotite) which is more
profound in the borax solution. Another explanation could be the effect of boron on
the sediment sample (effecting different mineral sites of different isotopic
composition), this potential mechanism, however, requires further investigation.
4.5 The dissolution experiments of various siliciclastic sediments
In two experiments (Yehoshafat granite and Amram rhyolite) the sediment was
subjected only to seawater solution. In both Amram rhyolite experiment (shaking
bath and rolling device) an initial sharp increase in Al concentration after 3days and a
decrease immediately afterwards is observed (Figure 13b, page32). An explanation
may be the fine size particles used in these experiments (0-63µm) and the
precipitation of secondary phases in later stages. The possible difference in the size
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
GSI/01/2015
50
Chapter 4
Discussion
distribution between the samples, may also explain the difference in the Al release
rate between the experiments.
Among the 3 silicates in sea-water experiments; the Roded quartz diorite has the
highest Si concentration towards the end of the experiment, followed by Amram
rhyolite and Yehoshafat granite (115,82 and 45μM, respectively. See Figure 21a, page
52). This may be explained both by the mineralogy and by the size fraction of the
samples. The ratio between plagioclase and K-feldspar in the samples is important
since plagioclase dissolution rate is faster than that of K-feldspar (Langmuir, 1997).
The ratio of plagioclase to K-feldspar is highest in Roded quartz-diorite (~50; Bogoch
et al.2002) and indeed it has the highest Si concentration at steady-state (Figure 21a).
The plagioclase to K-feldspar ratio in Yehoshafat granite is much lower (~0.3; Steinitz
et al.2009) which may explain the lower Si release rate (compared to Roded quartzdiorite). As for Amram Rhyolite, this ratio is probably very low (<~0.5;Mushkin et
al.2002), but not as in the other experiments, Amram rhyolite consists of the most
fine particles (0-53μm, compared to the others, 60-90μm), and therefore probably
dissolves faster than Yehoshafat granite.
There is a similar decrease in the Si concentration in the two independent Amram
rhyolite experiments, after ~54 days. This similar decrease strengthens the
suggestion that this decrease is indeed a real phenomenon (Figure 13a, page 32). This
is probably due to secondary phases precipitation which could not be tested since
other constitutes (Ca2+,K+,Mg2+,Fe2+) could not be measured in seawater due to the
high ionic background. With time, however, (after 172days) Si continues to rise. The
rise in the Si concentration indicates that the Amram rhyolite continues to dissolve.
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
51
GSI/01/2015
Chapter 4
Discussion
Si [µM]
a
140
120
100
80
60
40
20
0
Amram Rhyolite
Roded Q.Diorite
Yehoshafat Granite
0
20
40
60
80
100
time [days]
120
140
160
180
b
0.70870
Amram Rhyolite
Roded Quartz-Diorite
Yehoshafat Granite
87Sr/86Sr
0.70860
0.70850
0.70840
0.70830
0.70820
0.70810
0.0
0.5
1.0
1.5
2.0
2.5
1/Sr [1/µM]
3.0
c
0.70845
87Sr/86Sr
0.7084
0.70835
QDR-SW
QDR-Bx
0.7083
0.70825
0.7082
0.70815
0
20
40
60
80
100
120
140
160
Time [days]
Figure 21: Comparison between the dissolution rates of various siliciclastic sediments in
Seawater (a) Si concentration variations in the unwashed experiments (b) 87Sr/86Sr versus the
reciprocal of Sr concentration in these experiment (c) Comparison of the
87
Sr/86Sr values
between the two Roded quartz diorite experiments.
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
52
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Chapter 4
Discussion
4.6 Mineral dissolution rates
The dissolution rates of the albite and K-feldspar were ~2-3 orders of magnitude
slower than the dissolution rates obtained by Ganor et al. (2005) who examined the
dissolution rates under very acidic(pH=1)conditions (Table 5). At extream pH range,
the dissolution rate of feldspars is very rapid, while in neutral range (pH 6-8) the
dissolution rate reaches a minimum (Drever, 1994). In both experiments albite
dissolved faster than K-feldspar. The dissolution rate in the borax solution was faster
than in the seawater solution, and the dissolution rate enhancement was more
profound in the albite than the K-feldspar (~3 times faster for the albite in borax
solution and ~2times faster for the K-feldspar in borax solution).
Table 5 Comparison of dissolution rates of albite and K-feldspar
Dissolution rates [mol gr-1sec-1]
Seawater (pH=8.2) Borax
solution HNO3
dilute
(pH=8.2)
solution (pH=1) *
albite
1.8±0.1*10-14
5.8±0.5*10-14
6.2±1.2*10-11
K-feldspar
1.1±0.1*10-14
1.8±0.1*10-14
1.6±0.3*10-11
*Ganor et al.(2005)
4.7 Si release rates in the various experiments:
Table 6 summarizes the Si release rates throughout the conducted experiments
which were separated to 3 stages. The initial stage (usually the first 20 days) is
characterized by a high Si release rate which later on decreases, as a result of
distinction of the most-reactive fine particles. It can be noticed the Si release rate in
the borax experiments is higher than those in the seawater experiments. Except
that, one can notice the effect of 'washing' (two-times replacement of solution prior
to the experiment) on the Si release rate. For example, the rate for Roded quartzdiorite seawater experiment without pre-washing treatment ('unwashed') during the
initial 20 days (3.24±0.26µM-Si/day) is ~3 times higher than that for the washed
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
53
GSI/01/2015
Chapter 4
Discussion
sample ('after washing period', 1.13±0.09µM-Si/day). The pre-washing treatment
leads to the dissolution of the finest particles and thus allows a better determination
of the true dissolution rate during the long-term period.
Table 6 :Comparison of Si release rates [µM/day] in the various experiments (the range in
parenthesis is the time-interval in days):
Experiment
Stage 1
Stage 2
Stage 3
albite-seawater
0.369
0.069
0.042
[3-20]
[20-80]
[80-172]
0.444
0.203
0.007
[3-20]
[20-80]
[80-152]
-0.074
0.049
0.028
[3-10]
[10-40]
[40-159]
0.173
0.157
0.048
[3-10]
[10-40]
[40-152]
Amram rhyolite-seawater
0.865
-0.302
0.304
[bath]
[3-40]
[40-80]
[80-172]
Amram rhyolite-seawater
0.423
-1.059
0.345
[rolling device]
[3-40]
[40-80]
[80-174]
Yehoshafat granite- seawater
1.176
0.447
-0.056
[3-20]
[20-80]
[80-140]
0.436
0.128
[20-80]
[80-140]
0.369
0.195
[20-80]
[80-152]
Roded quartz diorite- borax solution 1.400
0.602
0.198
[after washing period]
[3-20]
[20-80]
[80-152]
Eilat granite – seawater
0.310
0.194
0.013
[3-40]
[40-80]
[80-162]
0.674
0.290
0.145
[3-40]
[40-80]
[80-162]
albite-borax solution
K-feldspar-seawater
K-feldspar-borax solution
Roded
quartz
diorite-
seawater 3.239
[unwashed]
Roded
quartz
[3-20]
diorite-
seawater 1.128
[after washing period]
Eilat granite – borax solution
[3-20]
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
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Chapter 5
Summary and Conclusions
5 Summary and Conclusions
1
Albite dissolves incongruently in the seawater experiment. The isotopic composition of
Sr decreases on hyperbolic shape, suggesting a mixture of two components, probably
albite and trace amounts of apatite and biotite.
2
K-feldspar dissolves congruently in Sea-Water (Si:Al ratio 3:1). K-feldspar does not
contribute Sr, and thus has no effect on the 87Sr/86Sr in solution.
3
The dissolution rate in the Borax-HCl solution (compared to dissolution in seawater) is
enhanced, even though the pH is similar.
4
Usually the first dissolution stage, which is characterized by the highest release rate of
cations to the solution, lasts approximately ~20 days. Later on, the dissolution rate is
decreasing. In the initial stage the sediment sample consists of ultra-fine particles which
are very reactive (high surface area to volume ratio) and contribute Si and other cations
readily to the solution.
5
Replacement of solution after one week of experiment enables the dissolution of the
ultra-fine most reactive particles and allows tracking of the dissolution process at the
long-term run without the effect of the fine particles. In both seawater and borax
solution in the first week the dissolution rate was up to 7 times faster than the long-term
experiment.
6
A difference in the isotopic composition of Sr between the two types of solutions
(seawater and borax) was observed. The difference is more pronounced in the albite and
Roded quartz-diorite experiments in which a shift in the
87
Sr/86Sr values is observed,
though the trend is similar. The shift may be explained by a difference in the degree of
saturation with respect to biotite at the beginning of the experiment.
7
Finally, the conducted experiments show that interaction between seawater and
sediments cause dissolution which in turn releases significant amount of Sr with distinct
isotopic composition. Though further work is much needed, the result of the current
study may suggests that seawater–sediment interaction is significant in contributing Sr
to the seawater with distinct isotopic composition and should be taken in consideration
in the Sr ocean budget.
Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
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Chapter 6
References
6 References
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Armstrong, R. L. (1971). Glacial erosion and the variable isotopic composition of strontium in
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Barrante, J. (1974). Applied mathematics for physical chemistry. New Jersey: Pearson
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Be’eri-Shlevin, Y., Katzir, Y., Blichert-Toft, J., Kleinhanns, I., & Whitehouse, M. (2009). Nd–Sr–
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Berger, G., Schott, J., & Guy, C. (1988). Behavior of Li, Rb and Cs during basalt glass and
olivine dissolution and chlorite, smectite and zeolite precipitation from seawater:
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Beyth, M., Eyal, Y., & Garfunkel, Z. (2011). Geological Map of Eilat Region. Jerusalem:
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Blum, A., & Stillings, L. (1995). Feldspar dissolution kinetics. Reviews in Mineralogy, 31.
Blum, J., & Erel, Y. (1995). A silicate weathering mechanism linking increases in marine 87Sr/
86Sr with global glaciation. Nature , 373, 415 - 418.
Bogoch, R., Avigad, D., & Weissbrod, T. (2002). Geochemistry of the quartz diorite––granite
association, Roded area, southern Israel. Journal of African Earth Sciences, 35(1), 5160.
Brantley, S., Chesley, J., & Stillings, L. (1998). Isotopic ratios and release rates of strontium
measured from weathering feldspars. Geochimica et Cosmochimica Acta, 62(9),
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Silicate sediments dissolution during interaction with Seawater / Daniel Winkler
60
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Chapter 7
Appendix
7 Appendix
7.1 Albite Sea-Water Experiment
dSi/dAl
Sample
Mass
Mass
Sediment
solution
[gr]
[gr]
with
Start
Finish
time [days]
Si [µM]
Al [µM]
respect to
pH
Sr [µM]
Sr [mg/L]
87Sr/86Sr
initial
conc.
blank SW
0
1.6
1.447
/
8.13
0.274
0.024
0.3999
40.0064
13/02/2012
3
6.1
6.7
0.9
7.90
1.260
0.110
Alb2-SW
0.3998
40.0054
16/02/2012
6
6.6
5.4
1.2
7.95
1.321
0.116
Alb3-SW
0.4001
39.9934
20/02/2012
10
8.2
5.4
1.7
8.20
1.461
0.128
Alb4-SW
0.4001
40.0002
01/03/2012
20
12.2
6.0
2.3
7.98
1.560
0.137
Alb5-SW
0.4001
40.0042
21/03/2012
40
14.14
7.1
2.2
8.2
1.957
0.171
Alb6-SW
0.4
40.0037
30/04/2012
80
16.4
7.2
2.6
8.2
2.348
0.206
Alb7-SW
0.3999
40.0099
31/7/2012
172
20.3
6.5
3.7
8.0
3.117
0.273
10/02/2012
Alb1-SW
A1
-Appendix-
0.70849
0.70595
0.70581
0.70561
0.70545
0.70519
0.70697
0.70580
Chapter 7
Appendix
7.1.1 Albite-Seawater Experiment: Ion activities estimations and degree of Saturation for specific minerals:
Sample
Time
a[Na+]
aAl+3
a[Al(OH)4-]
a[H4(SiO4)]
a[H2O]
a[H+]
IAP Albite
[days]
IAP
IAP
Gibbsite
Kaolinite
ΩAlbite
ΩGibbsite
ΩKaolinite
Blank SW
0
0.317
3.787E-16
9.046E-07
1.158E-06
0.98
8.51E-09
0.04
5.81E+08
496296.394
6.95E-05
10.58
0.16
Alb1-SW
3
0.317
1.753E-15
4.189E-06
4.414E-06
0.98
8.51E-09
9.81
2.69E+09
154656563
1.78E-02
48.98
51.21
Alb2-SW
6
0.317
1.413E-15
3.376E-06
4.775E-06
0.98
8.51E-09
10.01
2.17E+09
117607164
1.82E-02
39.48
38.94
Alb3-SW
10
0.317
1.413E-15
3.376E-06
5.933E-06
0.98
8.51E-09
19.20
2.17E+09
181539731
3.49E-02
39.48
60.11
Alb4-SW
20
0.317
1.570E-15
3.751E-06
8.827E-06
0.98
8.51E-09
70.25
2.41E+09
496105297
1.28E-01
43.86
164.28
Alb5-SW
40
0.317
1.858E-15
4.439E-06
1.023E-05
0.98
8.51E-09
129.43
2.85E+09
933179033
2.36E-01
51.90
309.00
Alb6-SW
80
0.317
1.884E-15
4.501E-06
1.187E-05
0.98
8.51E-09
204.78
2.89E+09
1290920334
3.73E-01
52.63
427.46
Alb7-SW
172
0.317
1.701E-15
4.063E-06
1.469E-05
0.98
8.51E-09
350.61
2.61E+09
1611984328
6.38E-01
47.52
533.78
A2
-Appendix-
Chapter 7
Appendix
7.2 Albite Borax-Solution Experiment
7.2.1 Two-weeks washing period
Sample
Sediment [gr]
Solution [gr] Start
Finish
Time [days] Si [µM]
Al [µM]
Alb-Bx-1
0.4000
40.0077
1/12/2012 10:00
1/12/2012 18:00
0.3
1.19
2.06
26.9499
1/12/2012 18:00
9/12/2012 15:00
7.9
11.74
11.01
40.0251
9/12/2012 15:00
9/12/2012 21:00
0.3
0.64
1.39
26.2529
9/12/2012 21:00
16/12/2012 15:00 6.8
8.47
6.75
40.0077
1/12/2012 10:00
2/12/2012 14:00
1.2
1.54
2.55
25.9272
2/12/2012 14:00
9/12/2012 15:00
7.0
7.18
9.97
40.0142
9/12/2012 15:00
10/12/2012 15:00 1.0
1.63
2.23
26.0146
10/12/2012 15:00 16/12/2012 15:00 6.0
8.47
7.86
40.0078
1/12/2012 10:00
3/12/2012 13:00
2.1
2.10
2.84
25.8062
3/12/2012 13:00
9/12/2012 15:00
6.1
10.49
9.77
40.0116
9/12/2012 15:00
11/12/2012 17:00 2.1
1.88
2.26
25.8137
11/12/2012 17:00 16/12/2012 15:00 4.9
9.72
12.85
40.0019
1/12/2012 10:00
5/12/2012 16:00
4.3
3.96
5.15
26.1592
5/12/2012 16:00
9/12/2012 15:00
4.0
8.43
9.21
Alb-Bx-2
Alb-Bx-3
Alb-Bx-4
0.4000
0.3999
0.4000
A3
-Appendix-
Chapter 7
Alb-Bx-5
Alb-Bx-6
Alb-Bx-7
Alb-Bx-8
Appendix
0.3999
0.3999
0.4000
0.3999
40.0064
9/12/2012 15:00
13/12/2012 15:00 4.0
3.76
3.78
25.8052
13/12/2012 15:00 16/12/2012 15:00 3.0
7.51
10.25
40.0090
1/12/2012 10:00
1/12/2012 18:00
0.3
0.34
2.35
25.3774
1/12/2012 18:00
9/12/2012 15:00
7.9
8.79
13.67
40.0233
9/12/2012 15:00
9/12/2012 21:00
0.3
0.89
1.71
25.6343
9/12/2012 21:00
16/12/2012 15:00 6.8
8.42
6.98
40.0097
1/12/2012 10:00
2/12/2012 14:00
1.2
1.74
3.57
26.3235
2/12/2012 14:00
9/12/2012 15:00
7.0
9.46
14.37
40.0087
9/12/2012 15:00
10/12/2012 15:00 1.0
1.24
2.06
25.5357
10/12/2012 15:00 16/12/2012 15:00 6.0
8.72
6.81
40.0084
1/12/2012 10:00
3/12/2012 13:00
2.1
2.20
3.37
25.1917
3/12/2012 13:00
9/12/2012 15:00
6.1
7.55
10.51
40.0168
9/12/2012 15:00
11/12/2012 17:00 2.1
1.53
2.20
25.1615
11/12/2012 17:00 16/12/2012 15:00 4.9
7.96
6.14
40.0011
1/12/2012 10:00
5/12/2012 16:00
4.3
4.46
5.00
25.5210
5/12/2012 16:00
9/12/2012 15:00
4.0
7.81
10.03
40.0252
9/12/2012 15:00
13/12/2012 15:00 4.0
3.07
2.78
25.6673
13/12/2012 15:00 16/12/2012 15:00 3.0
8.52
5.82
A4
-Appendix-
Chapter 7
Appendix
7.2.2 Long-term (after-washing period) experiment
Sample
Mass
Mass
Sediment
Solution
[gr]
[gr]
Start
Finish
Blank Borax
Si
Al
Ca
Mg
Sr
K
Fe
[µM]
[µM]
[mg/L]
[mg/L]
[mg/L]
[mg/L]
[mg/L]
0
0.83
1.62
<2
≤1
< 0.01
4.00
< 0.1
8.24
0.70873
Time [days]
pH
87Sr/86Sr
1/Sr
[1/ppm]
0.4000
40.0117
19/12/2012 12:00
3
2.70
7.31
5.00
<1
0.057
2.89
< 0.1
8.24
0.70628
17.34
Alb-Bx-2
0.4000
40.0021
23/12/2012 13:00
7
5.37
7.56
8.00
<1
0.090
3.17
< 0.1
8.24
0.70573
11.15
Alb-Bx-3
0.3999
40.0161
26/12/2012 19:30
10
6.52
8.29
8.00
<1
0.102
2.76
< 0.1
8.2
0.70606
9.79
Alb-Bx-4
0.4000
39.9994
6/1/2013 11:00
21
10.95
11.36
13.00
<1
0.153
2.80
< 0.1
8.27
0.70575
6.55
Alb-Bx-5
0.3999
40.0195
25/1/2013 17:00
40
17.92
14.67
19.00
<1
0.227
2.99
< 0.1
8.3
0.70571
4.40
Alb-Bx-6
0.3999
40.0138
10/3/2013 12:30
84
24.47
18.56
19.29
<1
0.256
1.84
< 0.1
8.27
0.70548
3.90
Alb-Bx-7
0.4000
40.0030
17/5/2013 15:00
152
24.95
26.65
20.00
<1
0.240
1.80
< 0.1
8.26
0.70554
4.16
16/12/2012 15:00
Alb-Bx-1
A5
-Appendix-
Chapter 7
Appendix
7.3 K-Feldspar Sea-Water Experiment
7.3.1 Pre-washing period [41days]
Sample
Sediment [gr]
Solution [gr] Start
Finish
Blank SW
KSP-SW-1
KSP-SW-2
KSP-SW-3
KSP-SW-4
KSP-SW-5
KSP-SW-6
KSP-SW-7
0.3999
0.3999
0.3999
0.4
0.3999
0.4001
0.4
Al [µM]
0
0.79
1.64
40.0074
29/10/2012 12:00
1/11/2012 19:00
3
1.67
1.76
25.3523
1/11/2012 19:00
9/12/2012 15:00
38
13.69
5.64
40.0088
29/10/2012 12:00
4/11/2012 15:00
6
2.42
2.07
25.603
4/11/2012 15:00
9/12/2012 15:00
35
12.11
5.64
40.0044
29/10/2012 12:00
7/11/2012 12:00
9
3.70
2.55
24.8932
7/11/2012 12:00
9/12/2012 15:00
32
11.65
5.32
40.009
29/10/2012 12:00
11/11/2012 10:30 13
4.69
2.96
24.4641
11/11/2012 10:30
9/12/2012 15:00
11.60
6.34
40.0043
29/10/2012 12:00
13/11/2012 11:15 15
5.33
2.83
24.8305
13/11/2012 11:15
9/12/2012 15:00
10.62
10.80
40.0066
29/10/2012 12:00
25/11/2012 10:30 27
7.39
4.48
24.6184
25/11/2012 10:30
9/12/2012 15:00
10.78
6.66
40.0056
29/10/2012 12:00
28/11/2012 17:10 30
8.17
4.18
A6
-Appendix-
time [days] Si [µM]
28
26
14
Chapter 7
KSP-SW-8
KSP-SW-9
Appendix
0.4
0.4
KSP-SW-10 0.4001
25.4508
28/11/2012 17:10
9/12/2012 15:00
11
9.39
5.20
40.001
29/10/2012 12:00
1/12/2012 8:00
33
7.71
4.45
25.4259
1/12/2012 8:00
9/12/2012 15:00
8
10.42
4.94
40.0017
29/10/2012 12:00
3/12/2012 9:00
35
8.11
4.91
25.6872
3/12/2012 9:00
9/12/2012 15:00
6
9.50
7.19
39.9983
29/10/2012 12:00
5/12/2012 20:00
37
8.58
4.50
25.5619
5/12/2012 20:00
9/12/2012 15:00
4
10.01
5.03
7.3.2 Long-term experiment
Sample Sediment Solution Start Finish
time [days] Si [µM] Al [µM] Ca [mg/L] Mg [mg/L] Sr [mg/L]† K [mg/L] Fe [mg/L] pH
Blank SW
0
KSP-
0.3999
40.0207
12/12/2012 3
SW-1
0.3999
40.0034
SW-2
KSP-
1.64
267
1370
0.052
464
< 0.1
8.18
4.46
2.38
315.23
1449.26
0.018
492.83
< 0.1
8.15
4.36
2.38
317.52
1453.45
0.019
497.75
< 0.1
8.16
3.86
4.51
315.33
1457.59
0.021
499.08
< 0.1
8.20
10:00
0.3999
SW-3
40.0045
9/12/2012 15:00
KSP-
0.785
16/12/2012 7
8:00
20/12/2012 11
17:00
A7
-Appendix-
Chapter 7
KSP-
0.4
Appendix
39.9996
3/1/2013
SW-4
KSP-
0.3999
40.0106
20/1/2013
4.62
310.21
1448.97
0.018
498.06
< 0.1
8.18
42
5.40
5.47
309.31
1468.35
0.017
503.56
< 0.1
8.06
80
6.92
4.67
269.06
1271.57
0.020
409.29
< 0.1
8.09
159
8.76
5.09
281.4
1449
0.032
415.3
< 0.1
7.91
12:00
0.4001
40.0194
27/2/2013
SW-6
KSP-
5.42
20:00
SW-5
KSP-
25
10:00
0.4
40.0028
17/5/2013
SW-7
15:00
†87Sr/86Sr was not measured because no change in Sr concentration was observed
7.3.3
Long-term K-feldspar dissolution experiment in seawater: ion activity products and degree of saturation for selected minerals:
time [days]
a[H2O]
a[K+]
a[Al+3]
a[Al(OH)4-]
a[H+]
a[Na+]
a[H4(SiO4)]
IAP Albite
Omega Albite
IAP K-feldspar
Omega K-feldspar
IAP Gibbsite
Omega Gibbsite
IAP Kaolinite
Omega Kaolinite
0
0.98
7.78E-03
2.06E-16
1.03E-06
7.08E-09
3.17E-01
5.37E-07
4.34E-03
7.89E-06
1.43E-27
5.37E-07
5.49E+08
1.00E+01
9.54E+04
3.16E-02
3
0.98
8.25E-03
2.99E-16
1.49E-06
7.08E-09
3.17E-01
3.05E-06
1.15E+00
2.10E-03
4.05E-25
1.52E-04
7.96E+08
1.45E+01
6.48E+06
2.15E+00
7
0.98
8.33E-03
2.99E-16
1.49E-06
7.08E-09
3.17E-01
2.98E-06
1.08E+00
1.96E-03
3.82E-25
1.43E-04
7.96E+08
1.45E+01
6.19E+06
2.05E+00
11
0.98
8.35E-03
5.66E-16
2.82E-06
7.08E-09
3.17E-01
2.64E-06
1.42E+00
2.58E-03
5.04E-25
1.89E-04
1.51E+09
2.75E+01
1.74E+07
5.77E+00
25
0.98
8.34E-03
5.80E-16
2.89E-06
7.08E-09
3.17E-01
3.71E-06
4.02E+00
7.32E-03
1.43E-24
5.34E-04
1.55E+09
2.81E+01
3.61E+07
1.19E+01
42
0.98
8.43E-03
5.74E-16
2.86E-06
7.08E-09
3.17E-01
3.69E-06
3.93E+00
7.16E-03
1.41E-24
5.28E-04
1.53E+09
2.78E+01
3.50E+07
1.16E+01
80
0.98
6.87E-03
5.87E-16
2.93E-06
7.08E-09
3.18E-01
4.73E-06
8.46E+00
1.54E-02
2.47E-24
9.24E-04
1.57E+09
2.85E+01
6.02E+07
1.99E+01
159
0.98
6.96E-03
6.39E-16
3.19E-06
7.08E-09
3.17E-01
5.99E-06
1.87E+01
3.40E-02
5.53E-24
2.07E-03
1.70E+09
3.10E+01
1.14E+08
3.79E+01
A8
-Appendix-
Chapter 7
Appendix
7.4 K-Feldspar Borax Experiment
7.4.1 Two weeks washing period
Sample
Sediment [gr] Solution [gr] Start
KSP-Bx-1 0.4001
KSP-Bx-2 0.4
KSP-Bx-3 0.4001
KSP-Bx-4 0.4
time [days]
Si [µM]
Al [µM]
40.0087
1/12/2012 8:30
1/12/2012 18:00
0.4
0.64
2.67
26.1318
1/12/2012 18:00
9/12/2012 15:00
7.9
6.25
5.29
40.0097
9/12/2012 15:00
9/12/2012 21:00
0.3
0.40
2.38
25.9571
9/12/2012 21:00
16/12/2012 15:00 6.8
3.51
3.83
40.0035
1/12/2012 8:30
2/12/2012 14:00
1.2
0.49
2.41
25.998
2/12/2012 14:00
9/12/2012 15:00
7.0
9.05
4.71
40.0212
9/12/2012 15:00
10/12/2012 15:00 1.0
0.79
2.41
26.1546
10/12/2012 15:00 16/12/2012 15:00 6.0
3.46
3.60
40.0062
1/12/2012 8:30
3/12/2012 13:00
2.2
1.04
2.73
25.9846
3/12/2012 13:00
9/12/2012 15:00
6.1
6.41
5.12
40.0047
9/12/2012 15:00
11/12/2012 17:00 2.1
1.53
2.64
25.8463
11/12/2012 17:00 16/12/2012 15:00 4.9
4.36
3.83
40.0017
1/12/2012 8:30
5/12/2012 12:00
4.1
2.00
2.87
24.8278
5/12/2012 12:00
9/12/2012 15:00
4.1
5.58
4.53
A9
-Appendix-
Finish
Chapter 7
KSP-Bx-5 0.3999
KSP-Bx-6 0.3999
KSP-Bx-7 0.4001
KSP-Bx-8 0.4
Appendix
39.9998
9/12/2012 15:00
13/12/2012 15:00 4.0
1.68
2.81
25.8634
13/12/2012 15:00 16/12/2012 15:00 3.0
3.01
3.40
40.0044
1/12/2012 8:30
1/12/2012 18:00
0.4
0.03
2.61
26.3805
1/12/2012 18:00
9/12/2012 15:00
7.9
7.03
5.17
40.0224
9/12/2012 15:00
9/12/2012 21:00
0.3
0.54
2.38
25.4515
9/12/2012 21:00
16/12/2012 15:00 6.8
3.76
2.00
40.0033
1/12/2012 8:30
2/12/2012 14:00
1.2
0.79
2.41
25.3253
2/12/2012 14:00
9/12/2012 15:00
7.0
5.01
4.53
40.0173
9/12/2012 15:00
10/12/2012 15:00 1.0
0.94
2.46
25.637
10/12/2012 15:00 16/12/2012 15:00 6.0
3.16
2.46
40.0095
1/12/2012 8:30
3/12/2012 13:00
2.2
1.24
2.52
25.4949
3/12/2012 13:00
9/12/2012 15:00
6.1
4.50
4.45
40.0085
9/12/2012 15:00
11/12/2012 17:00 2.1
1.04
2.67
25.3012
11/12/2012 17:00 16/12/2012 15:00 4.9
3.36
2.44
40.0092
1/12/2012 8:30
5/12/2012 12:00
4.1
1.69
2.90
25.4676
5/12/2012 12:00
9/12/2012 15:00
4.1
4.29
4.01
40.0224
9/12/2012 15:00
13/12/2012 15:00 4.0
1.58
2.61
25.7606
13/12/2012 15:00 16/12/2012 15:00 3.0
2.86
2.55
A10
-Appendix-
Chapter 7
Appendix
7.4.2 K-feldspar in Borax solution: long-term experiment
Sample Sediment Solution Start
Finish
Blank Bx
Bx-1
KSPBx-2
KSPBx-3
KSPBx-4
KSPBx-5
KSPBx-6
KSPBx-7
0.4
40.0198
0.4001
40.0074
0.4
40.0043
0.3999
40.0093
0.3999
40.007
0.4001
40.0032
0.4
40.0065
19/12/2012
12:00
23/12/2012
13:00
26/12/2012
16/12/2012 15:00
KSP-
19:00
6/1/2013
11:00
25/1/2013
17:00
10/3/2013
12:30
17/5/2013
15:00
time [days] Si [µM] Al [µM] Ca [mg/L] Mg [mg/L] Sr [mg/L] K [mg/L] Fe [mg/L]
0
0.83
1.61
3
1.29
3.97
7
2.00
4.32
10
2.55
4.68
21
4.61
5.44
40
7.33
4.65
84
10.50
5.45
152
12.81
6.84
A11
-Appendix-
<2
≤1
<2
≤1
<2
≤1
<2
≤1
<2
≤1
<2
≤1
<2
≤1
<2
≤1
< 0.01
4.00
< 0.01
5.53
< 0.01
4.26
< 0.01
4.02
< 0.01
3.43
< 0.01
3.38
< 0.01
2.93
< 0.01
2.12
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
pH
8.24
8.22
8.23
8.22
8.23
8.23
8.21
8.16
Chapter 7
7.4.3
Time
Appendix
K-feldspar dissolution experiment in Borax solution: ion activities estimations and degree of saturation
a(K+)
a(Al3+)
[days]
a
a
a
Al(OH)4
Na+
H2O
aH4SiO4
aH+
IAP
Omega
K-feld
Kfeld
IAP Gibbsite
Omega
IAP
Omega
IAP
Omega
Gibbsite
Kaolinite
Kaolinite
Albite
Albite
0
9.07E-05
1.05E-16
1.41E-06
0.01
1.00
7.92E-07
5.62E-09
6.37E-29
6.37E-08
5.88E+08
1.07E+01
2.17E+05
7.19E-02
6.81E-04
1.24E-06
3
1.25E-04
2.57E-16
3.46E-06
0.01
1.00
1.23E-06
5.62E-09
8.05E-28
8.05E-07
1.44E+09
2.63E+01
3.14E+06
1.04E+00
6.23E-03
1.13E-05
7
9.65E-05
2.80E-16
3.77E-06
0.01
1.00
1.90E-06
5.62E-09
2.52E-27
2.52E-06
1.57E+09
2.86E+01
8.97E+06
2.97E+00
2.53E-02
4.60E-05
10
9.11E-05
3.03E-16
4.08E-06
0.01
1.00
2.43E-06
5.62E-09
5.33E-27
5.33E-06
1.70E+09
3.10E+01
1.71E+07
5.67E+00
5.68E-02
1.03E-04
21
7.77E-05
3.52E-16
4.74E-06
0.01
1.00
4.39E-06
5.62E-09
3.12E-26
3.12E-05
1.98E+09
3.60E+01
7.55E+07
2.50E+01
3.90E-01
7.09E-04
40
7.66E-05
3.01E-16
4.06E-06
0.01
1.00
6.97E-06
5.62E-09
1.06E-25
1.06E-04
1.69E+09
3.08E+01
1.40E+08
4.62E+01
1.34E+00
2.44E-03
84
6.64E-05
3.53E-16
4.75E-06
0.01
1.00
9.99E-06
5.62E-09
3.16E-25
3.16E-04
1.98E+09
3.61E+01
3.93E+08
1.30E+02
4.62E+00
8.40E-03
152
4.81E-05
4.44E-16
5.97E-06
0.01
1.00
1.22E-05
5.62E-09
5.21E-25
5.21E-04
2.49E+09
4.53E+01
9.24E+08
3.06E+02
1.05E+01
1.92E-02
A12
-Appendix-
Chapter 7
Appendix
7.5 Amram rhyolite dissolution experiments in Seawater
Sample
Sediment
Solution
[gr]
[gr]
Start
Finish
Rolling device
Thermostatic bath
blank SW
time [days] Si [µM]
Al [µM]
pH
Sr [µM]
Sr [ppm]
87Sr/86Sr
0
1.6
1.45
8.13
0.274
0.024
0.70849
YJ6A
0.4003
40.0039
10/02/2012
13/02/2012
3
36.5
2.6
8.1
2.907
0.255
0.708460
YJ6B
0.4
40.0028
10/02/2012
16/02/2012
6
36.9
2.2
8.2
2.915
0.255
0.708378
YJ6C
0.3999
39.998
10/02/2012
20/02/2012
10
41.2
1.8
8.2
2.976
0.261
0.708443
YJ6D
0.3999
40.0056
10/02/2012
01/03/2012
20
55.6
2.0
8.0
3.013
0.264
0.708514
YJ6E
0.3999
40.0032
10/02/2012
21/03/2012
40
66.6
1.9
8.0
3.059
0.268
0.708403
YJ6F
0.3999
40.0043
10/02/2012
30/04/2012
80
54.5
1.8
8.2
3.054
0.268
0.708421
YJ6G
0.3999
40.0016
10/02/2012
31/07/2012
172
82.4
1.7
7.9
3.130
0.274
0.708438
Rhy1
0.4
40.0051
21/02/2012
23/02/2012
2
38.3
2.2
8.2
2.886
0.253
0.708389
Rhy2
0.4001
40.0043
21/02/2012
27/02/2012
6
52.4
2.6
8.0
2.963
0.260
0.708451
Rhy3
0.4
39.9937
21/02/2012
01/03/2012
9
52.1
1.69
8.2
2.924
0.256
0.708436
Rhy4
0.4
40.0073
21/02/2012
18/03/2012
26
58.8
2.2
8.1
2.960
0.259
0.708426
Rhy5
0.4
39.9987
21/02/2012
15/04/2012
54
66.4
2.26
8.2
3.015
0.264
0.708431
Rhy6
0.4
39.9936
21/02/2012
29/04/2012
68
51.6
2.02
8.0
3.043
0.267
0.708384
Rhy7
0.3999
40.0071
21/02/2012
13/08/2012
174
88.1
1.81
8.2
3.196
0.280
0.708404
A13
-Appendix-
Chapter 7
Appendix
7.6 Yehoshafat granite dissolution experiment in Seawater
Sample
sediment
solution
[gr]
[gr]
Start
Finish
blank SW
time
Si
Al
Si/Al
[days]
[µM]
[µM]
0
1.6
1.447
1.1
pH
Sr
Sr
87Sr/86Sr
[µM]
[ppm]
8.13
0.274
0.024
0.708491
Yt1
0.4002
40.0029
09/04/2012
12/04/2012
3
0.6
7.55
0.1
7.98
0.437
0.038
0.708193
Yt2
0.4001
40.0029
09/04/2012
15/04/2012
6
16.8
2.30
7.3
8.19
0.399
0.035
0.708401
Yt3
0.4001
40.0065
09/04/2012
18/04/2012
9
12.6
3.48
3.6
8.06
0.510
0.045
0.708371
Yt4
0.4001
39.9976
09/04/2012
29/04/2012
20
21.5
2.73
7.9
7.97
0.555
0.049
0.708255
Yt5
0.3999
39.9946
09/04/2012
19/05/2012
40
35.4
2.49
14.2
8.06
0.469
0.041
0.708310
Yt6
0.4
40.0056
09/04/2012
28/06/2012
80
49.3
2.17
22.7
8.16
0.471
0.041
0.708464
Yt7
0.4
40.0001
09/04/2012
27/08/2012
140
45.9
2.50
18.3
8.22
0.628
0.055
0.708283
A14
-Appendix-
Chapter 7
Appendix
8.7 Roded quartz-diorite dissolution experiments
8.7.1 Roded quartz-diorite dissolution experiment in Seawater (without pre-wash treatment)
Sample
Sediment
Solution
[gr]
[gr]
Start
Finish
time
Si [µM]
[days]
blank SW
Al
pH
[µM]
Sr
Sr
[µM]
[mg/L]
87Sr/86Sr
0
1.6
1.45
8.13
0.274
0.024
0.70849
Rd1
0.4002
40.0029
09/04/2012
12/04/2012
3
24.3
1.89
8.05
0.642
0.056
0.708486
Rd2
0.4001
40.0029
09/04/2012
15/04/2012
6
41.2
1.86
8.07
0.630
0.055
0.708308
Rd3
0.4001
40.0065
09/04/2012
18/04/2012
9
48.0
2.08
8.02
0.608
0.053
0.708523
Rd4
0.4001
39.9976
09/04/2012
29/04/2012
20
81.9
1.75
8.20
0.678
0.059
0.708308
Rd5
0.3999
39.9946
09/04/2012
19/05/2012
40
94.9
2.01
8.05
0.813
0.071
0.708316
Rd6
0.4
40.0056
09/04/2012
28/06/2012
80
109.0
1.62
8.07
0.840
0.074
0.708603
Rd7
0.4
40.0001
09/04/2012
27/08/2012
140
116.7
1.55
8.01
0.799
0.070
0.708385
A15
-Appendix-
Chapter 7
Appendix
8.7.2 Roded Quartz-diorite dissolution experiment in Seawater after washing period
Sediment [gr]
Solution [gr]
Start
Finish
Time [days]
Blank SW
Si
Al
Ca
Mg
Sr
K
Fe
pH
87Sr/86Sr
[µM]
[µM]
[mg/L]
[mg/L]
[mg/L]
[mg/L]
[mg/L]
0
0.485
2.4631
355
1410
0.045
463
< 0.1
7.64
0.708300
40.0059
19/12/2012 12:00
3
10.45
3.40
327.86
1390.2
0.0428
455.9
< 0.1
8.16
0.70830
QDR-SW-2
0.4001
40.0168
23/12/2012 13:00
7
16.08
3.35
358.83
1408.2
0.0477
462.84
< 0.1
8.1
0.70822
QDR-SW-3
0.4
39.9996
26/12/2012 19:00
10
17.29
3.46
344.67
1405.7
0.047
464.23
< 0.1
8.07
0.70821
QDR-SW-4
0.4
40.0032
6/1/2013 11:00
21
31.03
3.10
356.99
1394.4
0.0499
460.68
< 0.1
8.17
0.70792
QDR-SW-5
0.4
39.9997
25/1/2013 17:00
40
46.35
1.30
355
1400
0.052
456
< 0.1
8.06
0.70823
QDR-SW-6
0.3999
39.9996
10/3/2013 12:30
84
56.16
1.65
320.18
1312.7
0.0472
407.58
< 0.1
7.97
0.70820
QDR-SW-7
0.3999
40.0004
17/5/2013 15:00
152
69.41
1.62
313.3
1337
0.057
366.1
< 0.1
8.16
0.70825
15:00
0.4
16/12/2012
QDR-SW-1
8.7.3 Roded quartz-diorite dissolution experiment in seawater: washing period
Sample
Sediment [gr]
Solution
Start
Finish
t [days]
Si [µM]
Al [µM]
0.00
0.485
2.46
[gr]
Blank Seawater
QDR-SW-1
QDR-SW-2
0.4
0.4001
40.0059
1/12/2012 8:30
1/12/2012 18:00
0.4
13.57
2.82
25.907
1/12/2012 18:00
9/12/2012 15:00
7.9
71.55
1.75
40.0051
9/12/2012 15:00
9/12/2012 21:00
0.3
3.92
1.44
25.7295
9/12/2012 21:00
16/12/2012 15:00
6.8
38.62
1.552
40.0168
1/12/2012 8:30
2/12/2012 14:00
1.2
16.20
1.58
A16
-Appendix-
Chapter 7
QDR-SW-3
QDR-SW-4
QDR-SW-5
QDR-SW-6
QDR-SW-7
Appendix
0.4
0.4
0.4
0.3999
0.3999
26.405
2/12/2012 14:00
9/12/2012 15:00
7.0
80.83
1.69
39.999
9/12/2012 15:00
10/12/2012 15:00
1.0
7.40
2.43
25.5658
10/12/2012 15:00
16/12/2012 15:00
6.0
43.691
1.468
39.9996
1/12/2012 8:30
3/12/2012 13:00
2.2
23.50
1.41
26.6387
3/12/2012 13:00
9/12/2012 15:00
6.1
62.75
1.81
40.0294
9/12/2012 15:00
11/12/2012 17:00
2.1
11.49
2.57
25.513
11/12/2012 17:00
16/12/2012 15:00
4.9
33.811
1.637
40.0032
1/12/2012 8:30
5/12/2012 12:00
4.1
32.03
1.95
25.6958
5/12/2012 12:00
9/12/2012 15:00
4.1
57.97
2.82
40.0065
9/12/2012 15:00
13/12/2012 15:00
4.0
11.49
2.57
25.2435
13/12/2012 15:00
16/12/2012 15:00
3.0
31.201
2.823
39.9997
1/12/2012 8:30
1/12/2012 18:00
0.4
11.47
1.92
25.2135
1/12/2012 18:00
9/12/2012 15:00
7.9
72.02
1.52
40.0089
9/12/2012 15:00
9/12/2012 21:00
0.3
31.20
2.51
25.1912
9/12/2012 21:00
16/12/2012 15:00
6.8
38.879
1.468
39.9996
1/12/2012 8:30
2/12/2012 14:00
1.2
17.09
1.50
24.8233
2/12/2012 14:00
9/12/2012 15:00
7.0
73.43
1.75
40.0233
9/12/2012 15:00
10/12/2012 15:00
1.0
4.12
1.58
25.0168
10/12/2012 15:00
16/12/2012 15:00
6.0
39.647
3.727
40.0004
1/12/2012 8:30
3/12/2012 13:00
2.2
23.32
2.57
25.1865
3/12/2012 13:00
9/12/2012 15:00
6.1
77.83
3.11
A17
-Appendix-
Chapter 7
QDR-SW-8
Appendix
0.4001
40.0176
9/12/2012 15:00
16/12/2012 15:00
7.0
7.60
1.47
25.0078
11/12/2012
16/12/2012 15:00
4.9
42.053
3.699
40.0007
1/12/2012 8:30
5/12/2012 12:00
4.1
38.17
1.44
25.402
5/12/2012 12:00
9/12/2012 15:00
4.1
59.00
1.50
40.0221
9/12/2012 15:00
11/12/2012 17:00
2.1
11.13
1.55
25.5247
13/12/2012
16/12/2012 15:00
3.0
31.764
1.665
8.7.4 oded quartz-diorite dissolution experiment in Borax solution: washing period
Sample
Sediment [gr]
Solution
Start
Finish
t [days]
Si [µM]
Al [µM]
0.00
0.832
1.618
[gr]
Blank Borax
QDR-Bx-1
QDR-Bx-2
0.3999
0.3999
40.0065
1/12/2012 8:30
1/12/2012 18:00
0.4
11.70
2.12
26.1315
1/12/2012 18:00
9/12/2012 15:00
7.9
43.64
2.09
40.0212
9/12/2012 15:00
9/12/2012 21:00
0.3
5.71
2.82
25.9147
9/12/2012 21:00
16/12/2012 15:00
6.8
47.91
1.89
40.0084
1/12/2012 8:30
2/12/2012 14:00
1.2
25.72
2.34
25.9956
2/12/2012 14:00
9/12/2012 15:00
7.0
42.05
2.96
40.0106
9/12/2012 15:00
10/12/2012 15:00
1.0
12.62
2.77
25.9208
9/12/2012 21:00
16/12/2012 15:00
6.8
43.40
1.95
A18
-Appendix-
Chapter 7
QDR-Bx-3
QDR-Bx-4
QDR-Bx-5
QDR-Bx-6
QDR-Bx-7
Appendix
0.4001
0.4
0.3999
0.4
0.3999
40.0044
1/12/2012 8:30
3/12/2012 13:00
2.2
31.10
1.98
26.0777
3/12/2012 13:00
9/12/2012 15:00
6.1
40.06
2.43
40.0046
9/12/2012 15:00
11/12/2012 17:00
2.1
14.00
4.38
25.992
9/12/2012 21:00
16/12/2012 15:00
6.8
37.993
1.976
40.0051
1/12/2012 8:30
5/12/2012 12:00
4.1
45.33
1.95
25.9188
5/12/2012 12:00
9/12/2012 15:00
4.1
38.16
3.19
40.0095
9/12/2012 15:00
13/12/2012 15:00
4.0
43.82
2.99
25.9403
9/12/2012 21:00
16/12/2012 15:00
6.8
43.82
2.31
40.006
1/12/2012 8:30
1/12/2012 18:00
0.4
12.93
2.09
25.4914
1/12/2012 18:00
9/12/2012 15:00
7.9
44.05
2.09
40.0136
9/12/2012 15:00
9/12/2012 21:00
0.3
8.99
3.13
25.1304
9/12/2012 21:00
16/12/2012 15:00
6.8
46.35
2.54
39.9997
1/12/2012 8:30
2/12/2012 14:00
1.2
25.06
2.06
25.6532
2/12/2012 14:00
9/12/2012 15:00
7.0
41.64
3.25
40.0173
9/12/2012 15:00
10/12/2012 15:00
1.0
10.37
2.80
25.3026
9/12/2012 21:00
16/12/2012 15:00
6.8
45.54
2.29
40.001
1/12/2012 8:30
3/12/2012 13:00
2.2
31.92
2.29
25.3108
3/12/2012 13:00
9/12/2012 15:00
6.1
39.70
2.23
40.0136
9/12/2012 15:00
11/12/2012 17:00
2.1
14.77
2.85
A19
-Appendix-
Chapter 7
QDR-Bx-8
Appendix
0.4
25.5196
9/12/2012 21:00
16/12/2012 15:00
6.8
37.63
1.92
40.0013
1/12/2012 8:30
5/12/2012 12:00
4.1
44.05
2.26
25.0203
5/12/2012 12:00
9/12/2012 15:00
4.1
37.45
3.08
40.0202
9/12/2012 15:00
13/12/2012 15:00
4.0
39.74
2.15
26.0698
9/12/2012 21:00
16/12/2012 15:00
6.8
39.74
2.06
8.7.5 Roded quartz-diorite dissolution experiment in Borax solution: long-term experiment
Sediment [gr]
Solution [gr]
Start
Finish
Time [days]
Si [µM]
Al [µM]
Ca
Mg
Sr
K
Fe
[mg/L]
[mg/L]
[mg/L]
[mg/L]
[mg/L]
pH
87Sr/86Sr
0.00
0.83
1.62
44
≤1
< 0.01
5
< 0.1
8.26
0.7083
Blank Borax
QDR-Bx-1
0.3999
40.0058
16/12/2012 15:00
19/12/2012 12:00
3
11.05
5.11
43
3
0.016
5
< 0.1
8.28
0.7083336
QDR-Bx-2
0.3999
40.017
16/12/2012 15:00
23/12/2012 13:00
7
20.01
4.89
44
0.1
0.02
3
< 0.1
8.28
0.7083688
QDR-Bx-3
0.4001
40.0091
16/12/2012 15:00
26/12/2012 19:00
10
25.80
4.95
42
0.1
0.016
3
< 0.1
8.27
0.7083328
QDR-Bx-4
0.4
40.0155
16/12/2012 15:00
6/1/2013 11:00
21
37.22
4.81
42
0.1
0.016
3
< 0.1
8.28
0.7082894
QDR-Bx-5
0.3999
40.0118
16/12/2012 15:00
25/1/2013 17:00
40
40.45
3.28
42
0.1
0.018
3
< 0.1
8.28
0.7083427
QDR-Bx-6
0.4
40.0155
16/12/2012 15:00
10/3/2013 12:30
84
73.23
2.93
42.95
0.1
0.02
2.88
< 0.1
8.25
0.7084226
QDR-Bx-7
0.3999
40.0157
16/12/2012 15:00
17/5/2013 15:00
152
86.72
3.06
41.8
0.1
0.025
<10
< 0.1
8.25
0.7083884
A20
-Appendix-
Chapter 7
Appendix
8.8 Eilat granite dissolution experiments
8.8.1 Eilat granite dissolution experiment in Seawater: two times washing period
Sample
Sediment [gr]
Start
Finish
Blank SW
GE-SW-1
GE-SW-2
GE-SW-3
GE-SW-4
0.3999
0.4
0.4
0.4
Si [µM]
Al [µM]
0.0
0.79
1.64
40.001
29/10/2012 10:00
29/10/2012 16:30
0.3
8.50
2.17
24.6153
29/10/2012 16:30
6/11/2012 10:00
7.7
35.21
2.14
40.0341
6/11/2012 10:00
6/11/2012 18:00
0.3
3.25
2.94
26.6588
6/11/2012 18:00
14/11/2012 8:30
7.6
22.38
2.30
40.0191
29/10/2012 10:00
30/10/2012 10:00
1.0
10.81
2.04
26.2635
30/10/2012 10:00
6/11/2012 10:00
7.0
33.71
2.35
40.0114
6/11/2012 10:00
7/11/2012 12:00
1.1
4.31
2.88
24.8304
7/11/2012 12:00
14/11/2012 8:30
6.9
24.50
2.52
40.0005
29/10/2012 10:00
31/10/2012 13:20
2.1
13.97
2.07
25.1687
31/10/2012 13:20
6/11/2012 10:00
5.9
31.35
2.19
39.9922
6/11/2012 10:00
8/11/2012 15:20
2.2
6.04
2.53
25.4413
8/11/2012 15:20
14/11/2012 8:30
5.7
21.90
2.32
40.0122
29/10/2012 10:00
3/11/2012 10:00
5.0
20.56
1.99
25.5482
3/11/2012 10:00
6/11/2012 10:00
3.0
29.33
2.60
40.0225
6/11/2012 10:00
11/11/2012 10:00
5.0
12.60
2.45
A21
-Appendix-
time [days]
Chapter 7
GE-SW-5
GE-SW-6
GE-SW-7
GE-SW-8
GE-SW-9
Appendix
0.4001
0.4001
0.3999
0.3999
0.4
24.5566
11/11/2012 10:00
14/11/2012 8:30
2.9
18.53
2.47
40.0184
29/10/2012 10:00
6/11/2012 10:00
8.0
24.10
2.27
40.0173
6/11/2012 10:00
14/11/2012 8:30
7.9
18.72
2.35
40.0016
29/10/2012 10:00
29/10/2012 16:30
0.3
7.89
2.14
24.6157
29/10/2012 16:30
6/11/2012 10:00
7.7
42.85
3.34
40.0271
6/11/2012 10:00
6/11/2012 18:00
0.3
18.72
2.35
25.9449
6/11/2012 18:00
14/11/2012 8:30
7.6
21.76
2.58
40.001
29/10/2012 10:00
30/10/2012 10:00
1.0
10.29
2.02
24.3029
30/10/2012 10:00
6/11/2012 10:00
7.0
35.21
2.58
40.0231
6/11/2012 10:00
7/11/2012 12:00
1.1
3.58
2.53
28.1498
7/11/2012 12:00
14/11/2012 8:30
6.9
21.32
2.29
40.0156
29/10/2012 10:00
31/10/2012 13:20
2.1
13.50
2.22
24.871
31/10/2012 13:20
6/11/2012 10:00
5.9
33.38
2.45
40.008
6/11/2012 10:00
8/11/2012 15:20
2.2
6.14
2.42
24.5312
8/11/2012 15:20
14/11/2012 8:30
5.7
20.89
2.55
40.0207
29/10/2012 10:00
3/11/2012 10:00
5.0
20.59
1.87
25.4825
3/11/2012 10:00
6/11/2012 10:00
3.0
31.92
1.99
40.0064
6/11/2012 10:00
11/11/2012 10:00
5.0
10.14
2.65
27.7239
11/11/2012 10:00
14/11/2012 8:30
2.9
18.96
2.42
A22
-Appendix-
Chapter 7
Appendix
GE-SW-10
GE-SW-11
0.4001
0.3999
40.0055
29/10/2012 10:00
6/11/2012 10:00
8.0
24.38
1.99
40.013
6/11/2012 10:00
14/11/2012 8:30
7.9
19.63
2.37
40.0064
29/10/2012 10:00
6/11/2012 10:00
8.0
24.38
2.37
40.0238
6/11/2012 10:00
14/11/2012 8:30
7.9
23.10
2.73
8.8.2 Eilat granite dissolution experiment in Seawater: Long term period
Sample
Sediment
Solution
[gr]
[gr]
Start
Finish
Blank Seawater
Ca
Mg
Sr
K
Fe
[mg/L]
[mg/L]
[mg/L]
[mg/L]
[mg/L]
1.64
267
1370
0.052
464
Time [days]
Si [µM]
Al [µM]
0
0.79
pH
87Sr/86Sr
< 0.1
8.18
0.70873
0.3999
40.001
28/11/2012 17:15
3
8.39
3.78
317
1444
0.020
486
< 0.1
8.13
0.70807
GE-SW2
0.4
40.0191
1/12/2012 8:00
6
9.34
3.92
317
1447
0.020
491
< 0.1
8.2
0.708202
GE-SW3
0.4
40.0005
5/12/2012 13:00
10
10.20
4.95
308
1457
0.021
494
< 0.1
8.23
0.708443
GE-SW4
0.4
40.0122
16/12/2012 14:00
21
14.42
4.19
304
1351
0.021
436
< 0.1
8.17
0.70848
GE-SW5
0.4001
40.0184
3/1/2013 20:00
39
19.46
3.65
314
1432
0.024
488
< 0.1
8.15
0.708311
GE-SW6
0.4001
40.0016
13/2/2013 16:45
80
27.40
2.25
305
1368
0.026
444
< 0.1
8.12
0.70837
GE-SW7
0.3999
40.001
6/5/2013 9:00
162
28.47
2.32
381.4
1771
0.017
522.8
< 0.1
8.19
0.708282
25/11/2012 11:00:00
GE-SW1
A23
-Appendix-
Chapter 7
Appendix
8.8.3 Eilat granite dissolution experiment in Borax solution: two times washing period
Sample
Sediment
Solution [gr]
Start
Finish
[gr]
GE-Bx-2
GE-Bx-3
GE-Bx-4
0.3999
0.3999
0.4
0.4001
Al [µM]
0.00
0.83
1.62
40.0062
1/12/2012 8:30
1/12/2012 18:00
0.4
7.24
6.63
25.1459
1/12/2012 18:00
9/12/2012 15:00
7.9
53.42
4.56
40.0281
9/12/2012 15:00
9/12/2012 21:00
0.3
3.31
3.92
26.0881
9/12/2012 21:00
16/12/2012 15:00
6.8
26.07
5.52
40.0029
1/12/2012 8:30
2/12/2012 14:00
1.2
15.10
6.75
25.8079
2/12/2012 14:00
9/12/2012 15:00
7.0
54.40
5.14
40.0165
9/12/2012 15:00
10/12/2012 15:00
1.0
7.96
4.10
25.3178
10/12/2012 15:00
16/12/2012 15:00
6.0
32.14
5.55
40.0008
1/12/2012 8:30
3/12/2012 13:00
2.2
20.27
5.82
26.0247
3/12/2012 13:00
9/12/2012 15:00
6.1
42.04
5.29
40.0223
9/12/2012 15:00
11/12/2012 17:00
2.1
14.22
4.50
25.5206
11/12/2012 17:00
16/12/2012 15:00
4.9
26.00
5.58
40.0024
1/12/2012 8:30
5/12/2012 12:00
4.1
31.90
5.87
25.8801
5/12/2012 12:00
9/12/2012 15:00
4.1
42.30
5.58
40.029
9/12/2012 15:00
13/12/2012 15:00
4.0
15.83
5.26
A24
-Appendix-
Si [µM]
[days]
Blank Borax solution
GE-Bx-1
time
Chapter 7
Appendix
GE-Bx-5
GE-Bx-6
GE-Bx-7
GE-Bx-8
GE-Bx-9
0.3999
0.4001
0.3999
0.4001
0.4
25.6421
13/12/2012 15:00
16/12/2012 15:00
3.0
23.20
5.84
40.0063
1/12/2012 8:30
9/12/2012 15:00
8.3
39.61
5.52
40.0106
9/12/2012 15:00
16/12/2012 15:00
7.0
20.28
5.49
40.0092
1/12/2012 8:30
1/12/2012 18:00
0.4
7.81
4.12
25.1488
1/12/2012 18:00
9/12/2012 15:00
7.9
50.93
4.36
40.0078
9/12/2012 15:00
9/12/2012 21:00
0.3
3.31
3.77
25.3058
9/12/2012 21:00
16/12/2012 15:00
6.8
25.37
6.60
40.0003
1/12/2012 8:30
2/12/2012 14:00
1.2
15.67
4.12
25.3690
2/12/2012 14:00
9/12/2012 15:00
7.0
36.20
4.27
40.0012
9/12/2012 15:00
10/12/2012 15:00
1.0
6.41
4.30
25.8743
10/12/2012 15:00
16/12/2012 15:00
6.0
30.33
5.20
40.001
1/12/2012 8:30
3/12/2012 13:00
2.2
16.23
4.56
25.5798
3/12/2012 13:00
9/12/2012 15:00
6.1
39.20
4.27
40.0202
9/12/2012 15:00
11/12/2012 17:00
2.1
10.32
4.53
25.3744
11/12/2012 17:00
16/12/2012 15:00
4.9
29.34
5.20
40.0078
1/12/2012 8:30
5/12/2012 12:00
4.1
28.49
4.59
26.1598
5/12/2012 12:00
9/12/2012 15:00
4.1
49.54
4.94
39.9994
9/12/2012 15:00
13/12/2012 15:00
4.0
12.94
4.18
25.5801
13/12/2012 15:00
16/12/2012 15:00
3.0
25.37
4.21
A25
-Appendix-
Chapter 7
Appendix
GE-Bx-10
0.3999
GE-Bx-11
0.4
40.0028
1/12/2012 8:30
9/12/2012 15:00
8.3
43.54
4.68
40.0063
9/12/2012 15:00
16/12/2012 15:00
7.0
23.15
5.44
40.0083
1/12/2012 8:30
9/12/2012 15:00
8.3
43.64
5.29
40.0185
9/12/2012 15:00
16/12/2012 15:00
7.0
17.75
5.52
8.9 Eilat granite dissolution experiment in Borax solution: long term experiment
Sample
Sediment [gr]
Solution [gr]
Start
Finish
Blank borax solution
Time [days]
Si
Al
Ca
Mg
Sr
K
Fe
pH
87Sr/86Sr
[µM]
[µM]
[mg/L]
[mg/L]
[mg/L]
[mg/L]
[mg/L]
0
0.83
1.62
44
≤1
< 0.01
5.4
< 0.1
8.26
0.70873
QDR-Bx-1
0.3999
40.0249
16/12/2012 15:00
19/12/2012 12:00
3
9.24
7.09
45.0
≤1
0.014
5.4
< 0.1
8.26
0.708710
QDR-Bx-2
0.3999
40.0161
16/12/2012 15:00
23/12/2012 13:00
7
15.53
5.32
45.7
<1
0.017
4.2
< 0.1
8.26
0.708420
QDR-Bx-3
0.4
40.0111
16/12/2012 15:00
26/12/2012 19:00
10
18.30
7.23
45.7
<1
0.020
4.0
< 0.1
8.24
0.708420
QDR-Bx-4
0.4001
40.0099
16/12/2012 15:00
6/1/2013 11:00
21
26.45
7.01
45.6
<1
0.023
3.4
< 0.1
8.27
0.708680
QDR-Bx-5
0.3999
40.014
16/12/2012 15:00
25/1/2013 17:00
40
35.76
5.21
44.8
<1
0.032
3.2
< 0.1
8.27
0.708790
A26
-Appendix-
Chapter 7
Appendix
QDR-Bx-6
0.4001
40.019
16/12/2012 15:00
10/3/2013 12:30
84
48.45
4.41
44.4
0.47
0.033
2.9
< 0.1
8.26
0.708890
QDR-Bx-7
0.3999
40.008
16/12/2012 15:00
17/5/2013 15:00
152
58.30
4.24
20
< 0.1
0.040
2.4
< 0.1
8.14
0.708332
8.10
Bulk Sediment Analysis
%
GE
KSP
Alb
QDR
Rhy
YJ6
Yt
[Eilat granite]
[K-Feldspar]
[albite]
[Roded
[Amram
[Amram
[Yehoshafat
quartz
rhyolite]
rhyolite]
granite]
diorite]
SiO2
66.57
65.44
64.78
64.94
68.5
66.18
52.5
Al2IO3
7
19
21.1
10.5
6.5
7.6
9.5
Fe2O3
3.1
0.06
0.2
6.9
3.5
3.3
6.5
TiO2
0.76
<0.01
0.01
1.44
0.71
0.64
1.9
CaO
17.3
<0.02
2.1
7.2
16.1
17.8
24.1
MgO
2.4
<0.05
<0.02
5
2.3
2
3.5
MnO
0.07
<0.01
0.01
0.12
0.09
0.08
3.9
Na2O
1
2.5
10.9
1.8
0.6
0.6
0.0
K2O
1.5
13
0.9
1.4
1.5
1.6
2.9
-End of Report A27
-Appendix-
‫המסת סדימנטים סיליקטיים באינטראקציה עם מי ים‬
‫‪Silicate sediments dissolution during interaction with seawater‬‬
‫תמיסה בתמיסה חדשה מביאה לכך שבניסוי ארוך הטווח קצב ההמסה בניסויים אלו נמוך יותר ביחס‬
‫לניסוי שלא עבר שטיפה ראשונית (תוצאה של הסרת חלק מהגרגרים הדקים בדוגמא)‪.‬עם הזמן‬
‫יורדת הריאקטיביות של הסדימנט וקצב ההמסה מאט עד להגעה למצב עמיד שבו לא מובחן שינוי‬
‫בריכוז הסיליקון או אלומיניום עם הזמן‪.‬‬
‫במחקר זה נמצא כי דוגמת האלביט עוברת המסה אינקונגרואנטית במי‪-‬ים וכי ההרכב האיזוטופי של‬
‫‪87‬‬
‫סטרונציום יורד בצורה היפרבולית עם הזמן‪ .‬היחס ‪Sr/86Sr‬‬
‫כנגד ‪ 1/Sr‬בניסוי מעיד על ערבוב בין‬
‫שני מרכיבי קצה(שני מינרלים בעלי ריכוז סטרונציום והרכב איזוטופי שונים)‪ .‬ככל הנראה דוגמת‬
‫מכילה גם כמות זעירה של ביוטיט ואפטיט נוסף על האלביט‪ ,‬כפי שאכן זוהה ב‪.)SEM-‬‬
‫בניסוי ההמסה של פלדספר אשלגני נמצא כי המינרל עובר המסה קונגרואנטית (סטויכומטרית) במי‪-‬‬
‫ים (יחס ‪ .)Al:Si=1:3‬כיוון שמינרל זה מכיל סטרונציום בכמות מועטה (‪ ,)0.2ppm‬הוא לא תרם‬
‫סטרונציום לתמיסת הניסוי‪.‬‬
‫מהשוואה בין תמיסת מי‪-‬ים לתמיסת ‪ borax‬עולה כי ‪ ).( :‬קצב ההמסה בתמיסת ‪borax‬מהיר יותר‬
‫מקצב ההמסה בתמיסת מי‪-‬ים‪ ,‬על אף שערך ה‪ pH-‬בשניהם זהה (‪ .)8.2‬תמיסת ה‪ borax -‬רחוקה‬
‫יותר משוו"מ ולכן הקצב מהיר יותר (‪ )8‬מגמת השינוי בהרכב האיזוטופי של סטרונציום עם הזמן‬
‫(ירידה היפרבולית) שומרת על תבנית דומה אך עם הסטה בערכים ב‪ 8-‬הניסוייים שבוצעו‬
‫באלביט‪.‬סיבה אפשרית לכך יכולה להיות שבניסוי תמיסת ה‪ borax-‬המרחק משוו"מ ביחס למינרלים‬
‫ביוטיט‪/‬אפטיט בתחילה הניסוי הוא גבוה יותר‪ ,‬כך שהם מתמוססים במהירות ותורמים לירידה חדה‬
‫בערך האיזוטופי שהוא שונה מההרכב הכללי של האלביט בדוגמא (תבנית דומה אך לא זהה נצפתה‬
‫גם בניסוי של קוורץ‪-‬דיוריט רודד)‪.‬‬
‫לסיכום ניתן לומר כי סדימנטים סיליקטים אכן עוברים המסה באינטראקציה עם מי‪-‬ים וכי יש לנו‬
‫היכולת לעקוב אחר השינויים בהרכב הכימי של התמיסה בעקבות המסה זו‪.‬‬
‫מילות מפתח‪:‬‬
‫גיאוכימיה של מים‪ ,‬קצב המסה במי‪-‬ים‪ ,‬סדימנטים סילקטיים מהרי אילת‪ ,‬הרכב איזוטופי של סטרונציום‬
‫‪Report GSI/01/2015‬‬
‫המסת סדימנטים סיליקטיים באינטראקציה עם מי ים‬
‫‪Silicate sediments dissolution during interaction with seawater‬‬
‫תקציר‬
‫במהלך ההיסטוריה הגיאולוגית היחס ‪Sr/86Sr‬‬
‫‪87‬‬
‫במי‪-‬האוקיאנוסים השתנה משמעותית כנראה‬
‫‪87‬‬
‫בעקבות תרומה של ‪ Sr‬למי‪-‬הים מבלייה של סלעים בעלי יחסי ‪Sr/86Sr‬‬
‫שונים ו‪/‬או תהליכי שחלוף‬
‫הידרותרמליים ברכסים מרכז‪-‬אוקייניים‪ .‬זמן השהות של ‪Sr‬באוקיאנוסים (‪ )4*106yr‬קצר ביחס לזמן‬
‫‪87‬‬
‫הגיאולוגי ומכאן ששינויים ביחס ‪Sr/86Sr‬‬
‫מאפשרים תיעוד של השינויים הגיאוכימיים‪ ,‬הטקטוניים‬
‫והאקלימיים של כדורה"א‪ .‬בבסיס ההבנה של המקור לשינוי של היחס האיזוטופי של סטרונציום עם‬
‫הזמן במי האוקיינוס מונחת ההנחה שהתרומה של סטרונציום למי הים מקורה רק במי נהרות‬
‫וברכסים מרכז אוקייניים‪ ,‬אולם גם סדימנטים המונחים על קרקעית האוקיאנוס יכולים באופן עקרוני‬
‫לשחרר סטרונציום למי הים עקב אינטראקציה איתם‪ .‬עבודה זו בחנה את קצבי ההמסה של‬
‫סדימנטים ושחרור הסטרונציום מהם באינטראקציה עם מי ים‪.‬‬
‫מחקרים קודמים עסקו בקינטיקת המסה ושחרור של ‪ Sr‬ממינרלים סילקטיים ספציפיים כגון‬
‫ל ברדוריט‪ ,‬מיקה ופלגיוקלז‪ ,‬אך מעט מחקר נעשה על קבוצות סלעים שהם מטבעם פולי‪-‬מינרליים‪.‬‬
‫כמו כן‪ ,‬רוב המחקרים בוצעו על דוגמאות טהורות שלרוב הופרדו מפגמטיטים‪ ,‬מעורקים‬
‫הידרותרמליים ואף על מינרלים סינטטים‪ .‬אולם‪ ,‬בטבע המינרלים לעיתים אינם טהורים ולרוב מכילים‬
‫אינקלוזי ות של מינרלים שונים או ציפויים עקב אלטרציה מאוחרת‪ .‬בנוסף‪ ,‬מחקרים אלו נעשו לרוב‬
‫בתמיסות חומציות מאוד (‪ )pH=1-3‬ומעט נערכו עם תמיסות מי‪-‬ים (‪ .)pH=8.2‬ברור כי ל‪pH -‬ולחוזק‬
‫היוני יש השפעה ישירה על האקטיביות של יונים שונים בתמיסה ובשל כך גם על המסיסות של‬
‫המינרלים השונים‪ ,‬ומכאן גם על קצב ההמסה‪.‬‬
‫במחקר הנוכחי נבדקה תחילה האפשרות שאינטראקציה בין מי ים וסדימנט בקרקעית הים מביאה‬
‫להמסה משמעותית של הסדימנט ושחרור של סטרונציום אל מי הים‪ .‬במסגרת המחקר תוכננו ונערכו‬
‫שבעה ניסויי המסה )‪ (closed batch experiment‬שבמהלכם נמדדו פרמטרים שונים ובכללם ריכוזי‬
‫אלומיניום‪ ,‬סיליקה וסטרונציום‪.‬במסגרת הניסויים נעשה שימוש בשתי תמיסות סינטטיות‪ :‬האחת‬
‫תמיסת מי ים עם ריכוז סטרונציום נמוך )‪ )17 ppb‬והשנייה תמיסת ‪ .borax‬לתמיסות ‪ pH‬זהה (‪)2.8‬‬
‫אך חוזק יוני שונה (‪ 7.0‬במי‪ -‬ים לעומת ‪7.7.0‬מול‪/‬ק"ג בתמיסת ‪.)borax‬ניסויי ההמסה נערכו עם‬
‫סדימנטים נחליים שנאספו מאגנים שמנקזים יחידות סלע הומוגניות(קוורץ‪-‬דיוריט רודד‪ ,‬גרניט‬
‫יהושפט‪ ,‬גרניט אילת וריוליט עמרם)‪.‬כמו כן‪ ,‬נערכו ניסויי‪-‬המסה עם שני מינרלים‪ :‬אלביט מאונטריו‬
‫קנדה‪,‬ופרטיט פלדספר אשלגני שהופרד מפגמטיט אילת‪.‬קצבי ההמסה חושבו עפ"י שינוי ריכוז‬
‫הסיליקון עם הזמן ונמדדו השינויים בריכוז ובהרכב האיזוטופי של סטרונציום (‪.)87Sr/86Sr‬‬
‫במחקר זה הובחנו שינויים בריכוזי הסיליקון והאלומיניום בפרקי זמן קצרים של ימים בודדים‬
‫המאששים את ההנחה הבסיסית שאכן מתרחשת אינטראקציה משמעותית של מי‪-‬ים עם סדימנטים‬
‫ומינרלים‪ .‬כמו כן נמצא שהחלפת תמיסה בתמיסה חדשה לפני תחילת ניסויי ארוך הטווח (שטיפה‬
‫ראשונית) מאפשרת המסה ראשונית של החלקיקים הדקים (הריאקטיביים) ביותר בסדימנט‬
‫(ריאקטיביים‪ ,‬משום ששטח הפנים שלהם ביחס לנפחם הוא גדול מאוד)‪ .‬המסה ראשונית זו והחלפת‬
‫‪Report GSI/01/2015‬‬
‫המכון הגיאולוגי‬
‫משרד התשתיות הלאומיות‬
‫האנרגיה והמים‬
‫המסת סדימנטים סיליקטים באינטראקציה עם מי‪-‬ים‬
‫דניאל וינקלר‬
‫עבודה זו הוגשה כחיבור לקבלת תואר מוסמך במדעי הטבע (‪ )M.Sc‬במחלקה למדעי הגיאולוגיה והסביבה‪,‬‬
‫אוניברסיטת בן‪-‬גוריון בנגב‪.‬‬
‫העבודה נעשתה בהדרכתם של‪:‬‬
‫פרופ' יבחר גנאור‪ ,‬המחלקה למדעי הגיאולוגיה והסביבה‪ ,‬אוניברסיטת בן גוריון בנגב‬
‫ד"ר יהודית הרלבן‪ ,‬המכון הגיאולוגי‪ ,‬ירושלים‪.‬‬
‫דוח מס' ‪GSI/01/2015‬‬
‫ירושלים‪ ,‬שבט תשע"ה‪ ,‬ינואר ‪1025‬‬