South Finland Unit
Q29.1/2006/2
Espoo
29.8.2006
Paleomagnetism and magnetic
mineralogy of samples from the Kahama
region, Tanzania
Satu Mertanen
Kahama paleomagnetism
Satu Mertanen
GEOLOGICAL SURVEY OF FINLAND
DOCUMENTATION PAGE
Date / Rec. no.
29.8.2006
Authors
Type of report
Satu Mertanen
Research report
Commissioned by
GTK
Title of report
Paleomagnetism and magnetic mineralogy of samples from the Kahama region, Tanzania.
Abstract
The report shows paleomagnetic and rock magnetic results of samples from Archean rocks from the Kahama
region in Tanzania. Altogether 18 samples, part of which were oriented, were measured at the Geophysics
laboratory of GTK. 16 samples were taken from different types of granitoids; granites, pegmatites and gneisses.
One sample was taken form a BIF and one from a dolerite dyke. The foremost aim of the studies was to resolve the
main ferromagnetic minerals of the samples and to see the stability of remanent magnetization of the rocks. For
mineral identification, three samples were subjected to special rock magnetic studies, comprising the acquisition of
isothermal remanent magnetization (IRM) and the so called Lowrie tests where the minerals are identified based
on their magnetic coercivities and unblocking temperatures. The rest of the samples were thermally demagnetized.
All studied rocks are highly magnetic and in most samples remanent magnetization dominates over the induced
magnetization. Based on rock magnetic and paleomagnetic studies, most of the granitic rocks and the BIF sample
contain both hematite and magnetite and/or titanomagnetite. Five granitic samples and the sample from the
dolerite dyke contain magnetite and/or titanomagnetite, but no hematite. Paleomagnetic results show that the
remanence directions of all samples are stable and that the remanent magnetization direction residing in magnetite
or hematite is almost similar, suggesting that the minerals were formed in the same or temporally close geological
processes. Because the remanent magnetization directions were highly scattered, no mean values were calculated.
Keywords
rock magnetism, paleomagnetism, remanent magnetization, multicomponent analyses, magnetite, hematite
Geographical area
Tanzania, Kahama
Map sheet
QDS 62 and 78
Other information
Report serial
Archive code
Q29.1/2006/2
Total pages
Language
7 + 10 appendices
English
Price
public
Unit and section
Project code
South Finland Unit
7501002
Signature/name
Signature/name
Satu Mertanen
Confidentiality
Kahama paleomagnetism
Satu Mertanen
GEOLOGIAN TUTKIMUSKESKUS
KUVAILULEHTI
Päivämäärä / Dnro
29.8.2006
Tekijät
Raportin laji
Satu Mertanen
Tutkimusraportti
Kieli
Englanti
Raportin nimi
Paleomagnetism and magnetic mineralogy of samples from the Kahama region, Tanzania.
Tiivistelmä
Raportissa esitetään paleomagneettiset ja kivimagneettiset tulokset arkeeisista kivinäytteistä Kahaman alueelta
Tansaniasta. GTK:n Geofysiikan laboratoriossa mitattiin yhteensä 18 näytettä, joista osa oli suunnattuja. 16
näytettä oli otettu eri tyyppisistä granitoideista; graniiteista, pegmatiiteista ja gneisseistä. Yksi näyte oli otettu BIFmuodostumasta ja yksi näyte doleriittijuonesta. Tutkimusten päätavoitteena oli selvittää näytteissä esiintyvät
ferromagneettiset mineraalit ja tutkia näytteiden paleomagneettista stabiilisuutta. Mineraalien tunnistamista varten
kolmelle näytteelle tehtiin erityiset kivimagneettiset mittaukset, jotka käsittivät isotermisen remanentin
magnetoituman (IRM) syntykäyrien tuoton ja ns. Lowrie-testit, joissa käytetään hyväksi eri mineraaleille
ominaisia magneettisia koersiviteetteja ja lukkiutumislämpötiloja. Muut näytteet demagnetoitiin termisesti.
Kaikki tutkitut näytteet ovat voimakkaasti magneettisia. Useimmissa näytteissä remanentti magnetoituma on
vahvempaa kuin indusoitu magnetoituma. Kivimagneettisten ja paleomagneettisten tulosten perusteella
useimmissa graniittinäytteissä sekä BIF-näytteessä esiintyy sekä hematiittia että magnetiittia ja/tai
titanomagnetiittia. Viidessä graniittinäytteessä sekä doleriittijuonessa esiintyy magnetiittia ja/tai titanomagnetiittia,
mutta ei hematiittia. Kaikkien näytteiden remanentin magnetoituman suunta on stabiilia. Sekä magnetiitissa että
hematiitissa esiintyvän remanenssin suunta on lähes sama, mikä osoittaa mineraalien syntyneen samassa tai
ajallisesti hyvin lähekkäisessä geologisessa prosessissa. Koska eri näytteiden väliset remanenssisuunnat
poikkeavat huomattavasti toisistaan, ei suunnista laskettu keskiarvoja.
Asiasanat (kohde, menetelmät jne.)
kivimagnetismi, paleomagnetismi, remanentti magnetoituma, monikomponenttianalyysi, magnetiitti, hematiitti
Maantieteellinen alue (maa, lääni, kunta, kylä, esiintymä)
Tansania, Kahama
Karttalehdet
QDS 62 ja 78
Muut tiedot
Arkistosarjan nimi
Arkistotunnus
Q29.1/2006/2
Kokonaissivumäärä
Kieli
7 + 10 Liitettä
Englanti
Hinta
Julkinen
Yksikkö ja vastuualue
Hanketunnus
Espoon yksikkö, 213
7501002
Allekirjoitus/nimen selvennys
Allekirjoitus/nimen selvennys
Satu Mertanen
Julkisuus
Kahama paleomagnetism
Satu Mertanen
Contents
Documentation page
Kuvailulehti
1
INTRODUCTION
1
2
METHOS AND ANALYSIS
1
3
RESULTS
2
4
CONCLUSIONS
6
5
IMPLEMENTATION
6
LITERATURE
TABLE 1
APPENDICES 1-10
Kahama paleomagnetism
Satu Mertanen
1
1 INTRODUCTION
Paleomagnetic and rock magnetic measurements for 18 Archean rock samples from the Kahama
region in Tanzania have been carried out at the Laboratory of Geophysics in GTK during spring
2006. The studied samples form part of the samples that were collected by geologists in
Tanzania in 2004. Fieldwork was carried out as part of project NDF277 between GTK and the
Geological Survey of Tanzania (GST). Petrophysical measurements were done at GST in
Dodoma, Tanzania with the equipment provided by GTK in February 2005, and remeasured at
GTK, Espoo in order to verify that the results are comparable. The measurements in Tanzania
were supervised by Dr. Meri-Liisa Airo (head of the Laboratory of Geophysics in GTK) who is
also the supervisor of the M.Sc. work of Sudian Chiragwile of the University of Dar-es-Salaam.
One of the study objects was to resolve the magnetic mineralogy of the studied Archean rocks.
Most of the studied samples are granites, gneisses and pegmatites. One studied sample was taken
from a dolerite dyke and another one from a banded iron formation (BIF). Thin section studies
had revealed the occurrence of hematite and magnetite, but further investigations were needed in
order to confirm the total magnetic mineralogy. Therefore, rock magnetic measurements for the
identification of magnetic minerals were carried out in the Laboratory of Geophysics in GTK. In
order to study the stability of remanent magnetization and the occurrence of different remanence
components, progressive demagnetization was carried out for the studied samples. Furthermore,
because part of the samples were oriented in the field, they provided test material for calculating
the paleomagnetic poles which could be used preliminary in determining the position of the
Congo craton during Archean. However, as shown in the report, the scatter of remanence
directions between different samples prevented calculation of mean remanence directions and
determination of the paleomagnetic poles. The report shows the results of rock magnetic studies
for mineral identification and the results of paleomagnetic studies – that is, progressive
demagnetizations and measurements of remanent magnetizations combined with
multicomponent analysis.
2 METHOS AND ANALYSIS
All the samples were already prepared to standard cylindrical specimens (diameter 2.4 cm and
hight 2.1 cm) before the measurements. Petrophysical properties; density and magnetic
susceptibility were measured for each cylinder before rock magnetic and paleomagnetic
measurements.
Rock magnetic measurements for mineral identification were done for three selected samples.
The samples were first stepwise demagnetized with alternating field (AF) in 15 steps up to field
of 1600 mT. The remanent magnetization was measured with cryogenic three-axes Squid (RF)magnetometer. Then, isothermal remanent magnetization (IRM) was produced by subjecting the
magnetically cleaned samples to increasing magnetic fields in 17 steps, the highest field being
1.5 T (Fig. 1). Magnetization was done with Molspin pulse magnetizer. Because different
magnetic minerals have their characteristic highest coercivities (hematite 1.5-5 T, magnetite 0.3
T, Butler 1982), they acquire IRM distinctively when submitted to external magnetic fields.
Based on that property it is possible to detect whether the samples include low or/and high
coercivity minerals.
Then, the so called Lowrie tests (Lowrie, 1990) were carried out for the three specimens (Fig. 2).
In the Lowrie test the mineral identification is based on the combination of specific remanent
coercivities and unblocking temperatures (maximum unblocking temperature for hematite 680°C
Kahama paleomagnetism
Satu Mertanen
2
and for magnetite 580°). First, a magnetization (IRM) was produced along the z axis of the
specimen up to the highest magnetic field of 1.5 T. Next, the magnetization was produced along
the y axis in a magnetizing field of 0.4 T. Now all those mineral grains that have coercivities
lower than 0.4 T were aligned along the y axis while those grains that have corcivities higher
than 0.4 T prevailed their magnetization. Then, the samples were subjected to the magnetizing
field of 0.12 T along the x axis, when all grains with coercivities below 0.12 T were aligned
along the x axis and those with higher coercivites remained untouched. After acquisition of IRM
along the three orthogonal axes, the samples were thermally demagnetized in the same fields as
other specimens of paleomagnetic studies (see below). Intensity curves of each axis were
produced separately and the magnetic minerals could then be determined based on the slopes
(unblocking temperatures) in the intensity curves.
For paleomagnetic studies, 15 specimens were thermally demagnetized so that the Curie (highest
unblocking) temperature properties could be used also for mineral identification.
Demagnetization was done in incremental steps of 200, 300, 350, 400, 500, 520, 540, 560, 570,
580, 600, 620, 640, 660 and 680 °C. The heating and cooling times for the samples varied
between 30 to 60 minutes, depending on the used temperature. The remanent magnetizations
(declination, inclination and intensity) between the demagnetizations were measured with
spinner-magnetometer. The intensities of remanence were well above the noise level (0.3 mA/m)
of the spinner-magnetometer and in some cases the intensities were too high to be measured with
the more sensitive Squid magnetometer.
Separation of remanent components was done by using least square method of the Tubefind
program (Leino, 1991). Fitting of lines, with the minimum of three demagnetization points was
done automatically with the maximum angular deviation of the line (E.A.) being 6°. In addition,
most specimens were treated manually and in three such cases the error angel of the vector
component was 9-12° (Table 1). Results of the rock magnetic studies are shown in Figures 1 and
2, and the results of the paleomagnetic studies in Table 1 and Appendices 1-10. Declination and
inclination are given only for those samples that were oriented in the field.
3 RESULTS
3.1. Rock magnetic studies
3.1.1. Acquisition of IRM
Isothermal remanent magnetization measurements for all three samples (Fig. 1) show a rapid
increase up to about 100 mT, indicating the occurrence of magnetite or titanomagnetite. In
samples SAC-2 and SAC-9 the magnetization continues to increase to the highest field of 1.5 T
without saturation, which is an indication of the occurrence of a high coercivity mineral, possibly
hematite. This is obvious especially for sample SAC-2. Sample SAC-24 achieves saturation
below 500 mT which indicates that the sample does not contain high coercivity minerals and that
magnetite or titanomagnetite is probably the only carrier of magnetization.
3.1.2. Lowrie tests
Results of the Lowrie tests are shown in Fig. 2. Coercivity intervals of 1.4-0.4 T, 0.4-0.12 T and
<0.12 T are referred as hard (z), medium (y) and soft (x) fractions, respectively. For all
Kahama paleomagnetism
Satu Mertanen
3
1.0
SAC-2
SAC-9
SAC-24
0.8
0.6
0.4
0.2
0.0
0.1
0.5
1.0
1.5
Magnetizing field (T)
Figure 1. Acquisition of isothermal remanent magnetization (IRM) of the three studied granite samples.
samples, hard fractions are dominant. In samples SAC-2 and SAC-9 the hard fraction (z, Fig. 2)
is demagnetized at around 680°C, indicating the presence of hematite. In addition, both samples
and also sample SAC-24 show an abrupt drop of the hard fraction at around 580°C, indicating
the presence of magnetite. On the other hand, in sample SAC-24 there is no indication of
hematite. In all samples the medium coercivity fraction (y, Fig. 2) is very low, close to the noise
of the Squid magnetometer. The soft fraction (x, Fig. 2) of samples SAC-9 and SAC-24 show a
drop of magnetization at around 580°C, evidencing the presence of magnetite. In sample SAC-24
the hard and soft coercivity fractions show a slight drop of intensity at 400°C which may indicate
the presence of titanomagnetite.
The IRM acquisition curves and the Lowrie tests give comparable results and confirm the
occurrence of hematite in two of the three studied samples and high and low coercivity magnetite
in all three samples. In addition, high-titanium titanomagnetite is possibly present in one of the
samples. Thermal demagnetizations for the paleomagnetically studied samples give further
evidence for the occurrence of magnetite and hematite.
3.2. Paleomagnetic studies
All studied samples are highly magnetic (Table 1). Magnetic susceptibilities of different types of
granites vary between 2 900 and 35 800 x 10-6 SI. Magnetic susceptibility of the BIF sample is
around 24 400 x 10-6 SI and that of the dolerite dyke around 41 600 x 10-6 SI. Intensities of
remanent magnetization of the granites are within the range of 235-5 680 mA/m, the BIF 15 410
mA/m and of the dolerite dyke 5 550 mA/m. Koenigsberger ratios (Q values) of the granites are
typically high being in the range of 0.5-34.7. In most granite samples the Q value is well above
Kahama paleomagnetism
Satu Mertanen
4
Normalized magnetization
1.0
0.8
0.6
0.4
Z
SAC-2
0.2
Y
X
0.0
0
100
200
300
400
500
600
700
Temperature ( C)
Normalized magnetization
1.0
0.8
0.6
Z
SAC-9
0.4
X
0.2
Y
0.0
0
100
200
300
400
500
600 700
Temperature ( C)
Normalized magnetization
1.0
0.8
Z = hard
Y = medium
X = soft
0.6
0.4
SAC-24
0.2
Z
Y
X
0.0
0
100
200
300
400
500
600
700
Temperature ( C)
Figure 2. Lowrie tests for the studied granite samples showing thermal demagnetizations after isothemal
remanent acquisition along three orthogonal directions (z, y and x) with fields of 1.5 T, 0.4 T and 0.12 T,
respectively. The unblocking temperatures of the hard (1.5-0.4 T), medium (0.4-0.12 T) and soft (<0.12 T)
coercivity fractions, and accordingly the magnetic minerals, can be estimated from the slopes in the
magnetization curves.
Kahama paleomagnetism
Satu Mertanen
5
1, indicating the dominance of remanent magnetization over the induced magnetization. In the
BIF sample the Q-value is 15.9 and in the dolerite, 3.4.
The characteristic feature of most of the studied samples is the high stability of remanence
directions which is shown as straight lines in Zijderveld plots (Appendices 1-10). No particular
difference was observed in the behaviour of different types of granites. Demagnetization
behaviours are described below and examples are shown in Appendices 1-10.
The remanence carriers in most granite samples (11 samples) are both magnetite and/or
titanomagnetite and hematite which is shown in the slopes of the intensity decay curves and the
vector analysis (Table 1). However, the directions of remanence components residing in
magnetite and hematite deviate only slightly from each other. This indicates that magnetite and
hematite were formed either in the same geological process or in successive processes with only
a small age difference. Samples SAC-11 (pink gray granite, Appendix 1), SAC-35 (pegmatite,
Appendix 2) and SAC-50 (gray granite, Appendix 3) demonstrate these cases where, in order to
emphasize the similarity of directions of the remanence components, a line fitting was done for
different temperature ranges (typically 300-570°C for magnetite and 570-680°C for hematite)
although the fitting could have been done for the whole range of temperatures. Sample SAC-53
(gray granite, Appendix 4) is an example of a single component case, where the vector goes
straight to the origin in the whole temperature range, and shows that magnetite and hematite
were formed simultaneously. Typically, the remanence component residing in magnetite is much
larger, and only a small component residing in hematite is found in the highest temperature
ranges. Sample SAC-23 (gneissose sheared granite, Appendix 5) provides an example of a very
large magnetite component and a small hematite component that is shown only in the
enlargement of the origin area (Appendix 5a). The remanence direction of the hematite
component is not so well defined, evidenced by the large error angle, but anyway, its occurrence
is obvious.
In five granite samples the remanence resides in magnetite, but there are no indications of
hematite (Table 1). In sample SAC-24 the remanence carriers were suggested to be
titanomagnetite and magnetite by Lowrie tests (see section 3.1). In the other four samples that
were thermally demagnetized, the remanence looses its intensity and stability of direction below
580°C, indicative of magnetite. In part of the samples, like SAC-12 (white pinkish granite,
Appendix 6) and SAC-18 (sheared gray granite, Appendix 7) there is a drop of intensity at
around 400°C and at around 580°C which can be signatures of distributed grain sizes of
magnetite or of the occurrence of two phases of magnetic minerals, possibly titanomagnetite and
magnetite. Both components have the same remanence direction.
Sample SAC-69 (gray granite, Appendix 8) represents the only sample that shows three
components with clearly deviating remanence directions. The low unblocking temperature
component is isolated in a temperature range of 300-500°C and an intermediate component in
temperatures between 500 and 570°C. These temperatures can be indications of the occurrence
of Ti-rich titanomagnetite and magnetite. Because they have deviating remanence directions,
they were formed at different times. The dominating difference in remanence directions is in the
angle of inclinations (Table 1) which suggests considerable latitudinal plate movement between
the acquisition of titanomagnetite and magnetite components. A high-temperature component,
residing in hematite, was poorly isolated in a temperature range of 620-660°C (Appendix 8a). Its
remanence direction, especially the inclination, also differes from the previous directions, thus
suggesting further plate movement. The relative age order for different components cannot be
defined based on the unblocking temperatures alone, because the temperatures are dependent on
Kahama paleomagnetism
Satu Mertanen
6
the magnetic mineralogy. Therefore, more paleomagnetic studies combined with geological
evidences are needed, in order to resolve the relative succession of different remanence
components, if desired.
In samples SAC11 and SAC12 (Table 1, Appendices 1 and 6) a low unblocking temperature
component was isolated in a temperature range of 0-300°C. Its direction deviates only slightly
from the higher unblocking temperature component and is probably due to viscous remanent
magnetization (VRM) which has no geological meaning. In both cases, however, the remanence
direction deviates from the present Earth's magnetic field direction of the area (declination 0.3°,
inclination –32°) thus suggesting that the VRM was formed in earlier times.
Paleomagnetic results of the sample SAC-42 (Appendix, 9) from BIF and of the sample SAC-66
(Appendix 10) from the dolerite dyke do not differ significantly from the results of the granites
(Table 1). In the BIF sample the remanence resides both in magnetite and hematite. The
remanence directions are close to each other, the main difference being in inclination that is
about 20° lower for the hematite component (Table 1). In the sample from dolerite dyke there is
no hematite, but magnetite occurs as two different phases with deviating remanence directions.
4 CONCLUSIONS
Most of the studied granite samples contain magnetite and hematite. They are also the carriers of
remanent magnetization. Typically the remanence directions residing either in magnetite or
hematite do not differ significantly from each other, probably signifying that they were formed in
the same or temporally close geological processes. In part of the samples, no hematite was
observed, but the magnetic mineral is magnetite and /or titanomagnetite. Remanence directions
of separate samples are quite stable, but the scatter of directions between samples is high, and no
mean remanence direction, and consequently, no mean paleomagnetic pole was calculated for
the granites. It is suggested that the reason for the scattered directions is either the age
differences of studied samples, or in case that they should represent coeval formations,
difficulties in orientation of the samples in the field. Compared to Archean rocks that have been
so far studied in Finland, the studied rocks from Kahama region are exceptionally stable, and
thus would be suitable for further paleomagnetic studies. In Finland, comparable high stability
results from Archean rocks have been obtained only from dry granulite grade granitoids which
have preserved from later metamorphic events.
5 IMPLEMENTATION
The samples were provided by Meri-Liisa Airo. Sample preparation was done by Satu
Vuoriainen and petrophysical, paleomagnetic and rock magnetic measurements by Tuula Laine.
Matti Leino was responsible for the functioning of equipments and software.
LITERATURE
Butler, R. ,1992. Paleomagnetism: Magnetic domains to geologic terranes. Blackwell Scientific Publications, 238 p.
Leino, M.A.H., 1991. Paleomagneettisten tulosten monikomponenttianalyysi pienimmän neliösumman
menetelmällä. Paleomagnetismin laboratorio, Geofysiikan osasto, Geologian tutkimuskeskus, Q29.1/91/2, 15 s (in
Finnish).
Lowrie, W., 1990. Identification of ferromagnetic minerals in a rock by coercivity and unblocking temperature
properties. Geophys. Res. Lett. 17, 159-162.
Kahama paleomagnetism
Satu Mertanen
Table
7
Kahama paleomagnetism
Satu Mertanen
8
APPENDICES 1-10
(A) Stereoplot
Change of direction of the remanence vector during progressive thermal demagnetization. NRM
gives the total remanent magnetization direction before demagnetization. Solid circles are
pointing downwards and open circles upwards.
(B) Intensity
Intensity decay curve during progressive thermal demagnetization. J/J0 of the vertical axes gives
the relative intensity and T (°C) shows the demagnetization temperature. In Appendices 3, 5, 9
and 10 the increase of intensity in the first demagnetization steps is due to antiparallel vector
components.
(C) Zijderveld plot
Remanence component vectors separated from the total remanent magnetization vector NRM,
shown as straight lines. The vectors are projected on horizontal (W-N) and vertical (U-N) planes.
Appenndices 5a and 8a are zoomed from the vector plots near the origin area.
TABLE 1. Magnetic parameters and multicomponent analysis of the samples from Kahama, Tanzania (Lat = 4 S, Long = 32.25 E)
Sample
SAC-3
SAC-6
SAC-11
SAC-12
x
394487
398028
441325
441020
y
9611479
9607319
9580754
9581015
Rock type
pink gray granite
pink granite
pink gray granite
white pinkish granite
Density Q-value Susc.
kg/m3
x 10-6
2684
2625
2624
2630
10,6
0,5
13,3
5,2
11915
19507
6786
6342
J
(mA/m)
5046,4
359,7
3594,3
1319,4
NRM
D
(o)
296,3
305,3
192,7
I
(o)
3,4
-37,7
-64,0
SAC-18
SAC-23
443435
441066
9561276
9570731
sheared gray granite
gneissose sheared granite
2683
2628
0,8
8,6
18308
13692
582,6
4682,4
SAC-35
417986
9555359
pegmatite
2694
22,4
4519
4020,8
SAC-37
SAC-40
SAC-42
418469
423479
430581
9562966
9558632
9552230
gray granite
sheared granite
BIF
2682
2645
3159
1,0
2,7
15,9
SAC-44
431555
9554023
granite
2642
0,7
8820
238,2
SAC-50
398265
9525364
gray granite
2743
4,0
35787
5678,5
SAC-53
SAC-66
413566
424458
9535466
9559333
gray granite
dolerite dyke
2625
2999
20,6
3,4
2940
41612
2406,0
5553,3
179,0
204,8
-30,1
24,6
SAC-69
429379
9565234
gray granite
2641
3,6
7659
1103,7
159,2
46,1
SAC-2
SAC-9
SAC-24
392313
441791
441053
9609068
9580742
9570380
pink granite
gray granite
granite with pegmatite
2700
2639
2683
34,7
24,5
3,1
3320
8579
8474
4586,5
8448,4
1031,0
302,7
77,1
169,3
87,5
-46,2
-24,7
6066
234,6
12442 1335,9
24387 15412,0
310,0
170,8
25,9
-46,5
111,6
280,6
30,3
-65,7
255,0
21,3
NRM components
Range
D
I
(oC)
(o)
(o)
E.A.
300-660
0-580
0-300
370-570
580-680
0-300
300-580
350-570
200-570
580-680
300-570
570-680
200-560
300-680
200-600
600-680
350-520
540-620
300-570
570-660
200-660
200-520
520-570
300-500
500-570
620-660
2,3
5,1
1,2
2,6
2,5
2,1
1,8
2,4
3,4
9,0
2,1
1,5
4,7
4,6
5,5
2,0
5,8
11,7
2,2
4,9
1,5
1,3
2,1
3,6
3,3
11,4
295,3
313,6
304,8
305,9
197,7
189,3
307,5
169,3
166,2
4,2
-47,1
-36,7
-33,8
-67,7
-60,5
32,8
-45,9
-27,3
110,8
280,4
279,2
260,6
234,9
22,5
-34,4
-14,6
1,6
20,9
178,3
198,4
186,4
150,0
162,9
168,5
-31,0
16,1
63,2
72,7
31,4
-21,4
Magnetic minerals
Appendix
magnetite + hematite
magnetite
1
magnetite
hematite
6
magnetite
magnetite
magnetite
hematite
magnetite
hematite
titanomagnetite
magnetite + hematite
magnetite
hematite
magnetite
hematite
magnetite
hematite
magnetite + hematite
titanomagnetite
magnetite
titanomagnetite
magnetite
hematite
magnetite + hematite
magnetite + hematite
titanomagnetite + magnetite
7
5
5a
2
9
3
4
10
8
8a
Figs. 1 and 2
Figs. 1 and 2
Figs. 1 and 2
Note: Samples written in bold were oriented in the field. x, y = sampling coordinates, Q-value = Koenigsberger ratio, Susc. = magnetic susceptibility, J = intensity of remanent magnetization (NRM)
before demagnetization, D = declination, I = inclination (given for oriented samples), NRM components = components separated with multicomponent analysis, Range = temperature range of a
single component, E.A. = error angle of the component, Magnetic mineral = identified with thermal demagnetization or by rock magnetic studies.