Georgia State University
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Geosciences Theses
Department of Geosciences
5-7-2011
Mineralogy and Geochemistry of the Bauxite
Deposits (Cretaceous), Wilkinson County,
Georgia.
Adebayo O. Ayorinde
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Ayorinde, Adebayo O., "Mineralogy and Geochemistry of the Bauxite Deposits (Cretaceous), Wilkinson County, Georgia.." Thesis,
Georgia State University, 2011.
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MINERALOGY AND GEOCHEMISTRY OF THE BAUXITE DEPOSITS (CRETACEOUS),
WILKINSON COUNTY, GEORGIA.
by
ADEBAYO O. AYORINDE
Under the Direction of W. Crawford Elliott
ABSTRACT
Cretaceous bauxite deposits from Hall and Veneer mines, Wilkinson County, Georgia are
composed of kaolinite, gibbsite, goethite, anatase, nordstrandite and bohemite. Quartz and micas
are absent in the samples. The presence of boehmite and goethite are evidence of intense
weathering forming the bauxite deposits. The extremely high values of the Chemical Index of
Alteration (CIA) which is over 99, and the low values of the alkali metals and alkali earth metals,
support an intense weathering origin for the bauxite deposit. There is evidence of deposition in
the mines based on the presence of pisoids in the bauxite samples and the composition of the
parent materials, which vary markedly by the non-uniform TiO2/Al2O3 values which represent
the accumulation of transported materials from contrasting source areas. Kaolin minerals were
first produced by the hydrolytic weathering of aluminous sediments and then gibbsite was
formed as early kaolin was desilicated.
INDEX WORDS: Mineral deposits, Georgia, Bauxite, Cretaceous.
MINERALOGY AND GEOCHEMISTRY OF THE BAUXITE DEPOSITS (CRETACEOUS),
WILKINSON COUNTY, GEORGIA.
by
ADEBAYO O. AYORINDE
A Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of
Master of Science
In the College of Arts and Sciences
Georgia State University
2011
Copyright by
Adebayo Olujinmi Ayorinde
2011
MINERALOGY AND GEOCHEMISTRY OF THE BAUXITE DEPOSITS (CRETACEOUS),
WILKINSON COUNTY, GEORGIA.
by
ADEBAYO O. AYORINDE
Committee Chair:
Committee:
W. Crawford Elliott
Daniel M. Deocampo
Eirik J. Krogstad
Electronic Version Approved:
Office of Graduate Studies
College of Arts and Sciences
Georgia State University
May 2011
iv
DEDICATION
This thesis is dedicated to the Almighty God, and to my lovely wife and daughters for their love,
encouragement, and support.
v
ACKNOWLEDGEMENTS
I would like to thank Dr. Crawford Elliott, my thesis committee chair and advisor, for his
continued support and patience during the research and writing of this thesis. I thank Dr. Daniel
Deocampo for his input as a member of my committee and helping me with the X-ray
fluorescence analysis at Georgia State University. I thank Dr. Eirik Krogstad for his advice on
CIA and Rare Earth Element determinations and agreeing to act as member of my committee. I
would like to thank Dr. Jessica Kogel and Greg Hatfield at IMERYS for their support with
sample collection. I would also like to thank Dr. Douglas Dvoracek and Dr. Paul Schroeder at
the University of Georgia for their help with re-analyzing my samples for major and trace
elements. Thanks also go to the faculty and staff of the Department of Geosciences at Georgia
State University.
Thank you Pastor Ken, Donna, Kelvin, Lia, Bryne, Angie, Micheal, Jonathan, Heather,
Stephen, Thompson, Shade, Randle, Mary Beth, Ebenezer Ikenebomeh, Kunle Olabosinde,
Wunmi, Segun Olawale, Dixson, Roda, Ginny, Federico, Fortune, Biola, Segun, Ayodele,
Olufemi, Helen Fahanmi, Olufunke , Kemi, and Funmi Atilola for your friendship and support.
I thanks my mother Bolaji Ayorinde, my siblings (Adekunle, Adenola, Adetoun, Adejumoke) for
their support and encouragement.
Thanks to my lovely daughters Divine, Mary and to my precious wife Gisele for your
unending encouragement and support throughout my education.
vi
TABLE OF CONTENTS
Page Number
ACKNOWLEDGEMENTS
v
LIST OF TABLES
viii
LIST OF FIGURES
ix
1.
1
INTRODUCTION
1.1
Bauxite Deposits of Southeastern United States.
1
1.2
Bauxite Deposits of Irwinton District, Georgia.
3
1.3
Bauxite Deposits of Hall Mine and Veneer Mine, Wilkinson County, Georgia.
7
1.4
Purpose of Study.
2.
METHODS
10
11
2.1
Field Data Methods.
11
2.2
Sample Preparation.
11
2.3
X-ray diffraction (XRD).
12
2.4
X-ray Fluorescence (XRF) Analysis.
13
2.5
Chemical Index of Alteration (CIA) Analysis.
14
vii
3.
RESULTS
14
3.1
Sample Description
14
3.2
Mineralogy Results.
15
3.3
Major Element Determinations.
19
3.4
Chemical Index of Alteration (CIA) Results.
20
3.5
Trace Element Results.
20
4.
DISCUSSION
24
5.
CONCLUSION
28
6. REFERENCES
29
APPENDICES
35
viii
Page Number
LIST OF TABLES
Table 1: The d-spacings of minerals in the bauxite samples from Hall and Veneer Mines.
12
Table 2: Major Element analyses for Hall and Veneer mines.
19
Table 3: Trace Element analyses for Hall and Veneer mines.
21
Table 4: Mineralogy and Geochemical data of the bauxite deposit in Hall Mine
and Veneer Mine.
23
ix
LIST OF FIGURES
Page Number
Figure 1: Map of the bauxite districts in Southeastern United States.
2
Figure 2: Stratigraphy of the Irwinton bauxite district, Georgia.
5
Figure 3: Highway map of Wilkinson County, Georgia showing the study area.
8
Figure 4: X-ray diffraction pattern of Hall Mine samples (HA-1 and HA-2).
16
Figure 5: X-ray diffraction pattern of Veneer Mine samples (VE-3 and VE-4).
17
Figure 6: X-ray diffraction pattern of Veneer Mine samples (VE-5Aand VE-5B).
18
Figure 7: Major element analysis of bauxite deposits in the Hall and Veneer Mines.
19
Figure 8: TiO2/Al2O3 ratios of bauxite deposits in the Hall and Veneer Mines.
20
Figure 9: Trace element analyses of bauxite deposits in the Hall and Veneer Mines.
21
1
1
INTRODUCTION
1.1
Bauxite Deposits of Southeastern United States
Bauxite deposits are found in the Coastal Plain and in the Ridge and Valley Province in
Southeastern United States (Figure 1). These deposits are found in 15 districts in Alabama,
Georgia, Tennessee, Virginia, and Mississippi (Overstreet, 1964). The mining of bauxite in
these areas has been continuous since 1888 (Overstreet, 1964). The reserves of commercial
bauxite in the southeastern United States are about 1,071,000 metric tons (Overstreet, 1964).
The first mined bauxite deposit in the United States was from the southeastern states, and this
region has been the primary source of aluminum ore for many decades (Overstreet, 1964).
Bauxite mined from this region is chiefly used in making refractories and chemicals, and minor
amounts of the deposits are used in the manufacture of abrasive and for petroleum refining and
water purification (Overstreet, 1964). These deposits are an important source of low iron
aluminous materials (Overstreet, 1964).
Overstreet (1964) described the bauxite and the associated kaolin deposits in the Coastal
Plain as hosted within sedimentary rocks of Cretaceous, Eocene and Paleocene age. Bridge
(1950) stated that the bauxite deposits in rocks of Paleocene and Eocene age are located along a
discontinuous arc (outer line) (Figure 1). This outer line passes through southwestern Georgia,
southern Alabama, and northern Mississippi. Deposits of the Cretaceous age are also found in
belts ( inner line) which lie 50 to 100 miles the outer lines and that passes through central
Georgia, northwestern Alabama and northwestern Tennessee (Overstreet 1964).
2
LIST OF DISTRICTS AND AREAS
1 Trippah Benton district, Mississippi
2 Pontotoc district, Mississippi
9 Warm Springs district, Georgia
10 Spottswood district, Virginia
3 Winston-Noxubee-Kemper district, Mississippi
16 Fort Payne area, Alabama
17 Congo area, Alabam
18 Rock Run and Goshen Valley areas, Alabama
4 Margerum district, Alabama
11 Indian Mound district, Tennessee
19 Ashville area, Alabama
5 Eufaula district, Alabama
12 Elizabethton district, Tennessee
20 Jacksonville area,Alabama
6 Springvale district, Georgia
13 Chattanooga district, Tennessee
21 Nances Creek area, Alabama
7 Andersonville district, Georgia
8 Irwinton district, Georgia
14 Summerville area, Georgia
22 Anniston area, Alabama
15 Hermitage Cave Springs and Babo areas, Georgia 23 DeArmanville area, Alabama
24 Talladega area, Alabama
Figure 1: Map of the bauxite districts in Southeast United States, relative bedrock to geologic
formation and to physiographic provinces (modified from Gordon et al., 1958). Outer line and
inner line are shown.
3
The origin of the bauxite deposits in southeast United States is not clear (Lukas et al.,
1982). Different hypotheses are proposed for the origin of these bauxite deposits. These
hypotheses are: (1) the infilling karst origin; (2) an in situ weathering origin within karst; (3) the
detrital or sedimentary origin; or (4) post-depositional alteration (Lukas et al., 1982). Hurst and
Pickering (1997) proposed that the kaolin and bauxite deposits in southeastern United States are
produced by the same post-depositional alteration as noted by Lukas et al. (1982). The Eufaula
bauxite deposit also was formed in situ and intense leaching to transform the clay minerals and
other detrital minerals, and leaving bauxite as a residual phase [Rettger (1925), Burst (1974),
MacNeil (1945)]. Clarke (1972) described that the Eufaula bauxite deposit was formed by
weathering in sinkholes extending into the underlying Eocene Clayton Formation. Burst (1974)
argued that this theory proposed by Clarke was not valid in the Andersonville area due to the
lack of sinkholes (Karst weathering), and that the bauxites were found within the sand facies.
1.2 Bauxite Deposits of Irwinton District, Georgia
The first discovery of bauxite in central Georgia was located in Wilkinson county in 1907
(Veatch, 1909, Watkins, 1915). This discovery led to the formation of Irwinton Mining District
at Wilkinson, Twiggs and Washington counties. Irwinton District in Central Georgia (No. 8), in
Figure 1, is located at the inner margin of the Coastal Plain province.(Lang et al., 1965). Mining
of bauxite deposits in the Irwinton District began in 1912, and deposits in several other counties
were discovered within the same year (Smith, 1929). Mining of bauxite deposits in this district
ceased in 1928, and Lang et al. (1965) reported renewed activities of mining in 1941 and 1942.
Irwinton district is also the principal source of kaolin deposits in the United States (Lang et al.,
1965).
4
The basement that underlines the Irwinton District is composed of crystalline rocks
(Milton and Hurst, 1965). These crystalline rocks of the nearby Piedmont Province are the
oldest exposed rocks in the District (Lang et al., 1965). Crickmay (1952) also described the
major units that comprise this area and described the Piedmont basement as being made up of a
great diversity of metamorphic rocks which include very slightly to highly re-crystallized metavolcanic and meta-sedimentary rocks. In the Coastal Plain, crystalline rocks are overlain by nonmarine sedimentary rocks which include micaceous sands, gravels, bauxite and lenses of kaolin
of Late Cretaceous age and younger (Lang et al., 1965). Walter et al. (1943) correlated these
unconsolidated non-marine Cretaceous rocks with the Tuscaloosa Formation. Eargle (1955) also
proposed that only the lower part of the unconsolidated Cretaceous rocks is equivalent to the
Tuscaloosa Formation of Western Georgia. Claiborne group and Jackson Group (Figure 2) are
the Tertiary rocks exposed in the Irwinton District (Lang et al., 1965).
Cooke and MacNeil
(1952) treated these groups as a single unit of Eocene age. The Claiborne and Jackson Group
(Figure 2) consist of sand, shale, limestone and fullers earth (Lang et al., 1965).
5
PERIOD (EPOCH)
GROUP
IRWINTON DISTRICT
Jackson
Jackson
Claiborne
Claiborne
TERTIARY
(EOCENE)
Wilcox
TERTIARY
(PALEOCENE)
Midway
Selma
LATE CRETACEOUS
Tuscaloosa
Kaolin
Bauxite
Kaolin
Upper Cretaceous
Undifferentiated
MISSISSIPPIAN
Figure 2: Stratigraphy of the Irwinton bauxite district, Georgia (modified from Overstreet, 1964).
A distinct unconformity separates the Cretaceous sediments from the Tertiary sediments
in this district. Austin, (1972) described the bauxite deposits in this district to occur as beds or
broad lenses within or at the top of the Cretaceous kaolin and sandy kaolin units just below the
Cretaceous- Tertiary unconformity. Kaolin and bauxite deposits occur within the Cretaceous
sediments, but recent studies have shown that some of the bauxite deposits are of Eocene age
(Austin, 1972). The age of these deposits is difficult to determine due to lack of fossils. An
unpublished report by Stephenson and Thompson cited by LaMoreaux (1946) reported that some
6
plant fossils were found in sandy carbonaceous clay that is overlain by kaolinitic clay near
Gordon in Wilkinson County. Scrudato (1969) described the age of the east central Georgia
kaolin deposits based on the pollen found within the kaolin-bearing sediments as Eocene.
The Irwinton bauxite deposits range in thickness from a few centimeters to over 3 meters
(Lang et al., 1965). Austin (1972) described the bauxite deposits in the Irwinton District are
rarely more than 2 meters thick. Smith (1929) had described some bauxite deposits that are as
thick as 8 meters. Lenses of the kaolin are larger than the lenses of the bauxite (Lang et al.,
1965). The kaolin lenses are more than 6 meters thick (Lang et al., 1965). The reserves of
bauxite and bauxitic clay in this area are about 406,000 metric tons (Lang et al., 1965). The
reserves of the kaolin are about 76 million metric tons (Lang et al., 1965).
Bauxite deposits have gibbsite pisoids throughout the district (Lang et al., 1965). Hard and soft
pisoids are present in the Irwinton bauxites (Lang et al., 1965). Hard pisoids are composed of
high gibbsite content, and are common in high grade bauxite deposit. Soft pisoids are common
in kaolin or bauxitic clay, and have low gibbsite content (Lang et al., 1965). The bauxite deposit
in the Irwinton district resembles the associated kaolin in color. Predominant colors of the
bauxite in this district are gray, white cream, and buff (Lang et al., 1965). Lang et al., (1965)
described the mineralogy of the bauxite deposit in Irwinton district as a mixture of gibbsite and
kaolinite with some minor impurities. The gibbsite and the kaolinite were indicated as crystalline
and not amorphous, though they are fine grained (Lang et al., 1965). It was also stated that the
chief impurity in the bauxite is silica which occurs in the kaolinte. Samples analyzed in this
study did not show the presence of silica in the form of quartz (Lang et al., 1965).
7
1.3 Bauxite Deposits of Hall Mine and Veneer Mine, Wilkinson County, Georgia
The Hall Mine and Veneer Mines (Figure 3) are located in Wilkinson County, Georgia.
Wilkinson County (Figure 3) at the central margin of the coastal plain physiographical province
is approximately 30 miles east of Macon (Emmons, 1917). The Hall and Veneer Mines are
presently operated by Imerys.
There is no present mining activity of bauxite deposit in the Hall and Veneer Mines.
However, there is an extensive mining operation of kaolin in the two mines, which provide
opportunity to observe exposed bauxite deposits. The bauxite deposit in these mines is spottily
distributed. These bauxite deposits are different from the Andersonville deposit which are
extensive as described by Hurst and Pickering (1997).
Bauxite deposits found in Hall and Veneer Mines occur near the contact between the
Upper Cretaceous undifferentiated formation, and the Tertiary Claiborne formation (Figure 2).
These bauxites are flat lying unconsolidated clays and sands with some pisoids (Emmons, 1917).
Bauxite deposits of Hall and Veneer Mines are hosted by kaolin deposits. Hurst and
Pickering (1989) subdivided the sedimentary hosted kaolin deposits by texture into hard and soft
types. The hard kaolin is difficult to break, they are greater than 70% kaolin by weight and show
rough, hackly fracture. The soft kaolins are less than 70% kaolin by weight and can easily break
to show smooth, conchoidal fractures (Pruett, 2000). The Bauxite deposit in the Hall mine is
associated with hard kaolin, and the Veneer bauxite deposit is also associated with hard kaolin.
Schroeder et al., (2004) described the kaolin deposit in the lower to the middle Eocene Huber
formation in Hall mine as hard kaolin. This kaolin displays color zones, which are evidence of
an oxidative weathering front. The kaolin zones in the Hall mine vary from grey to pink to
8
cream. White et al., (1991) stated that grey kaolin is colored by pyrite, kerogen and ferrous
silicates.
0
0
6
12
18
Miles
29
Kilometers
Figure 3: Highway Map of Wilkinson County, Georgia showing the Hall Mine (32 ° 46’
16.02’’N 83 ° 08’ 13.26’’W ) and Veneer Mine (32 ° 49’ 50 .07”N 83 ° 04’ 07.49”W)
9
Lang et al. (1965) described a site located between Cowpea Branch of Big Sandy Creek
and Highway 57, which is close to the location of the Hall Mine in a profile. The constructed
section is based on drilled holes over 1000 feet and spaced between 200 to 300 feet apart. A
micaceous sand is at the base, which is overlain by a high grade kaolin within which are several
lenses of bauxite. Lang et al., (1965) reported that the sand, clay and fuller’s earth that are
above the kaolin in the area are of Eocene age.
Shearer (1917) also described some bauxite that cropped out along stream which is about
seven and half meters north of Wilkinson County. This location is close to Veneer Mine. He
described the base of the outcrop as light colored kaolinitic sand and interbedded layers of white
clay. A white kaolin is above and this grade upward into the soft red bauxite which consists of a
red pissolite in a matrix of white sandy clay. At the top, the bauxite grade into kaolin, the kaolins
grade laterally into sandy bauxite. The bauxite in this area occupies the center and top portion of
the kaolin deposit. An unconformity separates this from the deposits above which are of Eocene
Jackson Group. The formation in this group is the Barnwell formation which consists of sandy
clay with some conglomerate and small pieces of bauxite and kaolin.
The geologic framework of the bauxite deposit in Australia and coastal British Guiana
now: Guyana and Surinam are similar to the study area (Austin, 1972). The deposits in Australia
occur in sedimentary rocks of Cretaceous to Tertiary age (Loughnan and Bayliss, 1961).
10
1.4 Purpose of Study
The purpose of this study is to constrain an origin for the bauxite deposits in Hall and
Veneer Mines in Wilkinson County by examining the mineralogy and chemistry of the bauxite.
The data from this study is compared with the data published by Lukas et al., (1982) on the
origin of bauxite deposits in Eufaula, Alabama, and the results by Hurst and Pickering (1997).
11
2
METHODS
2.1 Field Data Methods
Representative samples of bauxite deposits were collected from Hall and Veneer Mines
operated by Imerys in Wilkinson County, Georgia. These samples were collected with guidance
from Mr. Greg Hatfield to show the variety of samples present in their mines. The samples
collected were from strip mines. Bauxite deposits are exposed in the kaolin and bauxite samples
were collected from different places in the mines. Some associated kaolins were also collected
to establish the type of kaolin that are associated with the bauxite deposit in the two mines. Two
samples were collected from the Hall Mine and three samples were collected from the Veneer
Mine. A sixth sample used in the analysis is part of sample 5 which show evidence of
transformation of kaolin to bauxite.
A rock hammer was used for the collection and the samples were stored in a plastic bag.
Each sample collected was labeled to determine their locations. About 2 kg of samples were
collected from each location. Bauxite deposit of the Hall mine is hosted by hard kaolin and the
bauxite of the Veneer mine is hosted by soft kaolin. The bauxite samples have the same color
with the host kaolin.
2.2 Sample Preparation
Representative samples collected from the two mines (Hall and Veneer Mines) were
gently crushed into powder by a mortar and pestle. These powdered samples were used for both
X-ray diffraction (XRD) and X-ray fluorescence (XRF) analyses to determine respectively the
mineralogy and major element composition. The sample mount for the X-ray diffraction were
12
prepared using the back-fill techniques to produce a random oriented mount (Moore and
Reynolds 1997).
2.3 X-ray diffraction (XRD)
Powder X-ray diffraction analyses were conducted on the randomly oriented bauxite
samples using a Philips X-ray diffractometer at Georgia State University with CuKα radiation.
Random back filled mounts were scanned from 10 degrees 2θ to 60 degrees 2θ, X-rays were
generated at 35KV and 15mA. The mineralogical identification from the diffraction pattern was
conducted by comparison to Moore and Reynolds (1997), Brindley and Brown (1980), and Berry
(1974). The d-spacings used to identify the minerals in the bauxite are shown in Table 1.
Aluminum corresponds to the sample holder.
Table 1: The d-spacings (Angstroms) used to identify minerals in bauxite samples.
Gibbsite Kaolinite Anatase Goethite Boehmite Nordstrandite
4.84
7.12
3.51
4.19 6.122
3.86
4.39
4.4
2.43
3.37
3.35
3.57
2.37
2.55
3.19
2.55
2.33
2.48
2.48
2.49
1.89
2.29
2.49
2.43
1.69
2.23
2.28
2.37
1.66
2.18
2.24
2.29
1.49
2.16
2.16
1.48
2.02
2.03
1.91
2.02
1.83
1.99
1.78
1.91
1.69
1.8
1.66
1.75
1.61
1.69
1.56
1.68
1.5
1.65
1.58
Aluminum
2.33
2.02
13
2.4 X-ray Fluorescence (XRF) Analysis
Major elements oxides and trace elements concentration were determined by X-ray
fluorescence (XRF) spectrometry at the University of Georgia, Athens. Six samples of bauxite
deposits were prepared following borate (50:50 Li2B4O7: LiBO2) fusion techniques and ten drops
of LiNO3 and NH3 were added to the crucible to make the sample more liquid. The crucible is
placed into an oven at 1050oC for major element analyses. Ten (10.000) grams of the powdered
bauxite samples were pressed into 40 mm diameter briquettes for trace element analysis using a
polymethacrylate binder that is dissolved in acetone. Both the glass disk and the briquettes were
analyzed on a Philips 2.4KW sequential spectrometer fitted with flow detectors, PX1, PE002,
Ge111 crystals and LiF 200, and collimators using method of Mee et al., (1996) and Taggart and
Siems (2002). A previously prepared calibration curve was used to determine the
concentration, which is derived from analyses of reference materials of USGS. The loss of
ignition (LOI) of the bauxite samples were determined gravimetrically by roasting 0.8 g separate
sample of the bauxite powders at 925oC for 45 minutes.
Major and trace element concentration of bauxite samples from Hall and Veneer mines were
also carried out at Georgia State University using a computer controlled Rigaku 3270
wavelength dispersive X-ray fluorescence (XRF) spectrometry with a 60 kilowatt generator. The
data from this equipment was not used for the study. The data contain a very high value (105 wt
%) of total composition of major elements when added to the loss of ignition. The high value of
total composition of major elements in the bauxite samples obtained from Georgia State
University lab could be from the method of sample preparation and the time of roasting of the
sample. There are differences in the methods used in the Georgia State and in the University of
Georgia lab. In Georgia State lab, the bauxite samples were not kept in desiccators to preserve
14
moisture after weight measurement was carried out before roasting the samples in the oven at
1100 oC. In the University of Georgia lab, the bauxite samples were placed in a desiccator
immediately after the weight measurement before roasting the samples in the oven at 925oC.
2.5 Chemical Index of Alteration (CIA) Analysis
The Chemical Index of Alteration, developed by Nesbitt and Young (1982), is a useful index of
the degree of weathering on sedimentary rocks. The measure of the degree of weathering of
bauxite deposit in Hall and Veneer Mines is obtained by calculation of the chemical index of
alteration (CIA) using molecular proportions where CIA= [Al2O3/ (Al2O3+ CaO*+ Na2O+
K2O)]x100. CaO was not corrected for calcite due to absence of calcite in the samples.
3.0 RESULTS
3.1 Sample Description
Sample HA-1 from the Hall mine is 5Y8/1 from Munsell soil color chart. The bauxite
grains are mixture of sand and clay and are round in shape. This sample is hard and pisolitic in
texture.
Sample HA-2 from Hall mine is 5Y8/1 from Munsell soil color chart. It is hard and
pisolitic in texture. The grains are rounded and a mixture of sand and clay.
Sample VE-3 from Veneer mine is 5Y8/1 from Munsell soil color chart. This sample is
composed of sand and clay and round in shape. The sample is soft and pisolitic in texture.
Sample VE-4 from Veneer mine is 5Y8/1 from Munsell soil color chart. The sample is
soft and pisolitic in texture. The grains are round in shape and composed of sand and clay.
15
Sample VE-5A from Veneer mine is 5Y8/1 from Munsell soil color chart. The sample is
soft and pisolitic in texture. The grains are round in shape and composed of sand and clay
Sample VE-5B from Veneer mine . is 5Y8/1 from Munsell soil color chart. It is hard like
samples from the Hall mine. There are little visible pisoids in the sample. The grains are round
and composed of sand and clay.
3.2 Mineralogy Results
The whole rock samples include presence of kaolinite (Al2Si2O5(OH)4), goethite FeO(OH),
gibbsite (Al(OH)3), anatase (TiO2), nordstrandite (Al(OH)3), and boehmite (γ-AlO(OH). All the
samples analyzed from the Hall Mine have kaolinite, goethite, anatase, nordstrandite and
gibbsite. Gibbsite is present in two of the samples from the Veneer Mine (VE-3) and (VE-4).
Sample VE-4 from the Veneer Mine also contains some boehmite. The two samples without
gibbsite (VE-5A and VE-5B), only contain kaolinite, goethite, nordstrandite and anatase. Quartz
was not found in the bauxite deposits in the two mines. No muscovite and biotite were found in
the samples.
HA-1
HA-2
16
VE-3
VE-4
17
VE-5A
VE-5B
VE-5A
18
19
3.3 Major Element Determinations
Major element data of the bauxite deposits from Hall and Veneer Mine are presented in
Table 2 and Figure 7. The SiO2 in the bauxite samples ranges from 27.79 to 54.52 wt.%, the TiO2
content ranges from 1.28 to 6.57 wt.%. The Al2O3 content ranges from 27.99 to 46.88 wt.%, and
the Fe2O3 content in the sample ranges from 0.7 to 12.11 wt.%. MnO, MgO, CaO, Na2O, P2O5
and K2O are < 1 wt.% in all samples. The major element data is good to +/- 0.01% absolute.
Table 2: Major Element analyses for Hall and Veneer Mines. All values are reported as wt. %.
Samples
LOI
TOTALS
HA-1
36.51
1.276
41.05
0.7
0.004
0.3
0.02
0.02
0.04
0.033
21.0
101.0
HA-2
27.79
2.792
46.88
1.38
0.005
0.36
0.02
0.03
0.04
0.042
21.8
101.1
VE-3
46.29
6.572
34.09
1.1
0.01
0.25
0.05
0.03
0.03
0.086
12.8
101.3
VE-4
31.41
2.1
42.01
1.74
0.007
0.32
0.06
0.02
0.07
0.061
23.9
101.7
VE-5A
36.19
3.601
27.99
12.11
0.01
0.19
0.02
0.04
0.03
0.06
21.7
101.9
VE-5B
54.52
3.752
30.5
0.76
0.014
0.22
0.12
0.02
0.04
0.118
10.6
100.7
CIA
99.81
99.82
99.76
99.63
99.74
99.44
SiO2
TiO2
Al2O3
Fe2O3
MnO
MgO
CaO
Wt.%
Na2O
K2O
P2O5
60
50
40
30
20
10
0
HA-1
HA-2
VE-3
VE-4
VE-5A
VE-5B
Figure: 7 Major Element analysis of bauxite deposits in Hall and Veneer Mines.
20
The values of the ratio of the oxides of titanium (TiO2) to alumina (Al2O3) in the bauxite deposit
in the Hall and Veneer Mines are also shown in Figure 8. There are non uniform TiO2/Al2O3
values in the bauxite samples.
0.25
0.2
TiO2/Al2O3
0.15
0.1
TiO2/Al2O3
0.05
0
HA-1
HA-2
VE-3
VE-4
VE-5A
VE-5B
Figure 8: TiO2/Al2O3 ratios of bauxite deposits in Hall and Veneer Mines.
3.4 Chemical Index of Alteration (CIA) Results
The CIA values of the bauxite deposit in Hall and Veneer Mines range from 99.4 to 99.8
(Table 2).
3.5 Trace Element Results
Trace elements data of samples from Hall and Veneer Mines are presented in Table 3. Zr
is the most abundant trace element in the bauxite samples. The values of the Zr in the samples
(Figure 9) range from 460 to 1790 ppm. Low amounts (<100ppm) of Ni, Cu, Zn, Rb, Sr, Y, Nb,
21
Ce, La, and Pb are present in all the samples. The values of V and Cr are higher: V ranges from
210ppm to 416ppm. Cr ranges from 108ppm to 326ppm.
Table 3: Trace Element analyses for Hall and Veneer mines. All values are reported in ppm.
Samples
V
Cr
Ni
Cu
Zn
Rb
Sr
Y
Zr
Nb
Ce
La
Pb
HA-1
210
267
1
1
11
9
23
17
460
26
68
6
3
HA-2
221
253
2
3
10
9
31
38
948
61
81
14
7
VE-3
416
187
8
50
27
9
61
69
1790
127
170
89
58
VE-4
324
326
6
9
10
10
17
40
921
43
67
6
6
VE-5A
256
170
30
54
17
8
53
29
785
60
146
69
42
VE-5B
257
108
25
148
27
8
88
66
1585
76
218
108
55
2000
1800
ppm
1600
1400
HA-1
1200
HA-2
1000
VE-3
800
VE-4
600
VE-5A
400
VE-5B
200
0
V
Cr
Ni
Cu
Zn
Rb
Sr
Y
Zr
Nb
Ce
La
Figure 9: Trace element analyses (ppm) of bauxite deposits in Hall and Veneer mines.
Pb
22
From the trace element analysis, Zr is the most abundant element in the all the samples
from Hall and Veneer Mine ( Figure 9). V, Cr, Nb and Ce are also high in all the bauxite
samples.
The mineralogy and geochemical data collected from Hall and Veneer Mines are presented in
Table 4. ‘
23
Table 4: Mineralogical and Geochemical data of the bauxite deposit in Hall Mine and Veneer
Mine.
Samples
SiO2
HA-1
36.51
HA-2
27.79
VE-3
46.29
VE-4
31.41
VE-5A
36.19
VE-5B
54.52
TiO2
1.276
2.792
6.572
2.1
3.601
3.752
Al2O3
41.05
46.88
34.09
42.01
27.99
30.5
Fe2O3
0.7
1.38
1.1
1.74
12.11
0.76
MnO
MgO
CaO
Na2O
0.004
0.3
0.02
0.02
0.005
0.36
0.02
0.03
0.01
0.25
0.05
0.03
0.007
0.32
0.06
0.02
0.01
0.19
0.02
0.04
0.014
0.22
0.12
0.02
K2O
0.04
0.04
0.03
0.07
0.03
0.04
P2O5
0.033
0.042
0.086
0.061
0.06
0.118
21
101
21.8
101.1
12.8
101.3
23.9
101.7
21.7
101.9
10.6
100.7
210
267
1
1
11
9
23
17
460
26
68
6
3
221
253
2
3
10
9
31
38
948
61
81
14
7
416
187
8
50
27
9
61
69
1790
127
170
89
58
324
326
6
9
10
10
17
40
921
43
67
6
6
256
170
30
54
17
8
53
29
785
60
146
69
42
257
108
25
148
27
8
88
66
1585
76
218
108
55
X
X
X
X
X
_
X
X
X
X
X
_
X
X
X
X
X
_
X
X
X
X
X
X
X
_
X
X
X
_
X
_
X
X
X
_
LOI
TOTALS
CIA
V
Cr
Ni
Cu
Zn
Rb
Sr
Y
Zr
Nb
Ce
La
Pb
Minerals
Kaolinite
Gibbsite
Goethite
Anatase
Nordstrandite
Boehmite
24
4
DISCUSSION
The bauxite deposits in Hall and Veneer mines, Wilkinson County, Georgia are different
in mineralogy and chemistry from the deposit in Eufaula, Alabama as studied by Lukas et al.,
(1982). Minerals present in the bauxite deposits of the Hall and Veneer Mines are kaolinite,
gibbsite, anatase, goethite, nordstrandite and boehmite. The Eufaula deposit, however, contains
kaolinite, gibbsite, muscovite and quartz (Lukas et al., 1982). Boehmite is absent in the Eufaula
deposit (Lukas et al., 1982). The absent of quartz and micas in the Hall and Veneer bauxite
deposit is an evidence of complete alteration of the clay phases (micas and feldspars) into
bauxite. Several lines of data are discussed supporting weathering origin for bauxite in the Hall
and Veneer mines.
Gibbsite will break down under suitable acidic conditions to boehmite, which reacts with
depolymerized silica solution to form kaolin (De Kimpe et al., 1964). The reverse is the
situation in sample VE-4 of the Veneer mine which contains some traces of boehmite and a
higher alumina value compared to kaolinite. Silica is gradually removed from the kaolin in this
area, leaving behind traces of boehmite. The presence of boehmite in this sample is an evidence
of intense weathering of kaolin to form bauxite deposit. This idea is readily testable by use of
Transmission Electron Microscopy (TEM) data.
The Chemical Index of Alteration (CIA) values derived from major element composition
of the bauxite deposit in Hall and Veneer Mines (Table 2), show extremely high values (99).
Calculated CIA value of the average of the major element composition of river sediments
published by Hurst and Pickering (1997) is also extremely high (96). Alkaline and Alkaline
earth metals (Na, Ca, Mg, K) elements are low in the bauxite deposits of the Hall and Veneer
25
Mines due to intense chemical weathering. The low values of these elements also establish a
weathering origin for the deposits. The immobile elements (Al, Si, and Fe) during weathering
maintain their enriched values. These immobile elements are high in the bauxite deposits of the
Hall and Veneer Mines. These CIA values, high residual elements (Al, Si, Fe), and low alkali
metals support an intense weathering origin for these bauxite deposits.
The cause of intense chemical weathering may result from reaction with groundwater and
precipitation. High temperature, rainfall and regional groundwater system in this region have
induced an intense weathering on the deposit (Hurst and Pickering, 1997). The bauxite deposits
in the Hall and Veneer Mines are located near recharge areas where intense post depositional
chemical weathering occurs.
Goldschmidt (1954) states that titanium and aluminum form hydrolyzate ions (ions with
excess water) and should be concentrated in weathered sequences on a homogeneous parent
rock. The TiO2/Al2O3 values plotted in Figure 8 of the bauxite deposits in the Hall and Veneer
Mines were variable. Given the high CIA values, this data shows that the amount of detrital
parent materials differed in amounts, and that the parent materials are likely a mixture in the
area. The TiO2/Al2O3 values plotted in Figure 8 are similar to the TiO2/Al2O3 values published
by Lukas et al., (1982) which also show variation in parent materials. The plot by Lukas et al.,
(1982) also did not yield a straight line as expected in an in situ weathering condition.
The presence of pisoids in the bauxite deposit in Hall and Veneer Mines show that the
parent materials were transported within and to the Coastal Plain. This is an evidence of
transported origin for the parent material. Pisoids are also found in the Eufaula bauxite deposit
(Lukas et al., 1982).
26
Hurst and Pickering, (1997) proposed that goethite and hematite form only in unsaturated
oxic zones, where groundwater contained chelating organics from bacteria. Iron oxide is the first
product of the chemical weathering of biotite (Farmer and Wilson 1970). Bacteria are the most
versatile and abundant organisms on the earth (Margulus and Sagan 1986; Gould 1996; Brown
and Sherif 1996). They are virtually in all surface and subsurface environment (Chapelle 1993).
Bacteria drive a low temperature reaction that is not thermodynamically spontaneous to enhance
weathering. Fe, Mn and V are immobile and insoluble except in soluble complexes at low pH.
The rate of weathering was relatively high in the unsaturated zone. The abundance of trace
fossils in the kaolins of Southeastern United States show that bacteria were involved during the
period of sediment deposition (Barker 1985; Barker and Hurst 1992). The mineralogy of the
bauxite deposits in Hall and Veneer Mines show the presence of goethite. This mineral is only
formed in the unsaturated oxic zones, where post depositional weathering is most intense. The
values of iron oxide in the bauxite samples of Hall and Veneer mines range from 0.7 to 12.11
wt.%. This value is similar to the Fe value of the kaolin deposit studied by Hurst and Pickering
(1997). Fe in the samples from Hall and Veneer Mines is insoluble and immobile, and these
support post depositional alteration in the area. Given the CIA of river sediments (Hurst and
Pickering, 1997), significant weathering likely occurred in Piedmont source area of these Coastal
plain sediments prior to the deposition of Coastal Plain sediments.
The bauxite deposit in these mines can be described as bauxitic-kaolin. Sample VE-5A
and VE-5B collected from the Veneer mine show bauxitization of the kaolin in the mine to
bauxite. VE-5A and VE-5B of the Veneer mine are kaolins in chemistry and mineralogy. The
VE-5B sample is close to kaolin while VE-5A is close to bauxite in chemistry. Hurst and
Pickering (1997) also proposed that the same post depositional alteration that produced kaolin
27
also produced bauxite. They state that kaolin was first formed and when total weathering was
greater, bauxitic-kaolin was formed, and when total weathering was greater still then bauxite
deposit as in the Andersonville was formed.
28
5
CONCLUSION
In the Hall and Veneer mines, there is evidence of transportation of bauxite sediments
based on non uniform TiO2/Al2O3 values and the presence of pisoids. Considerable weathering
of Piedmont source rocks is likely based on CIA of river sediments. However, post depositional
weathering of coastal plain sediments also takes place to form the bauxite deposits in this area.
The weathering processes that take place in the unsaturated oxic zones where these bauxite
deposits are found are capable of producing large deposit of the bauxite ore in the area. The
presence of boehmite, goethite low values of the alkali metals, alkali earth metals, extremely
high CIA values which is over 99 are evidence of a weathering origin for the deposits.
Mineralogy, major element determinations and trace element analysis (Zr in particular)
of the bauxite deposits in Hall and Veneer Mines is consistent with an intense weathering in the
recharge oxic zone and the bauxite deposit can only be formed by a post depositional alteration
of parent mud that was transported from the Piedmont and deposited in the Coastal Plain.
The post depositional weathering that produce the kaolin, also produce the bauxite
deposits in the area. The kaolin was first formed and when total weathering was greater, bauxitic
kaolin was formed, and when total weathering was greater still bauxite deposit was formed. This
mechanism can be tested further through TEM analysis.
29
6
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35
APPENDICES
Hall 1
7.12
4.83
4.41
4.17
3.84
3.56
3.37
3.11
2.54
2.48
2.43
2.37
2.32
2.24
2.19
2.16
2.03
2
1.97
1.92
1.88
1.83
1.8
1.78
1.74
1.68
1.66
1.58
1.55
K
G
K
g
N
K,
G, K, g
G
K, g
G, K, g
G, K, g,
G, K, A
A
G, K, g
G, g
G
A
g
G, K
G, g
K, A
g
G, g
K, g
G
K, A, g
K, g, A,
G
G, g
Hall 2
7.23
4.88
4.39
4.19
3.86
3.59
3.37
3.19
2.56
2.5
2.46
2.38
2.34
2.29
2.25
2.19
2.16
2.03
1.99
1.92
1.89
1.8
1.75
1.69
1.66
1.59
1.57
1.55
K
G
K, G
g
N
K, A
G, g
G
K, g
K
G, A, g
G, A
A
g, G,
G
G, g
G
A
G
g, G
A, K
G, g
G
G, A, g
K, g, A,
G
G, g
G
Ven 3
7.18
4.35
4.15
3.86
3.57
3.35
3.1
2.74
2.56
2.49
2.38
2.33
2.29
2.18
2.02
1.98
1.94
1.89
1.83
1.77
1.66
1.58
1.54
K
G
g
N
A, K
G
G
g
K
g, K
G, A, K
A
G, K
g
A
G, K
g
A, K
g
g, K
G, A, K g
G
G, K
ven 4
7.12
6.12
4.85
4.37
4.15
3.84
3.56
3.37
3.17
3.1
2.55
2.49
2.44
2.37
2.33
2.28
2.23
2.16
2.04
1.99
1.91
1.89
1.8
1.75
1.68
1.65
1.59
K
B
G
G
g
N
K, A
G, g
G
G
G, g
K, g
K, g
K, G, A
A, K
G
G, g
G, g
A
G, K
G, g
A, K
G, g
G, K
K, G,
K, G
G
36
Ven 5a
7.23
4.15
3.84
3.56
3.38
2.73
2.55
2.49
2.38
2.34
2.18
2.02
1.99
1.93
1.9
1.78
1.66
1.61
1.58
1.55
K
g
N
K, A
g
g
K
K, A, g
K, A
A
g
A
g
g
K, g
K, A, g
g
g
Ven 5b
7.1
4.45
4.15
3.86
3.35
2.56
2.5
2.38
2.33
2.19
2.02
1.99
1.94
1.9
1.83
1.78
1.66
1.62
1.54
K
K
g
K, A
g
K, g
K
K,A, g
A
K, g
A
K, g
g
A, g
g
K, g
K, A, g
g
K