Genesis and alteration of the Kalahari and Postmasburg manganese deposits, Griqualand West

490 Pages·2017·29.08 MB·English

by  Gutzmer Jens .

Genesis and alteration of the
Kalahari and Postmasburg manganese deposits,
Griqualand West, South Africa
by
Jens Gutzmer
THESIS
presented in fullfillment of the requirements for the degree of
PHILOSOPHIAE DOCTOR
in
Geology
in the
FACULTY OF SCIENCE
of the
RAND AFRIKAANS UNIVERSITY
JOHANNESBURG
Promoter
Prof. N. J. Beukes
May 1996
Minerals are the basic stuff of the Earth, and their study will always remain at
the core of the Earth Sciences.
The message is simple: If you can't recognize minerals, you won't find mines!
Frank C. Hawthorne
Canadian Mineralogist (1993), Vol. 31, pp. 253-296
(cid:9)(cid:9)
Table of Contents
Acknowledgements (cid:9)
Uittreksel iii
Abstract vii
Kurzfassung (cid:9) xi
Chapter 1: Introduction
General (cid:9) 1
Previous Work (cid:9) 4
Postmasburg manganese field (cid:9) 4
Kalahari manganese field (cid:9) 6
Objective and outline of this thesis (cid:9) 9
Geological Setting (cid:9) 12
General (cid:9) 12
Geological Setting of the Kalahari manganese field (cid:9) 18
Geological Setting of the Postmasburg manganese field (cid:9) 20
References (cid:9) 26
Chapter 2: Metasomatic and supergene alteration
of Early Proterozoic sedimentary manganese ore
at Mamatwan Mine, Kalahari manganese field, South Africa.
Abstract (cid:9) 33
Introduction (cid:9) 33
Geological Setting (cid:9) 35
Analytical Techniques (cid:9) 38
Lateral macroscopic zonation in ore composition (cid:9) 39
Alteration along faults (cid:9) 39
Alteration along joints and veins (cid:9) 43
Lateral mineralogical variation (cid:9) 44
Alteration along faults (cid:9) 44
Alteration along veins and joints (cid:9) 47
Petrographic zonation and paragenetic relationships (cid:9) 49
Alteration along faults (cid:9) 49
Alteration around veins and joints (cid:9) 54
- Mineral chemistry (cid:9) 54
Geochemistry (cid:9) 58
Stable isotope geochemistry (cid:9) 64
Discussion (cid:9) 67
Conclusions (cid:9) 72
Acknowledgements (cid:9) 72
References (cid:9) 73
Chapter 3: Minerogenesis of the Kalahari manganese field,
South Africa
Abstract (cid:9) 75
Introduction (cid:9) 76
Previous mineralogical work (cid:9) 78
Geological setting (cid:9) 79
Paragenesis of the chemosedimentary braunite-lutite mineral association (cid:9) 84
Late diagenetic/ lower greenschist facies metamorphic mineral association (cid:9) 84
The Wessels event of hydrothermal alteration (cid:9) 86
Sugilite calc-silicate association (cid:9) 89
Hausmannite-rich association (Wessels-type ore) (cid:9) 91
Vein and vug-hosted association (cid:9) 96
The Mamatwan event of hydrothermal alteration (cid:9) 98
The Smartt event of hydrothermal alteration (cid:9) 102
Supergene weathering along the Kalahari unconformity (cid:9) 104
Discussion (cid:9) 105
Conclusions (cid:9) 107
Acknowledgements (cid:9) 108
References (cid:9) 108
Appendix 1: Minerals of the Kalahari manganese field (cid:9) 112
Chapter 4: Effects of mass transfer, compaction and secondary porosity on
hydrothermal upgrading of Paleoproterozoic sedimentary manganese ore
in the Kalahari manganese field, South Africa
Abstract (cid:9) 117
Introduction (cid:9) 117
Geology (cid:9) 120
Sampling and analytical methods (cid:9) 126
Quantitative mineralogical composition and density of manganese ores (cid:9) 127
Geochemistry (cid:9) 134
Estimating compaction amd secondary porosity (cid:9) 135
Mass balance calculations (cid:9) 140
Method (cid:9) 140
Ferruginous style of alteration (cid:9) 142
Siliceous style of alteration (cid:9) 143
Conclusions (cid:9) 144
Acknowledgements (cid:9) 146
References (cid:9) 147
Chapter 5: Tropical terrestrial weathering
and vegetation in the Paleoproterozoic:
Evidence from a pisolithic paleolaterite from South Africa
Abstract (cid:9) 149
Introduction (cid:9) 149
Description of the paleolaterite profile (cid:9) 151
Conclusions (cid:9) 155
References (cid:9) 157
Chapter 6: Petrography and geochemistry of the karst-hosted manganese deposits
in the Postmasburg manganese field, Northern Cape Province, South Africa
Abstract (cid:9) 159
Introduction (cid:9) 160
Analytical techniques (cid:9) 162
Regional geological setting (cid:9) 165
Detailed geological setting (cid:9) 168
Eastern Belt (cid:9) 168
Western Belt (cid:9) 170
Mineralogy and petrography (cid:9) 177
Siliceous manganese ores (cid:9) 177
Fine crystalline bedded ferruginous manganese ores (cid:9) 181
Coarse crystalline ferruginous manganese ores (cid:9) 184
Supergene ores (cid:9) 185
Shales (cid:9) 186
Conglomerates (cid:9) 186
Geochemistry (cid:9) 187
Siliceous ores and Wolhaarkop breccia of the Eastern Belt (cid:9) 187
Ferruginous ores of the Western Belt (cid:9) 188
Supergene ores (cid:9) 191
Dolomite of the Reivilo Formation and wad (cid:9) 192
Geochemical associations (cid:9) 195
Depositional environment and evolution of the manganese ore deposits (cid:9) 195
Wolhaarkop breccia and siliceous manganese ore (cid:9) 195
Ferruginous manganese ore (cid:9) 198
Metamorphism (cid:9) 203
Conclusions (cid:9) 205
Acknowledgements (cid:9) 205
References (cid:9) 206
Chapter 7: Mineralogy and mineral chemistry of the manganese ores of the
Postmasburg manganese field, Northern Cape Province, South Africa
Abstract (cid:9) 209
Introduction (cid:9) 209
Analytical techniques (cid:9) 213
Geological setting (cid:9) 214
Petrography of siliceous ores of the Eastern Belt (cid:9) 222
Petrography of ferruginous ores of the Western Belt (cid:9) 224
Petrography of supergene ores (cid:9) 226
Mineral chemistry (cid:9) 226
Braunite (cid:9) 226
Bixbyite (cid:9) 231
Hausmannite (cid:9) 234
(cid:9)
Manganomelane group of minerals and pyrolusite (cid:9) 236
Gamagarite, apatite and barite (cid:9) 238
Diaspore and silicate minerals (cid:9) 240
Discussion (cid:9) 241
The braunite group 241
Other minerals (cid:9) 244
Metamorphism (cid:9) 245
Supergene alteration (cid:9) 247
Conclusions (cid:9) 247
Acknowledgements (cid:9) 248
References (cid:9) 248
Chapter 8: Conclusions
Genesis and alteration of manganese ores in the Kalahari manganese field (cid:9) 253
Genesis and alteration of manganese ores of the Postmasburg manganese field (cid:9) 258
Two manganese fields - one story 9 (cid:9) 261
Suggestions for future work (cid:9) 263
References (cid:9) 264
Appendix I: Analytical techniques
I.1 (cid:9) Sample preparation (cid:9) A 1
1.2 (cid:9) Analytical Chemistry (cid:9) A 1
1.2.1 X-ray fluorescence spectrometry (cid:9) A2
1.2.2 Inductively coupled - atomic emission spectrometry (ICP-AES) . (cid:9) A4
12.3 Atomic absorption spectrometry (AAS) (cid:9) A8
1.2.4 Inductively coupled plasma - mass spectrometry (ICP-MS) (cid:9) A8
1.2.5 Titrimetric Feootal) determination (cid:9) A10
1.2.6 CO2 (total) determination by coulometric titration (cid:9) A 1 0
1.2.7 H2O determination by drying (cid:9) A 1 1
1.2.8 Loss on ignition determination (L.0.1) (cid:9) Al2
1.2.9 Electron microprobe analysis (EMPA) (cid:9) A13
8180,
1.3 (cid:9) Stable (VC, 834S) and radiogenic (87Sr/86Sr) isotope analysis (cid:9) A16
1.4 (cid:9) Density measurement (cid:9) Al6
1.5 (cid:9) X-ray powder diffraction analysis (XRD) (cid:9) Al9
1.6 • Petrography and ore petrography (cid:9) A20
1.7 (cid:9) Fluid inclusion studies (cid:9) A21
1.8 (cid:9) References (cid:9) A22
Appendix II: Sample Descriptions
General (cid:9) A25
II.1 (cid:9) Samples from the Postmasburg manganese field (cid:9) A26
11.2 (cid:9) Samples from the Kalahari manganese field (cid:9) A38
Appendix III: Whole rock geochemical data
General (cid:9) A41
Major and trace element geochemistry of manganese ores (cid:9) A42
III.2 Geochemistry of host-rocks of Mn-ores (cid:9) A62
III.3 Trace element and REE geochemistry of Mn-ores, KMF (ICP-MS) . . . (cid:9) A64
Appendix IV: Phase chemistry
General (cid:9) A69
IV.1 Lower oxides of manganese (cid:9) A70
N.2 Higher oxides of manganese (cid:9) A75
IV.3 Silicates (cid:9) A76
ni.4 Carbonates (cid:9) A81
N.5 Hydroxides, sulphates, phosphates, and vanadates (cid:9) A83
IV.6 Minerals associated with bostonite dykes, KMF (cid:9) A85
IV. 7.1 Igneous phases (cid:9) A85
IV. 7.2 Alteration phases (cid:9) A86
Appendix V: Stable isotope data
Stable isotope data (cid:9) A89
Appendix VI: Fluid inclusion data
Fluid inclusion data (cid:9) A97
Appendix VII: Fault-controlled metasomatic alteration
of Early Proterozoic sedimentary manganese ores in the
Kalahari manganese field, South Africa.
Abstract (cid:9) A113
Introduction (cid:9) A114
Regional geology (cid:9) A115
Distribution of major ore types and zones of ferruginization (cid:9) A118
Sampling (cid:9) A122
Mineralogical variations (cid:9) A125
Petrographical variations (cid:9) A127
Western side of Traverse S (cid:9) A127
Eastern side of Traverse S (cid:9) A131
Traverse 28S-E (cid:9) A132
Traverse 43S-E (cid:9) A133
Mineral chemistry (cid:9) A135
Whole rock geochemistry (cid:9) A141
Discussion (cid:9) A143
Mineral paragenetic model (cid:9) A143
Conceptual hydrothermal model (cid:9) A146
Conclusions (cid:9) A150
Acknowledgements (cid:9) A151
References (cid:9) A151
Appendix VIII: Fault controlled hydrothermal alteration
of Paleoproterozoic manganese ore
in Wessels mine, Kalahari manganese field.
Abstract (cid:9) A153
Introduction (cid:9) A154
Regional geological setting (cid:9) A156
Detailed geological setting (cid:9) A159
Definition of ore types and lateral zonation along sections (cid:9) A164
Lateral mineralogical variations (cid:9) A167
Lateral petrographic zonation and paragenetic relationships (cid:9) A169
Chemical composition of selected minerals (cid:9) A175
Whole rock geochemistry (cid:9) A179
Integrated model of lateral zonation in ores (cid:9) A182
Conceptual genetic model (cid:9) A185
Conclusions (cid:9) A189
Acknowledgements (cid:9) A190
References (cid:9) A191
Appendix IX: Magnetic hausmannite from hydrothermally altered
manganese ore in the Palaeoproterozoic Kalahari manganese deposit,
Transvaal Supergroup, South Africa.
Abstract (cid:9) A193
Introduction (cid:9) A193
Geological setting (cid:9) A195
Petrography and sample preparation (cid:9) A196
Mineral chemistry (cid:9) A200
Crystallography (cid:9) A201
Magnetic mineralogy (cid:9) A203
Discussion (cid:9) A204
Conclusions (cid:9) A209
Acknowledgements (cid:9) A209
References (cid:9) A210