Aspects of volcanism and metamorphism of the Onverwacht group lavas in the southwestern portion of the Barberton Greenstone Belt:
Saved in:
| Main Author: | |
|---|---|
| Format: | Book |
| Language: | English |
| Published: |
Pretoria
Council for Geoscience
1999
|
| Series: | South Africa / Council for Geoscience: Memoir
84 |
| Subjects: | |
| Online Access: | Inhaltsverzeichnis |
| Physical Description: | VII, 232 S. Ill., graph. Darst., Kt. |
| ISBN: | 1875061630 |
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| 100 | 1 | |a Cloete, M. |e Verfasser |4 aut | |
| 245 | 1 | 0 | |a Aspects of volcanism and metamorphism of the Onverwacht group lavas in the southwestern portion of the Barberton Greenstone Belt |c by M. Cloete |
| 264 | 1 | |a Pretoria |b Council for Geoscience |c 1999 | |
| 300 | |a VII, 232 S. |b Ill., graph. Darst., Kt. | ||
| 336 | |b txt |2 rdacontent | ||
| 337 | |b n |2 rdamedia | ||
| 338 | |b nc |2 rdacarrier | ||
| 490 | 1 | |a South Africa / Council for Geoscience: Memoir |v 84 | |
| 650 | 4 | |a Greenstone belts |z South Africa | |
| 650 | 4 | |a Rocks, Igneous |z South Africa | |
| 650 | 4 | |a Rocks, Metamorphic |z South Africa | |
| 651 | 4 | |a Südafrika (Staat) | |
| 651 | 4 | |a Barberton Greenstone Belt (South Africa and Swaziland) | |
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| 999 | |a oai:aleph.bib-bvb.de:BVB01-008712400 | ||
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| adam_text | IMAGE 1
CONTENTS
ABSTRACT VII
1. INTRODUCTION 1
1.1 GEOLOGICAL SETTING AND SIGNIFICANCE OF THE BARBERTON GREENSTONE BELT
1 1.2 STRATIGRAPHY 2
1.3 INTRUSIVE ROCKS 7
1.4 GEOCHRONOLOGY 7
1.5 METAMORPHISM AND PREVIOUS WORK 8
1.5.1 BARBERTON GREENSTONE BELT METAMORPHISM 8
1.5.2 AUSTRALIAN GREENSTONE BELT METAMORPHISM 9
1.5.3 CANADIAN GREENSTONE BELT METAMORPHISM 9
1.6 AIMS AND MOTIVATION 10
1.7 OBJECTIVES 11
1.8 SAMPLE PREPARATION AND ANALYTICAL TECHNIQUES 11
2. VOLCANOLOGY OF THE KOMATI AND HOOGGENOEG FORMATIONS 14
2.1 INTRODUCTION 14
2.2 NOMENCLATURE 14
2.3 FLOW-ROCK MORPHOLOGY 14
2.3.1 MASSIVE FLOWS 15
2.3.2 FEEDER DYKES 19
2.3.3 PILLOWED FLOWS 19
2.3.4 PILLOW BRECCIA 19
2.3.5 HYALOTUFFS 21
2.4 INTERNAL PILLOW STRUCTURES 21
2.4.1 DRAIN-AWAY CAVITIES 21
2.4.2 PILLOW TEXTURES 22
2.4.3 RELICT IGNEOUS MINERALS ; 25
2.5 LAVA RHEOLOGY 27
2.5.1 VISCOSITY 27
2.5.2 VESICULATION . 29
2.6 ESTIMATION OF EMPLACEMENT DEPTHS 31
2.6.1 OCEAN DEPTH DURING KOMATI FORMATION TIME 31
2.6.2 OCEAN DEPTH DURING HOOGGENOEG FORMATION TIME 34
2.7 AGE OF VOLCANISM 35
2.8 DISCUSSION 35
2.8.1 QUENCHED MAGMA 36
2.8.2 SUBAQUEOUS EMPLACEMENT OF FLOWS 36
2.8.3 SHEET-FLOOD FLOWS VS CHANNELISED FLOWS 37
2.8.4 EMPLACEMENT MECHANISMS 38
2.8.5 DEPTH OF EMPLACEMENT 38
2.8.6 EMPLACEMENT ENVIRONMENT 39
2.8.7 KOMATIITE GEOCHEMISTRY 39
2.8.8 ONVERWACHT OCEANIC PLATEAU 39
2.9 SUMMARY 40
2.10 CONCLUSIONS 43
3. SEA-FLOOR METAMORPHISM 44
3.1 INTRODUCTION 44
3.1.1 REVIEW OF SOME CONCEPTS OF SEA-FLOOR METAMORPHISM 44
3.1.1.1 SAMPLING OF HYDROTHERMAL VENTS 44
3.1.1.2 EXPERIMENTS SIMULATING SEA-FLOOR METAMORPHISM 45
3.1.1.3 BEHAVIOUR OF HEATED SEA WATER , 45
3.1.1.4 CONSTRAINTS FROM SEA-FLOOR METAMORPHOSED ROCKS 45
3.2 PETROGRAPHY OF PILLOW ALTERATION ZONES . 46
3.2.1 INTER-PILLOW CAVITIES 46
3.2.2 PILLOW RIMS 46
IMAGE 2
3.2.2.1 CHLORITISED/AMPHIBOLITISED PILLOW MARGINS 46
3.2.2.2 ALBITISED PILLOW RIMS 48
3.2.2.3 SILICIFIED PILLOW RIMS 48
3.2.3 PILLOW CORES 49
3.2.3.1 COOLING-CRACK VEINLETS 49
3.2.3.2 COOLING-CRACK SELVAGES 49
3.2.3.3 PILLOW CORE 51
3.3 SULPHIDE PETROGRAPHY 51
3.3.1 MODAL DISTRIBUTION OF SULPHIDES 53
3.3.2 SULPHIDE CHEMISTRY 55
3.3.2.1 CHALCOPYRITE 55
3.3.2.2 PYRRHOTITE 55
3.3.2.3 PYRITE 57
3.4 GEOCHEMISTRY OF PILLOW ALTERATION 59
3.4.1 PILLOW CORE VS PILLOW-EXTERIOR ELEMENT PLOTS 62
3.4.2 PILLOW CORE-COOLING-CRACK SELVAGE ABUNDANCE PLOTS 65
3.4.3 ELEMENT FLUXES 71
3.4.3.1 SELECTION OF LEAST-ALTERED SAMPLE 71
3.4.3.2 SELECTION OF IMMOBILE ELEMENTS 71
3.4.3.3 ELEMENT-FLUX RELATIONSHIPS 73
3.5 SULPHUR ISOTOPES 79
3.6 INTERPRETATION OF RESULTS 82
3.6.1 ALTERATION PETROGRAPHY 82
3.6.1.1 PHYSICAL PARAMETERS OF ALTERATION 82
3.6.1.2 ALTERATION SEQUENCES 83
3.6.2 SULPHIDE PETROGRAPHY 88
3.6.2.1 PILLOW-CORE SULPHIDES 89
3.6.2.2 INTER-PILLOW SULPHIDES 90
3.6.3 SULPHUR ISOTOPES 91
3.6.4 ALTERATION GEOCHEMISTRY 92
3.6.4.1 ELEMENT DISTRIBUTIONS 92
3.6.4.2 ELEMENT FLUXES 93
3.6.5 A SUMMARY OF RESULTS 94
3.7 DISCUSSION 95
3.7.1 HYDROTHERMAL CONVECTION IN THE KOMATI FORMATION 95
3.7.1.1 HEAT INPUT 95
3.7.1.2 PERMEABILITY DISTRIBUTION 95
3.7.1.3 MODEL FEASIBILITY 95
3.7.2 FLUID CIRCULATION OF THE HOOGGENOEG FORMATION 98
3.8 CONCLUSIONS 98
4. METAMORPHISM OF THE KOMATI AND HOOGGENOEG FORMATIONS 99 4.1
INTRODUCTION 99
4.2 PETROGRAPHY AND METAMORPHIC ZONES 99
4.2.1 ZONE A 101
4.2.2 ZONE B ! 101
4.2.3 ZONE C 106
4.2.4 ZONE D 106
4.2.5 BULK COMPOSITION 108
4.2.6 ATTAINMENT OF EQUILIBRIUM 108
4.3 MINERAL CHEMISTRY 109
4.3.1 CHLORITE 109
4.3.2 EPIDOTE -. 110
4.3.3 PLAGIOCLASE I LL
4.3.4 AMPHIBOLE 113
4.4 GEOTHERMOMETRY AND GEOBAROMETRY 117
4.4.1 GEOTHERMOMETRY 117
4.4.2 PRESSURE PLOTS 117
4.4.3 GEOTHERMOBAROMETRY 119
IV
IMAGE 3
4.5 FLUID INCLUSIONS 119
4.5.1 NATURE AND OCCURRENCE 119
4.5.2 FLUID-INCLUSION PETROGRAPHY 119
4.5.2.1 FLUID INCLUSIONS OF ZONE A METABASITES 122
4.5.2.2 FLUID INCLUSIONS OF ZONE B METABASITES 122
4.5.2.3 FLUID INCLUSIONS OF ZONE D METABASITES 122
4.5.3 FLUID-INCLUSION MICROTHERMOMETRY 123
4.5.3.1 AQUEOUS INCLUSIONS 123
4.5.3.2 H 2 O-CO 2 INCLUSIONS 130
4.5.4 SALINITY ESTIMATES 130
4.6 CONDITIONS OF METAMORPHISM 131
4.6.1 MINERAL EQUILIBRIA 131
4.6.2 FLUID-INCLUSION THERMOBAROMETRY 134
4.6.3 RELATIONSHIP BETWEEN FLUID INCLUSIONS AND METAMORPHISM 136
4.6.3.1 STATIC METAMORPHISM 136
4.6.3.2 DYNAMIC METAMORPHISM 137
4.6.4 FLUID-INCLUSION INTEGRITY 137
4.6.5 RELATIONSHIPS BETWEEN STRATIGRAPHIC LOAD AND CALCULATED PRESSURE
138 4.6.6 RELATIONSHIPS BETWEEN STRATIGRAPHY AND TEMPERATURE 138
4.6.7 BURIAL METAMORPHISM 139
4.6.8 P-T PATHS 139
4.6.8.1 STATICALLY METAMORPHOSED ROCKS 140
4.6.8.2 DYNAMICALLY METAMORPHOSED ROCKS 140
4.6.9 GEOTHERMS 141
4.6.10 CONSTRAINTS ON CRUSTAL SHORTENING 146
4.6.11 METAMORPHISM SUBSEQUENT TO CRUSTAL SHORTENING 146
4.7 SUMMARY 149
4.8 CONCLUSIONS 150
5. TECTONIC DEVELOPMENT OF THE KOMATI AND HOOGGENOEG FORMATIONS:
VOLCANOLOGICAL AND METAMORPHIC PERSPECTIVES 152
INTRODUCTION 152
CRITERIA FOR MODEL CONSTRUCTION 152
SCHEMATIC HISTORY OF THE SOUTHERN PART OF THE BGB 156
THE PERIOD 3 540-3 470 MA 156
THE PERIOD 3 470-3 450 MA 156
THE PERIOD 3 445-3 416 MA 156
THE PERIOD 3 416-3 260 MA 156
THE PERIOD 3 260- 3 2)6 MA 156
THE PERIOD AROUND 3 216 MA 156
DISCUSSION . 156
ARCHAEAN PLATE TECTONICS 156
PRE-ONVERWACHT CRUSTAL HISTORY 157
FORMATION OF THE ONVERWACHT OCEANIC PLATEAU 157
THEESPRUIT FORMATION 158
EMPLACEMENT OF THE OOP ALLOCHTHON (~3 449 MA) 158
MAIN EVENT OF TRONDHJEMITE MAGMATISM 159
KROMBERG AND MENDON FORMATIONS : 159
BUCK RIDGE/MAPEPE HIATUS 160
FIG TREE AND MOODIES SEDIMENTATION 161
BASIN CLOSURE (D 2 ) 162
TONALITIC MAGMATISM 162
IMPLICATIONS FOR ARCHAEAN GEOLOGY 163
ORIGIN OF OCEANIC CRUST 163
SIGNIFICANCE OF THE ONVERWACHT ALLOCHTHON 164
HYDRATION AND DENSITY OF ARCHAEAN OCEANIC CRUST 164
METAMORPHISM OF THE BARBERTON GREENSTONE BELT 166
SEA-FLOOR METAMORPHISM 166
BURIAL METAMORPHISM 167
5.1 5.2 5.2.
5.2. 5.2. 5.2. 5.2. 5.2.1 5.2.1 5.3 5.3.
.1 .2 .3 ,4 .5 .6
[
5.3.2
5.3.:5 5.3.4 5.3.! 5.3.6
5.3. 5.3., 5.3.! 5.3.
5.3. 5.4 5.4.
7 ? ) 10 11
1
5.4.2 5.4. 5.4. 5.4.
5.4.
3 4 4.1 4.2
IMAGE 4
5.4.4.3 DYNAMIC METAMORPHISM 168
5.4.5 METAMORPHISM OF THE THEESPRUIT FORMATION 169
5.4.6 GREENSTONES AND FUTURE METAMORPHIC STUDIES 170
5.5 SUMMARY 170
5.6 CONCLUSION 172
REFERENCES 173
LEGEND: APPENDIX ABBREVIATIONS 185
APPENDIX AMPHIBOLE: A LIST OF AMPHIBOLE ANALYSES OF KOMATI AND
HOOGGENOEG FORMATIONS KOMATIITIC METABASALT 186
APPENDIX CHLORITE: A LIST OF CHLORITE ANALYSES OF KOMATI AND HOOGGENOEG
FORMATIONS PILLOWED KOMATIITIC BASALT 199
APPENDIX EPIDOTE: A LIST OF EPIDOTE ANALYSES OF KOMATI AND HOOGGENOEG
FORMATIONS KOMATIITIC BASALT 204
APPENDIX PLAGIOCLASE: A LIST OF PLAGIOCLASE ANALYSES OF KOMATI AND
HOOGGENOEG FORMATIONS PILLOWED KOMATIITIC BASALT 214
VI
|
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| geographic | Südafrika (Staat) Barberton Greenstone Belt (South Africa and Swaziland) |
| geographic_facet | Südafrika (Staat) Barberton Greenstone Belt (South Africa and Swaziland) |
| id | DE-604.BV012809438 |
| illustrated | Illustrated |
| indexdate | 2024-07-09T18:34:03Z |
| institution | BVB |
| isbn | 1875061630 |
| language | English |
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| physical | VII, 232 S. Ill., graph. Darst., Kt. |
| publishDate | 1999 |
| publishDateSearch | 1999 |
| publishDateSort | 1999 |
| publisher | Council for Geoscience |
| record_format | marc |
| series2 | South Africa / Council for Geoscience: Memoir |
| spelling | Cloete, M. Verfasser aut Aspects of volcanism and metamorphism of the Onverwacht group lavas in the southwestern portion of the Barberton Greenstone Belt by M. Cloete Pretoria Council for Geoscience 1999 VII, 232 S. Ill., graph. Darst., Kt. txt rdacontent n rdamedia nc rdacarrier South Africa / Council for Geoscience: Memoir 84 Greenstone belts South Africa Rocks, Igneous South Africa Rocks, Metamorphic South Africa Südafrika (Staat) Barberton Greenstone Belt (South Africa and Swaziland) Council for Geoscience: Memoir South Africa 84 (DE-604)BV013601842 84 SWB Datenaustausch application/pdf http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&local_base=BVB01&doc_number=008712400&sequence=000001&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA Inhaltsverzeichnis |
| spellingShingle | Cloete, M. Aspects of volcanism and metamorphism of the Onverwacht group lavas in the southwestern portion of the Barberton Greenstone Belt Greenstone belts South Africa Rocks, Igneous South Africa Rocks, Metamorphic South Africa |
| title | Aspects of volcanism and metamorphism of the Onverwacht group lavas in the southwestern portion of the Barberton Greenstone Belt |
| title_auth | Aspects of volcanism and metamorphism of the Onverwacht group lavas in the southwestern portion of the Barberton Greenstone Belt |
| title_exact_search | Aspects of volcanism and metamorphism of the Onverwacht group lavas in the southwestern portion of the Barberton Greenstone Belt |
| title_full | Aspects of volcanism and metamorphism of the Onverwacht group lavas in the southwestern portion of the Barberton Greenstone Belt by M. Cloete |
| title_fullStr | Aspects of volcanism and metamorphism of the Onverwacht group lavas in the southwestern portion of the Barberton Greenstone Belt by M. Cloete |
| title_full_unstemmed | Aspects of volcanism and metamorphism of the Onverwacht group lavas in the southwestern portion of the Barberton Greenstone Belt by M. Cloete |
| title_short | Aspects of volcanism and metamorphism of the Onverwacht group lavas in the southwestern portion of the Barberton Greenstone Belt |
| title_sort | aspects of volcanism and metamorphism of the onverwacht group lavas in the southwestern portion of the barberton greenstone belt |
| topic | Greenstone belts South Africa Rocks, Igneous South Africa Rocks, Metamorphic South Africa |
| topic_facet | Greenstone belts South Africa Rocks, Igneous South Africa Rocks, Metamorphic South Africa Südafrika (Staat) Barberton Greenstone Belt (South Africa and Swaziland) |
| url | http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&local_base=BVB01&doc_number=008712400&sequence=000001&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA |
| volume_link | (DE-604)BV013601842 |
| work_keys_str_mv | AT cloetem aspectsofvolcanismandmetamorphismoftheonverwachtgrouplavasinthesouthwesternportionofthebarbertongreenstonebelt |