Chapter 31: Geologic Evidence of Syngenetic Gold in the Witwatersrand Goldfields, South Africa

2020 ◽  
pp. 645-668
Author(s):  
Hartwig E. Frimmel ◽  
Glen T. Nwaila
Keyword(s):  
South Africa ◽  
Land Surface ◽  
Microbial Mats ◽  
Gold Mineralization ◽  
Flood Basalt ◽  
Gold Deposits ◽  
Kaapvaal Craton ◽  
Exceptional Preservation ◽  
Placer Deposits ◽  
Geologic Setting

Abstract The Mesoarchean Witwatersrand Basin in the central Kaapvaal craton, South Africa, has been the largest gold-producing province in history. Although mining has reached a very mature state, this ore province remains the biggest regional gold anomaly in the world. Most recent research on the Witwatersrand gold deposits has focused on postdepositional processes, often on a microscale, thereby constraining conditions of gold transport in the host conglomerates. Here we review past and current observations on the geologic setting of the orebodies and first-order controls on gold mineralization, all of which strengthen the argument for a primarily syngenetic model. The Witwatersrand deposits are regarded as remnants of a gold megaevent at 2.9 Ga when environmental conditions are suggested to have been suitable for intense gold flux off the Archean land surface and early photosynthesizing microbes could act as trap sites for riverine and possibly shallow-marine gold. Sedimentary reworking of gold-rich microbial mats led to rich placer deposits which, in turn, became sources of younger placers higher up in the stratigraphy. The same gold concentration mechanism most likely operated on all Mesoarchean land masses, not only on the Kaapvaal craton. The uniqueness of the Witwatersrand gold province is explained by exceptional preservation of these easily erodible, largely continental sediments beneath a thick cover of flood basalt and a later impact melt sheet in the middle of a buoyant craton, with little tectonic overprint over the past two billion years.

scholarly journals Neoarchean large igneous provinces on the Kaapvaal Craton in southern Africa re-define the formation of the Ventersdorp Supergroup and its temporal equivalents

2020 ◽  
Vol 132 (9-10) ◽  
pp. 1829-1844 ◽  
Author(s):  
Ashley Gumsley ◽  
Joaen Stamsnijder ◽  
Emilie Larsson ◽  
Ulf Söderlund ◽  
Tomas Naeraa ◽  
...  
Keyword(s):  
Mantle Plume ◽  
Southern Africa ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
Kaapvaal Craton ◽  
Ionization Mass ◽  
Flood Basalts ◽  
Large Igneous Provinces ◽  
Igneous Provinces ◽  
World Class

Abstract U-Pb geochronology on baddeleyite is a powerful technique that can be applied effectively to chronostratigraphy. In southern Africa, the Kaapvaal Craton hosts a well-preserved Mesoarchean to Paleoproterozoic geological record, including the Neoarchean Ventersdorp Supergroup. It overlies the Witwatersrand Supergroup and its world-class gold deposits. The Ventersdorp Supergroup comprises the Klipriviersberg Group, Platberg Group, and Pniel Group. However, the exact timing of formation of the Ventersdorp Supergroup is controversial. Here we present 2789 ± 4 Ma and 2787 ± 2 Ma U-Pb isotope dilution-thermal ionization mass spectrometry (ID-TIMS) baddeleyite ages and geochemistry on mafic sills intruding the Witwatersrand Supergroup, and we interpret these sills as feeders to the overlying Klipriviersberg Group flood basalts. This constrains the age of the Witwatersrand Supergroup and gold mineralization to at least ca. 2.79 Ga. We also report 2729 ± 5 Ma and 2724 ± 7 Ma U-Pb ID-TIMS baddeleyite ages and geochemistry from a mafic sill intruding the Pongola Supergroup and on an east-northeast–trending mafic dike, respectively. These new ages distinguish two of the Ventersdorp Supergroup magmatic events: the Klipriviersberg and Platberg. The Ventersdorp Supergroup can now be shown to initiate and terminate with two large igneous provinces (LIPs), the Klipriviersberg and Allanridge, which are separated by Platberg volcanism and sedimentation. The age of the Klipriviersberg LIP is 2791–2779 Ma, and Platberg volcanism occurred at 2754–2709 Ma. The Allanridge LIP occurred between 2709–2683 Ma. Klipriviersberg, Platberg, and Allanridge magmatism may be genetically related to mantle plume(s). Higher heat flow and crustal melting resulted as a mantle plume impinged below the Kaapvaal Craton lithosphere, and this was associated with rifting and the formation of LIPs.

Studi Awal Geologi di Daerah Beruang Kanan Kabupaten Gunung Mas Propinsi Kalimantan Tengah

PROMINE ◽  
2018 ◽  
Vol 6 (1) ◽  
pp. 1-11
Author(s):  
Retno Anjarwati ◽  
Arifudin Idrus ◽  
Lucas Donny Setijadji
Keyword(s):  
Gold Mineralization ◽  
Volcanic Rocks ◽  
Gold Deposits ◽  
Central Kalimantan ◽  
Magmatic Arc ◽  
Tertiary Sediment ◽  
Copper Gold ◽  
Regional Tectonic ◽  
Mineralization Processes ◽  
High Yields

The regional tectonic conditions of the KSK Contract of Work are located in the mid-Tertiary magmatic arc (Carlile and Mitchell, 1994) which host a number of epithermal gold deposits (eg, Kelian, Indon, Muro) and significant prospects such as Muyup, Masupa Ria, Gunung Mas and Mirah. Copper-gold mineralization in the KSK Contract of Work is associated with a number of intrusions that have occupied the shallow-scale crust at the Mesozoic metamorphic intercellular junction to the south and continuously into the Lower Tertiary sediment toward the water. This intrusion is interpreted to be part of the Oligocene arc of Central Kalimantan (in Carlile and Mitchell 1994) Volcanic rocks and associated volcanoes are older than intrusions, possibly aged Cretaceous and exposed together with all three contacts (Carlile and Mitchell, 1994) some researchers contribute details about the geological and mineralogical background, and some papers for that are published for the Beruang Kanan region and beyond but no one can confirm the genesis type of the Beruang Kanan region The mineralization of the Beruang Kanan area is generally composed by high yields of epithermal sulphide mineralization. with Cu-Au mineralization This high epithermal sulphide deposition coats the upper part of the Cu-Au porphyry precipitate associated with mineralization processes that are generally controlled by the structure

PALEOGEOGRAPHIC CONSTRAINTS FROM THE KAAPVAAL CRATON (SOUTH AFRICA) IN THE IMMEDIATE AFTERMATH OF THE GREAT OXIDATION EVENT

2020 ◽  
Author(s):  
Sarah Slotznick ◽  
◽  
David A.D. Evans ◽  
Francis Sousa ◽  
Nicholas L. Swanson-Hysell
Keyword(s):  
South Africa ◽  
Kaapvaal Craton ◽  
Great Oxidation Event

scholarly journals Genesis of the Late Cretaceous Longquanzhan Gold Deposit in the Central Tan-Lu Fault Zone, Shandong Province, China: Constraints from Noble Gas and Sulfur Isotopes

Minerals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 250
Author(s):  
Chuanpeng Liu ◽  
Wenjie Shi ◽  
Junhao Wei ◽  
Huan Li ◽  
Aiping Feng ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Fault Zone ◽  
Late Cretaceous ◽  
Genetic Model ◽  
Gold Mineralization ◽  
Sulfur Isotopes ◽  
Noble Gas ◽  
Gold Deposits ◽  
Shandong Province ◽  
Magma Sources

The Longquanzhan deposit is one of the largest gold deposits in the Yi-Shu fault zone (central section of the Tan-Lu fault zone) in Shandong Province, China. It is an altered-rock type gold deposit in which ore bodies mainly occur at the contact zone between the overlying Cretaceous rocks and the underlying Neoarchean gneissic monzogranite. Shi et al. reported that this deposit formed at 96 ± 2 Ma using pyrite Rb–Sr dating method and represents a new gold mineralization event in the Shandong Province in 2014. In this paper, we present new He–Ar–S isotopic compositions to further decipher the sources of fluids responsible for the Longquanzhan gold mineralization. The results show that the δ34S values of pyrites vary between 0.9‰ and 4.4‰ with an average of 2.3‰. Inclusion-trapped fluids in ore sulfides have 3He/4He and 40Ar/36Ar ratios of 0.14–0.78 Ra and 482–1811, respectively. These isotopic data indicate that the ore fluids are derived from a magmatic source, which is dominated by crustal components with minor mantle contribution. Air-saturated water may be also involved in the hydrothermal system during the magmatic fluids ascending or at the shallow deposit site. We suggest that the crust-mantle mixing signature of the Longquanzhan gold deposit is genetically related to the Late Cretaceous lithospheric thinning along the Tan-Lu fault zone, which triggers constantly uplifting of the asthenosphere surface and persistent ascending of the isotherm plane to form the gold mineralization-related crustal level magma sources. This genetic model can be applied, to some extent, to explain the ore genesis of other deposits near or within the Tan-Lu fault belt.

scholarly journals Oxygen Fugacity and Volatile Content of Syntectonic Magmatism in the Neoarchean Abitibi Greenstone Belt, Superior Province, Canada

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 966
Author(s):  
Baptiste Madon ◽  
Lucie Mathieu ◽  
Jeffrey H. Marsh
Keyword(s):  
Oxygen Fugacity ◽  
Greenstone Belt ◽  
Inductively Coupled Plasma ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
Hydrothermal Systems ◽  
Chemical Diversity ◽  
Temporal Association ◽  
Volatile Content ◽  
Abitibi Subprovince

Neoarchean syntectonic intrusions from the Chibougamau area, northeastern Abitibi Subprovince (greenstone belt), may be genetically related to intrusion related gold mineralization. These magmatic-hydrothermal systems share common features with orogenic gold deposits, such as spatial and temporal association with syntectonic magmatism. Genetic association with magmatism, however, remains controversial for many greenstone belt hosted Au deposits. To precisely identify the link between syntectonic magmas and gold mineralization in the Abitibi Subprovince, major and trace-element compositions of whole rock, zircon, apatite, and amphibole grains were measured for five intrusions in the Chibougamau area; the Anville, Saussure, Chevrillon, Opémisca, and Lac Line Plutons. The selected intrusions are representative of the chemical diversity of synvolcanic (TTG suite) and syntectonic (e.g., sanukitoid, alkaline intrusion) magmatism. Chemical data enable calculation of oxygen fugacity and volatile content, and these parameters were interpreted using data collected by electron microprobe and laser ablation-inductively coupled plasma-mass spectrometry. The zircon and apatite data and associated oxygen fugacity values in magma indicate that the youngest magmas are the most oxidized. Moreover, similar oxygen fugacity and high volatile content for both the Saussure Pluton and the mineralized Lac Line intrusion may indicate a possible prospective mineralized system associated with the syntectonic Saussure intrusion.

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