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.

A Tentative Study of Relationship between Mantle Plumes, Supercontinents and Orogenic Gold Deposits

2013 ◽  
Vol 734-737 ◽  
pp. 265-268
Author(s):  
Jun Hao Cui ◽  
Tao Ren
Keyword(s):  
Mantle Plume ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
Orogenic Gold ◽  
Upper Crust ◽  
Orogenic Gold Deposits ◽  
Orogenic Gold Deposit ◽  
The Earth ◽  
Tectonic Environment ◽  
The Relationship

On the basis of predecessors study, this paper found that outbreak frequency of mantle plume is increase, while scale is reduce. The mantle plume provides ore-forming minerals to orogenic gold deposits, as well as affords force to supercontinent formation and decomposition, for the more controls the global tectonic. Supercontinent is the movement of upper crust that could be cause by combine factors of cold and heat mantle plume. Supercontinent supply suitable tectonic environment for orogenic gold deposits. Further, we discuss the relationship between mantle plume, supercontinent and orogenic gold deposit on space and time. With the evolution of the earth, especially the energy loss, the frequency of orogenic gold mineralization is increasing, while the scale is reducing.

scholarly journals Deep Carbon and the Life Cycle of Large Igneous Provinces

Elements ◽  
2019 ◽  
Vol 15 (5) ◽  
pp. 319-324 ◽  
Author(s):  
Benjamin A. Black ◽  
Sally A. Gibson
Keyword(s):  
Life Cycle ◽  
Plate Boundary ◽  
Flood Basalts ◽  
Relative Significance ◽  
Large Igneous Provinces ◽  
Igneous Provinces ◽  
Alkaline Magmas ◽  
Low Volume ◽  
Potential Carbon

Carbon is central to the formation and environmental impact of large igneous provinces (LIPs). These vast magmatic events occur over geologically short timescales and include voluminous flood basalts, along with silicic and low-volume alkaline magmas. Surface outgassing of CO2 from flood basalts may average up to 3,000 Mt per year during LIP emplacement and is subsidized by fractionating magmas deep in the crust. The large quantities of carbon mobilized in LIPs may be sourced from the convecting mantle, lithospheric mantle and crust. The relative significance of each potential carbon source is poorly known and probably varies between LIPs. Because LIPs draw on mantle reservoirs typically untapped during plate boundary magmatism, they are integral to Earth's long-term carbon cycle.

Coupled supercontinent–mantle plume events evidenced by oceanic plume record

Geology ◽  
2019 ◽  
Vol 48 (2) ◽  
pp. 159-163 ◽  
Author(s):  
Luc S. Doucet ◽  
Zheng-Xiang Li ◽  
Richard E. Ernst ◽  
Uwe Kirscher ◽  
Hamed Gamal El Dien ◽  
...  
Keyword(s):  
Mantle Plume ◽  
Shear Velocity ◽  
Temporal Variations ◽  
Large Igneous Provinces ◽  
First Order ◽  
The Past ◽  
Igneous Provinces ◽  
Island Basalt ◽  
Supercontinent Cycle ◽  
Low Shear

Abstract The most dominant features in the present-day lower mantle are the two antipodal African and Pacific large low-shear-velocity provinces (LLSVPs). How and when these two structures formed, and whether they are fixed and long lived through Earth history or dynamic and linked to the supercontinent cycles, remain first-order geodynamic questions. Hotspots and large igneous provinces (LIPs) are mostly generated above LLSVPs, and it is widely accepted that the African LLSVP existed by at least ca. 200 Ma beneath the supercontinent Pangea. Whereas the continental LIP record has been used to decipher the spatial and temporal variations of plume activity under the continents, plume records of the oceanic realm before ca. 170 Ma are mostly missing due to oceanic subduction. Here, we present the first compilation of an Oceanic Large Igneous Provinces database (O-LIPdb), which represents the preserved oceanic LIP and oceanic island basalt occurrences preserved in ophiolites. Using this database, we are able to reconstruct and compare the record of mantle plume activity in both the continental and oceanic realms for the past 2 b.y., spanning three supercontinent cycles. Time-series analysis reveals hints of similar cyclicity of the plume activity in the continent and oceanic realms, both exhibiting a periodicity of ∼500 m.y. that is comparable to the supercontinent cycle, albeit with a slight phase delay. Our results argue for dynamic LLSVPs where the supercontinent cycle and global subduction geometry control the formation and locations of the plumes.

scholarly journals Lithospheric mantle evolution monitored by overlapping large igneous provinces: Case study in southern Africa

Lithos ◽  
2009 ◽  
Vol 107 (3-4) ◽  
pp. 257-268 ◽  
Author(s):  
F. Jourdan ◽  
H. Bertrand ◽  
G. Féraud ◽  
B. Le Gall ◽  
M.K. Watkeys
Keyword(s):  
Southern Africa ◽  
Lithospheric Mantle ◽  
Large Igneous Provinces ◽  
Mantle Evolution ◽  
Igneous Provinces

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.

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