SummaryOrogenic gold deposits represent a coherent deposit class that were deposited from low-salinity CO2-rich fluids over a range of crustal depths from 3 to 20 km. They are widely considered to have formed from crustal metamorphic fluids generated at the amphibolite-greenschist-facies transition. However, recent research, particularly in China, shows that only a sub-crustal source of fluid is viable and that devolatilization of subduction slabs and overlying sediment wedges is the most plausible source of the auriferous fluids. An alternative source is devolatilization of fertilized mantle lithosphere that was earlier metasomatized by subduction-related fluids. This recognition of a subduction-related origin allows the orogenic gold deposits to be placed into a coherent, subduction-related dynamic model in which all epigenetic gold deposits formed during evolution of a convergent margin. The earliest deposits that formed from subduction-related magmatic-hydrothermal fluids during mild compression are inter-related porphyry Cu-Au, high-sulfidation epithermal Ag-Au and skarn deposits in volcanic and continental arcs. Subsequent mild extension resulted in formation of low-sulfidation epithermal Ag-Au in volcanic and continental back-arcs and gold-rich VMS systems in volcanic back-arcs. Orogenic gold deposits then developed under transpression during late orogenesis in the convergent margin. The initiation of orogenic collapse saw the formation of IRGDs and Carlin-type gold deposits related to hybrid magmas, formed by melting of subduction-related metasomatized lithosphere, in far back-arc environments. Finally, following supercontinent assembly, IOCG deposits formed on the margins of continental blocks during extension, mantle up-welling and melting of subduction-related fertilized lithosphere that released highly volatile magmatic-hydrothermal fluid systems into the crust.
The Jiaodong gold province in northeastern China is the country's premier gold resource and globally one of the most important gold provinces. The late Early Cretaceous gold metallogeny in this belt remains an enigma as it is hosted in the Archean Jiaobei Terrane of the North China Block and, to a lesser extent, within the Palaeoproterozoic Sulu Terrane of the South China Block. The driving force for widespread Late Jurassic and Early Cretaceous granitic magmatism, the switchover from a compressional to extensional tectonic regime, and gold mineralization are considered to be a combination of plate subduction with lithospheric delamination and consequent asthenospheric upwelling. Although many aspects related to the genesis of the gold deposits in Jiaodong have been resolved, the spatial distribution of the world‐class gold deposits in this belt, which is of vital importance to brownfields and greenfields exploration, has been poorly understood in terms of the structural evolution of the province. In the northwestern segment of the Jiaobei Terrane, the world‐class gold deposits of Sanshandao in the west, through Jiaojia, to Linglong in the east define a broadly E–W corridor. This corridor links a series of east‐verging jogs on ore‐controlling NNE‐trending oblique‐slip faults that are subparallel to an lithospheric‐scale Tan‐Lu Fault to the west. There is cryptic evidence that these jogs line up in the E–W trend due to reactivation of Palaeoproterozoic to Mesozoic faults and folds that were part of the structural architecture of the terranes prior to the gold event. These jogs induced deviations in the local principal stresses relative to regional equivalent stresses, with resultant heterogeneous strain, increased rock permeability, and focussed ore‐fluid ingress. Both disseminated/microbreccia‐stockwork and vein‐type gold deposits formed in this corridor, with the former being predominant and the latter having a higher gold grade. In contrast, predominant vein‐type gold deposits in the eastern segment of the Jiaobei and Sulu terranes tend to form N–S corridors. These vein‐type ores may relate to rotational strain induced by movement on pairs of more linear NNE‐trending faults with the same kinematic movement sense.
Orogenic lode gold deposits formed within a range of crustal environments over most of the Yilgarn craton from 2640 to 2630 Ma, but there is little evidence for a causative widespread tectonomagmatic event at this time in the most highly mineralized greenstone terranes. In the exposed deeper crustal levels of the southwest Yilgarn craton, however, field, geochemical, Pb isotope, and SHRIMP U-Pb zircon studies define a continent-continent collisional event with a widespread thermal anomaly, probably due to lithospheric delamination at this time. It is proposed that this event was of sufficient scale to drive the giant upper-crustal fluid circulation systems, with lateral and vertical flow at the scale of hundreds and tens of kilometers, respectively, that produced the widespread gold mineralization.
Research Article| September 01, 1987 Archean cratons, diamond and platinum: Evidence for coupled long-lived crust-mantle systems David I. Groves; David I. Groves 1Department of Geology, University of Western Australia, Nedlands 6009, Western Australia Search for other works by this author on: GSW Google Scholar Susan E. Ho; Susan E. Ho 1Department of Geology, University of Western Australia, Nedlands 6009, Western Australia Search for other works by this author on: GSW Google Scholar Nicholas M.S. Rock; Nicholas M.S. Rock 1Department of Geology, University of Western Australia, Nedlands 6009, Western Australia Search for other works by this author on: GSW Google Scholar Mark E. Barley; Mark E. Barley 1Department of Geology, University of Western Australia, Nedlands 6009, Western Australia Search for other works by this author on: GSW Google Scholar Maureen T. Muggeridge Maureen T. Muggeridge 1Department of Geology, University of Western Australia, Nedlands 6009, Western Australia Search for other works by this author on: GSW Google Scholar Author and Article Information David I. Groves 1Department of Geology, University of Western Australia, Nedlands 6009, Western Australia Susan E. Ho 1Department of Geology, University of Western Australia, Nedlands 6009, Western Australia Nicholas M.S. Rock 1Department of Geology, University of Western Australia, Nedlands 6009, Western Australia Mark E. Barley 1Department of Geology, University of Western Australia, Nedlands 6009, Western Australia Maureen T. Muggeridge 1Department of Geology, University of Western Australia, Nedlands 6009, Western Australia Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1987) 15 (9): 801–805. https://doi.org/10.1130/0091-7613(1987)15<801:ACDAPE>2.0.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation David I. Groves, Susan E. Ho, Nicholas M.S. Rock, Mark E. Barley, Maureen T. Muggeridge; Archean cratons, diamond and platinum: Evidence for coupled long-lived crust-mantle systems. Geology 1987;; 15 (9): 801–805. doi: https://doi.org/10.1130/0091-7613(1987)15<801:ACDAPE>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Diamondiferous intrusions and magmatic Pt-Pd deposits are both concentrated on, or adjacent to, the oldest cratons, those with >3.0 Ga high-grade gneiss terranes and/or greenstone belts. Given the old age (>3.0 Ga) of peridotitic inclusions both in diamonds and in kimberlites, diamonds presumably grew in mantle depleted in basaltic major elements near the base of thickened lithosphere and below early sialic nuclei. Most genetic models for magmatic Pt-Pd deposits require a Pt-Pd–enriched, high–Mg-Si melt generated from analogously depleted mantle. The depleted mantle was most likely formed by removal of basaltic melts that contributed to Archean intracratonic greenstone belts. Extensive melting also decreased density and increased rigidity beneath ancient cratons, favoring stabilization and preservation of thick Archean continental lithosphere. Overall, these considerations suggest that localized, thick sialic crust and rigid lithosphere developed before 3.0 Ga, forming enduring, coupled crust-mantle systems below ancient sialic nuclei, the sites of selectively preserved greenstone belts. The data confirm that Early Archean terranes are highly prospective for post-Archean magmatic ore deposits. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
The Southern Cross Province in the Archean Yilgarn Block of Western Australia comprises large dome-shaped granitoid bodies surrounded by narrow greenstone belts. Determination of the emplacement mechanism of these domes is fundamental for understanding the tectonic history of this region. Many structures in the greenstone belts show trends which reflect their tectonic relationships with the granitoid domes. Some of these structures host large gold occurrences. The domes have concentric foliation patterns, both within the granitoids themselves, and in the neighbouring greenstone belts. The smaller domes only have radial mineral lineation patterns in their wall rocks, but the largest dome, the Ghooli Dome, has also a tangential pattern. The prevailing gentle dip of the foliation in the centre of this dome and the abundance of greenstone xenoliths suggest that the present exposures are close to its roof. Geothermometry and geobarometry on mineral assemblages in the Ghooli granitoid and its xenoliths show that its crystallisation temperature was just above 700 °C at a relatively high pressure of 4.3 to 6.2 kbar. These P-T conditions are higher than those inferred for peak metamorphism in the greenstones. Therefore, this granitoid must have been emplaced initially at crustal levels deeper than the maximum burial of the greenstones which flank the dome. The Ghooli Dome has a SHRIMP U-Pb zircon age of 2691 ± 7 Ma. Diapiric rise of the granitoid plutons taking place in a regional compressive tectonic regime is considered to be the most likely mechanism for the final emplacement of these bodies into their host rock at about 2636–2620 Ma. This concept is preferred over the alternatives because it best reconciles the calculated P-T data, the observed structural patterns, the presence of pegmatites and aplites in the host rock, and the orientation of the mineral-bearing structures.
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