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Craton and thick lithosphere margins: The sites of giant mineral deposits and mineral provinces
Gondwana Research ( IF 6.1 ) Pub Date : 2020-07-01 , DOI: 10.1016/j.gr.2020.06.008 D.I. Groves , M. Santosh
Gondwana Research ( IF 6.1 ) Pub Date : 2020-07-01 , DOI: 10.1016/j.gr.2020.06.008 D.I. Groves , M. Santosh
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Abstract Although most economic geology research is concentrated at the deposit or mineral-system scale for a single well-defined deposit group with a consistent metal association, there are both academic and economic advantages in considering the similar geodynamic setting of deposits having contrasting metal compositions that are traditionally considered unrelated. As an example, there are a range of mineral deposit types or systems that are spatially associated with the margins of long-lived, relatively cold, buoyant Precambrian cratons or lithosphere with thick mantle lithosphere roots. These diverse hypogene deposit groups include world-class to giant BIF-derived iron ores, Kiruna-type Fe-P deposits, anorthosite-hosted ilmenite deposits, IOCG deposits, carbonatite-associated REE-P-Nb-(Cu) ores, intrusion-hosted Ni-Cu-PGE sulfide ores, SEDEX (and MVT) Pb-Zn-Cu deposits, Zambian Copperbelt-type Cu-Co, and IOCG deposits, that provide a high proportion of the global metal inventory. Their preservation, some older than 2 Giga-years, is due to the buoyancy of the thick, cold cratonic lithosphere. Deep extensional fault systems develop on these craton margins during rifting, leading to deposition of continental-shelf sedimentary sequences that provide both suitable host rocks for mineralization and metal and sulfur-rich high-salinity fluid sources. The long-lived lithosphere margins with fluctuating stress fields enhance the Pb-Zn-Cu endowment potential of these basins by promoting syn-basinal or later gravity-driven flow of high-salinity brines. Compressional or transpressional reactivation drives syn-orogenic fluid flow to produce the Cu-Co ores of the Zambian Copperbelt, or provide the pre-ore thrust architecture of fluid seals over reactive carbonate sequences for Carlin-type gold ores. The deep faults provided preferred conduits for the emplacement of mafic-ultramafic intrusions, with Ni-Cu-PGE sulfide deposits formed within complexities in the magma plumbing systems. The magmatic–hydrothermal group of carbonatite-related REE-P-Nb-Cu, IOCG deposits, and IRGD systems, and the hydrothermal Carlin-type deposits, all formed under extensional high heat-flow tectonic regimes and derived their ore fluids, with the probable exception of Carlin-type ores, from metal- and volatile-fertilized sub-continental lithosphere below the craton margin. The orogenic gold deposits on craton margins in China were also formed during transpressional geodynamic episodes from ore fluids with a fertilized mantle lithosphere source. A detailed analysis shows that most deposit types are sited within 100 km of the margins of Archean cratons, although sediment-hosted Pb-Zn-Cu deposits, that show no obvious relationships to craton margins, require a buffer of 200 km for thick Paleoproterozoic lithospheric blocks. These features brought out in this paper can potentially aid mineral exploration in terms of initial area selection within the available search space, but precise definition of these buffer zones is difficult due to heterogeneity of constraints on the precise location of craton and thick lithosphere boundaries globally. However, the search space for this diverse group of deposits is limited to between 10 and 35% of the continental crust in different regions, within which geophysical methodologies can further constrain more prospective targets.
更新日期：2020-07-01
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