A metasomatized lithospheric mantle control on the metallogenic signature of post-subduction magmatism

Abstract

Ore deposits are loci on Earth where energy and mass flux are greatly enhanced and focussed, acting as magnifying lenses into metal transport, fractionation and concentration mechanisms through the lithosphere. Here we show that the metallogenic architecture of the lithosphere is illuminated by the geochemical signatures of metasomatised mantle rocks and post-subduction magmatic-hydrothermal mineral systems. Our data reveal that anomalously gold and tellurium rich magmatic sulfides in mantle-derived magmas emplaced in the lower crust share a common metallogenic signature with upper crustal porphyry-epithermal ore systems. We propose that a trans-lithospheric continuum exists whereby post-subduction magmas transporting metal-rich sulfide cargoes play a fundamental role in fluxing metals into the crust from metasomatised lithospheric mantle. Therefore, ore deposits are not merely associated with isolated zones where serendipitous happenstance has produced mineralisation. Rather, they are depositional points along the mantle-to-upper crust pathway of magmas and hydrothermal fluids, synthesising the concentrated metallogenic budget available.

Fluxing of mantle carbon as a physical agent for metallogenic fertilization of the crust

“…5e) 6 . The dissolution of sulfide will return chalcophile metals and S into the silicate melts 54 (Fig. 5e), which would then only be able to form upper crustal magmatic sulfide deposits if sulfide supersaturation is triggered again, e.g., by assimilation of crustal S 59 or prolonged fractional crystallization.…”

The Role of Magma Mixing in Generating Granodioritic Intrusions Related to Cu–W Mineralization: A Case Study from Qiaomaishan Deposit, Eastern China

“…Our results suggest that Qiaomaishan adakites have high Ce 4+ /Ce 3+ and Eu/Eu* ratios (Figure 14a), coupled with high log f O 2 located above the FMQ buffer, as shown in Figure 14b; these ratios are similar to those of other Cu-Au-bearing adakites in the MLYRB and clearly higher than those of the granitoids related to the W-Cu deposits in the Jiangnan Tungsten Belt (Figure 14a), indicating the high oxygen fugacity in the magma source. Importantly, it is widely accepted that the mantle wedges [64] metasomatized by the fluids/melts produced by subducted plates [65] have high oxygen fugacity [66][67][68][69]. Furthermore, in the Lower Yangtze River area, there are widespread mafic magmas underplated at LCC depth as revealed by deep seismic reflection profiles [70].…”

Gold endowments of porphyry deposits controlled by precipitation efficiency

“…The processes leading to the formation of these deposits, to their highly variable metal endowments (<1 to >100 Mt Cu and tens to thousands of tons Au) and to their association with rocks of different chemistry are complex, multi-step, and not well understood [3][4][5] . The majority of porphyry Cu-Au deposits are associated with typical calc-alkaline magmas (often high Sr/Y) in Andean-type subduction zones 1 .…”