Incipient carbonate melting drives precious metal and sulfur mobilisation in the mantle

Abstract

We present results from high-pressure, high-temperature experiments that generate incipient carbonate melts at mantle conditions (~90km depth and temperatures between 900 - 1050℃). We show that these melts can effectively sequester sulfur, in its oxidised form of sulfate, platinum group elements, and first-row transition metals from mantle lithologies of peridotite and pyroxenite. These primitive oxidised melts may be effective agents to dissolve, redistribute and concentrate sulfur as well as chalcophile metals within the mantle, and from the mantle to shallower regions within the Earth, where localised dynamic physio-chemical processes can lead to ore genesis at various crustal depths. It is proposed that these carbonate-sulfur rich melts may be more widespread than previously thought, and may play a first order role in the metallogenic enhancement of localised and predictable lithospheric domains.

The effects of local variations in conditions on carbon storage and release in the continental mantle

“…High platinum group elements (PGE) contents in nephelinites and basanites in eastern China may be caused by oxidative breakdown of sulphides and the transport of PGEs in carbonate melts [ 110 ]. On a smaller scale, coupled transmission electron microscopy and Laser-ICP-MS investigations of experimental carbonate melts indicate that Ni, Co, Cu and PGE may be scavenged by carbonate melts [ 111 ] and thus remobilized when melting occurs at the continents’ base.…”