Concentration of Platinum Group Elements during the Early Earth Evolution: A Review*

Abstract

Numerous unique geological processes [1] took place during the early Earth evolution; several of them, especially those occurring in the Hadean-Early Archean and later, are reflected in the modern geological (geophysical, geochemical, etc.) pattern. One such significant enigmatic feature is the preservation of extremely dense and heavy platinum group elements (PGEs): Pt, Pd, Rh, Ru, Ir, Os. Concentration of PGEs during this period could have taken place in two ways: 1) presence of particular matter capable of preserving PGEs near the earth's surface, 2) transportation of PGEs by magma flows from deep lithospheric (asthenospheric) layers (slabs) to the subsurface. Clearly, much of the dense and heavy PGEs did not sink through to the Earth's mantle (core) at the time of the magma-ocean, and occur near Earth's surface in abundances for formation of ore deposits with PGE concentrations found to be 2 -3 orders of magnitude greater than those in their host media. Their enrichments are associated in numerous cases with such enigmatic phenomena as formation of anorthosites and anorthosite-bearing layered magmatic intrusions. PGE deposits and mineralization zones are also found in associations with chromitites, dunites and serpentinites. In this review, problems related to the initial concentration and preservation of PGEs, their association with anorthosites, and formation of layered intrusions are discussed in detail. The main aim of this article is analysis of the requirements-initial concentration and preservation of PGE and PGM (Platinum Group Minerals) during the early Earth evolution, as well as examination of the distribution behavior of some PGEs in different ore deposits and meteorites. It is supposed that meteoritic bombardment of Earth has played a significant role in formation of PGEs deposits. Some conclusions made in this article may be useful for developing and enhancing strategies of prospecting for PGEs deposits.

Platinum Group Elements in Geosphere and Anthroposphere: Interplay among the Global Reserves, Urban Ores, Markets and Circular Economy

“…For example, during 2015, 70% of the world's Pt was produced in South Africa [53] and almost exclusively at the Bushveld Complex [1]. Considering that PGEs are crucial as precious metals for investment and critical components for catalytic converters, the strategic importance of South Africa is immense as it holds 80-90% of the world's PGEs reserves [106]. Likewise, 50% of the world's production of rare earth elements comes from the Bayan Obo mine in Mongolia [107].…”

Hydrogen Drives Part of the Reverse Krebs Cycle under Metal or Meteorite Catalysis

“…However, it may be premature to dismiss Rh in a prebiotic context since it is found in meteorites. Platinum metals are found to be locally concentrated in nature in amounts many orders of magnitude higher than their average abundance on earth,[ 56 , 57 , 58 ] and simple mechanisms for the concentration of Rh have been described. [59] Perhaps more importantly, self‐organized chemistry can happen on local, microscopic scales.…”

Wasserstoff ermöglicht Teile des reduktiven Krebs‐Zyklus unter Katalyse von Metallen oder Meteoriten

“…Es ist jedoch verfrüht Rh in einem präbiotischen Kontext auszuschließen, da es in Meteoriten vorkommt. Platinmetalle sind in der Natur lokal in Mengen konzentriert, die um viele Größenordnungen höher sind als ihre durchschnittliche Häufigkeit auf der Erde , [56–58] und es wurden einfache Mechanismen für die Konzentration von Rh beschrieben [59] . Vielleicht noch wichtiger ist, dass selbstorganisierte Chemie auf lokaler, mikroskopischer Ebene stattfinden kann.…”