Amazing stuff! Precious metals should have collected towards the core of the earth not on or near the surface.
"... Recent research from scientists around the world has established that precious metals such as gold and platinum came to Earth billions of years ago after the early proto-Earth collided with large, moon-sized bodies in space, which left behind deposits of materials that were folded into what is today’s Earth. ...
theory centers around a thin, “transient” region of the mantle, where the shallow part of the mantle melts and the deeper part remains solid. The researchers found that this region has peculiar dynamic properties that can efficiently trap falling metallic components and slowly deliver them to the rest of the mantle.
Their theory posits that this delivery is still ongoing, with the remnants of the transient region appearing as “large low-shear-velocity provinces” — well-known geophysical anomalies in the deep mantle.
“This transient region almost always forms when a big impactor hits the early Earth ..." ... "
From the significance and abstract:
"Significance
Earth’s mantle abundance of highly siderophile elements (HSEs), such as gold and platinum, is inexplicably high, given their strong tendency to be contained in its core. This problem has long been thought to be explained by the delivery of HSEs via bombardment of leftover planetesimals. We show that this explanation in its conventional form is geodynamically implausible because of the inability of Earth’s mantle to retain the impactor’s metals and their HSE budget. However, large impacts can still deliver a sufficient amount of HSEs to the mantle, if we consider the effects of local magma oceans generated by these collisions. We also show that this process provides a natural explanation for the enigmatic seismic structure observed in the present-day Earth’s mantle.
Abstract
Highly siderophile elements (HSEs; namely Ru, Rh, Pd, Re, Os, Ir, Pt, and Au) in Earth’s mantle require the addition of metals after the formation of Earth’s core. Early, large collisions have the potential to deliver metals, but the details of their mixing with Earth’s mantle remain unresolved. As a large projectile disrupts and penetrates Earth’s mantle, a fraction of its metallic core may directly merge with Earth’s core. Ensuing gravitational instabilities remove the remaining projectile’s core stranded in Earth’s mantle, leaving the latter deprived of HSEs. Here, we propose a framework that can efficiently retain the metallic components during large impacts. The mechanism is based on the ubiquitous presence of a partially molten region in the mantle beneath an impact-generated magma ocean, and it involves rapid three-phase flow with solid silicate, molten silicate, and liquid metal as well as long-term mixing by mantle convection. In addition, large low-shear-velocity provinces in the lower mantle may originate from compositional heterogeneities resulting from the proposed three-phase flow during high-energy collisions."
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