Record of mid-Archaean subduction from metamorphism in the Barberton terrain, South Africa

Article Abstract:

Mineral assemblages of garnet-albite that record pressures of 1.2-1.5 GPa at temperatures 600-650 degrees Celsius from supracrustal amphibolites are reported from the mid- Archaean Barberton granitoid-greenstone terrain in South Africa, which exhibit geothermal gradients of 12-15 degrees Celsius, similar to subduction zones. The high-pressure, low-temperature conditions present metamorphic evidence for cold and strong lithosphere, and also subduction-driven tectonic processes during the evolution of the early Earth.

Science & research, Research, Subduction zones (Geology), Subduction zones, Metamorphism (Geology), Petrogenesis

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Discovery of a 25-cm asteroid clast in the giant Morokweng impact crater, South Africa

Article Abstract:

The discovery of a large, unaltered, fossil meteorite and several smaller fragments within the impact melt of the giant, 145 Myr old Morokweng crater, South Africa was reported. It was discovered that the chondritic chromium isotope ratios and identical platinum-group element ratios to the bulk impact melt, allows the unambiguous characterization of an impactor at a large crater that suggests the meteorite incorporated part of the LL chondrite parent body, not represented by objects reaching the earth.

Analysis, Discovery and exploration, Craters, Meteorites, Impact craters

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