It is not known whether environmental O2 levels increased in a linear fashion or fluctuated dynamically between the evolution of oxygenic photosynthesis and the later Great Oxidation Event. New rhenium-osmium isotope data from the late Archean Mount McRae Shale, Western Australia, reveal a transient episode of oxidative continental weathering more than 50 million years before the onset of the G...

Modern plate tectonic brings down oceanic crust along subduction zones where it either dehydrates or melts. Those hydrous fluids or melts migrate into the overlying mantle wedge trigerring its melting which produces arc magmas and thus additional continental crust. Nowadays, melting seems to be restricted to cases of young (< 50 Ma) subducted plates. Slab melts are silicic and strongly sodic (t...

The 80-km-wide Vredefort dome is a deeply eroded remnant of the central uplift of the Vredefort Impact Structure. It exposes upturned Archean to Paleo-proterozoic supracrustal strata and a core of Archean crystalline gneisses that have previously been interpreted as an on-edge profile of the crust and upper mantle. Our structural analysis of the gneisses in the core of the dome indicates that s...

The temperature and salinity histories of the oceans are major environmental variables relevant to the course of microbial evolution in the Precambrian, the bage of microbesQ. Oxygen isotope data for early diagenetic cherts indicate surface temperatures on the order of 55–85 8C throughout the Archean, so early thermophilic microbes (as deduced from the rRNA tree) could have been global and not ...