illite and mica

Today the terrestrial surface drives biogeochemical cycles on Earth through chemical weathering reactions mediated by the biological influence of soils. Prior to the expansion of life on to land, abiotic weathering may have resulted in different boundary conditions affecting the composition of the biosphere. Here we show a striking difference in weathering produced minerals preserved in the Mesoproterozoic Velkerri Formation. While the bulk chemistry and mineralogy is dominated by illite similar to many modern mudstones, application of a novel microbeam technology reveals that the initial detrital minerals were composed of mica (28%) and feldspar (45%) with only a trace amount (<2%) of typical soil formed clay minerals. The majority of illite and the high Al

Topics: Aluminum Silicates; Australia; Chemical Phenomena; Chemistry, Physical; Clay; Environmental Monitoring; Geological Phenomena; Geology; Minerals; Oceans and Seas; Potassium Compounds; Soil; Trace Elements; Weather