Geologists discover a new window into Earth’s interior
Geologists discover a new window into Earth’s interior
Geologists Larissa Dobrzhinetskaya and Harry Green and colleagues report in the Oct. 26-30 online early edition of the Proceedings of the National Academy of Sciences their discovery of ultrahigh-pressure minerals from a paleoocean-spreading center, a place "forbidden" for such mineral associations according to existing geological concepts. The authors describe a fragment of metallic alloy and aluminum-silicate rock extracted from a chromite ore deposit of a Tibetan ophiolite (a section of the Earth's paleooceanic crust and the underlying upper mantle), which consists of unusual minerals. The mineral assemblage is the first record of a highly reduced (low-oxygen concentrations) mantle environment occurring at a depth of at least 300 km was and had not been seen before in any terrestrial rocks. The researchers rule out that the discovered minerals are formed as the result of a meteorite impact and propose a mechanism of large-scale mantle convection that "amalgamates" the deep-mantle fragment with shallower host rocks of ophiolite formation. They emphasize that ophiolites, therefore, are a new "window" into the Earth's deep interior. Dobrzhinetskaya and Green were joined in the research by scientists at GeoForschungsZentrum, Germany; the Institute of Geology, China; and the Lawrence Livermore National Laboratory, Calif.
