Mineral studies applied to geological problems

点击翻译按钮获取中文摘要

The Mantle is essentially composed of anhydrous minerals (contain no water) but geological processes carry water down into the Mantle along subduction zone mainly in rocks called serpentinites. Water can also have access to the Mantle along fracture systems that develop when Mantle rocks are obducted onto crustal rocks when tectonic plates collide. I am studying a series of mantle and upper crustal rocks called an ophiolite complex that has been thrust up in Cornwall, UK. These rocks have been studied before but no one has recognized the importance of a complex and extensive vein system in these rocks. These fractures have allowed water into the heart of the ophiolite complex altering the rocks, filling the fractures with new minerals and lubricating the rocks so that they could be obducted to their present position. The mineralogy of the veins reflects the falling temperature regime in which they form: high-temperature veins with feldspar, amphibole and clinochlore, medium-temperature veins with talc, clinochlore and serpentine and low-temperature veins with clinochlore, saponite and sepiolite. Determining the mineralogy and the chemical composition of these vein minerals will allow me to determine the conditions they formed under and the source of the water.