The Paragenesis of Synthetic Phyllosilicates on the Talc-phlogopite Join

Résumé du livre

Trioctahedral phyllosilicates are much less common on the continents than are the dioctahedral phyllosilicates. The continental occurrences of the trioctahedral clays are restricted mostly to the hydrothermal alteration or weathering of magnesium-rich rocks, whereas dioctahedral clays form abundantly from the weathering of granitic continental rocks. Dioctahedral clays therefore constitute the major proportion of the clay sediments which accumulate on continents and on the continental margins. Because of their great abundance and geologic importance, dioctahedral clay minerals have received a great deal of study, whereas the trioctahedral clays have been studied much less. Recently, however, the Deep Sea Drilling Project has produced a substantial amount of data which show that the alteration of submarine volcanics, by both cold and hot circulating seawater, produces huge amounts of magnesium-rich phyllosilicates. In fact, alteration processes acting on oceanic crust may play a key role in controlling the concentrations of several important elements in the oceans ... It is vitally important, therefore, to understand the alteration processes as completely as possible, and that can only be done if the alteration mineralogy is interpreted thoroughly and correctly. The purpose of this research is to examine the experimental paragenesis of phyllosilicates on the talc-phlogopite join at temperatures of 300C to 550C and one kilobar pressure. The systematic study of trioctahedral phyllosilicates provides new information about a little-studied system, and may aid in the identification and interpretation of natural trioctahedral phyllosilicates such as those that form in the ocean basins.