High temperature or metamorphic vermiculites |
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Authors: | B Velde |
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Institution: | (1) Laboratoire de Pétrographie, Université P. et M. Curie, 4, place Jussieu, 75230 Paris Cedex 05, France |
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Abstract: | New chemical data from four different geological occurrences and published information are used to define, approximately, the chemistry of vermiculite of high temperature and pressure origin. Geologic occurrence indicates that this mineral is present towards the upper limit of the muscovite-chlorite zones in pelitic rocks. Geologic conditions range from glaucophane-lawsonite metamorphism to hydrothermal zones such as the Salton Sea area.The mineral has a composition distinct from chlorite and biotite, two commonly accompanying phases, being more silica rich than metamorphic chlorites from pelitic rocks and more aluminous than biotites. Vermiculites characteristically show significant but low K2O and CaO concentrations. |
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