Crystal-chemical and morphologic-genetic properties of chlorites in the earth's mantle. Article 2. Chlorite-based minerals in sedimentary rocks
In the earth's mantle they distinguish mainly trioctahedral chlorites and less often di-, ditri- or tridioctahedral varieties of this mineral. They also identified chlorites with «defective» structure the varieties of chlorite-»swelling chlorite» type and chlorite-based mixed-layered minerals in combination with saponite, vermiculite, and montmorillonite layers, which are characterized by diffraction pattern for trioctahedral variations. The latter originate either in deposits of sea genesis or those of saline lakes. At he same time, in clay rocks of this facial type the chlorites are formed due to transformation along beidellite, and in sand-siltstone rocks they are formed as «crustified» edgings due to Fe2+ and Mg that are present in stratal water. Trichlorite is generated at the earliest stages of post-sedimentation transformations in closed system of mineral formation with reduction medium. Chlorites of di-, ditri- or tridioctahedral type originate in the course of slow hydrothermal processes under the conditions of relatively open system of mineral formation with low dynamics of oxidizing medium development.