Vermiculite association with chlorite

Chlorite is abundant in Cu-Pb-Zn-rich deposits but is scarce in Au-Ag-rich deposits. Fe chlorite is the most common and Fe-Mg chlorite is subordinate (Shirozu, 1969). Almost all of the chlorite is classified as orthochlorite which can be regarded as part of the clinochlore-daphnite solid solution series. In general, chlorite is intimately associated with sulfide minerals such as sphalerite, galena, pyrite, chalcopyrite, and pyrrhotite. A 7 A septechlorite was reported from the Toyoha Pb-Zn deposits (Sawai, 1980). Interstratified chlorite-smectite and vermiculite-saponite are rather common minerals in Au-Ag deposits (e.g., Yoneda and Watanabe, 1981), but they have not yet been reported from other deposits. 

In addition to swelling chlorite (vermiculite) there is also in association with mixed-layer minerals of the ilUte-montmorillonite type (sometimes Fe-bearing) a chlorite that is unstable on thermal treatment. The diffractogram of oriented samples is char-... 

Shimane, H., and T. Sudo, 1958. A chloritic mineral found associated with vermiculite. Clay Min, Bull, 3 297. 

The clay mineral spectrum is characterized by the paragenesis of dioctahedral chlorites exhibiting primary crystallochemical features with dioctahedral illites sometimes containing swelling layers. This association is quite typical for continental deposits or those from brackish-water basins. In addition to chlorites with a stable structure we also observe swelling chlorites which are unstable on heat treatment and which occupy a sort of intermediate position between chlorite and vermiculite. It appears to represent a process of incomplete crystallization of minerals of the chlorite-vermiculite group in continental basins or under freshwater to brackish conditions. The minerals may thus be considered as metastable intermediate forms. 

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