Alterations of Country Rocks and Paragenesis of Minerals in Some Mercury Deposits

Abstract

1. Alterations of country rocks of some mercury deposits in Hokkaido are generally known as silicification, carbonatization and iron sulfide mineralization, as well as argillitization comprising sericitization, montmorillonitization and kaolinitiiation.
After collecting and interpreting the data by X-ray powder method on alterated country rocks, the author obtained the following results : When the deposits are the vein type, intensity of clay minerals has a peak near the vein but in the impregnation type the intensity shows little change; sericite and montmorillonite occur remarkably in the deposits that accompany mainly cinnabar as ore mineral, whereas kaolinite is intensive in the deposits accompanying much native mercury.
2. In these deposits the range of crystallization of mercurial minerals is relatively wide if we take iron sulfide as the index-mineral.
Cinnabar is generally crystallized from weak-alkaline ore solution in later stage than pyrite, but in the deposits which accompany abundant native mercury, it is found to have been deposited at the same time with native mercury possibly from weak-acidic ore solution during the stage later than marcasite. This is well in accord with the results obtained by the X-ray powder analysis.