POTASSIUM FELDSPAR FROM VEIN SYSTEMS AND THEIR AUREOLES AT THE EPITHERMAL ASACHIN GOLD-SILVER DEPOSIT, SOUTHERN KACHATKA

Abstract

Potassium feldspars are typical of propylite and gangue mineral assemblages of epithermal low-sulfide and sulfide gold–silver deposits in Kamchatka, Japan, New Zealand, Indonesia, Papua New Guinea, Eastern Australia, the western coast of the United States, and other regions of the Pacific metallogenic belt. It is generally considered that K-feldspars at these deposits are mainly represented by adularia. According to the modern classification of alkali feldspars, adularia is a water-transparent low-temperature K-feldspar with a low content of isomorphous admixtures of any structural modifications, including sanidine, orthoclase, and microcline. Recent decades have been marked by the publication of numerous works devoted to triclinic and monoclinic varieties of adularia, including sanidine, orthoclase, and microclines determined by structural methods. However, adularia is traditionally referred to monoclinic feldspars or intermediate microclines with insignificant deviation from monoclinic symmetry.