Characteristics and genesis of the minerogenetic series of the Axi type gold deposits in the West Tianshan

Abstract: Several types of volcanics-related gold deposits are found in the Tulasu basin of the West Tianshan. According to their mineralization features, ore-controlling factors and geological environment, three basic types may be distinguished: low-sulfur epithermal type, porphyry type and stratabound epithermally modified type. They are an association of gold deposits formed in the same tectonic setting and in a unifying hydrothermal fluid field, i. e. the Axi type gold minerogenetic series. Secondary fluid fields and specific tectonic environments determined the certain regularities: the low-sulfur epithermal type formed in the Early Carboniferous and occurs in marginal faults of volcanic edifices; the porphyry and stratabound epithermally modified types formed in the Middle-Late Carboniferous and occur respectively in the fracture systems inside acid porphyries and their margins and in the Second Member of the Dahalajun Formation.