Major Types and Characteristics of Late Paleozoic Ore Deposits, East Tianshan, Northwest China

Abstract

One of the largest and most important metallogenic provinces in China is the East Tianshan, where seven major types of Late Paleozoic metal deposits have been recognized: (1) porphyry-type Cu-Mo-(Au) ore; (2) volcanic Fe-Cu; (3) orogenic lode gold; (4) magmatic Cu-Ni sulfide; (5) epithermal gold; (6) volcanic hydrothermal Cu; and (7) skarn Cu-Ag. Tectonically, the development of these Late Paleozoic mineral deposits was closely associated with subduction and closure of the ancient Tianshan ocean, lying between the Tarim craton and the Junggar-Kazakhstan composite block. In Late Devonian to Early Carboniferous time, the northern edge of the Tarim craton existed as a passive continental margin, whereas the ancient Tianshan oceanic crust was subducted beneath the southern margin of the Junggar-Kazakhstan block, resulting in the formation of the Dananhu-Tousuquan magmatic arc and associated porphyry-type Cu-Mo-(Au) deposits. In Middle Carboniferous time, the ancient Tianshan oceanic crust began to subduct beneath the northern margin of the Tarim craton, leading to the formation of the Aqishan-Yamansu magmatic arc and associated volcanic Fe-Cu deposits. In the Late Carboniferous, the ancient Tianshan ocean closed, and a continent-arc collision occurred, leading to the formation of the Tianshan orogen. Following collision, an extensional event, associated with the emplacement of voluminous ultramafic-mafic complexes and formation of a number of large- to medium-scale magmatic copper-nickel ore deposits, occurred along the Kangger suture zone. In Early Permian time, East Tianshan entered into a post-collision stage associated with widespread emplacement of granitoid bodies and within-plate volcanism, which led to the formation of hydrothermal copper deposits, skarn-type Cu-Ag deposits, post-orogenic gold deposits, and epithermal gold deposits.