Geological and Geochemical Characteristics of Porphyry Copper Deposits in Core Part of Central Asian Metallogenic Domain: A review

Plenty of large and ultra-large porphyry copper deposits are occurred in the Central Asia Metallogenic Domain, which are mainly concentrated in the Balkhash of Kazakhstan and west Junggar and the eastern Tianshan of Xinjiang in China.In this paper, the research statuses of the main porphyry copper deposits in the above areas have been reviewed from the aspects of petrology, geochemistry, magmatic properties, deposit geology and ore-forming fluid properties.The similarities and differences between porphyry copper deposits in China and abroad have also been summarized.The ore-bearing porphyries are mainly diorite, diorite porphyrite, granodiorite porphyry and quartz monzonite.Most of the ore-bearing porphyries, except for Nurkazgan in Kazakhstan, have the geochemical characteristics of adakite.The crystallization temperature of ore-bearing porphyries range from 668℃ to 836℃, and the crystallization pressure of porphyry phase is 0.8~3.2kbar.The oxidation state of porphyries in the Balkhash region (ΔQFM=2.9~4.8)is significantly higher than that in the west Junggar and the eastern Tianshan area (ΔQFM=0.3~1.8).The (⁸⁷Sr/⁸⁶Sr)_i and εNd(t)of all the ore-bearing porphyries range from 0.702 5 to 0.706 7 and from 4.9 to 8.8, respectively, indicating that the new oceanic crust is the main source of the ore rock, and a small amount of continental crustal material is also involved.The hydrothermal alteration is mainly composed of potassium alteration, sericitization and propylitization.The geochemical studies show that the sulfur of ore-forming system is mainly derived from the magma (δ³⁴S=-5‰~2‰).The ore-forming fluid in Balkhash and Tuwu-yandong is oxidized H₂O-NaCl-CO₂-SO₂ system, while the ones in Baogutu is a reductive H₂O-NaCl-CO₂-SO₂ system.