Indosinian movement and metallogeny in Xinjiang,China

With an increase of high-resolution isotope chronological data,some geological bodies that have long been considered to be Hercynian and even Caledonian in age have been identified to be formed during the Indosinian period.Indosinian movement in Xinjiang and its adjacent areas is manifested as follows:(1)magmatic intrusions represented mainly by small intermediate-acid bodies and pegmatite,aplite,diabase and lamprophyre dikes,occasionally with gabbro-diorite bodies,which usually show the characteristics of gold-copper-rare metal mineralizations and some of which are just orebodies or contain ores;(2)many ductile shear zones were active during the Indosinian period,and in most cases the last ductile shear deformation occurred during the Indosinian;and(3)most gold deposits related to ductile shear zones in the Tianshan Mountains,including the giant Muruntau and Wanfeng-Tianger gold deposits,formed during the Indosinian period.Indosinian thus is one of the most important metallogenic epochs in Central Asia.The behaviors and geodynamic settings of the Indosinian movement are different in the Tianshan and Altay mountains.