Age,geochemical features and possible petrogenesis mechanism of Early Permian magnesian diorite in Hatu,Xinjiang
新疆哈图早二叠世富镁闪长岩的时代、地球化学特征和可能的成因机制

Magnesian dioritic dikes and plutons widely occur in the Bieluagaxi region,Western Junggar and recorded the Late Paleozoic tectonic evolutionary history of the area.Ar-Ar dating on rock chips of the dikes has yielded a plateau age of 292Ma,indicating an Early Permian age for the dikes.The magnesian diorites are calc-alkaline suite with variable SiO2(51.9%～62.6%),and characterized by high Mg(Mg#>60),Cr(45.8×10-6～539×10-6),Ni(17.2×10-6～197×10-6)contents.The magnesian diorites are strongly enriched in large-ion-lithophile elements(such as K,Rb,Ba,Th and U)and light rare earth elements,and are characterized by depletion of high-field-strength elements(such as Nb,Ta,Ti)and heavy rare earth element.These geochemical features are analogous to those of sanukitoids in Setouchi volcanic belt.The Bieluagaxi magnesian diorite is generated by interaction of mantle peridotite with supercritical fluid derived from dehydration of subducting oceanic slab.The occurrence of Early Permian sanukitic rocks in the Bieluagaxi region suggest that the Western Junggar was dominated by subduction-related environment.The interaction between high oxygen fugacity supercritical fluid and mantle peridotite caused the decomposition of metal sulfides and the Cu and Au mineralization which have good metallogenic prospects in the Bieluagaxi region.