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7223435 
Journal Article 
Cenozoic orogenic gold system in Tibet 
Wang QingFei; Deng Jun; Weng WeiJun; Li HuaJian; Wang Xuan; Li GongJian; , 
2020 
SCIENCE PRESS 
BEIJING 
1315-+ 
WOS:000562485700002 
The orogenic gold deposits formed in the oceanic subduction processes have attracted much attention, yet those generated in the following continental collision stages have been less researched. Tibet Plateau is the youngest continental collision product which has provide a rare opportunity to study the genesis of orogenic gold systems formed in the complete course from the oceanic subduction to continental collision. Three orogenic gold belts were delineated in Tibet Plateau : (1) the mesozonal quartz vein type deposits formed in 60 -43Ma along the Yalung Tsangpo suture zone under a compressional regime; (2) the mesozonal gold deposits, consisting of both quartz vein and disseminated ores, developed along shear zones in the oblique continental collision zone from the initiation to termination of crustal shearing during 32 - 21Ma; and (3) the widely distributed mesozonal to epizonal disseminated and veinlet gold deposits produced in Himalayan doming belt within 19 - 15Ma in the background of Miocene rollback of Indian continental lithosphere, and these deposits are commonly related to antimony mineralization. The features of mineralization and alteration, together with oreforming fluids physiochemical parameters, consistently indicate systematic and gradual shallowing of metallogenic depth of these three gold belts. The Cenozoic orogenic gold deposits in Tibet were formed during peak to retrograde metamorphism of regional crustal rocks. The mutiperiodic mineralization was mostly synchronized with multi-stage drops of convergence rate between India and Eurasia plates, and significantly controlled by oceanic slab breakoff and continental slab rollback. Ore fluids migration and spatial location of orogenic gold deposits were much determined by lithospheric structure. Ore fluids migrating upwards were considered to be driven by higher pressure of thicker lithosphere into the thinner lithosphere with less pressure. Metal precipitation of mesozonal quartz vein type gold deposits was controlled by repetitive cracking-sealing processes and related fluid immiscibility, by contrast, the mesozonal to epizonal disseminated gold deposits by fluid-rock reaction. The median of ams values of pyrites in the three belts are mostly near 0, irrelevant to the different hosting strata. The 8 18 0 values of ore fluids are compatible with the fluids derived from enriched mantle. The 4 degrees Ar/ 36 Ar and 3 He/ 4 He features of ore-related pyrites show clear mantle signatures. Moreover, the platinum-group elements of ore-related sulfides show distinct compositions from those of sulfides precipitated from magmatic hydrothermal. Geochemical features, in combination of mineralization postdating prograde metamorphism and synchronizing with the disturbance of mantle, implies that the ore fluids and metal of the three orogenic gold belts mainly sourced from subcrustal level. This paper further provided possible explanation for the temporal and spatial variation of hydrogen and oxygen isotope of ore fluids. The decrease of 811) values in the younger gold deposits in PaleoceneEocene gold belt is implicative for the input of supercritical fluids. The increase of fluid 8 18 0 values from Paleocene-Eocene to Miocene gold belts could be related to the transition of mantle metasomatic agent from earlier oceanic sediments to later continental components. In terms of the dominantly subcrustal source of ore fluids and the generally shallow metallogenic depth, it is proposed that the orogenic gold deposits in Tibet own great prospect potential.