The big mantle wedge and decratonic gold deposits  

作　　者：Rixiang ZHU Weidong SUN 

机构地区：[1]State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing,100029,China [2]Laboratory for Marine Mineral Resources,Pilot National Laboratory for Marine Science and Technology(Qingdao),Qingdao,266237,China [3]Center of Deep Sea Research,Institute of Oceanology,Center for Ocean Mega-Science,Chinese Academy of Sciences,Qingdao,266071,China [4]School of Marine Sciences,University of Chinese Academy of Sciences,Being,100049,China

出　　处：《Science China Earth Sciences》2021年第9期1451-1462,共12页中国科学（地球科学英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant No.41688103);the“Deep Earth Resources Exploration and Exploitation”National Key Research&Development Program of the Ministry of Science and Technology of China(Grant No.2016YFC0600408);the Taishan Scholar Program of Shandong(Grant No.ts201712075);Aoshan Scholar Program of the Pilot National Laboratory for Marine Science and Technology(Qingdao)(Grant No.2017ASTCP-OS07)。

摘　　要：The Circum-Pacific subduction zone is a famous gold metallogenic domain in the world,with two important gold metallogenic provinces,the North China Craton and Nevada,which are related to the destruction of the North China Craton and the Wyoming Craton,respectively.Their ore-forming fluids were possibly derived from the stagnant slab in the mantle transition zone.The oceanic lithospheric mantle usually contains serpentine layers up to thousands of meters thick.During plate subduction,serpentine is dehydrated at depths of<200 km and transformed into high-pressure hydrous minerals,known as Phases A to E,which carries water to the depth of>300 km.The overlying big mantle wedge is hydrated during the breakdown of these hydrous facies in the mantle transition zone.The dehydration of the subducted slab in the big mantle wedge releases sulfur-rich fluid,which extracts gold and other chalcophile elements in the surrounding rocks,forming gold-rich fluid.Because the cratonic geotherm is lower than the water-saturated solidus line of lherzolite,the fluid cannot trigger partial melting.Instead,it induces metasomatism and forms pargasite and other water-bearing minerals when it migrates upward to depths of less than 100 km in the cratonic lithospheric mantle,resulting in a water-and gold-rich weak layer.During the destruction of craton,the weak layer is destabilized,releasing gold-bearing fluids that accelerate the destruction.The ore-forming fluids migrate along the shallow weak zone and are accumulated at shallow depths,and subsequently escape along deep faults during major tectonic events,leading to explosive gold mineralization.The ore-forming fluids are rich in ferrous iron,which releases hydrogen at low pressure through iron hydrolysis.Therefore,decratonic gold deposits are often reduced deposits.

关 键 词：Big mantle wedge SERPENTINE Pargasite Craton destruction Explosive gold mineralization Hydrogen 

分 类 号：P618.51[天文地球—矿床学]