The Central Asian Orogenic Belt,as one of world-class gold economic belts,preserves a number of giant,large black shale-hosted gold deposits,while it is still debated for origin of sulfides and gold mainly due to lack...The Central Asian Orogenic Belt,as one of world-class gold economic belts,preserves a number of giant,large black shale-hosted gold deposits,while it is still debated for origin of sulfides and gold mainly due to lack of identification for multiple stages of sulfides.The Haoyaoerhudong gold deposit is hosted in a sequence of Mesoproterozoic carbonaceous and pyritic slate,phyllite,and schist that form a tight syncline along the north margin of the North China Craton.Detailed petrography of the host rocks and mineralization have defined five stages of pyrites.The earliest form of pyrite(Py_(1))occurs as fine-grained dispersed pyrite in black carbonaceous slate and medium-to coarse-grained disseminated pyrite in pyrite-rich layers,contains relative low gold and high arsenic content,indicating a syn-sedimentary or diagenetic in origin.Stage Ⅱ pyrite(Py_(2))occurs with garnet and quartz inclusions and Py_(3) occurs as pyrite veins,contains higher gold and lower As content,and are interpreted to have formed from the dissolution-reprecipitation of Py_(1) during the peak metamorphism or post-peak metamorphism.Stage Ⅳ pyrite(Py_(4))from the pyrite-quartz veins crosscut the metamorphic garnet,contains the highest gold concentrations and other trace elements,and is considered to have formed post-peak metamorphism.Abundant native gold,electrum,and maldonite occur as inclusions within Py_(4) and monazite and in fractures that crosscut garnet.While,Py_(5) with typical remobilized feature is thought to be a product of melting of former pyrites(Py_(1) to Py_(4))triggered by the large-scale Hercynian magmatism.The sedimentary/diagenetic Py_(1) have δ^(34)S values that range from +12.4‰to +16.2‰.Later generations of sulfides,including Py_(2) to Py_(5),and Ccp_(2) to Ccp_(3),have δ^(34)S values from +9.5‰to +12.7‰.Monazite with maldonite inclusions from quartz-pyrite veins yielded an intercept age of 341.3±6.6 Ma,while coarse grained monazite associated biotite along fractures in the reefs yielded an intercept age of 254.6±8.2 Ma.The paragenetic,textural,chemical,and isotopic data suggest three distinct gold producing episodes at Haoyaoerhudong gold deposit.Gold and arsenic were clearly initially concentrated in organic muds,and enriched along the structures of diagenetic arsenic-rich pyrite.Subsequently,accompanying metamorphism and deformation,gold was liberated from the dissolution of diagenetic pyrites to form the pyrite veins.Finally,accompanying transformation of pyrite into pyrrhotite,gold was released into the metamorphic fluids to become concentrated as native gold,electrum,and maldonite in pyrite-quart veins.Monazite with age of 341 Ma from quartz-pyrite veins suggests that the third major gold mineralizing event in Haoyaoerhudong occurred before the Hercynian magmatism,suggesting that the Haoyaoerhudong deposit is a typical orogenic gold deposit rather than intrusion-related deposit.展开更多
The Mesoproterozoic Bayan Obo Group located along the northern margin of the North China Craton(NMNCC)hosts a world’s largest known rare-earth element(REE)deposit(Bayan Obo Fe-REE-Nb deposit)[1,2]and a number of larg...The Mesoproterozoic Bayan Obo Group located along the northern margin of the North China Craton(NMNCC)hosts a world’s largest known rare-earth element(REE)deposit(Bayan Obo Fe-REE-Nb deposit)[1,2]and a number of large gold deposits(eg.,Haoyaoerhugong and Zhulazhaga gold deposits;Fig.1a)[3],and has a long and protracted thermal history spanning from1.3 Ga to 250 Ma[1].The tectonic history was associated with Proterozoic rifting with carbonatite magmatism at1.3 Ga[4]and subsequent subduction-accretion processes of the Paleo-Asian Ocean[5,6].The Paleo-Asian oceanic subduction beneath the North China Craton(NCC)initiated in the Middle Silurian[7,8]and the ocean was closed in the Permian to induce the accretion of arcs and terranes with the NCC[2].This long and protracted tectonic history increases the difficulties both in dating and understanding the genesis of the Bayan Obo REE deposit and black shale-hosted gold deposits(e.g.,Haoyaoerhudong deposit).Thus,it is important to understand the thermal history of the hosting strata in order to constrain the tectonic drive and timing of polymetallic mineraliza-tion.There have been few attempts to date the multistage thermal events which the Bayan Obo Group has witnessed,predominantly because of greenschist facies overprint of the host rocks and lack of reliable geochronometers[9,10].展开更多
基金the National Natural Science Foundation of China(Nos.41402042,41002064)Natural Sciences and Engineering Research Council of Canada Discovery Grant+1 种基金Fundamental Research Funds for the Central Universities(310827172006,300102278402)Geological Investigation Work Project of China Geological Survey(12120115069701).
文摘The Central Asian Orogenic Belt,as one of world-class gold economic belts,preserves a number of giant,large black shale-hosted gold deposits,while it is still debated for origin of sulfides and gold mainly due to lack of identification for multiple stages of sulfides.The Haoyaoerhudong gold deposit is hosted in a sequence of Mesoproterozoic carbonaceous and pyritic slate,phyllite,and schist that form a tight syncline along the north margin of the North China Craton.Detailed petrography of the host rocks and mineralization have defined five stages of pyrites.The earliest form of pyrite(Py_(1))occurs as fine-grained dispersed pyrite in black carbonaceous slate and medium-to coarse-grained disseminated pyrite in pyrite-rich layers,contains relative low gold and high arsenic content,indicating a syn-sedimentary or diagenetic in origin.Stage Ⅱ pyrite(Py_(2))occurs with garnet and quartz inclusions and Py_(3) occurs as pyrite veins,contains higher gold and lower As content,and are interpreted to have formed from the dissolution-reprecipitation of Py_(1) during the peak metamorphism or post-peak metamorphism.Stage Ⅳ pyrite(Py_(4))from the pyrite-quartz veins crosscut the metamorphic garnet,contains the highest gold concentrations and other trace elements,and is considered to have formed post-peak metamorphism.Abundant native gold,electrum,and maldonite occur as inclusions within Py_(4) and monazite and in fractures that crosscut garnet.While,Py_(5) with typical remobilized feature is thought to be a product of melting of former pyrites(Py_(1) to Py_(4))triggered by the large-scale Hercynian magmatism.The sedimentary/diagenetic Py_(1) have δ^(34)S values that range from +12.4‰to +16.2‰.Later generations of sulfides,including Py_(2) to Py_(5),and Ccp_(2) to Ccp_(3),have δ^(34)S values from +9.5‰to +12.7‰.Monazite with maldonite inclusions from quartz-pyrite veins yielded an intercept age of 341.3±6.6 Ma,while coarse grained monazite associated biotite along fractures in the reefs yielded an intercept age of 254.6±8.2 Ma.The paragenetic,textural,chemical,and isotopic data suggest three distinct gold producing episodes at Haoyaoerhudong gold deposit.Gold and arsenic were clearly initially concentrated in organic muds,and enriched along the structures of diagenetic arsenic-rich pyrite.Subsequently,accompanying metamorphism and deformation,gold was liberated from the dissolution of diagenetic pyrites to form the pyrite veins.Finally,accompanying transformation of pyrite into pyrrhotite,gold was released into the metamorphic fluids to become concentrated as native gold,electrum,and maldonite in pyrite-quart veins.Monazite with age of 341 Ma from quartz-pyrite veins suggests that the third major gold mineralizing event in Haoyaoerhudong occurred before the Hercynian magmatism,suggesting that the Haoyaoerhudong deposit is a typical orogenic gold deposit rather than intrusion-related deposit.
基金supported by the National Natural Science Foundation of China(41402042,41002064,and 42172090)the Natural Sciences and Engineering Research Council of Canada(NSERC)Discovery Grant。
文摘The Mesoproterozoic Bayan Obo Group located along the northern margin of the North China Craton(NMNCC)hosts a world’s largest known rare-earth element(REE)deposit(Bayan Obo Fe-REE-Nb deposit)[1,2]and a number of large gold deposits(eg.,Haoyaoerhugong and Zhulazhaga gold deposits;Fig.1a)[3],and has a long and protracted thermal history spanning from1.3 Ga to 250 Ma[1].The tectonic history was associated with Proterozoic rifting with carbonatite magmatism at1.3 Ga[4]and subsequent subduction-accretion processes of the Paleo-Asian Ocean[5,6].The Paleo-Asian oceanic subduction beneath the North China Craton(NCC)initiated in the Middle Silurian[7,8]and the ocean was closed in the Permian to induce the accretion of arcs and terranes with the NCC[2].This long and protracted tectonic history increases the difficulties both in dating and understanding the genesis of the Bayan Obo REE deposit and black shale-hosted gold deposits(e.g.,Haoyaoerhudong deposit).Thus,it is important to understand the thermal history of the hosting strata in order to constrain the tectonic drive and timing of polymetallic mineraliza-tion.There have been few attempts to date the multistage thermal events which the Bayan Obo Group has witnessed,predominantly because of greenschist facies overprint of the host rocks and lack of reliable geochronometers[9,10].
