The Study Of Two Stage Gold Mineralization In Tantou District,Western Henan Province

Xiong'ershan ore concentration area is one of the most significant gold-producer in the North China Craton?NCC?.The Luanlong Au deposit is a newly found“barite-quartz”vein-type gold deposit,which contains telluride and molybdenum.Relatively,the Beiling gold deposit is a typical altered rock type gold deposit.The two deposits were chosen to conduct detailed research,including ore-forming characteristics,mineralization age,the source of ore-forming meterials and fluids,mineralization mechanism,and tectonic settings.Based on above study,we aim to analyze the genesis of the gold deposits,summarize the ore-forming regularity and supervise ore prospecting.This will enrich the metallogenic theory in the southern margin of the NCC.The Luanling gold deposit occurs as barite-quartz vein hosted in the NW-trending fault.Au occurs as native gold,electrum or petzite in the fracture of sulfides.The characteristic of trace elements in pyrite indicate the pyrite in the Luanling deposit is mainly Au-free pyrite.In addition,there exists a kind of Au-As-bearing pyrite.The ore-froming temperature of pyrite-quartz stage???and sulfide-telluride stage???is 296³77°and 241³24°,respectively.During stage???,log?_S2 and log?_Te2e2 are estimated to be-14.3^-7.3 and-17.4^-9.4,respectively.The mineralization occurs in oxidation environment.The Re content of molybdenite indicates that the ore-formning materials origin from the mixture of crust and mantle.The bulk?³⁴S value is 0‰³.5‰,indicating the sulfur mainly origin from deep-seated magma.The H-O isotope data of quartz(?¹⁸O_?‰=5.2⁹.8‰,?D=-95⁷1‰)and the He-Ar isotope signature of pyrite indicate the ore-forming fluid is from the mixture of crust and mantle.The model age of molybdenite?162¹64Ma?implys the Luanling gold deposit formed in late Jurassic.The Beiling gold deposit mainly occurs as mineralized altered rock hosted in NW-trending fault zone.The Luanling deposit is characterized by the occurrence of smoky gray color quartz vein or stocks.The pyrite is dominatedly As-bearing pyrite and Au occurs as solid solution or native gold inclusions in pyrite.The late generation pyrite contains minor Au-As-free pyrite.The Sr isotope of sulfides indicates the ore-forming materials are derived from the mixture of crust and mantle.The C-O isotope of calcite indicated C come from magma,affected by low-temperature alteration.The H-O isotope of quartz indicates the ore-forming fluid is mainly derived from magmatic or metamorphic hydrothermal fluids,mixed with meteoric water in late stage.The Rb-Sr isochron age of sulfides is 124.2±3.1Ma,indicating the mineralization occurred in late Cretaceous.The Luanling gold deposits formed in the early stage of the subduction of the Paleo-Pacific Ocean,as a result of asthernosphere upwelling and thickened lower crust melting.While the Beiling gold deposit is associated the destruction of the NCC,triggered by the large-scale lithosphere thinning.