Metallogenesis Of Bairendaba-Weilasituo Silver-polytmetallic Deposit And Its Geodynamic Setting, In The Southern Segment Of Great Xing’an Range, NE China

Sitting in the eastern segment of the Central Asian Orogenic Belt, the southernGreat Xing’an Range (SGXR) is a tectonic superposition positon of Paleo-AsianOcean, Mongol-Okhotsk Ocean, and Paleo-Pacific Ocean. Because of this and its richin non-ferrous mineral resources, this region in particularly caught the attention ofChinese and foreign geologists. Fruitful results has been accumulated, since thefounding of New China, in the geological science of the southern Great Xing’anRange metallogenic belt. With the deepening of the studies, however, a range ofissues increasing prominent. Previous studies focused on single deposit, single type ofdeposit, and single metallogenic rich region have not solve the deeper thinking.Anatomy of the large and super-large deposits and combine with the remainingdeposits, however, is the study of the key in the area. In this context, theBairendaba-Weilasituo ore field in the SGXR is selectd for study with the aim atsummarizing the regional metallogenic regularity. This study obtained the follwingpoints of understanding:1) There are slightly differences on fluid inclusion type and mechanism ofmineralization between the Bairendaba and Weilasituo deposits, however, similarchatacteristics were exhibited on deposit geology, ore texture, mineralization zoning,ore-forming fluid characteristics, metallogenic chronology, and ore depositgeochemistry. The above phenomenons show that both of the Bairendba andWeilasituo deposits are magmatic–hydrothermal vein type, and they forming arerelated to the Early Crataceous magmatism. They are the products of the samemagmatic–hydrothermal fluid migrating, depositing, and enriching in differentspatial position.2) Five metallogenic series were identified in the SGXR, including Permianexhalative lead-zinc deposit series, Triassic magmatism related Mo-Cu-Pb-Zn-Agseries, Early Jurassic magmatism related Ag-Pb-Zn series, Late Jurassic magmatismrelated Cu-Mo-Pb-Zn-Ag series, and Early Cretaceous magmatism relatedSn-Fe-Cu-Mo-W-Ag-Pb-Zn-rare metals and rare earth metals series. For the last, itcan be subdived into four series further. There are the granodiorite porphyry relatedCu-Mo-Ag-Pb-Zn series, the plutonic intrusion related Ag-Pb-Zn-Cu series, the acidic magmatism related Sn-Fe-W-Cu-Ag-Pb-Zn series, and the alkaline granite related raremetals and rare earth metals series. The tectonic background differences and theresulting magma activity differences are the main controlling factors for the regionalmineralization zoning.3) Mesozoic mineralization in northeast China and its adjacent areas can bedivided into five pluses: Triassic (240-205Ma), Early-Middle Jurassic (190-165Ma),Late Jurassic Jurassic (155-145Ma), early stage of Early Cretaceous (140-120Ma),and late stage of Early Cretaceous (115-100Ma). They were formed under the jointactions of the closure of Paleo-Asian Ocean and Mongol-Okhotsk Ocean, and thesubduction of Paleo-Pacific Ocean. However, in a certain mineralization pluse, therole of these three events are varied. The Triassic (240-205Ma) magmatism andassociated mineralisation occurred during in a post-collisional tectonic settinginvolving the closure of the Paleo-Asian Ocean. The Early-Mid Jurassic (190-165Ma) events are related to the subduction of the Paleo-Pacific plate in the eastern Asiancontinental margin, whereas in the Erguna block, these are associated with the closureof the Mongol-Okhotsk Ocean. From155to120Ma, large-scale continentalextension is developed in NE China and surrounding regions. However, the LateJurassic magmatism and mineralization events in these areas are evolved in apost-orogenic extensional environment of the Mongol–Okhotsk Ocean subductionsystem. Whereas, the early stage of the Early Cretaceous events are the compositionaleffects of the closure of the Mongol-Okhotsk Ocean and the subduction of thePaleo-Pacific Ocean. The widespread extension ceased during the late phase of EarlyCretaceous (115-100Ma), following the rapid tectonic changes resulting from thePaleo-Pacific Oceanic plate reconfiguration.