The Mesozoic Tectonic-magmatic Constraints On The Gold Mineralization In Wulong Gold Mining Area,Eastern Liaoning

The Liaodong Peninsula is located in the northeastern margin of the eastern North China Craton,which is an important part of the Palaeoproterozoic Jiao-Liao-Ji orogenic belt.In recent years,plentiful studies are reported on the ages of volcanism,sedimentation and metamorphism of the Paleoproterozoic Liaohe Group in the Liaodong Peninsula.The study on the Mesozoic intrusive rocks,however,is relatively weak.Moreover,there is still no agreement on the petrogenesis,diagenetic evolution process,geological background,and the relationship between magmatism and mineralization.The Liaodong Peninsula is known to have experienced a transition from a compressional orogeny to extension and lithospheric thinning,which led to the large-scale magmatism and gold mineralization in the Mesozoic.Therefore,in this paper,we take the Wulong gold mining area as an example,to solve the key scientific problem of the relationship between Mesozoic tectono-magmatism and gold mineralization.Based on regional geology,deposit geology,and route and profile geology survey,we performed zircon SHRIMP U-Pb isotopic dating,in-situ micro-area zircon Lu-Hf isotopic analysis,major elements,trace elements and S-Pb isotopic analyses of Mesozoic Sanguliu pluton and Wulong pluton closely related to the Wulong gold deposit.Through a 1:50000 tectonic-construction mapping in Dandong area,Liaoning Province,we established the Mesozoic magmatic evolution sequence and tectonic framework.In addition,combined with the interpretation of the deep geological bodies through gravity,magnetic and electrical profiles,we analyzed the origin of rock and the source of metallogenic materials,discussed the Mesozoic tectonic setting and the relationship between tectono-magmatism and gold mineralization,and summarized the genesis of the deposit.According to the study,the Wulong pluton is acidic intrusive rock formation,forming in the Late Jurassic(157 Ma~161 Ma),and belongs to peraluminous,high potassium calc-alkalinity and mesothermal granitic magma rock series.It is a continental crust remelting granite that recrystallized from Paleoproterozoic granites and Liaohe group that were affected by Late Jurassic(ca.160 Ma)crustal remelting.Magma source area is derived from the recycling of crustal material from Archean to Paleoproterozoic.The Sanguliu pluton is acidic-intermediate acidic intrusive rock formation,forming in the Early Cretaceous(127 Ma~123 Ma),and belongs to lack aluminous-peraluminous,high potassium calc-alkalinity and mesothermal granitic magma rock series.It is an I-type granite with characteristic of adakitic rocks.Magma source area is derived from crustal material from Archean to Paleoproterozoic,with its protoliths likely to be intermediate-basic rocks.Wulong gold deposit is located on the north of Sanguliu pluton,with metallogenic age ranging from 122.8 Ma to 119.1 Ma.It is closely related to the Sanguliu pluton in time and space.During the Middle-Late Jurassic(180-155 Ma),the Liaodong region is affected by the Paleo-Pacific plate subduction to the Eurasia plate.Continuous subduction resulted in regional overthrust and compression events(143-132 Ma),forming ductile shear belts which is beneficial to the accumulation,migration and precipitation of ore-bearing hydrothermal solution.In the Early cretaceous(132-120 Ma),affected by the post-subduction rebound and extension of the Paleo-Pacific plate,the region experienced intense lithospheric thinning and tectonic regime transition,forming brittle fault zones with different stages,directions and properties.The Sanguliu pluton which is derived from crustal material during Archean to Paleoproterozoic began to emplace upward along the thinning weak part of the crust.Magmatic hydrothermal fluid produced by crystallization differentiation migrates along structural fissures,reacting with the residual carbonaceous Liaohe Group and extracting gold from the source bed.The ore-forming fluid filled in the same tectonic fault zones accompanied by the emplacement of diorite dikes,or filled in rock structural fissures in the form of reticular veins.And then gold-bearing quartz veins formed at these suitable sites.It is the Wulong deposit,a magmatic hydrothermal gold deposit.According to the ore-controlling characteristics of source horizon,ore-hosting structure and magmatism and regional metallogenic regularity,combined with geophysical,geochemical and remote sensing anomalies,the Wanjiabao-Xiejia gold prospecting target area and the deep prospecting target area of Wulong gold deposit have been delineated.