Petrogenesis,Mineralization And Geodynamic Evolution In Jueluotage Area,Eastern Tianshan,Northwest China

The Jueluotage area is geographically located in the south part of Hami City, which is within the district of the89°00’-96°00’ in east longitude and41°40’-42°40’ north latitude. This area is about560km from east to west and110km from north to south, with about62000km2in covering district. The Jueluotage area is geologically defined as the volcano-sediment exposure belt between the Tu-Ha-(Turpan-Hami) Basin (north) and Middle Tianshan terrene (south), which is within the aggregate places of Siberia and Tarim plates tectonically. The Jueluotage area can be geologically subdivided into3subunits from north to south, including:Xiaorequanzi-Jingerquan volcanic belt (North belt), Kangguer-Huangshan ductile shear belt (Middle belt) and Aqishan-Yamansu volcanic belt (South belt). There intensive late Paleozoic magmatism with multi-types mineralized deposits widely distribute in Jueluotage area, which has been regarded as a key metallogenic belt in North Xinjiang Uygur Autonomous Region.After comprehended and summarized the previous petrogenesis and matallogenesis researches on the geological objects in Jueluotage area, the author firstly systematically introduced the regional geological characters in Jueluotage area, and then detailed illustrated:(1) the petrogenesis of the native copper mineralized basalt(NCMB),(2) the petrogenesis of the late Paleozoic granitoid intrusions,(3) the matallogenesis of native copper mineralization in basaltic strata,(4) the matallogenesis of the multi-type mineralization related with the granitoid intrusions according to their geological and geochemical characters. Moreover, based on the above4research points, petrogenesis and matallogenesis comparative analysis between the NCMB and Cu-Ni mineralized mafic intrusion, and comprehensive analysis of the strata, structure, and geophysical characters in Jueluotage area, the author further identified the late Paleozoic geodynamic process, established the tectonic-magmatism-mineralization coupled evolution model, and predicted regional metallogenic target of multi-type mineralization in study area. The detailed research can be described as follows:The native copper mineralized basalt (NCMB) was erupted in the end of Carboniferous (～310-303Ma). The basaltic magma was derived from depleted lithosphere mantle without distinct crust contamination during its emplacement. Its magmatic source was characterized as90-100km in depth, garnet peridotite face, and crust contaminated by early subduction through their elements and isotopes geochemistry. The NCMB is formed by delamination of thickening lithosphere within post-collisional stage and distinctly different from magmatism in island-arc and mantle plume systems. The NCMB is unrelated with the early Permian Tarim mantle plume, whereas it shared similar magmatic source with the late Carboniferous-early Permian mafic-ultramafic intrusions in Jueluotage area.The native copper mineralization occurred within basaltic strata was formed by hydrotbermal alteration, which is younger than basaltic magma eruption. During metallogenic process, the Cu is probably from the basaltic strata, and its ore-forming fluids was mainly mixed by basin brine, atmospheric water and organic fluid, which is characterized as lower temperature (<250℃), low salty and strong reduction. The participation of the organic matter was probably controlled the migration and deposition of Cu as native copper state in the ore-forming fluids. The metallogenesis of NCMB was similar with hydrothermal alternated deposits, rather than the magmatic Cu-Ni sulfide mineralization in Jueluotage area. The industrial native copper mineralized bodies are probably explored within the thick basalt layer with intensive structure positions, whereas there is little possibility to explore copper-nickel deposits in the NCMB distribution area.The late Paleozoic granitoid intrusions in Jueluotage area can be subdivided into5granitoid belts, including:Late Devonian Jingerquan granitoid belt, Early Carboniferous Tuwu-Yandon granitoid belt, Early Carboniferous Changtiaoshan-Bailingshan granitoid belt, Early Permian Kangguer shear zone granitoid belt and Late Permian-Middle Triassic Tundun-Shuangchagou granitoid belt. These5granitoid belts exhibit spatial and temporal distribution as:North belt (Late Devonian Jingerquan granitoid belt), North belt (Early Carboniferous Tuwu-Yandon granitoid belt), South belt (Early Carboniferous Changtiaoshan-Bailingshan granitoid belt), Middle belt with its both sides (Early Permian Kangguer shear zone granitoid belt), Middle belt (Late Permian-Middle Triassic Tundun-Shuangchagou granitoid belt). The magmatic sources of late Paleozoic granitoid intrusions were indicated as:Metasomatised depleted lithosphere mantle (Late Devonian Jingerquan granitoid belt), Metasomatised depleted lithosphere mantle with adakitic feature (Early Carboniferous Tuwu-Yandon granitoid belt), crust-mantle mixing source with increasing lithosphere mantle proportion (Early Carboniferous Changtiaoshan-Bailingshan granitoid belt), Crust-mantle mixing source(Early Permian Kangguer shear zone granitoid belt), Juvenile crust source(Late Permian-Middle Triassic Tundun-Shuangchagou granitoid belt). The petrogenetic background of the late Paleozoic granitoid intrusions can be analyzed as:subduction island-arc environment (Late Devonian Jingerquan granitoid belt), back-arc basin environment with subduction side (Early Carboniferous Tuwu-Yandon granitoid belt), back-arc basin environment with passive continent (Early Carboniferous Changtiaoshan-Bailingshan granitoid belt), post-collisional environment (Early Permian Kangguer shear zone granitoid belt), post collisional-intraplate transitional environment (Late Permian-Middle Triassic Tundun-Shuangchagou granitoid belt).There are6types granitoid genetically related metal deposits in Jueluotage area, including: Early Carboniferous porphyry Cu deposits, Early Carboniferous granitoid related Fe deposits, Early Carboniferous granite porphyry related VMS type Cu (Pb-Zn) deposits, Early Permian porphyry (skarn) Cu polymetallic deposits, Early Permian granite related Au deposits and Middle Triassic porphyry Mo deposits. The spatial and temporal distribution of granitoid genetically related metal deposits in Jueluotage area can be summarized as both in North belt and South belt (340-320Ma), Middle belt to both North and South belts (290-270Ma), within Middle belts (240-220Ma), which symmetrically distribute along the Middle belt. Their metallogenic favorites are characterized as Cu in North belt, Fe in South belt and Au-Ni-Cu-Mo in Middle belt, and their ore-forming fluids mainly composed by magmatic water. The granitoid genetically related metal deposits in Jueluotage area can be attributed to3metallogenic systems, including:Early Carboniferous tectonic-granitoid metallogenic system in island arc background, Early Permian tectonic-granitoid metallogenic system in extensional background, and Middle Triassic structure-magmatic metallogenic system in compressive background, and the porphyry types mineralization occurred in each metallogenic system.The Jueluotage area experienced the "Hyperplasia type" orogen evolution process, which was formed by the subduction of the Kalamaili oceanic plates (north) into the middle Tianshan block (south). The late Paleozoic geodynamic evolution of Jueluotage area can be subdivided into5stages, including:Juvenile island arc stage (390-360Ma), ack-arc basin stage (360-320Ma), Collisional stage (320-310Ma), Lithosphere delamination stage in post-collisional background (310-300Ma), Shearing and deformation stage in post-collisional background with mantle plume obstruction (300to270Ma), Shearing and deformation stage in post-collisional background (270-240Ma), Intraplate stage with Tethys remote impaction (240-220Ma). In Early Carboniferous (360-320Ma), The Jueluotage area was a back-arc basin, and the suture zone of North belt and South belt was gradually spreading into the Middle belt, where the lithosphere mantle is gradually thinner form both north and south sides toward centre in this system. In early Permian (290-270Ma), the Jueluotage was in the shearing and deformation stage of post-collisional environment, nevertheless, there intensive magmatism and mineralization distributed along the weak lithosphere zone (Middle belt) due to the "Lateral flow" of Tarim mantle plume, which probably delayed the evolution of hearing and deformation stage in Jueluotage area.The late Paleozoic evolution between geodynamic and magmatism-mineralization in the Jueluotage area can be coupled summarized as follows:Late Devonian granitoid magmatism without distinct mineralization in juvenile island-arc stage (Jingerquan granitoid belt), Early Carboniferous adakitic granite magmatism with copper mineralization close with the subduction side of back-arc basin with (Tuwu-Yandon Porphyry Cu deposits); Early Carboniferous granitoid magmatism with iron mineralization close with passive continent of back-arc basin (Changtiaoshan-Bailingshan granitoid related Fe deposits), Early Carboniferous volcano- granitoid magmatism with copper polymetallic mineralization in back-arc extensional background (VMS type Cu-Pb-Zn deposits), Late Carboniferous mafic magmatism with copper-iron mineralization in early post-collisional background (hydrothermal alternation Cu-Fe deposits), Early Permian mafic to felsic magmatism with multi-type metal mineralization distributing along the Kangguer ductile shear zone in post-collisional stage affected with lateral flow activity of Tarim mantle plume (magmatic Cu-Ni deposits; granite related with Au mineralization, porphyry-skarn type Cu-Ag deposits), Late Permian-Middle Triassic granitoid magmatism with gold and molybdenum mineralization within the Middle belt in post collision-intraplate transitional stage with Tethys remote extrusion (ductile shearing related Au mineralization, Porphyry Mo deposits).Jueluotage area is a high potential mining targeting area and widely distributes late Paleozoic multi-type metal deposits, which are significantly controlled by5key regional metallogenic factors, as:geodynamic setting, magmatism, tectonism, base sediments and late Paleozoic volcano-sedimentary strata. The exploration targets of different types metal deposits can be predicted as follow:the extension area of west-east direction of Tuwu-Yandon granitoid belt (Early Carboniferous Porphyry Cu exploration targets), within and around Carboniferous granitoid intrusions in South belt (Early Carboniferous granitoid related Fe exploration targets), the intensively extensional and structural margin positions in both South and North belts(Early Carboniferous granite porphyry related VMS Cu polymetallic exploration targets), the margin places of Carboniferous volcano-sediment strata along the Aqikuduke fault in South belt (Late Carboniferous hydrothermal alteration Cu-Fe exploration targets), the granitoid porphyry intruded along the Kangguer and Yamansu faults in both South belt and North belt(Early Permian porphyry-skarn Cu polymetallic exploration targets), the mafic intrusion distributes along the Kangguer, Yamansu and Aqikekuduke deep faults (Early Permian magmatic Cu-Ni exploration targets), granites intruded along the Kangguer ductile shear zone and strongly deformed by shearing activities (Early Permian-Middle Triassic Au exploration targets), granites intruded along the Kangguer ductile shear zone (Middle Triassic Mo exploration targets).After all the above research work on the late Paleozoic magmatism and mineralization with their related geodynamic evolution in Jueluotage area, it suggests that the Jueluotage experienced integrated orogenic activities in this duration (380-230Ma). The Jueluotage area can be regarded as a good case to research some forefront theories, such as "Hyperplasia-type orogenic evolution","post-collisional background" and "lateral flow of Mantle Plume".