Research On Metallogenesis Of Gold-silver-polymetallic Deposits In The Halaguole Area,Eastern Kunlun Orogenic Belt,Qinghai Province

The Halaguole area is located in the East Kunlun Orogenic Belt of Qinghai Province,which belongs to the Kunnan belt.This paper reports the prospecting results of the Halaguole area in recent years,focusing on the metallogenesis of the Luotuogou Cu polymetallic deposit,Halaguolebei Co-Ni deposit,Santonggoubei manganese deposit,Xingshugou Au deposit and Halaguole Ag polymetallic deposit.Based on the geological characteristics of the deposits,the mineralization conditions,the mineralogenetic epoch and the spatial and temporal distribution of mineralization,we establish the regional metallogenic model of the Phanerozoic metal deposits.The main achievements are as follows:The Halaguole area experienced the formation of the Wanbaogou Oceanic basalt plateau in Meso-and Neoproterozoic epoch,the evolution of the Proto-Tethys ocean tectonic domain(the early Caledonian epoch and the late Caledonian epoch),the evolution of the Paleo-Tethys ocean tectonic domain(the late Hercynian epoch and the late Indo-Chinese epoch).The subduction direction of the oceanic crust between the Wanbaogou oceanic basalt plateau and the Qaidam block was further determined as north-south bidirectional subduction,that is,the subduction of oceanic crust from south to north to Qaidam and from north to south to Wanbaogou Oceanic basalt plateau occurred simultaneously.The trench-arc-basin system in the southern margin of the Qaidam block and the arc-trench system in the northern margin of the Wanbaogou oceanic basalt plateau were formed respectively.The former belongs to an ocean-to-continent subduction,while Vthe latter,by contrast,belongs to an oceanic subduction environment.In the Caledonian epoch,Wanbaogou oceanic basalt plateau was in an oceanic environment,and the Luotuogou porphyry-type Cu polymetallic deposit and the Halaguolebei magmatic liquation Co-Ni sulfide deposit developed in Kunnan belt were formed during the subduction of the oceanic crust to the Wanbaogou oceanic basalt plateau.By the end of Caledonian epoch,the oceanic basalt plateau became a part of the continental crust after it was collaged to the Qaidam block along the current location of the Kunzhong fault.Studies on typical deposits show that:1)There are two periods of porphyry-type mineralization in the Halaguole area,respectively,the Luotuogou porphyry-type Cu polymetallic deposit(?473Ma)formed in the oceanic subduction environment related to the Wanbaogou oceanic basalt plateau and the Xingshugou porphyry-type mineralization formed during the Andean orogeny under the subduction of the Paleo-Tethys ocean.The determination of two stages of porphyry mineralization in Halaguole area has enriched the understanding of porphyry mineralization in eastern Kunlun area.Therefore,it can be summarized that there are four stages of porphyry mineralization in eastern Kunlun area,namely the early Caledonian epoch,the late Caledonian epoch,the late Hercynian epochearly Indo-Chinese epoch,the late Indo-Chinese epoch.Previous studies have emphasized the late Caledonian epoch and the late Indo-Chinese epoch mineralization.Furthermore,the discovery of the Luotuogou porphyry-type Cu polymetallic deposit(? 473Ma)indicates that porphyry-type mineralization can also be formed in the oceanic subduction environment of the early Caledonian epoch,which provides reference for further prospecting.2)There are several mafic-ultramafic complexes in Halaguole area,such as Halaguolebei,Luotuogou and Dongdakende complexes.The distribution of these mafic-ultramafic complexes coincide with that of the NWW high-accuracy ground magnetic anomaly,and formed a NWW “mafic-ultramafic complexes belt”.We consider that this mafic-ultramafic complexes belt may be a subduction collage zone.Compared with the Halaguolebei Co-Ni deposit and Xiarihamu Cu-Ni deposit,we consider that the formation of the Halaguolebei Co-Ni deposit is controlled by the southward subduction of Proto-tethys ocean,which is the product of the oceanic subduction process.This process will lead to a small proportion of the upper mantle melting.The small-scale melting VI mechanism will lead to the low intensity of the mafic-ultramafic magmatic activity of the Halaguolebei Co-Ni deposit.So it is concluded that large magmatic liquation Cu-Ni sulfide deposit cannot be generated during the oceanic subduction process.3)The ore bodies are stratified and in conformity with the Nachitai group,which have obvious sedimentary characteristics.The manganese-bearing mineral of Santonggoubei manganese deposit is rhodochrosite.The geochemical characteristics of manganese ore and siliceous rock indicate that hot water sedimentation plays an important role in the formation of the deposit.We define the deposit type as hot water depositional ore deposit.There are two landmark strata in the mining area: siliceous rock and carbonaceous black rock series.They are closely related to the manganese ore bodies,so the “double sedimentary formation” model of hydrothermal sedimentary rock plus carbonaceous black rock series are put forward.4)Based on the studies of the Xingshugou Au deposit,we determine the porphyry system controlled by the subduction of the Paleo-tethys ocean of the late Hercynian epoch(? 254Ma)and the mineralized bodies controlled by structure in the post-collisional environment of the late Indo-Chinese epoch.The alteration and mineralization of the former are controlled by granite porphyry and distributed around the inner and outer zones.The wall rock alteration has the characteristics of wide scope and high strength and consists of propylitization,argillization and phyllic.The ores are mainly disseminated and veinlet-disseminated.We consider that belong to the typical porphyry mineralization.The wall rock alteration of the latter are mainly silicification,sericitization and ferrodolomite,and the ore-forming fluid is medium and low temperature and low salinity.O-H isotopes indicate that the ore-forming fluid are composed of meteoric water and magmatic water.The genetic type should be low sulfidation epithermal deposit.The late Hercynian igneous activity is widely distributed in Xingshugou area,including gabbro and granodiorite and so on,which are closely related to gold orebodies.Combined with the field geological characteristics and the crosscutting relationships between mineralization periods,we consider that Xingshugou Au deposit has the characteristics of porphyry-type mineralization superimposed epithermal mineralization.5)The orebodies of Halaguole Ag polymetallic deposit are controlled by faulted structure.The ore minerals are largely hessite,argentite and chlorargyrite,and wall rock alteration are mostly silicification,carbonatization,kaolinization and adularization.The presence of hessite in Halaguole gold-silver polymetallic deposit indicates that ore-forming materials have the characteristics of mantle-derived.The ore-forming fluids are low temperature and low salinity,and O-H isotopes show that large amounts of meteoric water was added into the ore-forming fluid.We consider that the genetic type should be low sulfidation epithermal deposit.Moreover,based on the study of four veins,we first put forward the concept of “group of orebodies”.Furthermore,the discovery of silver halide(chlorargyrite)and secondary silver mineral(acanthite)indicate that supergenic oxidation and secondary enrichment have occurred.Through the study of typical deposits in Halaguole area,we determine the porphyry-type deposit,magmatic liquation Cu-Ni sulfide deposit,sedimentary deposit and epithermal deposit.On this basis,combined with the metallogenic epoch and the tectonic setting of the several typical mineral deposits in Halaguole area,the metallogenic series are classified as follows: 1)The metallogenic series is related to the evolution of the Proto-tethys ocean in the early Paleozoic,which contain the typical mineral deposits of the Luotuogou porphyry-type Cu polymetallic deposit,Halaguolebei magmatic liquation Co-Ni sulfide deposit and Santonggoubei hot water depositional Mn deposit.2)The metallogenic series is related to the evolution of the Paleo-tethys ocean in the Mesozoic,which contain the typical mineral deposits of the Xingshugou porphyry+ epithermal Au deposit and Halaguole low sulfidation epithermal silver polymetallic deposit.Through systematic research of the geological characteristics,geological setting,geochemical characteristics,ore-forming age,ore-forming material source,metallogenic fluid,metallogenesis and ore-forming conditions of typical deposits in Halaguole are,we establish the regional metallogenic model of Au-Ag polymetallic deposits in the Halaguole area.