Magmatic Evolution And Mineralization Of Banchang Au-Mo Metallogenic Belt In Eastern Qinling,Western Henan

East Qinling orogenic belt is a major composite collision zone between North China and Yangtze Craton,which has experienced complex tectonic evolution,multi-stage magmatism and multi-stage metallogenic events.On the basis of data collection and field geological study,this thesis selected the typical Banchang Cu-Mo deposit,Henanzhuang and Xingshuping gold deposits distributed along the Zhuxia fault in the Banchang polymetallic metallogenic belt in Eastern Qinling Mountains and Western Henan province as the entry point.Within the ore deposit and Zhu Xia fault zone on both sides of the different times in the rock mass is a detailed petrographic,rock geochemistry,ore deposit geochemistry,isotope geochemistry study,discusses the late late Paleozoic and Mesozoic tectonic magma evolution and formation of the geodynamics background,summarizes the spatial and temporal distribution of ore deposits,ore deposit genesis and metallogenic model for the analysis.Combined with geophysical and geochemical information,prospecting prediction is carried out.The main research contents and understandings are as follows:1.The genesis of magmatic rocks has been classifiedThe formation of various types of rock bodies in Banchang area of eastern Qinling can be divided into two periods: the late Paleozoic(ca.450～420Ma)is the dynamic background of the tectonic regime from syn-collision to post-collision when the Yangtze plate subducted and extruded under the North China Plate along the Shangdan subduction zone.The tectonic regime transition period of intracontinental orogeny and extension after the collision of north China plate and Yangtze Plate in late Mesozoic(ca.150～120 Ma).Granite of Banchang suggest that the granite magma derived from the early proterozoic mature partial melting of continental crust material is given priority to,is similar to the deterioration of north qinling unit period of immature metamorphic complex in Paleozoic sedimentary rocks with inhomogeneous melt formed under the background of collision,mantle-derived melts has played an important role in the process of its formation;The study of biotite granites in Banchang area shows that the magma was mainly derived from partial melting of mature continental crust material in early Proterozoic,and mixed with more melting of depleted mantle material.The biotite granite and granodiorite in Henanzhuang belong to unfractionated I-or S-type granite.The study of gabbro in southern Banchang and diorite in Henanzhuang mining area shows that metasomatism occurred in the process of partial melting of gabbro.The Xingshuping biotite granite is a typical A-type granite with adakite characteristics.The magma originated from partial melting of enriched lithospheric mantle material in paleoproterozoic,or from melting of depleted mantle material obviously mixed with mature continental crust material.The Xingshuping granodiorite has obvious Eu negative anomaly,belonging to unfractionated I-type or S-type granites.They are the products of partial melting(slight crystallization separation)of clay-rich,plagioclase-rich lower continental crust at lower temperatures with participation of mantle-derived magma.The western granite beads in the south of the late Mesozoic granite mining area are derived from the early middle Proterozoic crustal material partially melted and mixed with some depleted mantle material in the clay-poor sandy source area.The Erlangping pluton was formed by partial melting of early and middle Proterozoic crustal material,which originated from the common source of the melting of clay-poor sandy rock and argillaceous rock.2.The tectonic magmatic evolution and diagenetic dynamic background are analyzed(1)Analysis of late Paleozoic tectonic environment and dynamic backgroundCombined with previous studies on the tectonic setting of the late Paleozoic in the Eastern Qinling area,it is considered that the late Paleozoic granites in Banchang and its surrounding areas were mainly formed by the melting of continental crust materials and the involvement of a small amount of mantle materials under the extensional environment of co-collision,and changed into the intrasplate-extensional environment with the change of magmatic activity and dynamic background.The tectonic evolution of this period is as follows: South qinling extrusion Shang Dan north ocean make it reduced gradually and eventually form a northward subduction Shang Dan suture zone,the north Qin Lingqun silurian and back-arc basin along the Zhu Xia tectonic belt forming passive impact extrusion,ancient basement rock in qinling complex rocks in crustal thickening caused by the impact extrusion process,and during the next pull during the process of lifting and has joined the lower crust to mantle source materials,The magma was formed by melting and further fused with continental crust materials during the upencroachment process.(2)Late Mesozoic tectonic environment and dynamic background analysisCombined with the evolution characteristics of granites in regional tectonic units in the late Mesozoic,we can reveal the changing process of tectonic environment in this period: In the first stage of late Mesozoic,late Jurassic-early Cretaceous(160～130Ma),the north China plate and north qinling began to transform from extrusion to extension,forming I-type granites mainly from partial melting of ancient crustal materials,with a small amount of mantle-derived materials.The second stage is the middle and late Early Cretaceous(～120Ma),and the main tectonic environment has formed an intracontinental extensional environment.3.The relationship between magmatic evolution and polymetallic mineralization is analyzed(1)Temporal and spatial relationship between magmatic evolution and polymetallic mineralization.The new understanding of the time and space of Banchang ore deposit formation from the scale of deposit is as follows:(1)The shallow part is Ag-Pb-Zn ore body obviously controlled by tectonic process,and the age of formation is 55.0～ 116.6Ma;The skarn ore bodies formed by the superimposition of strong water-salt exchange reaction between the multi-stage high-temperature magma and the low-temperature marble in the central part of the rock are also late Paleozoic products.The deep porphyry ore body with a metallogenic age of 138.6±2.2Ma indicates that it was formed in late Mesozoic and also significantly later than diagenetic age,indicating that the occurrence of rock mass is not the mother rock of mineralization,suggesting that the real mother rock of mineralization of Banchang ore deposit should be deep or near.From the perspective of regional metallogenic scale,the discovery of Yindonggou deposit confirms the existence of Caledonian collision-orogenic and metallogenic events in Qinling area,and Banchang Cu-Mo deposit belongs to yanshanian tectonic-metallogenic events.(2)The relationship between magmatic evolution and polymetallic ore-forming fluidThe three deposits are produced in the same tectonic background,have similar geological characteristics and similar spatial location within the same ore field.The H-O isotope characteristics of ore-forming fluid are mainly middle-low temperature,high salinity and magmatic water from deep.After leaving the magmatic system,the fluid entered different surrounding rocks and underwent different evolution processes due to the different degree of hydrothermal transformation.(3)The relationship between magmatic evolution and source of polymetallic ore-forming materialsThe study of S-Pb isotope characteristics of the mineralization of the three deposits shows that the Pb sulfide of Banchang deposit comes from mantle-derived but part of it is mixed with the material of the southern margin of the North China Plate,while the lead of galena comes from the mantle and part of it is mixed with the material of the lower crust of the North Qinling.The Pb in the Henanzhuang and Xingshuping gold deposits and the sulfide in the Xiaguan ore field share the same lead source,which is derived from the upper crust and orogenic belt of the North Qinling Mountains.The Pb isotope comparison between sulfide and granite shows that there is a certain connection between the source of magma and the source of ore-forming material,but there is a great difference.4.Prospecting prediction is carried out in the study area and a comprehensive metallogenic prediction model is constructed(1)Using the geological abnormal metallogenic theory and prediction methods,MAPGIS software to extract all kinds of geological information(such as strata,structure,magmatic rocks)reflects the different types of geological anomaly,with MORPAS software according to the calculation method of comprehensive prospecting information known mines with the ore metallogenic conditions of the value of metallogenicl favourability degree(or information),mapping the ore-forming geological elements,The study shows that Xingshuping-Banchang-Henanzhuang metallogenic belt has the greatest influence on the ore-controlled ore structure surface(fault and lithologic layer contact zone),followed by the ore-forming geological body(ore-bearing lithologic layer).(2)Regional Bouguer gravity shows that the Bouguer gravity anomaly of Xingshuping-Banchang-Henanzhuang metallogenic belt is generally distributed in NNW to SE direction,with a gravity field characteristic of high in the south and low in the north,reflecting the tectonic pattern of the metallogenic belt.The low-pass filtering component and high-pass filtering component of bouguer gravity field reflect that the density of the deep geologic body and the density of the middle-shallow geologic body have a gradual transition from the southeast to the northwest,and the density is low in the north and high in the south.The shallow geological structure of the 90-degree vertical second-derivative component of bougher gravity field is characterized by the distribution of several near-equiaaxial local high and low phase gravity fields.(2)Combined with the regional geophysical anomaly,the Bouguer gravity anomaly was used to analyze the geological body tectonic pattern characteristics of the study area.The study showed that the Bouguer gravity anomaly in the metallogenic belt generally distributed in WN-SE direction,with the gravity anomaly characteristics of high in the south and low in the north,and the mineralization was distributed in the part of the gravity anomaly gradient belt that became steeper.(2)The 1:50000 geochemical anomaly assemblage and 1:200000 regional geochemical anomaly are mainly distributed in the Zhuxia fault zone and the contact zone between the two plates and the composite rock mass.According to the anomaly intensity and element assemblage characteristics,the 1:50000 geochemical anomaly assemblage can be divided into four levels: A,B,C and D.Three type A anomalies mainly occur in the northeast of Henanzhuang,Banchang and Xingshuping mining areas.The correlation clustering analysis of 26 major metallogenic and associated element combinations in regional geochemical exploration shows that Au,Ag,Pb,Zn,As,Sb,Bi and Hg combinations indicate the co-enrichment of Au and Ag with Low temperature elements such As Pb,Zn,As,Sb,Bi and Hg,and constitute the best indicator element combinations for tectonic geochemical gold prospecting.The ore-forming elements Cu,W,Mo are grouped with the iron-loving elements Fe,Co,Ni,V,Ti and F,and Sn is aggregated with the elements indicating granites.(3)Using the characteristics of regional geochemical distribution analysis of the ore-forming elements distribution and clustering analysis,according to the anomaly intensity and element combination characteristic 1:50000 combination of geochemical exploration anomaly can be divided into A,B,C,D four grades,founded three class a abnormal in the northeast of Henanzhuang,Banchang and Xingshuping mining areas.The correlation clustering analysis of 26 main mineralization and associated element associations in regional geochemical exploration shows that Au and Ag mineralization are enriched with Pb,Zn,As,Sb,Bi,Hg and other low temperature elements,and constitute the best indicator element association for tectonic geochemical prospecting of gold.The ore-forming elements Cu,W,Mo are grouped with the siderophilet elements Fe,Co,Ni,V,Ti and F,and Sn is aggregated with the elements indicating granites.(3)According to the geological abnormal metallogenic theory and prospecting prediction method,the Xingshuping-Banchang-Henanzhuang metallogenic belt divided into three level(class A)favorable prospecting area,located in Xingshuping,Banchang,Henanzhuang mining area and the periphery,five secondary(class B)favorable prospecting area,and four levels(grade C)favorable prospecting area.