Characteristics And Prospecting Prediction Of Brittle-ductile Shear Zone Of Pangjiahe Gold Deposit In Feng County,Qinling

The tectonic location of the Pangjiahe Gold Mine is located at the core of the Qinling Orogenic Belt.It is located in the collision suture zone on the south side of the North China Plate and the north side of the Yangtze Plate.In or near Tangzang?Danfeng?Shangnan Great Fault Zone.The gold mine discovered the gold mineralized structural belts No.? and ? in the mine area when the 211 Brigade of the Central Shaanxi Nuclear Industry Group carried out 1:50,000 gold water system sediments;in 1989,a 1:10,000 soil survey was carried out within 20 km2 During the work of geological mapping,No.?,? and ? gold mineralization belts were found on the south side of No.? and ? gold mineralization belts;after that,the geology,structure and morphology and occurrence of the main ore body of the mining area were successively identified.The scale,spatial location and characteristics of ore quality have shown through comprehensive studies that the Pangjiahe Gold Mine is mainly deposited in terrestrial detrital gold-bearing strata in the Lower Donggou Formation(now the Devonian Shujiaba Formation)of the Devonian System.The formation of the bed plays an important role.The inter-layer extruded tectonic zone near the EW direction directly controls the spatial distribution of the ore body.The medium and low temperature hydrothermal alteration is closely related to gold metallogenesis.The eastward and deeper parts of the chemistry are still extending,and the prospecting potential is large.From 1995 to 2006,the surface survey of the west and east extensions of the Pangjiahe gold deposit was carried out,which confirmed that the ore-bearing structure has a large extension to the east.Gold mines such as Xiaosigou and Wujiagou;completed the resource exploration work of the Pangjiahe Gold Mine in Fengxian County,Shaanxi Province from 2007 to 2012,and basically found out that the Pangjiahe Mine ?,?,?,? and ? gold-bearing areas contain gold With the existence of tectonic fault zone,the size of the deposit has expanded from 600 m to 3000 m.Although predecessors have conducted several years of research on the formation lithology,tectonic alteration,source of ore-forming materials and genesis of the deposit,the ore-controlling characteristics of the brittle-ductile shear zone,the brittle-ductile shear zone and the ore The relationship between alteration and alteration,the influence of the shear strength of the brittle-ductile shear zone on mineralization,the characteristics of ore-forming fluids,whether and how the brittle-ductile shear zone controls the ore-forming fluid,and how to predict the depth of the gold deposit There is a lack of systematic research on many issues such as the future prospecting direction.The research work of this thesis mainly relies on the project "Integrating Achievements and Technical Support of Typical Ore Concentration Zones in the Qinling Metallogenic Belt"(Project No.61201506280;2017?2018)to carry out a special project on the ore-controlling brittle-ductile shear zone of the Pangjiahe Mine Research work,by investigating the variation characteristics of ore-controlling brittle-ductile shear occurrence in each middle section of the mining area and surface to reflect the spatial distribution of ore-controlling brittle-ductile shear zone and the spatial distribution characteristics of ore body;In the shear zone(or near the shear zone),the shear deformation tracks related to metallogenesis,study the geometric and kinematic characteristics of the deformation structure related to metallogenesis;observe and catalog the typical ore body sections to study ore control Distribution characteristics of brittle-ductile shear deformation and mineralization alteration.Secondly,collect and analyze samples related to metallogenesis in the mining area.This research work divided the quartz veins in the mining area based on the observation of quartz veins in the mining area and the intersecting relationship.Carry out systematic collection,comprehensively study the basic characteristics of ore-forming fluids in the mining area by measuring the temperature of fluid inclusions containing ore-bearing veins;systematically collect rock(mineral)rock samples in the shear zone,and organize and symbiosis them Identify the thin slices under the microscope to find out the occurrence status of metal minerals and the characteristics of rock micro-deformation;for intrusive rock bodies in the mining area(granite porphyry and diabase)and ores(including ore-bearing phyllite)Collect and analyze the characteristics of the main trace and rare earth elements with the surrounding rock(thousandite),and discuss the correlation between the intrusive rock mass and mineralization in the mining area On the basis of summarizing previous studies on the Pangjiahe gold deposit,it attempts to construct the genetic model of the Pangjiahe gold deposit and proposes a prospecting prediction model to provide scientific and reasonable suggestions for the next step of prospecting in the mine.The main conclusions of the research in this thesis are as follows:(1)The Pangjiahe gold deposit is affected by a multi-level brittle-ductile shear zone.The strength and weakness of the brittle-ductile shear fracture zone in the area have an important influence on the occurrence of the ore body.Through route survey,drawing of joint profiles of ore body exploration lines and measurement statistics of ore bodies in different middle sections,it is found that the ore bodies in the study area are distributed near EW in the lateral direction,and show “upward steepness and gentleness” in the depth direction.The distribution characteristics of the south side column.In addition,a series of high-angle regional brittle-ductile composite fault systems have been formed,which laid the basic structural framework of the region.Among them,the two fault systems that have a greater impact on the Pangjiahe gold mining area are F8(Nianzi Bay-Taoba)and F9(Luohansi-Wayao)brittle-ductile composite faults,secondary shear structure belts in the mining area(for example,three near-EW-oriented main ore-controlling brittle-ductile shear zones F3 and F4 in the mining area),F5)are the three main ore-bearing structures in the mine area,showing the control effect of multi-level brittle-ductile shear zone on the ore body.Through detailed cataloging of the geological profile and the middle section of the tunnel(for example,the middle section of Xishan 980),it is found that the section with strong shearing effect is often the main section produced by the gold ore body,and it is often accompanied by obvious and strong alteration intensity of silicification,Chlorite,sericite and limonite mineralization appear.On the contrary,in areas away from strong shearing,the degree of alteration becomes weaker and no obvious mineralization occurs.Therefore,the change of shear strength is an important research direction for ore prospecting(especially high-grade ore bodies)in this study area,and several types of alteration characteristics that are closely related to mineralization are one of the important signs of prospecting in this area.(2)From the characteristics of ore-forming fluids,the gold deposits in the Pangjiahe mining area are mesothermal hydrothermal deposits with medium-depth metallogenic characteristics.The metallogenic medium water is mainly formation water and deep-circulation atmospheric precipitation.This research work divides the silicification stages in the study area and believes that the silicification in this research area can be divided into three stages.The first and third stages of silicification occur before and after mineralization,and have no close relationship with mineralization.The second stage of silicification occurred during the mineralization period.The fluid inclusion test of the ore-bearing veins during the mineralization period revealed that the uniform temperature of the ore-forming fluid is a medium-temperature fluid as a whole,and the uniform temperature has a peak,mainly concentrated at 220?250?;There are three stages of temperature change,namely early 270?250?,middle 250?220?,and late 180?150?;the salinity peak value of Pangjiahe gold metallogenic fluid is 5.4%?9.8%,which belongs to medium-low salinity fluid;The peak fluid density is 0.80?0.85g/cm3,which is a medium-low density fluid;the fluid capture pressure is calculated,the fluid capture pressure is 40.62?89.53 MPa,and the gold metallogenic depth of the Pangjiahe mining area is estimated to be 1.50?3.32 km,The average metallogenic depth is 2.47 km,which belongs to the middle metallogenic depth.In addition,according to the homogeneous temperature-salinity diagram of the Wilkinson(2001)deposit,it is found that the ore-forming fluid data of the Pangjiahe gold deposit mainly falls in the intermediate temperature zone,which belongs to the intermediate temperature hydrothermal deposit;the oxygen isotope test of the ore-containing fluid inclusions shows that The 18 O value is between 10.3 and 15.45‰,with a certain dispersion,indicating that the ore-forming materials of the Pangjiahe gold deposit mainly come from crust sources,and the water of the ore-forming medium is mainly formation water and deep-circulation atmospheric precipitation.(3)The brittle-ductile shear zone in the Pangjiahe mining area shows the dual control of the ore body's ore control and gold mineralization.Through geometric and kinematic investigations of various structural types formed by shearing in the mining area,field characteristics and laboratory test analysis of ore-bearing veins under shearing,comprehensive research indicates that the brittle-ductile shear in the Pangjiahe gold mining area The cutting zone shows the dual control of the gold ore body morphology control and gold element enrichment(ie gold mineralization).The details are as follows:a.The control effect of the brittle-ductile shear zone on the ore body: the structural characteristics of the stratum and rock deformation in the brittle-ductile shear zone in the area indicate that there has been strong structural deformation in this area,and the deformation structure type is rich,for example,quartz lens Body,quartz veins,shear crumpling deformation,directional arrangement of breccia,interlayer cleavage,and “X” conjugate shear joints,etc.The macro and micro shear characteristics are very significant.Generally,the left-row compression torsion lens body and the right-row tensile torsion crack are developed.A series of tensile torsion and tensile cracks formed during the brittle-ductile deformation transformation process are often important for gold ore bodies.The output of the ore shows the control effect of the secondary brittle-ductile shear zone on the ore body.For example,the ore body often shows the characteristics of sharp reappearance,branching,compounding,expansion and shrinkage in the direction of space.Large lens-like,band-like and network-like characteristics are all important manifestations of the control effect of the brittle-ductile shear zone on the ore body in the region;b.The brittle-ductile shear zone is rich in gold elements(ie gold mineralization)Control effect: The control effect of the brittle-ductile shear zone on gold mineralization in the Pangjiahe mining area is mainly reflected in the control effect of the shear zone on the ore-forming fluid.Three deformation stages,namely the ductile shear stage,the ductile-brittle shear transition stage and the brittleness superposition stage,are continuously changed.The ore-forming fluids in these three deformation stages continuously change with the change of the brittle-ductile shear zone.(4)There is still great potential for prospecting in the deep and peripheral areas of the Pangjiahe Gold Mine.By collecting and comparing the data of the Maatigou gold deposit in the adjacent area,it is found that the two mines are located in the Tangzang-Shangdan mixed rock zone,and the deposits are controlled by the brittle-ductile shear fracture zone.The space tends to be gently inclined,with a tendency of 160-200° and an inclination of 20-45°.The Pangjiahe gold ore body tends to be relatively steep in space,and the ore body's occurrence is 160?175°?55?70°.The steeper the dip angle of the body,the slower the dip angle of the ore body in the deeper,for example,the dip angle of the ore body in the middle section of 1065 is generally 70?75°,while the dip angle of the ore body in the middle section of 980 is 50?55°.Based on this comparison,it is believed that the ore bodies proven in the Pangjiahe mining area are produced at a relatively high angle,and the deep dip ore bodies have not been discovered by exploration,so the research area still has great exploration potential.The Pangjiahe Gold Mine presents a "upward steepness and a slow slope" in the depth direction and a distribution trend toward the south side,and the distribution is near EW.Therefore,in the next step,the prospecting direction should be further deepened in the deep part of the discovered ore-bearing brittle-ductile shear zone,and the direction should continue to be tracked and surveyed in the EW direction,and appropriate engineering measures should be carried out to verify.