| Northeast Fujian is located in the central part of the volcanic belt of southeast China’s coast,in the middle and west of the Minzhong Rift Valley Belt in the eastern part of the South China Fold System and the northwest of the volcanic fault zone in east Fujian,Zhejiang Province.indicating that the geological conditions for mineralization in the area are good and the prospect for mineralization is broad.However,in recent years the effect of mineral search is not good,mainly because the mining before not surveyed,not grasp the law,the target area is unknown,work more and poor results,belong to the "chicken rib" mineralization survey area.Therefore,it is of great theoretical and practical significance to study the mineralization control structure system,mineralization elements,mineralization process and spatial and temporal structure of mineralization in this area from a holistic perspective.In this thesis,on the basis of gold and silver polymetallic mineralization in the system research area,the silver polymetallic deposit,gold deposit,east gold(silver)deposit as a typical deposit,the sulfide Rb-Sr isotope dating is studied to obtain higher accuracy of minerenic age,the fluid package temperature measurement and laser Raman test to explore the physical and chemical conditions and fluid composition,and the source of metallogenic fluid and mineral materials are analyzed.On the basis of thorough analysis of the metaleralization background of regional gold and silver polymetallic ore,the temporal structure of regional gold and silver polymetallic mineralization is analyzed,the spatial structure of regional gold and silver polymetallic mineralization is revealed,and the metallogenic law of gold and silver polymetallic mineralization is summarized.Based on the summary of the volcanic rock ore-forming regularity of northeast Fujian and the extraction of the geophysical and chemical prospecting information,the prospecting target area was delineated.The results of this thesis not only redefine the origin of gold and silver polymetallic deposits,but also provide a theoretical basis for the next prospecting work.New progress and new understanding have been made in the following aspects:1.The mineralization type and mineralization period are dividedThrough a comprehensive study and analysis of the known deposits(points)in the area,combined with the nature of the enclosing rocks,the relationship between ore-controlling structures and magmatic rocks,the source of ore-forming materials,the physical and chemical environment of ore-forming and the characteristics of ore-forming action,the known deposits in the area can be classified into three major genetic types,such as magmatic hydrothermal type,volcanic-subvolcanic hydrothermal type and contact account type,among which the volcanic-subvolcanic hydrothermal type is the main type of mineralization in the area.According to the comprehensive study of field observation and microscopy,the mineralization period of the study area is divided into the following stages: pyrite-quartz→ sulfide-rich → sulfide-silver → carbonate;secondly,the epigenetic oxidation stage,which is manifested by the oxidation of primary sulfide minerals under epigenetic oxidation conditions to produce oxidized ores.2.The structural deformation characteristics and the structural ore control rules are determinedThe study area is in a tectonic pivotal position,and there are frequent and strong tectonic effects in the area,mainly influenced by the multi-stage left-slip movement of the Zhenghe-Tai Po fault zone,and the stratigraphic rocks are developed with tectonic fissures.The fracture structures in this area can be divided into fracture structures with compressional as the main activity and multi-phase activity;shear structures with tectonic laminae developed in the early stage with mainly tough and brittle activities;and late stage brittle structures with mainly tensor-torsional and implosion activities.The main tectonic surface of the Zhenghe-Tai Po rift zone is a large scale north-east oriented rift zone,and the early stage is mainly tough-brittle activity,and the nature of the rifting activity is mainly left-slip shear,producing a group of north-east oriented rift valley,and the distribution of stratigraphy and volcanic rocks is controlled by it.During the metallogenic period,the main tectonic body position migrates in an eastward direction,and at the same time also shows left-slip characteristics,although this movement occurs in an extrusion environment during this stage.The brittle fracture activity in the surface crust is the main fracture activity,producing a combination of secondary fractures with different extensions and lateral rows of geese,forming tectonic schist and black fault mud as a fluid blocking layer in the lower and upper plates.The various types of breccias formed by the late brittle tectonic tectonics are used as ore-holding enclosures with good continuity and large cutting depths,which are conducive to large-scale migration of ore fluids from deep to shallow and formation of ore bodies.3.The metallogenic process and metallogenic regularity of gold-silver polymetallic ore are analyzed and summarized(1)The standardized distribution curves of spherical meteorites between ore and stratigraphy,magmatic rocks and vein rocks are all flat and right-dipping based on the research results of rare earth elements in the deposits of northeastern Fujian,which means that the source of ore contains surrounding rocks and deep rocks;the δ34S value is close to the original mantle sulfur as shown by the results of rock ore sulfur isotope analysis,which can be inferred that the initial sulfur source is mainly magmatic sulfur,and the ore Pb and volcanic rock Pb The isotopic composition of ore Pb and volcanic Pb is consistent,being mixed Pb of upper crustal and mantle origin;combined with the moderately radioactive(87Sr/86Sr)i composition of Pb-Zn sulphide,it shows that the mineralized material mainly originates from the crust,and a small amount of mantle origin material is added.The quartz oxygen isotope indicates that the mineralizing fluid is a mixture of circulating magmatic water and atmospheric precipitation,reflecting its homology and inheritance characteristics.In summary,the mineralization in the study area is closely related to the volcanic activity.(2)In terms of mineralization time evolution,the mineralization in this area shows the structural characteristics of inheritance and stage.To a certain extent,the mineralization evolution in this area matches the regional geological tectonic evolution,and the mineralization evolution in this area is divided into four mineralization periods,namely the mineralization pre-enrichment period,the initial,superimposed enrichment period,and the mineralization epigenetic oxidation period.(3)In terms of the spatial distribution of mineralization,the mineralization in this area presents structural characteristics such as clustering,equidistant,directional,and zoning.Mineralization and ore-controlling structures largely influence the output pattern of mineralized bodies.4.The regional prediction system was initially established and the metallogenic prediction was madeBy grasping the regional geological background of mineralization,analyzing the factors controlling mineralization,deeply exploring the process of mineralization and summarizing the spatial and temporal structure characteristics of mineralization,based on deepening the understanding of the regional mineralization law,a prediction system was constructed for the first time in northeastern Fujian,and three mineralization prediction areas were screened out by using a comprehensive mineralization search model and mineralization signatures,including one A-grade prediction area,one B-grade prediction area and one C-grade prediction area.2 mineralization target areas were selected among the prediction areas,which effectively guided the mineral exploration work in the study area. |
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