Metallogenic Regularity And Model Of Gold Deposits During Mesozoic Precious In Jiaodong Peninsula

Jiaodong Peninsula is an important focus area of gold deposits and gold industrial base.Previous studies have involved almost all aspects of metal deposit,and it's very systematic and comprehensive,such as classification of gold deposit types,source of ore-forming materials,geochemistry of mineral and rock,isotope,metamorphism,geological structure,geotectonic background and evolution about mineralization,etc.However,there are still many problems to be discussed and solved,why are the main gold deposits distributed in the Jiaobei block?Tanlu fault is not only the dividing line between Jiaodong block and luxi block,but also the dividing line between enrichment and non-enrichment of gold deposits,what relationship is there between gold deposits and Tanlu fault?The Tanlu fault is a deep and large fault,which cuts through the lithosphere,but only a few gold deposits have been found in the fault zone,instead,they are rich in the east side of the fault zone.Predecessors have put up many metallogenic models of Jiaodong gold deposits,such as lithospheric thinning non-orogenic type,collision orogenic type,mantle subthermal column type,thermal-extensional type,craton destructor type,and hydrothermal metallogenic type of magmatic core complex uplift and detachment zone.Which one or more models are more suitable?In addition,there are many different views on classifications of gold deposits base on the guidance of plate tectonics,activity time and evolution of Tanlu fault,and relation between magma activity period and formation time of gold deposits.Above all,it's very necessary to set up gold mineralization model base on the theory of plate tectonics,most important,the gold deposits are in the area of intra-craton or mixture area of orogenic-craton?Therefore,it is necessary to establish different genetic models of gold deposits according to crustal properties.This paper studies systematically in tectonic and its evolution,ore-forming materials,mineral geochemistry,magmatic rocks using theory of plate tectonics,and the relations among distribution of gold deposits,magmatic activity,Tanlu faults,and metallogenic model of gold deposits in Jiaodong according to the crustal properties of different units,the history of tectonic magma evolution and the distribution characteristics of gold deposits,furthermore,the different gold deposit areas and metallogenic models of Jiaodong block are studied.The following are main results and understanding.1.Magmatic rocks are closely related to the distribution of gold deposits,and four magmatic sequences in the Mesozoic correspond to the development of three gold deposits.The distribution of magmatic rock mass in this area is clarified based on the research on the development and distribution of magmatic rock mass and the formation of gold deposits in Jiaodong block,and 4 magmatic activity sequences of Mesozoic are summarized:(1)The Late Triassic(237-201 Ma),represented by the Jiazishan rock mass,this period is consistent with the Indosinian era,by the collision between North China and the Yangtze plate,which is the intrust magmatic rock mass in the extruded tectonic setting,no gold deposits were found in this magmatic rock mass;(2)Late Jurassic(163-145Ma),represented by the Jiaojia-Linglong-Yujiahe magmatic rock mass,crustal thickening and crustal remelting because of regional tectonic compression,it forms the continental arc granite in the regional extrusion tectonic setting,the 'Linglong' type gold deposits were formed in this period;(3)The Early Cretaceous(130-115Ma),represented by the Guojialing rock mass.The magmatism during this period has the characteristics of bimodal magmatism,reflecting the background of stretching dynamics;(4)The Late Cretaceous(115-100 Ma),represented by the Weideshan rock mass,which corresponds to the large-scale thinning period of the lithosphere in eastern China and is the peak period of the continental rift.It has relations closely among the tectonic-magmatic events,gold mineralization in the Jiaodong area and the interactions of the Tethyan,Paleo-Asian Ocean and Pacific plants,especially the emplacement of the mantle plume.2.There are four stages of magmatic development in Jiaodong area period,they are closely related to the subduction,sinking,reentry-magma,Tanlu fault activity,lithosphere thinning and tectonic transition in orogenic zone.The 3 metallogenic periods of gold deposits in Jiaodong are 163-145 Ma,130-115 Ma and 115-100Ma corresponding to the Linglong,Guojialing and Weideshan rocks,the most important period is 120-100Ma.The mineralization period and the maximum thinning of the lithosphere,the structural system changed from compression to extension,and the strongest period of right-slip normal fault are consistent.3.Based on the study of distribution of typical gold deposits,metallogenic age,ore-forming fluid and types of gold deposits in Jiaodong area,the gold deposits are divided into 5 categories based on the plate tectonics and the formation mechanism and evolution of plate tectonic activities.Deep fault type,base structure type,composite fracture type,detachment fault type and shear-tension type fracture type.It is proposed that the gold deposits are distributed on the uplift belt and it's proportional to the scale,size of the gold deposits and the distance from the Tanlu fault.4.The study on the formation and evolution of gold deposits in Jiaodong area,the types of gold deposits,the Tanlu fault and the geological structure of Jiaodong area,and their relationship with the ancient Asian region,the Pacific region,the Tetis region,and the Qinling-Dabe-Sulu tectonic belt,In this paper,the genesis type and mechanism of the gold deposit in Jiaodong area which belongs to plate collisional non-collisional type are proposed.It is divided into 4 major Jiaodong gold deposit mineralization area.s:plate collision subduction-demolition and reentry lava-gold deposit distribution area,stretch basin marginal fault zone-gold deposit development area in Early Cretaceous,Jiaobei magma-gold deposit distribution area and Tanlu fault zone magmatic rock-gold deposit area.Jiaobei district is the most favorable area for the development of gold deposits.5.Three metallogenic patterns of gold deposits were established:fracture-magmatic intrusion-upper crust-basal green schist-four-piece composite action,unconformity-interlayer fracture-magmatic Trinity and subduction-disassembly-return-magmatic gold deposit mode.Based on the study of the age and mode of activity of Tanlu fracture and the relationship with the formation of Jiaodong gold deposit,the conclusion is that the largest period of activity of Tanlu fracture is in the late Jura-cretaceous period.This is consistent with the output of Jiaodong gold deposit.The secondary NE and NNE fault associated with the Tanlu fault activity and its intersection with NW and near EW fault are the favorable enrichment areas of gold ore.Tanlu fracture cuts into the lithosphere-upper mantle,it's an upwelling channel for minerals,and also limits the formation of gold deposits in the Luxi block.On that basis,the complex metallogenic model is set up,the structure of Tanlu fracture activity-regional tectonic system transformation from extrusion to stretch)-lithosphere thinning-material upwelling-Jiaodong Group mineral migration-gathering at fracture intersection in different directions-curtain activity-formation of multi-stage secondary gold deposits-lithosphere changing tectonic-magmatic-metamorphic.Three major gold metallogenic patterns were established:marine green schist facies(East-West distribution)-Tanlu fracture-magmatic rock intrusion(Jiaobei)-upper crust-Jiaobei'Jiaojia'(fracture zone internal erosion type)-'Linglong style'(pulse rock)gold deposit metallogenic model,Metamorphic miscellaneous rocks and rock layers(magmatic rock mass)sliding broken gold ore metallogenic model and orogenic belt subduction-dismantling-reentry-magmatic gold deposit model.Above all,the research in the paper on the gold deposit types,metallogenic regularity and its mechanism,which provides a certain foundation in regional metallogenic regularity and prospecting exploration of gold deposits in Jiaodong.It has important practical and social significance.