The Mesozoic Tectonic Characteristics And Tungsten Mineralization In Maide Area,Tongde County,Qinghai Province

The Maidang area of Tongde County,Qinghai Province is located in the Gonghe Basin where the East Kunlun orogenic belt and the West Qinling orogenic belt are connected.The semi-deepwater gravity flow sedimentary system of the Middle-Lower Triassic Longwuhe Formation and the Indosinian-Middle Late magmatic rocks were developed.Rich in Au,W and other multi-metal medium-low temperature hydrothermal,porphyry and skarn deposits.Based on the analysis of the characteristics of regional tectonic deformation,this paper studies the characteristics of strata,tectonic deformation and tectonic activity of the mining area,clarifies the ore-controlling factors and metallogenic regularities of tungsten mines,establishes the metallogenic model,and has guiding significance for regional geological prospecting.The main findings are as follows:(1)The area roughly experienced the plate tectonic system before the Middle-Late Triassic and the intracontinental orogenic system since the Late Triassic.Based on the relationship between the tectonic deformation pattern and deformation strength of different tectonic layers in the Late Paleozoic-Early and Mesozoic strata,a three-stage tectonic deformation sequence was established,ie,the early(T2 end-T31)thrust nappe tectonic system in the near EW direction(Iso(Fig.3)Overlap thrust faults and closed folds structure),mid-term(T32-3)near-NW-trending superimposed fold structures,and late(J1)near-NW-fractured and left-lateral strike-slip faults;preliminary identification of deformation levels in shallow crusts Department of structural level,deformation time limit is roughly limited to the late Indosinian-Yanshan period.(2)The stratum of the study area is dominated by the Middle-Lower Triassic Longwuhe Group(T1-2),which is mainly distributed in the Bagou fold-thrusting structural belt in the west section of the West Qinling Orogenic Belt.The structural pattern is NW-NNW.The main trend is that the imbricate thrust faults and the folds are all developed.They are dominated by pressure and have slip-slip properties.(3)There are four groups of fault structures in the study area: Nearly EW,NW-NNW,and near SN and NE in space distribution;NW fault structure and early EW fracture-fold structure.The partial recombination and its secondary structures jointly reconstruct the local distribution of the Lower Triassic,and play an important role in controlling the medium-acid magmatic rocks and tungsten deposits(spots)in the area.(4)Ma Rideng tungsten ore bodies are mostly vein-like in the structural fractures and crushing and alteration belts in the Longwuhe Group.The orebodies are generally oriented in the NNE direction,with a high angle toward the SE;the orebodies have a soothing undulation and swelling.,narrow-minded,branching compound features,a total of five tungsten ore body(1-1,2-1,3-1,4-1,5-1 ore bodies),of which 5-1 ore body is blind The ore bodies;NW-controlled thrust belts control the distribution of orebodies,providing hydrothermal tungsten deposits as ore-guiding deposits;NEs are oriented to the secondary fault orebodies and are the main ore-bearing structures.