The Research Of The Main Fracture Structure’s Feature In Xiangshan Volcanic Basin

Xiangshan uranium ore field locates in the superimposed areas between Gan—Hanguranium metallogenic belt which belongs to volcanic—type and Dawang mountain—Yushan granitic uranium metallogenic belt. Jiang—Shao suture zone leaves50Km north ofit,and Yingtan—Anyuan major fracture locates25Km east of it, while Dexing—Suichuandeep fault lies its west. It has a good mining environment. As the largest volcanic uraniumore field, fracture ore-controlling takes an obvious position. The thesis is based on thegeological survey of l:50000regional mineral (map codes:G50E003008、G50E004007、G50E004008). On the basis of data including basement and cap rock structural feature andso on, the main faults’ feature in study area is studied systematicly with structural analysis,structural measured section, joints statistical analysis, microstructure and petrofabricanalysis. The thesis mainly achieves the following results and understanding:(1) Dexing—Suichuan, lies in the west of Xiangshan, is the first level deep fault instudy area, controlling the distribution of main faults in Xiangshan volcanic basin. Itsepisodic movement is obvious: it expressed as sinistral strike-slip from Caledonian toYanshanian, then in the late Yanshanian it expressed as extension and in the Himalayanperiod it mainly shows squeezing action.(2) There develops two ne-trending main faults in Xiangshan volcanic basin, whichare Zoujiashan—Shidong fault and Shang’an—Luoshan fault; there also exists twonw-trending faults, which are Shidong—Xiaopi fault and Shutang—Jihekou fault. It isconsidered that ne-trending faults are the main structure, low-order fracture of Dexing—Suichuan deep fault in the study area after analysis, which is influenced by Dexing—Suichuan deep fault.(3) Zoujiashan—Shidong and Shang’an—Luoshan fault had experienced multi-stagestectonic activities, and its manifestation is mainly normal-sinistral strike-slip, and alternative left lateral with right lateral slip is the structural feature, which is similar to theproperty of Dexing—Suichuan deep fault. Shidong—Xiaopi and Shutang—Jihekou faultare secondary fault of Zoujiashan—Shidong, whose properties are all norma-right lateralstrike-slip, and its scale and development degree are inferior to Zoujiashan—Shidong fault.According to mating and statistics of Joints, it confirms the formation of nw-trending andne-trending faults more: the early ne-trending and nw-trending faults formed at the sametime, then the late multiple tectonic activities of ne-trending faults lead nw-trending faultscut into norma-right lateral strike-slip fault.(4) On the basis of the study of microstructural features and deformation environmentof the main faults, the thesis believes that Zoujiashan—Shidong fault was active indifferential stress and shallow level, and associated tectonite formed in the environment ofprehnite-pumpellyite metamorphic facies. Shang’an—Luoshan fault had experiencedmulti-phase tectonic activity: the early fracture expressed as brittle-ductile deformation,and tectonic activity belonged to greenschist facies at middle crust level,while brittledeformation dominated later period. Deformation level of nw-trending fault belongs toshallow surface as secondary fracture.(5) Quartz fabric of tectonite in study area are measured using X-ray diffraction.Diffraction patterns show large circle girdle styles in metamorphic basement and earlydevonian granite, south of study area. Most of the trend of optic axis of quartz’s poledensity are similar to the trend of regional ne-trending faults. The results show that thestructure trackway of metamorphic basement has been integrated into the ne-trendingstrike-slip faults and granite in early devonian matches to the regional NE structure.It isconsidered that metamorphic basement and early devonian granite had experiencedbrittle-ductile deformation through petrofabric analysis. Diffraction patterns of volcaniccomplex in the early cretaceous are spherically symmetric in general and there is noobvious orientation in optic axis of quartz, which further confirms the the brittle tectonicsetting of early cretaceous.