Study Of The Geological Characters, Ore-controlling Conditions And Genesis For The Bawaiyang Lead-zinc Ore Deposit In Jianou County, Fujian Province

By investigating the stratigraphic and structural characters, rock association andgeochemistry of the Bawaiyang lead-zinc ore deposit in Jian'ou County, centralFujian Province, combining with the indoor testing and contrast researching into theregional tectonic setting, stratum sequence and paleo-setting, this paper suggests thatthe genesis of Pb-Zn deposit is largely related to tectonic and magmatic process.Based on the reformation of thermal fluid and later tectonic events, the lead-zinc orebodies formed in the Dongyan Formation of the Mamianshan Group,belonging toexhalative sedimentary massive sulfide deposit. The Dongyan Formation of theMamianshan Group is basically the source of ore deposit, structural controlling andreformation is the metallogenic condition, and magmatic thermal fluid in the Yanshanepoch is the important source of metallogenic materials. All above processes led to theformation of the lead-zinc deposit in the Bawaiyang area.In the light of recent SHRIMP zircon ages, the Neoproterozoic metamorphicstrata are re-established. The sequence from bottom to top of the Mamianshan Groupincludes the Longbeixi Formation (Pt3l), Dongyan (Pt3dy) and Daling Formation(Pt3dl). According to this new sequence, the Nanyuan-Bawaiyang fold in theBawaiyang ore district is the inverted syncline, and belongs to two-grade regionalhomoclinal syncline. Based on geochemical characters, the prolith of the DongyanFormation of the Mamianshan Group was bimodal volcanics. Basic volcanics wasmainly basalt;acid volcanics was mainly rhyolith, including minor dacite andtrachy-dacite. The petrochemical and geochemical characters suggest that theMamianshan Group was formed in island arc.Based on the outdoor investigation and indoor research (paleomagnetic researchand x-ray petrofabric analysis) and remote-sensing images, it is suggested that theMamianshan Group underwent three stages of tectonic events, as shown by intensivesuperimposition in outdoor outcrops and microstructures. The tectonic stress field inCaledonian epoch is nearly EW-trending, NNE-trending in Indosinian epoch, andNW-trending in Yanshan epoch, which can be regionally contrasted in central Fujianprovince. NEN-trending and NW-trending faults in ore district and its neighbor mightbe related to the regional nearly NS-trending sinistral shear stress field caused by thePacific Plate's subduction to Eurasian Plate during the Mesozoic era.The test data of the fluid inclusions indicate that superimposition and reformationof later thermal fluids played an important role in the formation of the Bawaiyanglead-zinc deposit. The metallogenetic epoch of the Bawaiyang lead-zinc deposit isdiscussed. The metallogenetic modal is established, and the orientation for oreprospecting is preliminarily founded.