Geologic, Geochemistry Characteristics And Ore Genesis Of The Taoxiba Tin Deposit In Huichang County, Jiangxi Province

Xikengjing ore field in recent years. In geographically, it is located in Huichang County, Jiangxi Province. In geologically, it is located in the southern segment of the west slope of Wuyishan Metallogenic Belt and in the northern part of the Mikengshan pluton of Xikengjing ore field. Comparatively, in the Xikengjiing ore field, basic research about the Taoxiba tin deposit is poor. In this study, based on the field study, the rock ore appraisal, the electron probe X- ray microanalysis, the pluton zircon dating, the rock ore geochemical analysis, the fluid inclusion measurement and the isotopic composition study, we attempt to clarify the geologic and geochemistry characteristics of the Taoxiba tin deposit, the petrological geochemistry and petrogenic age of the mineralization-related complex body, and ore genesis of the Taoxiba tin deposit. Some opinions were mainly gained as follows:1. The mineralization stages of the Taoxiba tin deposit were divided into magmatic hydrothermal period and supergene period. The hydrothermal period includes pre-metallogenic epoch potassic alteration stage and silicification （planar and threadlike） stage; major ore-forming stages, post-metallogenic epoch fluorite-pyrophyllite stage and carbonate stage. Major ore-forming stages include cassiterite-quartz-topaz stage, cassiterite-quartz-sulfide stage, cassiterite-quartz-mica-sulfide stage, and cassiterite-quartz-chlorite-sulfide stage;2. Mica in the mine area is mainly belonging to the high iron content mica series. Chemical formulate of some minerals were calculated according to the EPMA data: cassiterite-SnO2, topaz- Al1.98（Si1.02O4.06）F1.88, pyrite-（Fe1.02）S2 with some exception of Fe 1.01（As0.01S1.99）2, chalcopyrite-（CuFe）S₂ and （Cu0.99Fe1.01）S2, sphalerite-（Zn0.75Cu0.08Fe0.17）S and （Zn0.83Fe0.17）S. Sphalerite in the Taoxiba tin deposit is Fe-rich sphalerite which is usually occurrence in the mesothermal deposits, indicating its forming temperature is 200 300℃。3. The formation age of volcanic rock zircon U-Pb is 139-141Ma, and the one of intrusive rock is 137-142Ma. It shows volcanic rock and intrusive rock formed almost at the same time, Mikengshan magmatic age is 137-142Ma, magma intrusion and volcanic activity are almost at the same time. Through geochemical analysis, Na₂O/K₂O of rock is less than 1, indicating K-rich rock characteristics; A / NK value of rock is greater than 1, A / CNK values is greater than 1.1, indicating rock belongs to peraluminous rock series; K₂O-SiO₂ diagram of rock shows it belongs to high-K calc-alkaline series.Taoxiba tin deposit is other large size tin deposit that has been discovered in the 4. Fluid inclusions tests show that the first mineralization stage （cassiterite-quartz-topaz stage） fluid inclusion homogenization temperature is 141℃ 403℃, average of 265℃; salinity range of 2.24 10.49 （wt.NaCl%）, average of 6.0 （wt.NaCl%）; the main minerals are cassiterite, quartz, topaz, a small amount of sulfide （fluorite）. The second mineralization stage （cassiterite-quartz-sulfide stage） fluid inclusions homogenization temperature is 117℃ 373℃, average of 207℃; salinity range of 0.53 21.89 （wt.NaCl%） Average 5.7 （wt.NaCl% ）, the main minerals are cassiterite, quartz, sulfides, a small amount of fluorite. The third mineralization stage （cassiterite-quartz-mica-sulfidestage） fluid inclusions homogenization temperature is 129℃ 382℃, average of 200℃; salinity range of 0.35 10.61 （wt.NaCl%）, average of 4.8 （wt.NaCl %）; the main minerals are cassiterite, quartz, mica, lithium iron, sulfide, and a small amount of fluorite. The fourth mineralization stage （cassiterite-quartz-chlorite-sulfide stage） fluid inclusions homogenization temperature is 131℃ 243℃, average of 177℃; salinity range of 0.35 6.59 （wt.NaCl%）, average of 2.3 （ wt.NaCl%）; the main minerals are cassiterite, quartz, chlorite, sulfides （fluorite）. The whole temperature range is 117℃ 403℃, mainly concentrated in 185℃ 230℃. Overall salinity range is 0.35 21.89 （wt.NaCl%）, average of 2.3 6.0 （wt.NaCl%）. Taoxiba tin deposit ore-forming fluid is a kind of F, Cl, S complex which is rich of F, Cl, S, CO₂, H₂O and Sn, Fe, Cu, Zn and other metals, and SiO₂ low-density fluid in the medium temperature. The temperature is 177℃ 265℃, salinity range of 2.3 6.0 （wt.NaCl%）. With decreasing temperature, mineral precipitation in the order is the main precipitation mechanism of tin.5. As for the Taoxiba tin deposit, tectonic structure controlled its mineralization, tin directly originated from granite, and it is a porphyry deposit. Contact zone between the volcanic rock and granite with a tendency of its occurrence change from steep to gradual is a site favorable for mineralization. Sulfide and fluorite have a major implication of mineral prospecting.