Geology And Genesis Of The Liuhe'ao Tin Deposit,Guangxi Province

Xinlu tin-polymetallic ore field,located in the concave of southern granite of Guposhan,is an important component of Nanling W-Sn metallogenic belt.Liuhe'ao tin deposit,situated in the middle of the ore field,is one of the representative deposit in the ore field.Based on field geological investigation and data acquisition,the mineralogy,microphysiography,geochemical characteristics and rock-and-ore forming age are studied through mineral and rock identification,EPMA,fluid inclusion homotemperature measuring,stable isotope study,muscovite ⁴⁰Ar-³⁹Ar and SHRIMP dating.The main results are as follows:1?Liuhe'ao tin deposit is a stanniferous sulfide skarn type deposit.2?The EPMA analysis shows the garnet in skarn is andradite series,in which andradite is most abundant,second is grossularite,last is spessartite and almandine;pyroxene is diopside-hedenbergite series,in which the major is diopside and the minor is hedenbergite.3?The main type of fluid inclusion in the deposit is liquid-rich inclusion,the second is vapor-rich inclusion and the last is others.The study of fluid inclusion temperature measuring shows inclusion homogenization temperature of quartz-sulfide stage is 203°C to 310°C,salinity is 3.23 to 10.61 wt%and density is 0.77 to0.91g/cm³;and inclusion homogenization temperature of calcite-sulfide stage is175°C to 220°C,salinity is 2.07 to 5.86 wt%and density is 0.87 to 0.93 g/cm³.4?The analysis of sulfur isotope shows?³⁴S is-2.3‰to 4.3‰,mean value close to zero.The origin of sulfur isotope is homogeneous and possesses the characteristic of meteorolite,indicating the origination of hypomagma.5?Using muscovite ⁴⁰Ar-³⁹Ar dating to gain ore-forming age?160±2 Ma?and using SHRIMP dating to obtain diagenesis age?161.0±1.5 Ma?.Through synthesis comparison of petrology features of Guposhan granite units,the granite of the deposit is thought to be Wanggao Unit.6?The deposit's ore-forming and diagenesis ages are almost the same,petrogenesis and mineralization happened nearly homochromous,indicating the close metallogenic relations between ore-forming of the deposit and Wanggao Unit,ore-forming fluid derived from magmatic hydrothermal and the deposit a product of magmatic hydrothermal.