Geology Of Xiaobaozhuang Iron Deposit In The Luzong Volcanic Basin,Southern Anhui,China

Xiaobaozhuang iron deposit is located in Luzong volcanic basin,Middle-Lower Yangtze River metallogenie belt,which is one of important porphyry-like type iron deposits found in recent years.Based on the detailed field geological investigation and petrologic study,the study of EPMA,ICP-MS,sulfate isotope and fluid inclusion are carried on the wall rocks and main ore minerals.Our results show that the ?34S values of pyrite and gypsum are abnormally high in each alteration-mineralization stage of ores.Most of the ?34S values of pyrite are between 6‰ and 15‰,whereas most of the ?34S values of gypsum are between 16‰ and 24‰.The ?34S values of pyrite and gypsum gradually decreases with the depth from deep to shallow and alteration-mineralization stage from early to late.The ?34S value of gypsum is 30.1‰ in the Middle Triassic sulfate evaporates salt layers.The high ?34S values of sulfate and sulfide in the Xiaobaozhuang iron deposit indicate that sulfur of deposit is derived from the magmatism and Triassic Dongmaanshan Formation gypsum-salt layer.Microthermometry results show that the homogenization temperature of fluid inclusions in diopside-magnetite-anhydrite stage,epidote stage,carbonate-anhydrite-pyrite stage and anhydrite-quartz-pyrite stage are 326~496?,259~317?,178~280? and 107~189?,salinity are 14%~21%NaCleqv,11%~20% NaCleqv,6%~16% NaCleqv and 2%~13%NaCleqv.The ore-forming fluids evolution is from high temperature and high salinity to low temperature and low salinity.Compare with Luohe iron deposit from the characteristic of metallogenic rock,ore body,ore,alteration zoning and metallogenic temperature,Xiaobaozhuang iron deposit and Luohe iron deposit are two independent deposits.The double structure of Xiaobaozhuang iron deposit and Luohe iron deposit in space may be formed by the emplacement of dioritic magma at different degree of depths.