Study On Geochemical Characteristics And Tracer For Sedimentary Environment In Heqing Manganese Deposit, Yunnan Province

Heqing manganese deposit, located in Yunnan province, one of the deposits with lower P and Fe, is a typical manganese deposit formed in Late Triassic in our country. Predecessors’ research mainly focused on the origin and ore-controlling factors of the deposit. But research about the sedimentary environment is much weak. Predecessors’ research about the sedimentary environment of this deposit mainly based on macroscopic geological phenomenon, while neglected the microscopic physical and chemical features, which affected the formation of the deposit. This article study the structural, physical and geochemical features of sedimentary environment by using the method of geology, sedimentology, mineragraphy, petrogeochemistry, stable isotope and trace element, associating with other’s study we get some new achievement and discuss the sedimentary environment at the same time. Research about geological features and major elements of ore-bearing formation show that the deposit formed in a basin which located in the west margin of Yangtze platform, the formation and development of this basin is related to Runanshao fracture. The structural components of roof rock and zonation of metal minerals in space show higher altitude in the northwest while lower in the southeast of the terrain under water, and show that the hydrodynamic force of sea water was strong in the northwest while weak in the southeast. Considering the features of the floor, we think that the media was acidic in the early stage but alkaline in the late period. The ore body located in the transitional zone. The ratio of trace elements such as V and Cr, U and Th, associated with the abnormality of Ce show that the ore-bearing formation formed in the transitional zone from reduction and oxidization. The oxidization became weaker while the reduction became stronger from floor surrounding rock to roof surrounding rock. The mineral zonation and its structure show that the oxidization of media was stronger in the northwest while weaker in the southeast. Research about those can judge the salinity of the media such as Th/U, Sr/Ba and stable isotope of C and O show that the deposit formed in a salt environment as a whole, statistic analysis about Th/U and Sr/Ba reflect that the amount of injected fresh water from floor to roof increased. Research about the distribution of C and O isotope in space reflect that fresh water might inject in at the northwest part where near land. Calculated paleotemperature by Sr which is sensitive to temperature of sedimentary environment and by O isotope reflect that the paleotemperature of sedimentary environment in the normal range.