Geologic characteristics and genetic models for the talc deDosits in Parana and Bahia. Brazil
巴西Paraná和Bahia地区滑石矿床的地质特征与成因模式

This paper summarized geological characteristics of talc deposits from the two most important talc production districts (Parana and Bahia) in Brazil, and discussed their possible genetic models. The Brazilian participation in the world rank of reserves and production of talc played an important role. The talc deposits in the states of Parana and Bahia are mostly occurred in Precambrian terrains. Although there are many different occurrences of talc ores, those associated with metavolcanic and metasedimentary rock sequences are the most important type. Other types such as those associated with mafic-ultramafic rocks and in the contact between granites and dolomitic marbles or enclaves and roof pendants in granites are less significant. In Brazil magmatic activities leading to talc formation happened during Precambrian (at Bahia) and Cretaceous (at Parana ) times. There are two major genetic models related to the formation of talc deposits. One is hydrothermal metasomatism related to magmatic-derived fluids and another is hydrothermal replacement of metamorphic fluids that possibly derived from formation brines. The latter model may account for most of the large talc deposits in Brazil and elsewhere such as in Liaoning (China) and South Ural.