Abstract:

“Datangpo type” manganese deposits of Nanhua System studied in this paper are located in Songtao County of Guizhou Province. Based on years of exploration and research, there are three superficial deposits of Xixibao manganese deposit, Yangjiawan manganese deposit, Lijiawan manganese deposit, making up a new pattern of “Manganese Triangle”, in which Yangjiawan manganese deposit is a medium-large one. Geological and geochemical characteristics of manganese-bearing rock series of Yangjiawan manganese deposit indicate that in manganesebearing rock series exists volcanic material such as tuff, and mineral association of pyrite, barite and calcimangite, which shows a hydrothermal origin. Besides, this manganese ore falls on the hydrothermal deposition region according to illustrated diagrams of Fe-Mn-(Ni+Co+Cu)×10 and P₂O₅-Y, and contents of As, Sb, Ga, Ag, Ba, Zn, Co, Bi, W and Pb are higher than those of normal sedimentary rocks, moreover, ratios of Co/Ni, Y/Ho and Nb/Ta all show similar characteristics to hot fluid of ocean-floor black chimney. The overall content of rare earth elements of this manganese deposit is relatively high, and the differentiation of light and heavy rare earth are obvious, and distribution pattern is smooth, slightly lean to the right. In addition, δEu (0.49-0.71), δCe(0.94-1.25) and Ce/La-La/Yb diagrams also show features of hydrothermal participation. Besides,  δ¹³C_PDB and δ¹⁸O_PDB of the manganese deposit range from -3.80‰ to -4.17‰ and from -6.95‰ to 8.78‰, respectively; therefore,  the mineralization temperatures are estimated from 54.2 to 65.7 ℃, belonging to the low and medium temperature hydrothermal condition. In conclusion, the authors consider that Yangjiawan manganese deposit is of hydrothermal genesis.

Key words: hyderthermal sedimentation, geohemistry, manganese deposit, Yangjiawan, Guizhou