Abstract:

Studying if there took place extensive exhalative-sedimentary activities in the southeast Yunnan Province has been one of key factors to constrain origin of the Gejiu, Bainiuchang, and Dulong polymetallic deposits. The authors systematically study the geochemistry characteristics of host-rocks in the Bainiuchang Ag-polymetallic deposit in this paper. The host-rocks have the same distribution area with the sea-floor volcano or hotwater origin chert. Then normalized REE distribution patterns of hostrocks can be divided into two groups: One group with higher total REE contents indicates more normal sediments attendance. The other group with lower total REE contents possesses the similar normalized REE distribution patterns and parameters with rich-tourmaline banded hydrothermal sediments in the Canada Sullivan deposit and banded chert in iron-bearing formations in the Canada Agnico-Eugle deposit. And the pairs of trace elements show the similar characteristics with modern sea-floor hydrothermal sediments. In addition, the contents of As, Sb and Ag are similar with that of chert in the Dachang and the Gejiu mining districts. Based on above of all, it is indicated that the Bainiuchang Ag-polymetallic deposit is exhalative-sedimentary origin.

Key words: Bainiuchang；Ag-polymetallic deposit；exhalative-sediment； host-rock；geochemistry, southeast Yunnan Province