The Genesis of the Giant Dajiangping SEDEX-Type Pyrite Deposit, South China

摘要

The Late Devonian Dajiangping pyrite deposit in South China is a giant sediment-hosted stratiform deposit and contains 200 Mt of pyrite ores with an average grade of 30 wt % S. The orebodies are hosted in carbonaceous siltstone and black shale and consist mainly of laminated pyrite ore. Small euhedral pyrite crystals (pyrite 1) and larger subhedral pyrite crystals (pyrite 2) are the main ore mineral and occur as laminated aggregates of subhedral to euhedral grains. Anhedral pyrite crystals (pyrite 3) associated with pyrrhotite are present in the host rocks and are interbedded with the ore layers. Mass-balance calculations reveal that the pyrite ores have Al-normalized Ca, Mg, Mn, Si, Na, K, and organic carbon contents similar to the host sedimentary rocks, precluding substantial carbonate dissolution and a stratiform replacement origin for the ores.