The sedimentation-reworking genesis of Dongchuan-type stratiform copper deposits

Abstract

The Dongchuan-type copper deposits have long been studied and well reported because of their great economic significance. The present paper proposes a “sedimentation-reworking” origin for this type of deposits to challenge the current “sedimentation-metamorphism” model which has been widely accepted since 1970s. According to the new idea, orebodies were not directly deposited in the Luoxue dolomite where they are hosted. Instead, copper was preliminarily concentrated in the Yinmin Formation. During or after diagencsis. copper in the Yinmin Formation was mobilized and leached by hydrothermal solutions derived from the interstitial water of sediments under the high geothermal gradient of rift environment. Thus, copper was transported from the source bed (the Yinmin Formation) upward to the Luoxue algal dolomite where sulfur was produced by the reduction of sulfates. The copper sulfides were formed through replacement of initial sulfides by Cubearing solutions.