Post-depositional availability of sulphur and metals and formation of secondary textures and structures in stratiform sedimentary sulphide deposits

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Abstract
Finely-banded, stratiform, metal sulphide deposits in carbonaceous shales contain very significant proportions of the world's resources of lead, zinc and copper. The perfect conformability of the sulphide bands suggests that they formed syngenetically. However, there are also some sulphide minerals in these ores which have textures and structures that could only have formed after the deposition of the enclosing sediments. Many of these features can be explained by diagenetic and metamorphic recrystallization and remobilization, but others indicate precipitation of additional metal sulphides after syngenetic mineralization. This paper presents experimental data concerning the release of sulphur from organic matter and from pyrite, both of which are important constituents of stratiform sedimentary sulphide deposits. It is argued that sulphur made available by these, and other, post-depositional processes, and metals made available by concomitant processes, could be instrumental in the formation of later generations of metal sulphides in syngenetic ore deposits.