Major element geochemistry of the host rocks in some sediment- hosted copper deposits.

Abstract

The chemical compositions of fine-grained sedimentary rocks provide important genetic indications. Some 378 analyses on samples from deposits in the Zambian copper belt show that the relatively high Mg (and Li) contents are characteristic of magnesian clay minerals early in evaporite sequences and that primary fine-grained rocks rich in K-feldspar and low in quartz are inferred from very high K2O concentrations and K/Al ratios in the Ore shale formation. The feldspar is probably of diagenetic/hydrothermal origin. The Cu and Co concentrations in Shaba are carbonate-hosted, with very unusual chemical compositions in the underlying rocks, possibly derived from volcanic glass altered by reactions with brines. The German Kupferschiefer does not show major element compositions different from those of common black shales.-R.E.S.