An Overview of Sandstone Lead Deposits and their Relation to Red-Bed Copper and Carbonate-Hosted Lead-Zinc Deposits
A. Bjørlykke, D. F. Sangster, 1981. "An Overview of Sandstone Lead Deposits and their Relation to Red-Bed Copper and Carbonate-Hosted Lead-Zinc Deposits", Seventy-Fifth Anniversary Volume, Brian J. Skinner
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Deposits of galena occurring as disseminations in basal quartzitic sandstones constitute a distinct and characteristic deposit type. By world standards they are relatively minor yet they constitute an important resource in some countries.
Host rocks to the deposits are basal quartzitic sandstones deposited in low latitude positions on a sialic basement. In several areas, the basement is anomalously rich in lead relative to average granite. Depositional environments range from continental to shallow marine.
The deposits are characteristically low grade, lead dominant, pyrite free, and silver poor. A common feature is a high-grade core surrounded by a lower grade halo. If present, zinc occurs in a position stratigraphically higher than the lead.
Galena cements sand grains, with the higher grades occurring in originally more porous zones. Silica, commonly chalcedonic in the younger deposits, is the next most common cement.
The preferred genetic model involves transport of metals laterally from adjacent basement highs through permeable channels in sandstones to an environment with a sufficiently high H2S content to precipitate galena and minor amounts of other sulfides.
From a comparison of several features of these deposits with those of two other major intracratonic, sediment-hosted, base metal deposit types (red-bed copper and carbonate-hosted lead-zinc), it is concluded that these three deposit types are not only clearly separate entities in terms of their tectonic and sedimentary environments but were probably formed at different stages of continental evolution.
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