Mineralogical zoning in the lead‐zinc ores of the Zeehan field, Tasmania Part I: Introduction and review

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Abstract
The lead‐zinc ore veins of the Zeehan field have long been accepted as excellent examples of hydrothermal zoning centred around the Heemskirk Granite stock, despite several anomalies apparent in earlier descriptions and a general lack of detailed information about the distribution and textural relationships of the ore and gangue minerals. Mineralogical studies show that the zoning can be substantiated, and the apparent anomalies have arisen as a consequence of the combined effects of multiple mineralisation and post‐mineralisation faulting. When allowance is made for these effects, the zoning is seen to be manifested by progressive changes, with increasing distance from the parent stcok, in ore and gangue mineralogy. Although the changes are mostly transitional, they can be conveniently described in terms of four successive zones, namely, 1. Cassiteritic; 2. Pyritic; 3. Sidero‐pyritic; and 4. Sideritic. In general the zonal sequence closely parallels the paragenetic sequence, as determined from detailed textural studies. Systematic changes in sphalerite geochemistry also closely parallel the zonal sequence. The zoning is interpreted as having arisen from progressive changes in the physical and chemical environment of ore deposition, and hence provides an excellent basis for further geochemical and isotopic studies.