Abstract

Variations in thickness and metal content of selected stratigraphic units cut by drill holes in the East Tennessee zinc districts have been analyzed by regression techniques. Such analysis demonstrated that as the thickness of an underlying limestone unit is decreased chiefly by solution thinning, overlying fine-grained dolomite units increase in thickness by collapse dilation. Variation in metal content is closely associated with this inverse thickness relationship because of the deposition of the ore minerals in the dilation openings. Most of the ore is found where the fine-grained dolomite units were so dilated by collapse as to form a series of rubble to crackle breccias. Hypothetical cross sections synthesized from widely spaced drill-hole data show mineralized structures of a size, shape, and distribution of metal comparable to those diagrammed in the literature from actual field relations. From these composite models of hypothetical structures the relative position of a particular hole can be approximated within its own structure. The exploration geologist thus has a numerical aid for estimating the amounts of offset needed to penetrate the most favorable part of the mineralized collapse structure with second-stage drill holes.

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