Antimony ore deposit at Lepa Njiva

Abstract

In the past the antimony ore bearing rock of Lepa Njiva was differently designated and was supposed to be dolomite, hornstone, or even felsite porphyry. Nevertheless, this results from a strong silicification of the original rocks. These appear to have been limestone, quartz sandstone cemented by calcite, and siltstone. The silica content of the altered rocks amounts to 86—97 percent, whereas that of CaO + MgO is 0.3 percent only. The replacement by silica preceded the antimony ore deposition, as is evident from a rather uniform silicification degree without silica enrichment along the ore veins and nests. Characteristic features are irregular carbonate inclusions whithin quartz, that originated from the silicification, and the brecciated structure of the ore bearing rocks. Thereby, the replacements of the primary minerals and postmineral structural changes are indicated.