Abstract

Tin with associated tungsten and rare earth element mineralization at the Zaaiplaats mine is hosted by alkali feldspar granites of the Lebowa Granite Suite which intrude granophyric granites of the Rashoop Granophyre Suite. From the upper contact downward the alkali feldspar granites include a marginal pegmatite (stockscheider), the fine-grained Lease Granite, and the coarse-grained Bobbejaankop Granite. The major mineralization styles consist of subhor-izontal, tabular zones (low-grade orebodies) containing disseminated cassiterite in the Lease Granite, a zone of disseminated cassiterite mineralization (ZDM) in the Bobbejaankop Granite approximately 50 m below the Lease Granite, and a series of shallowly plunging and branching pipe orebodies which occur in both granite types and which show a close spatial relationship to zones of disseminated mineralization. The granites contain miarolitic cavities generally less than 5 mm in diameter which range from more than 10 vol percent in the upper facies of the Lease Granite to less than 1 vol percent in the deeper part of the Bobbejaankop Granite. Miarolitic cavities are filled or partially filled by hydrothermal minerals including quartz, albite, chlorite, sericite, fluorite, hematite,