Petrographic and geochemical evolution of pervasively altered Bushveld granites at the Zaaiplaats tin mine

The tin zone: sediment-hosted hydrothermal tin mineralization at Rooiberg, South Africa

“…suite (Strauss, 1947;Leube and Stumpfl, 1963;Phillips, 1982;Rozendaal et al, 1986), although this cannot be established with the present information. Differentiated (more evolved) phases of this suite, host similar metallization and alteration in the endo-granitic Zaaiplaats tin field suggesting that a similar fluid source for the Rooiberg manto-style deposits is likely (Taylor and Pollard, 1988;Pollard et al, 1991;McNaughton et al, 1993). Universally, formation of most tin deposits in veins, breccias and replacement bodies is attributed to saline hydrothermal fluids of essentially felsic magmatic origin (Taylor, 1979).…”

Evaluating the Changes from Endogranitic Magmatic to Magmatic-Hydrothermal Mineralization: The Zaaiplaats Tin Granites, Bushveld Igneous Complex, South Africa

“…These granites are capped by the Rashoop Granophyre Suite and the entire sequence dips conformably between 10 • and 15 • westward (Figures 2 and 3) [7,13,24]. The Nebo granite is a 1.5 to 2.5 km thick sheeted granitic intrusion, composed of equigranular quartz, perthitic alkali-feldspar, hornblende, and biotite [4,7,14,20,21]. The Nebo progressively evolves from a grey, coarse-grained, mesocratic hornblende-bearing granite at its base, to a finer-grained, pinkish-red biotite granite in its roof facies within the Zaaiplaats region [4,20,21].…”

“…The Bobbejaankop granite is characterized as a brick-red, coarse-grained facies that is primarily composed of alkali-feldspar and synneusis-textured quartz, forming linked aggregates. It has variably chloritized biotite and miarolitic cavities, which are occasionally filled with cassiterite and minor tourmaline [4,11,14,20,23,24]. The Lease granite is a relatively thin (120 m thick), lenticular sheet that is restricted to the roof of the Bobbejaankop granite, beneath the Rashoop Granophyre Suite (Figure 3).…”

“…The Lease granite is a relatively thin (120 m thick), lenticular sheet that is restricted to the roof of the Bobbejaankop granite, beneath the Rashoop Granophyre Suite (Figure 3). The Lease granite is described as a metasomatically altered red microgranite, exhibiting pervasive sericitic alteration in feldspars, extensive chloritization of biotite, patches of epidotization, and zones of disseminated cassiterite [4,7,13,14,26]. The mineralization at Groenfontein is confined to the upper 20 m of the Lease granite, 3 to 10 m below the contact pegmatite ( Figure 3) [7,[11][12][13]27].…”

“…Cassiterite is typically disseminated, although it does occur as small clusters and within lenticular and pipe-like ore bodies ( Figure 3) [7,12,13,26]. The mineralization at Zaaiplaats occurs dominantly as cassiterite with accessory scheelite, sulfides, fluorite, and molybdenite, compared to Groenfontein, which is mainly cassiterite, with minor scheelite, and molybdenite [7,[12][13][14]26]. The Lease granite is a relatively thin (120 m thick), lenticular sheet that is restricted to the roof of the Bobbejaankop granite, beneath the Rashoop Granophyre Suite (Figure 3).…”