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Fig. 3 | Progress in Earth and Planetary Science

Fig. 3

From: Weak hydrothermal carbonation of the Ongeluk volcanics: evidence for low CO2 concentrations in seawater and atmosphere during the Paleoproterozoic global glaciation

Fig. 3

Photomicrographs of basaltic andesites and hydrothermal jaspilites in the Ongeluk Formation. a A typical basaltic andesite in which the igneous minerals and glass have been replaced by secondary minerals but the igneous texture is well preserved. b Disseminated calcite-bearing basaltic andesite in which igneous plagioclase has been replaced by secondary albite, chlorite, quartz, and calcite. c A calcite vein cutting all alteration minerals and igneous texture. d A hematite-rich layer of interpillow hydrothermal jaspilite. e A microquartz-rich layer of the interpillow hydrothermal jaspilite that includes calcite and andradite. f A calcite vein cutting jaspilite

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