Hydrothermal metamorphism

Greenschist-facies transformation of gneiss and amphibolite in metasomatic zones at Rozynenbosch, Namaqualand Metamorphic Complex, S. Africa
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Group photograph of hand specimens DWK-303 is unaltered gneiss, DWK-310 is unaltered amphibolite. 302 and 303 were sampled directly adjacent to each other - note the contrast.
Group photograph of hand specimens
DWK-303 hand specimen DWK-303. External weathered surface of unaltered gneiss
DWK-303 hand specimen
DWK-303 hand specimen Broken surface, note pink feldspar
DWK-303 hand specimen
DWK-303 hand specimen Cut surface: quartz, pink microcline, white plagioclase, dark retrogressed biotite
DWK-303 hand specimen
DWK-303 x4 objective Quartz, dusty feldspar, opaque oxide, altered mica. These were upper amphibolite facies gneisses, c. 700 C, 5 kbar.
DWK-303 x4 objective
DWK-303 x4 objective Dusty plagioclase, deformed and recrystallized quartz
DWK-303 x4 objective
DWK-303 x4 objective Features microcline, and deformed quartz microstructures
DWK-303 x4 objective
DWK-302 hand specimen Sampled directly adjacent to DWK-303, same layer, <10 cm away across sharp reaction front
DWK-302 hand specimen
DWK-302 hand specimen Detail of cut surface with quartz (glassy), epidote (white to yellow-green), chlorite (dark)
DWK-302 hand specimen
DWK-302 x4 objective Epidote, quartz, chlorite, muscovite. Note complete absence of feldspar.
DWK-302 x4 objective