Phase relations and metamorphic history of a clinohumite-chlorite-serpentine-marble from the Western Tauern Area (Austria) |
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Authors: | G Franz D Ackermand |
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Institution: | (1) Institut für Angewandte Geophysik, Petrologie und Lagerstättenforschung, Straße des 17. Juni 135, D-1000 Berlin 12, Germany;(2) Mineralogisches Institut, Olshausenstr. 40-60, D-2300 Kiel, Germany |
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Abstract: | Several different metamorphic events — an early or prevariscian regional, a variscian contact and the alpine regional — on marbles from the Schlegeistal (Western Tauern Area, Tyrol, Austria) have resulted in a great variety of mineral assemblages. These assemblages include calcite, dolomite, tremolite, diopside, forsterite, clinohumite-titanianclinohumite-chondrodite, chlorite-serpentine, brucite, and boron minerals karlite and ludwigite.Microprobe analysis fo the minerals indicate that three different generations of chlorite minerals exist (clinochlor, penninite, Al-serpentine). The occurence of these chlorites is explained by formation of serpentine component during the last (alpine) regional metamorphism from the breakdown of forsterite, humite-minerals and diopside. The phase relations are described in the system CaO-MgO-SiO2-H2O-CO2-HF and a petrogenetic grid for the low
low X
F
mineral
region is given. The reactions are typical for ophicarbonate rocks, but include clinohumite and chlorite, due to the presence of F and minor amounts of Al2O3. |
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