ISSN:
1525-1314
Quelle:
Blackwell Publishing Journal Backfiles 1879-2005
Thema:
Geologie und Paläontologie
Notizen:
The impure marbles of the internal Sesia-Lanzo Zone underwent a multi-stage metamorphic evolution of Alpine age and retain early-Alpine eclogitic assemblages, partially recrystallized under blueschist to greenschist facies conditions. These high-P assemblages consist of carbonates, phengite, quartz, omphacite, grossular-rich (locally spessartinic) garnet, zoisite and Al-rich titanite. Retrogressive stages are characterized by the growth of glaucophane, paragonite, phlogopite, tremolite and albite. Halogen-rich biotite and amphibole are also present. P-T estimates of the early-Alpine metamophism have been calculated from these unique high-P assemblages, in order to test the applicability of some calibrations to impure carbonate systems. In particular, some Gt-Cpx calibrations and the phengite geobarometer give results (T= 575 ± 45° C at 15 kbar for the eclogitic climax and T≤ 500° C at PH2O ≤ 9 kbar for early-Alpine retrogressive stages) which are within the range obtained from the surrounding lithologies.Phase relationships in P-T-XCO2 space indicate that mineral assemblages in the impure marbles coexisted with H2O-rich fluids (XCO2 〈0.03) during their entire Alpine evolution.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1111/j.1525-1314.1991.tb00504.x
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