Petrology of whiteschists and associated rocks at Mautia Hill (Tanzania): Fluid infiltration during high-grade metamorphism?

Jöns, N. and Schenk, V. (2004) Petrology of whiteschists and associated rocks at Mautia Hill (Tanzania): Fluid infiltration during high-grade metamorphism? Journal of Petrology, 45 (10). pp. 1959-1981. DOI 10.1093/petrology/egh044.

Full text not available from this repository.

Supplementary data:

Abstract

Talc-kyanite schists (whiteschists), magnesiohornblende-kyanite-talc-quartz schists and enstatite-sapphirine-chlorite schists occur at Mautia Hill in the East African Orogen of Tanzania. They are associated with metapelites and garnet-clinopyroxene-quartz metabasites. Geobarometry (GASP/GADS equilibria) applied to the latter two rock types indicates a peak pressure of P = 10-11 kbar. These results are confirmed by the high fO(2) assemblage hollandite-kyanite-quartz and late-stage manganian andalusite that contains up to 19.5 mol. % Mn2SiO5. Maximum temperatures of T = 720degreesC are inferred from late-stage yoderite + quartz. A clockwise P-T evolution is constrained by prograde kyanite inclusions in metapelitic garnet and late-stage reaction rims of cordierite between green yoderite and talc that reflect conditions at least 3-4 kbar below the peak pressure. Oxidizing conditions are recorded throughout the metamorphic history of the whiteschists and chlorite schists, as indicated by the presence of haematite coexisting with pseudobrookite and/or rutile. Increasing water activity near peak pressures is thought to have led to the breakdown of the high-pressure assemblages (Tlc-Ky-Hem and Mg-Hbl-Ky-Hem) and the subsequent formation of certain uncommon minerals, e.g. yellow sapphirine, Mn-andalusite, green and purple yoderite, piemontite and boron-free kornerupine. The proposed increase in water activity is attributed to fluid infiltration resulting from the devolatilization of underlying sediments during metamorphism.

Document Type: Article
Keywords: fluid infiltration high-pressure amphibolite facies East African Orogen Pan-African whiteschist sar-e-sang high-pressure assemblage boron-free kornerupine dora-maira massif western alps system mgo-al2o3-sio2-h2o al2sio5 polymorphs quartz schist zambezi belt talc schist
Research affiliation: Kiel University
DOI etc.: 10.1093/petrology/egh044
ISSN: 0022-3530
Date Deposited: 24 Jan 2012 06:29
Last Modified: 08 Oct 2012 10:32
URI: http://eprints.uni-kiel.de/id/eprint/16140

Actions (login required)

View Item View Item