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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
earth and planetary sciences
P-T-t evolution and textural evidence for decompression of Pan-African high-pressure granulites, Lurio Belt, north-eastern Mozambique
Journal of Metamorphic Geology, Volume 25, No. 9, Year 2007
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Description
Pan-African high-pressure granulites occur as boudins and layers in the Lurio Belt in north-eastern Mozambique, eastern Africa. Mafic granulites contain the mineral assemblage garnet + clinopyroxene + plagioclase + quartz ± magnesiohastingsite. Garnet porphyroblasts are zoned with increasing almandine and spessartine contents and decreasing grossular and pyrope contents from core (Alm46Prp32 Grs21Sps2) to rim (Alm52Prp26 Grs19Sps3). This pattern is interpreted as a retrograde diffusion zoning with the preserved core chemistry representing the peak metamorphic composition. Mineral reaction textures occur in the form of monomineralic and composite plagioclase ± orthopyroxene ± amphibole ± biotite ± magnetite coronas around garnet porphyroblasts. Thermobarometry indicates peak metamorphic conditions of up to 1.57 ± 0.14 GPa and 949 ± 92 °C (stage I), corresponding to crustal depths of ∼55 km. Zircon yielded an U-Pb age of 557 ± 16 Ma, inferred to date crystallization of zircon during peak or immediately post-peak metamorphism. Formation of plagioclase + orthopyroxene-bearing coronas surrounding garnet indicates a near-isothermal decompression of the high-pressure granulites to lower pressure granulite facies conditions (stage II). Development of plagioclase + amphibole-coronas enclosing the same garnet porphyroblasts shows subsequent cooling into amphibolite facies conditions (stage III). Symplectitic textures of the corona assemblages indicate rapid decompression. The high-pressure granulite facies metamorphism of the Lurio Belt, followed by near-isothermal decompression and subsequent cooling, is in accordance with a long-lived tectonic history accompanied by high magmatic activity in the Lurio Belt during the late Neoproterozoic-early Palaeozoic East-African-Antarctic orogeny. © 2007 Blackwell Publishing Ltd.
Authors & Co-Authors
Engvik, Ane K.
Norway, Trondheim
Geological Survey of Norway
Tveten, Einar
Norway, Trondheim
Geological Survey of Norway
Bingen, Bernard
Norway, Trondheim
Geological Survey of Norway
Viola, Giulio
Norway, Trondheim
Geological Survey of Norway
Erambert, Muriel
Norway, Oslo
Universitetet I Oslo
Feito, P.
Mozambique, Maputo
National Directorate of Geology
de Azavedo, S.
Mozambique, Maputo
National Directorate of Geology
Statistics
Citations: 7
Authors: 7
Affiliations: 3
Identifiers
Doi:
10.1111/j.1525-1314.2007.00736.x
ISSN:
02634929
e-ISSN:
15251314
Study Locations
Mozambique