Lamproite-hosted xenoliths of Vestfjella: implications for lithospheric architecture in
samples of the unexposed continental crust at the rifted margin of western Dronning Maud Land (WDML). The exposed bedrock of the ice-covered study area comprises Jurassic tholeiites and minor Permian sedimentary rocks. The xenoliths comprise mainly granulite facies metamorphosed igneous and sediment...
| Main Authors: | , , |
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.503.9504 http://pubs.usgs.gov/of/2007/1047/ea/of2007-1047ea080.pdf |
| Summary: | samples of the unexposed continental crust at the rifted margin of western Dronning Maud Land (WDML). The exposed bedrock of the ice-covered study area comprises Jurassic tholeiites and minor Permian sedimentary rocks. The xenoliths comprise mainly granulite facies metamorphosed igneous and sedimentary rock types; sediments of shallower origin and cognate phlogopitite and silicocarbonatite inclusions are also found. This heterogeneous suite of crustal xenoliths shows textural and compositional affinity to Proterozoic rock types of Heimefrontfjella and Mannefallknausane area. Two leucocratic gneissic tonalites, which probably represent middle crustal levels, yielded U-Pb SHRIMP zircon ages of ~1.0–1.3 Ga. The granoblastic mafic granulites probably represent unexposed lower parts of the continental crust: Mineral–whole-rock Sm-Nd isotope results imply compositional affinity to Proterozoic lower crustal xenoliths from Lesotho, South Africa, and equilibration of the Sm-Nd system during Grenvillean and Jurassic magmatic events. Highest pressures, 11-17 kbars, were recorded by mafic garnet granulites. Overall, these lamproite-hosted crustal xenoliths indicate extension of the Proterozoic Maud Belt crust to Vestfjella. |
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