Granulite facies metasomatism: zoned calc-silicate boudins from the Rauer Group, East Antarctica

Article Abstract:

Regional metamorphism of the calc-silicate boudins from the Rauer Group of East Antarctica produced metamorphic rocks of the granulite facies. Analysis of the boudin cores showed a concentric core to rim zonation defined by systematic, gradual changes in the mineral assemblages. Plagioclase minerals were absent orlacking in the common core assemblages. The highly variable reaction zones in the granulite boudins were attributed to the a two-stage history consisted of fluid-infiltration and diffusion of the different components between the calc-silicates and the iron-rich paragneiss.

Environmental aspects, Rock mechanics, Granulite, Facies (Geology), Geologic facies

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Gabbroic intrusions and magmatic metasomatism in harzburgites from the Garrett transform fault: implications for the nature of the mantle-crust transition at fast-spreading ridges

Article Abstract:

An analysis of the mafic and ultramatic rocks taken from the Garrett transform fault on the East Pacific Rise was conducted. The objective was to examine the bulk chemical effects of magmarock interactions by calculations using the composition of the most residual harzburgite mixed with varying proportions of a range of selected basalts or intrusive gabbros. Results indicate that mid-ocean ridge peridotites are subject to both fractional melting and metasomatic mechanisms. It is also possible that mantle metasomatism is widespread in the entire Garrett peridotite massif.

Faults (Geology), East Pacific Rise, Rocks, Ultrabasic, Ultrabasic rocks

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Carbonate metasomatism in the lithospheric mantle: peridotitic xenoliths from a melilititic district of the Sahara basin

Article Abstract:

Research describing harzburgitic and dunitc xenoliths from the melititic district of In Teria (Algerian Sahara) is presented. The area's lithospheric mantle evolved under conditions of multi-stage metasomatism. The initial event triggered the crystallization of phlogopite and amphibole following the injection of alkali silicated melt. Mineral changes affected spinel peridotites which generated high-Cr endiopside formation and xenolith conversion.

Africa, Sahara, Rocks, Igneous, Basins (Geology), Xenoliths

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