A Paleoproterozoic mantle source modified by subducted sediments under the North China craton

Concordant ultramafic rocks are exposed in the lower crustal granulites of Sri Lanka. The ultramafic rocks at Rupaha had emplaced early. They had been subjected to deformation and granulite facies metamorphism at 850 o C at 9 kbar during the PanAfrican tectono-thermal episode. The results of thermometry of ultramafic rocks are consistent with those of geo-thermobarometry obtained from surrounding granulites. Fluids circulating in the deep crust had caused the formation of phlogopite blackwalls. Structure, texture and mineralogy of the blackwalls suggest that the K-metasomatism had taken place contemporaneous to the granulite facies metamorphism. The metasomatic reactions had started due to infiltration of K2O and SiO2 between ultramafic rocks and surrounding gneisses and diffusion of these elements between two wall rocks respectively. Carbonation and hydration had occurred in the blackwall rocks at the upper level of the crust on cooling together with surrounding rocks as indicated by textures of a partial retrogression to tremolite and dolomite, which formed through

Ultramafic rock

Metasomatism

Phlogopite

Tremolite

Source

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Citations (2)

Significance of hydrothermal reworking for REE mineralization associated with carbonatite: Constraints from in situ trace element and C-Sr isotope study of calcite and apatite from the Miaoya carbonatite complex (China)

Geochimica et Cosmochimica Acta (2020)

Yuan-Can Ying Wei Chen Antonio Simonetti Shao‐Yong Jiang Kui-Dong Zhao

Carbonatite

Metasomatism

Fluorapatite

Rare-earth element

Trace element

10.1016/j.gca.2020.04.028

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Citations (68)

Cr-rich magnesiokatophorite as an indicator of mantle metasomatism by hydrous Na-rich carbonatite

Journal of Mineralogical and Petrological Sciences (2013)

Murad Ali Shoji Arai

Na- and Cr-rich amphibole and clinopyroxene are commonly observed in hydrous mantle xenoliths hosted by Pliocene-Quaternary basalts from Yemen. The amphibole is Cr-rich magnesiokatophorite high in Na2O (3.66-5.65 wt%) and Cr2O3 (2.21-3.09 wt%), relatively low in K2O (0.23-0.66 wt %) and almost free of Cl and F. The clinopyroxene is characterized by high Cr2O3 (up to 5.64 wt%) and Na2O (up to 2.97 wt%), indicating appreciable amounts of kosmochlor. Both minerals show high REE concentrations as well as HFSE depletion, suggesting an involvement of carbonatitic melt in their formation. The magnesiokatophorites and kosmochlor-bearing diopside possibly formed through metasomatism by hydrous Na-rich carbonatite melt. Magnesiokatophorite is an indicator of metasomatism by hydrous Na-rich carbonatite in the upper mantle.

Carbonatite

Metasomatism

Amphibole

Diopside

Phlogopite

Xenolith

10.2465/jmps.120121

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Citations (6)

Prograde, Peak and Retrograde Metamorphic Fluids and Associated Metasomatism in Upper Amphibolite to Granulite Facies Transition Zones

Lecture notes in earth system sciences (2012)

Jacques Touret T.G. Nijland