Petrography and geochemistry of eclogites from the Mir kimberlite, Yakutia, Russia

Article Abstract:

The presence of zoned garnets and low oxygen content of the eclogites of the Mir kimberlite, Yakutia, Russia, suggests that the eclogites have been formed by metasomatism. High temperature seawater alterations have produced eclogites with a high Ca content. Low temperature seawater alteration have produced those with a low Ca content. The protoliths of the high-Ca level eclogites are probably an ophiolite's mid and lower regions, while those of the low-Ca group are the upper region. The difference in the Al and Ca content of these groups is due to a higher plagioclase in the high-Ca group.

Isotopes, Calcium, Calcium (Chemical element), Sakha, Russia, Kimberlite

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Petrogenesis of Variscan high-temperature Group A eclogites from the Moldanubian Zone of the Bohemian Massif, Czechoslavakia

Article Abstract:

The Variscan orogen in the Moldanubian Zone of the Bohemian Massif, Czechoslovakia, featured high-temperature Group A eclogites that originated from high-pressure crystallization and massive formation of garnet and clinopyroxene obtained from very deep basaltic sources. Chemical and isotopic analyses such as Rb-Sr and Sm-Nd were used to determine eclogite equilibration conditions. Results showed that the eclogites exhibited average minimum temperature and pressure indicative of a heterogenous mantle source which formed garnets and clinopyroxenes showing retrograde compositional natures.

Analysis, Usage, Peridotite, Rocks, Metamorphic, Metamorphic rocks, Czechoslovakia, Rubidium-strontium dating, Garnet, Isotope geology

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Petrogenesis of isotopically unusual Pliocene olivine leucitites from Deep Springs Valley, California

Article Abstract:

A study was conducted to analyze the petrogenesis of isotopically unusual Pliocene olivine leucitites from Deep Springs Valley, CA. Direct current plasma atomic emission spectroscopy was carried out to examine bulk rock major and trace-element concentrations. High-K mafic alkalic lavas from the area supported good correlations with compatible element contents in MgO. Results showed that olivine leucitites from Deep Springs Valley supported novel geochemical features.

California, Paleontology, Lava, Pliocene Epoch

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