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Phenocryst
About: Phenocryst is a research topic. Over the lifetime, 4132 publications have been published within this topic receiving 158441 citations.
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TL;DR: In this article, the authors report an integrated dataset of whole-rock K-Ar ages, major and trace elements and Sr-Nd-Pb isotopes, and olivine major and minor elements for the Abaga-Dalinuoer basalts (ADBs), and propose that mantle source lithology of the ADB magmas may consist of both pyroxenite and peridotite.
52 citations
TL;DR: In the past 5 ka volcanism has been very intense at Ischia, a densely populated and still active volcanic island in the Gulf of Napoli as mentioned in this paper, which is characterized by strong petrochemical disequilibria.
Abstract: In the past 5 ka volcanism has been very intense at Ischia, a densely populated and still active volcanic island in the Gulf of Napoli. Mineralogical, geochemical and isotopic investigations have been carried out on the pyroclastic deposits and lava flows of the historical eruptions of Fiaiano (530–960 A. D.) and Arso (1302 A. D.). These products are characterized by strong petro-chemical disequilibria. Mineralogical disequilibria are shown by the occurrence of resorbed and reversely zoned phenocrysts, and by the coexistence of phenocrysts and microlites with variable composition. Chemical inhomogeneity characterizes the glass of the juvenile fragments. Isotopic disequilibria have been detected among all separated mineral phases and whole-host rock. The detected disequilibria are interpreted as the result of a physical mixing process between variable fractionated and isotopically distinct batches of magmas. Petrochemical data suggest that mingling occurred between a highly crystallized alkali-trachytic and an isotopically distinct latitic to trachytic magmas, for both the eruptions. The pre-eruptive scenario proposed is the uprising of a latitic-to-trachytic magma (characterized by a Sr-isotope ratio of about 0.7068) from a deep reservoir and successive mingling with batches of more viscous, highly crystallized alkali-trachytic magma (with a Sr-isotope composition of about 0.7061) at shallow depth.
52 citations
TL;DR: The Late-Cretaceous Alto Paranaiba Igneous Province (APIP) comprises a variety of ultrapotassic rock types, including kimberlites, lamproites and large volumes of kamafugites, in addition to a number of carbonatite-bearing plutonic alkaline complexes as mentioned in this paper.
Abstract: The Late-Cretaceous Alto Paranaiba Igneous Province (APIP) comprises a variety of ultrapotassic rock-types, including kimberlites, lamproites and large volumes of kamafugites, in addition to a number of carbonatite-bearing plutonic alkaline complexes. Phlogopite-picrites are ultramafic fine-grained rocks typically composed of olivine phenocrysts set in a groundmass of phlogopite, carbonate, perovskite, apatite and chromite. They occur as dyke swarms in the carbonatite complexes, but are also scattered throughout the Province. The phlogopite-picrites represent the peralkaline, ultrapotassic, carbonate-rich, silicate magmas parental to the carbonatite-bearing complexes, and have strong chemical affinity with kamafugites. Together with petrographic similarities observed between silicate rocks from the carbonatite complexes and xenoliths occurring in APIP kamafugites, this provides a strong link between kamafugitic and carbonatitic magmatism in the Province.
52 citations
TL;DR: The Streltsovka caldera contains the largest uranium field associated with volcanics in the world as mentioned in this paper, and the presence of daughter minerals such as fluorite, F-rich mica and REE fluocarbonate, and the composition of the silicate melt after homogenization, indicate that the Streltska rhyolites correspond to highly fractionated mildly peralkaline melts.
52 citations
TL;DR: Tata Sabaya (19°08'S 68° 32'W; 5430 m a.s.l) is located on the northern shores of Salar de Coipasa on the Altiplano of Bolivia as discussed by the authors.
52 citations