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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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Journal ArticleDOI
TL;DR: In this article, electron microprobe analyses of coexisting magnetite and ilmenite phenocrysts from four compositionally zoned ash-flow sheets of the Paintbrush and Timber Mountain Tuffs, southern Nevada, show systematic variations in Fe-Ti oxide composition that correlate closely with bulk-rock composition and with the inferred position in the source magma chambers.
Abstract: Electron-microprobe analyses of coexisting magnetite and ilmenite phenocrysts from four compositionally zoned ash-flow sheets of the Paintbrush and Timber Mountain Tuffs, southern Nevada, show systematic variations in Fe-Ti oxide composition that correlate closely with bulk-rock composition and with the inferred position in the source magma chambers. Comparison with experimental data of Buddington and Lindsley (1964) indicates that the Fe-Ti oxides of rhyolitic upper parts of the differentiated magma chamber crystallized at 700° ± 50° C, whereas oxides of quartz latitic lower parts of the magma column crystallized at temperatures as high as 900° C. The trend of temperature and oxygen fugacity is parallel and intermediate to trends for Ni-NiO and $MnO-Mn_{2}O_{3}$ buffers. The low indicated temperatures for the rhyolites suggest that they were saturated, or nearly saturated, with water at the time of crystallization.

86 citations

Journal ArticleDOI
TL;DR: In this article, the authors used petrographic features (textures, crystal shapes and size distributions, phase associations, and modal abundances), mineral compositions, and melt compositions reconstructed from magmatic inclusions in olivine and chromite.

85 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present new measurements and estimates of pre-eruptive volatile concentrations in magma from the Hekla volcano in Iceland based on MIs in recent basalts and basaltic icelandites from the 2000 eruption.

85 citations

Journal ArticleDOI
TL;DR: White Island is an active composite stratovolcano in the Bay of of the North Island, the Pacific Plate is being subducted, New Zealand, that comprises many small volume westwards under the Australian Plate at a rate of ( 50 mm/yr to form the Taupo-Hikurangi arc-trench with phenocryst contents of >15-44% as mentioned in this paper.
Abstract: White Island is an active composite stratovolcano in the Bay of of the North Island, the Pacific Plate is being subducted Plenty, New Zealand, that comprises many small volume westwards under the Australian Plate at a rate of ( 50 mm/yr to form the Taupo–Hikurangi arc–trench with phenocryst contents of >15–44%. Minor high-Mg basaltic system. Volcanic activity is now concentrated in the andesite explosive eruptions, such as those of 1976–1992, may Taupo Volcanic Zone (TVZ), the youngest expression have occurred at intervals throughout the history of White Island, of 22 Ma Cenozoic continental margin arc volcanism in but are rarely preserved. These alternate with major episodes of the North Island of New Zealand (Cole, 1990). TVZ andesite–dacite lava extrusion. The high-Mg magmas form by (Fig. 1 inset) is at the southern end of the 2800 km hydrous melting of mantle, metasomatized by fluids from the Tonga–Kermadec–Taupo volcanic arc system and the dehydrating slab at the slab–mantle wedge interface, that rise Lau Basin–Havre Trough–Ngatoro Basin back-arc basin rapidly to shallow magma chambers (2–7 km?) where limited system. Southern Havre Trough and TVZ are offset mixing and contamination occurs before eruption. Some of this sinistrally by 40–50 km and Wright (1992) believes the magma remains in the magma chamber where it interacts with the offset to be accommodated by a series of dextrally oblique crystal mush, from which it inherits phenocrysts, to form so-called and en-echelon bookshelf faults. The southwestern limit ‘dirty’ lavas. Total phenocryst content of these lavas is correspondingly of this fault system is placed <20 km north of White higher. As more magma is intruded into the chamber, the heat flux Island and has NW–SE orientation (Fig. 1 inset). will increase and melt fraction will eventually rise to the surface to TVZ extends offshore into the Bay of Plenty as a form high-silica andesite–dacite magma (‘clean’ lavas) with fewer graben structure of 45 km width (Fig. 1) bounded by the inherited phenocrysts. Similar multi-magma chamber plumbing Tauranga Fault Zone to the west and the White Island systems, with complex evolution involving fractionation and conFault Zone to the east (Wright, 1992). The eastern side tamination, probably occur in most andesite–dacite arc volcanoes. of TVZ coincides with the current active volcanic front and a broadly linear alignment of andesitic volcanoes extends from Ruapehu in the southwest to Whakatane

85 citations

Journal ArticleDOI
TL;DR: In this article, the phenocrysts of four porphyritic obsidians from Pantelleria have been analyzed chemically, together with the residual glasses (liquids) and the relationship of these phenocryst to their liquids is considered.
Abstract: The phenocrysts of four porphyritic obsidians from Pantelleria have been analysed chemically, together with the residual glasses (liquids). Three new analyses of anorthoclase (one partial analysis), two of sodic ferrohedenbergite, one of fayalitic olivine, and two of cossyrite are presented together with their optical properties, and the relationship of these phenocrysts to their liquids is considered. The experimental studies in the system NaAlSi3O8-KAlSi3O8-SiO2-H2O show that for synthetic liquids of similar composition to the normative salic constituents of the pantelleritic liquids, a potassic alkali feldspar crystallizes, whereas in the pantelleritic liquids phenocrysts of anorthoclase (Ab67–Ab61) occur. It is suggested that sodium metasilicate, which appears in the norms of all the pantelleritic liquids, may be responsible for the divergence in trend between the synthetic feldspar-liquid tie-lines and the pantelleritic feldspar-liquid tie-lines.

85 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202399
2022142
2021105
2020100
2019103
2018109