Stability relations of the amphibole hastingsite

Thomas, Warren M.

doi:10.2475/ajs.282.2.136

Cited by 32 publications

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“…Postcaldera rhyolites differ markedly from the fayalitebearing Kane Wash Tuff, both in whole-rock chemistry and in their hydrous phenocryst assemblage. The presence of biotite and, particularly, amphibole phenocrysts in the postcaldera rhyolites seems to require cooler and/or more hydrous conditions during the later stages of the magma system [Naney and Swanson, 1980; Thomas, 1982]. Reasons for the shift from peralkaline to metaluminous rhyolite compositions are unclear, but the postcaldera rhyolites, with the exception of the topaz-bearing dome, have distinctly lower fluorine and chlorine contents than the comenditic tuff member V 2 (Table 2).…”

Section: Late Basaltsmentioning

confidence: 56%

Eruptive history of the rhyolitic Kane Springs Wash Volcanic Center, Nevada

Novak

1984

J. Geophys. Res.

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The 19×13 km Kane Springs Wash caldera formed 14 Ma ago following eruption of the three youngest members of the Kane Wash Tuff. Two older cooling units of the Kane Wash Tuff are dated 15.7±0.2 Ma and 14.7±0.2 Ma and apparently erupted from source areas west of the exposed caldera. Volcanic eruptions from the Kane Springs Wash center began about 14 Ma ago with extrusion of trachyte lavas now preserved north of the caldera. Member V1 of the Kane Wash Tuff overlies the trachytes and is zoned from rhyolite to trachyte. In contrast, overlying members V2 and V3 are slightly peralkaline rhyolites (comendite). Eruption of these tuffs 14.1±0.2 Ma ago initiated caldera collapse. Following collapse, trachyte lavas indistinguishable in age from the ash‐flow tuffs erupted within the caldera, forming a 5‐m‐diameter cumulodome whose interior portions crystallized to syenite. This magmatic resurgence formed an extrusive complex within the caldera rather than doming the cauldron block as in classic resurgent calderas. Metaluminous ferroedenite‐rhyolite lavas and associated ash‐flow tuffs then erupted in the “moat” surrounding the central trachyte/syenite complex. Pyroclastic deposits from the domes were covered by trachyandesite and basalt lava flows about 13.4 Ma ago. Biotiterhyolite domes dated 13.4±0.2 Ma continued to erupt in the northeastern moat and appear to be the last silicic eruptions from the Kane Springs Wash magma system. A 13.4 Ma metaluminous biotite‐rhyolite dome containing vapor‐phase topaz overlies the trachyandesite lavas and appears to be the youngest biotite‐rhyolite dome. These intracaldera units filled the moat, resulting in a caldera filled with its own eruptive products. Local basalt flows covered both intracaldera units and outflow sheets between 12.7 and 11.5 Ma ago, prior to Basin and Range faulting. The “dominant volume” of the system was trachytic, as trachyte lavas erupted both prior to and following caldera collapse, and trachyte inclusions occur as scoriaceous bombs at the top of member V2. Fractionation of this trachyte magma produced the slightly peralkaline rhyolitic magma that erupted as the Kane Wash Tuff. The shift from an anhydrous mineral assemblage in the tuffs to hydrous assemblages in the later intracaldera rhyolites shows that the system was cooling and was possibly more hydrous in its late stages. Petrographic characteristics of trachyandesite lavas erupted late in the history of the center suggest that they represent basaltic magmas contaminated with silicic material

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Section: Late Basaltsmentioning

confidence: 56%

Eruptive history of the rhyolitic Kane Springs Wash Volcanic Center, Nevada

Novak

1984

J. Geophys. Res.

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“…Nishimoto et al 2014). Moreover, hastingsite dehydration (Thomas 1982), granoblastic recrystallization of plagioclase ( Fig. 5b; Fossen and Cavalcante 2017; Rosenberg and Stünitz 2003; see also Raith et al 2014) and alkali feldspar compositions in the episyenites and their immediate margins (Fig.…”

Section: Discussionmentioning

confidence: 95%

Clinopyroxene episyenites in a Proterozoic rapakivi granite, SE Finland — recrystallization textures, mass transfer and implications for the petrology of A-type granite complexes

et al. 2019

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Na-metasomatic augite and aegirine-augite episyenites are hosted by subalkaline amphibole granites in the 1.644 Ga Suomenniemi rapakivi granite complex, southeastern Finland. In an examined drill core, episyenites are bordered by up to 50cm-wide zones of Na-enriched augite-bearing granite in which alkali feldspar forms rims on plagioclase, and aggregates of augite and magnetite have formed by fluid-induced dehydration of hastingsite and biotite. In the episyenites, quartz has been partially removed, alkali feldspar (An <1 Ab 50 Or 50 ) and plagioclase have been partially recrystallized to granoblastic polygonal aggregates, and clinopyroxene (augite or aegirine-augite) has coarsened and been enriched in the aegirine component. Mass balance modeling implies addition of mainly Na, depletion of Si, F, Rb, Ba, Sr and 10-20% volume loss (by quartz dissolution) in the episyenitized zones in the drill core. Quartz-depletion and recrystallization may have been caused by several superimposed stages of alteration, probably related to voluminous dike-and A-type granite magmatism in the Suomenniemi area 10-15 m.y. after the emplacement of the Suomenniemi complex. Because of the coarse recrystallization textures and near-solidus recrystallization temperatures, distinguishing these fenite-like metasomatic rocks from igneous syenites is not trivial. In epizonal A-type granite complexes, high-temperature episyenites may be more common than currently thought.

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“…The absence of amphibole suggests that the oxygen fugacity was more oxidizing than the QFM buffer, perhaps with logf O2 in the range À21 to À19 (Thomas, 1982;Gilbert and Popp, 1982). Indeed, the presence of an andradite-rich garnet might suggest an f O 2 as large as 10 À16 bar at 650ºC (Gustafson, 1974).…”

Section: Petrogenesis Of the Blairmorite Mineral Assemblage Emphasizimentioning

confidence: 90%

Phase equilibria in NaAlSiO₄–KAlSiO₄–SiO₂–H₂O at 100 MPa pressure: equilibrium leucite composition and the enigma of primary analcime in blairmorites revisited

2014

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Experiments in the system NaAlSiO 4 (Ne)ÀKAlSiO 4 (Ks)ÀSiO 2 (Qz)ÀH 2 O at 100 MPa show that the maximum content of NaAlSi 2 O 6 in leucite is~4 wt.% and that analcime is close to the stoichiometric composition (NaAlSi 2 O 6 .H 2 O). Analcime forms metastably on quenching the higher-temperature experiments; it is secondary after leucite in experiments quenched from 780ºC, while from 850ºC it forms by alteration of leucite, and by devitrification of water-saturated glass. Both processes involve reaction with Na-rich aqueous fluids. Stable analcime forms at 500ºC, well below the solidus, and cannot form as phenocrysts in shallow volcanic systems. New data for natural analcime macrocrysts in blairmorites are presented for the Crowsnest volcanics, Alberta, Canada. Other researchers have suggested that primary analcime occurs as yellow-brown, glassy, analcime phenocrysts. Our microprobe analyses show that such primary analcime is close to stoichiometric, with very low K 2 O (<0.1 wt.%), minor Fe 2 O 3 (0.5À0.8 wt.%) and CaO (~0.5 wt.%). An extrapolation of published experimental data for NeÀKsÀQz at >500 MPa P H 2 O , where Anl + melt coexist, suggests that at >800 MPa two invariant points are present: (1) a reaction point involving Kf + Ab + Anl + melt + vapour; and (2) a eutectic with Kf + Anl + Ne + melt + vapour. We suggest that the nepheline-free equilibrium mineral assemblage for Crowsnest samples is controlled by reaction point (1). In contrast, blairmorites from Lupata Gorge, Mozambique, form at eutectic (2), consistent with the presence of nepheline phenocrysts. Our conclusions, based on high-vs. low-pressure experiments, confirm the suggestion made by other authors, that Crowsnest volcanic rocks must have been erupted explosively to preserve glassy analcime phenocrysts during very rapid, upward transport from deep in the crust (H 2 O pressures >>500 MPa). Only rare examples survived the deuteric and hydrothermal alteration that occurred during and after eruption.

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Stability relations of the amphibole hastingsite

Cited by 32 publications

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Eruptive history of the rhyolitic Kane Springs Wash Volcanic Center, Nevada

Eruptive history of the rhyolitic Kane Springs Wash Volcanic Center, Nevada

Clinopyroxene episyenites in a Proterozoic rapakivi granite, SE Finland — recrystallization textures, mass transfer and implications for the petrology of A-type granite complexes

Phase equilibria in NaAlSiO₄–KAlSiO₄–SiO₂–H₂O at 100 MPa pressure: equilibrium leucite composition and the enigma of primary analcime in blairmorites revisited

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Stability relations of the amphibole hastingsite

Cited by 32 publications

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Eruptive history of the rhyolitic Kane Springs Wash Volcanic Center, Nevada

Eruptive history of the rhyolitic Kane Springs Wash Volcanic Center, Nevada

Clinopyroxene episyenites in a Proterozoic rapakivi granite, SE Finland — recrystallization textures, mass transfer and implications for the petrology of A-type granite complexes

Phase equilibria in NaAlSiO4–KAlSiO4–SiO2–H2O at 100 MPa pressure: equilibrium leucite composition and the enigma of primary analcime in blairmorites revisited

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Phase equilibria in NaAlSiO₄–KAlSiO₄–SiO₂–H₂O at 100 MPa pressure: equilibrium leucite composition and the enigma of primary analcime in blairmorites revisited