Phase relations of titan-phlogopite, K2Mg4TiAl2Si6O20(OH)4: a refractory phase in the upper mantle?

Forbes, Warren C.; Flower, Martin F. J.

doi:10.1016/0012-821x(74)90064-8

Cited by 110 publications

(41 citation statements)

References 22 publications

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“…Our analyses show that the Fe/Fe+ M g ratios of the southern Karnataka coexisting biotites and orthopyroxenes are nearly equal. being slightly greater for orthopyroxene (Hansen, 1983 orthopyroxene only slightly relative to biotite at a given XHIO Large TiO, contents will stabilize biotite to considerably higher temperatures (Forbes & Flower, 1974) and lower H,O pressures. Figure 6 is a plot of biotite TiO, contents as a function of latitude in southern Karnataka, which is essentially a measure of penetration into the high-grade terrane.…”

Section: T H E F L U I D Phase-indirect Deductions Water Activitymentioning

confidence: 99%

Fluid inclusions in rocks from the amphibolite‐facies gneiss to charnockite progression in southern Karnataka, India: direct evidence concerning the fluids of granulite metamorphism

Hansen

Newton

Janardhan

1984

Journal Metamorphic Geology

132

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Abstract. Fluid inclusion studies of rocks from the area suggests progressive decrease of the late Archaean amphibolite-facies to granulitewith increasing grade. Oxygen fugacities calcufacies transition zone of southern India provide lated from orthopyroxene-magnetitequartz are support for the hypothesis that C0,-rich H,Oconsiderably higher than the graphite C0,-0, poor fluids were a major factor in the origin of the buffer, which explains the absence of graphite in high-grade terrain. Charnockites, closely asthe charnockites. sociated leucogranites and quartzo-feldspathicThe present study quantifies the nature of the veins contain vast numbers of large C0,-rich vapours in the southern India granulite metainclusions in planar arrays in quartz and feldspar, morphism. It remains to be determined whether whereas amphibole-bearing gray gneisses of C0 Microthermometry of CO, inclusions shows that miscible CH, and N, must be small, probably less than 10 mol. %combined. Densities of CO, increase steadily from north to south across the transitional terrane. Entrapment pressures calculated from the CO, equation of state range from 5 kbar in the north to 7.5 kbar in the south at the mineralogically inferred average metamorphic temperature of 750"C, in quantitative agreement with mineralogic geobarometry. This agreement leads to the inference that the fluid inclusions were trapped at or near peak metamorphic conditions.Calculations on the stability of the charnockite assemblage biotite-orthopyroxene-K-feldsparquartz show that an associated fluid phase must have less than 0 . 3 5 H 2 0 activity at the inferred P and T conditions, which agrees with the petrographic observations. High TiO, content of biotite stabilizes it to lower H,O activities, and the steady increase of biotite TiO, southward in

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Section: T H E F L U I D Phase-indirect Deductions Water Activitymentioning

confidence: 99%

Fluid inclusions in rocks from the amphibolite‐facies gneiss to charnockite progression in southern Karnataka, India: direct evidence concerning the fluids of granulite metamorphism

Hansen

Newton

Janardhan

1984

Journal Metamorphic Geology

132

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“…Lloyd and Bailey, 1975;Harte et al, 1975;Boettcher et al, 1979;Boettcher and O'Neil, 1980;Farmer and Boettcher, 1981;Lloyd, 1981). The stability of phlogopites under mantle conditions has been determined by Kushiro et al (1967), Yoder and Kushiro (1969), and Forbes and Flower (1974); and in synthetic systems, corresponding to simplified K-enriched mantle compositions, in the systems K20-MgO-CaO-A1203-SiO2-H20 (Modreski and Boettcher, 1973), KA1SiO4-MgOSiO 2 H20-CO 2 (Wendlandt and Eggler, 1980),…”

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confidence: 99%

Conditions of phlogopite crystallization in ultrapotassic volcanic rocks

Edgar

Arima

1983

Mineral. mag.

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ABSTRACT. Phlogopite occurs as an early crystallizing mineral in many ultrapotassic lavas of basaltic affinities. Based on high-pressure experiments in lavas of these compositions, the early crystallization of phlogopite is controlled in large part by the bulk compositions of the liquids from which it crystallizes but also by the total pressure and by the aH20, with early phlogopite forming under a narrow range of aH20, less than that represented by H20-saturated conditions. Variations in fo~ do not appreciably affect phlogopite crystallization but high ac02 suppresses its crystallization. In ultrapotassic magmas, phlogopite will preferentially incorporate K20 , TiO2, MgO, and A1203 relative to the coexisting early silicate minerals, olivine and clinopyroxene, and thus, on fractionation of these minerals, phlogopite will be more effective in reducing these oxides in residual liquids. Phenocrysts and microphenocrysts of phlogopite in ultrapotassic lavas are directly related with respect to their K/Ti, K/A1, K/(K + Na), and Mg/(Mg + Fe) ratios. Textural relations suggest phlogopite may form by reaction relationships involving liquid with olivine, and/or clinopyroxene. Such relationships are supported by the experimental studies on ultrapotassic rock compositions.

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“…as proposed by [50]. An application of this concept shows, in the diagram Ti versus Mg + Fe 2+ , that vacancies may indeed exist in the Ba micas of FN (cf.…”

Section: Micasmentioning

confidence: 88%

The volcanic-subvolcanic rocks of the fernando de noronha archipelago, southern atlantic ocean: Mineral chemistry

Lopes

Ulbrich²,

Ulbrich³

2014

Open Geosciences

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Fernando de Noronha archipelago presents an older Remédios Formation with subvolcanic intrusions, belonging to two different alkaline series, the sodic (undersaturated: basanites, tephrites, essexites, tephriphonolites, phonolites), and potassic ones (mildly undersaturated to silicic, with alkali basalts, basaltic trachyandesites, trachyandesites, trachytes), and lamprophyres. The upper Quixaba Formation presents nephelinite flows and basanites. A third minor unit, São José, is constituted by basanites carrying mantle xenoliths. Magnesian olivines occur in the Remédios basanites and alkali basalts, and in nephelinites. Melilites are present as groundmass grains in melilite melanephelinites (MEM). Clinopyroxenes (cpx) are mostly salites to titaniferous salites (Remédios sodic series), grading into aegirines in the differentiated aphyric phonolites. Cpx in the lamprophyres show disequilibrium textures. In the Quixaba flows, cpx are salites, enriched in Mg (especially in MEM). Amphiboles, remarkably, are common in tephriphonolites and phonolites and in basaltic trachyandesites, sometimes with disequilibrum zoning textures, and a conspicuous phase in lamprophyres. Dark micas are present as groundmass plates in MEM, OLM and PYM (olivine and pyroxene melanephelinites), with compositional variety (enriched in Ti, Ba, Sr) depending on the composition of the parent rock; BaO can be as high as 16–19%. Feldspars crystallize as calcic plagioclases, sanidines and anorthoclases, depending on the rock types, as phenocrysts and in groundmass, both in Quixaba and Remédios rocks; they are absent in nephelinites. Nephelines are found in Remédios sodic series types and Quixaba rocks. Haüyne and noseane are rarely observed in Remédios rocks.

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Phase relations of titan-phlogopite, K2Mg4TiAl2Si6O20(OH)4: a refractory phase in the upper mantle?

Cited by 110 publications

References 22 publications

Fluid inclusions in rocks from the amphibolite‐facies gneiss to charnockite progression in southern Karnataka, India: direct evidence concerning the fluids of granulite metamorphism

Fluid inclusions in rocks from the amphibolite‐facies gneiss to charnockite progression in southern Karnataka, India: direct evidence concerning the fluids of granulite metamorphism

Conditions of phlogopite crystallization in ultrapotassic volcanic rocks

The volcanic-subvolcanic rocks of the fernando de noronha archipelago, southern atlantic ocean: Mineral chemistry

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