Silicate melt inclusions from a mildly peralkaline granite in the Oslo paleorift, Norway

Hansteen, Thor; Lustenhouwer, W. J.

doi:10.1180/minmag.1990.054.375.06

Cited by 17 publications

(5 citation statements)

References 27 publications

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“…In agreement with the bulk analytical work the presence of CO2 and high temperatures of homogenisation from these inclusions supports the interpretation that pulse 3 represents an influx of CO2-rich magma. The range of Na/K atomic ratio values for the Etive samples, excluding the pegmatite (0.45-5.24, mean 2.77) fall within the span of values QUARTZ 341 quoted for magmatic fluids by Wilkinson (1990) (3.95 atomic ratio) and Hansteen and Lustenhouwer (1990) (0.74 atomic ratio). In contrast, Wilkinson (op.cit.…”

Section: Resultssupporting

confidence: 76%

Composition of fluids in quartz: discrimination of magma pulses in a Caledonian granitoid

Batchelor¹,

Armstrong²,

Mcdonald³

1992

Mineral. mag.

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Fluids trapped inside fluid inclusions in quartz from the multiphase Starav monzogranite in Etive, Argyll, were extracted under vacuum and quantitative data for H20 and CO2 were obtained manometrically. Na and K were determined on an aqueous leach from the decrepitated grains. A bivariate diagram of H20/CO2 versus Na/K discriminates between magma pulses and mirrors the whole-rock trace-element chemistry. This work shows that compositional variations of fluids in quartz from a weakly mineralised granitoid intrusion are sensitive indicators of its magmatic history and identify subtle changes in its mineralogical composition.

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Section: Resultssupporting

confidence: 76%

Composition of fluids in quartz: discrimination of magma pulses in a Caledonian granitoid

Batchelor¹,

Armstrong²,

Mcdonald³

1992

Mineral. mag.

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“…No change was observed between 480° and 530° C. After quenching from 530° to 630° C, vapor bubbles contracted noticeably and a light brownish reaction rim, which is presumed to indicate a subsolidus reaction, was observed. Hansteen and Lustenhouwer (1990) also reported a rim-darkening before melting began and attributed this to spatial redistribution of the material within the inclusions (subsolidus reaction?). We also noted a minor change in the refractive index of the glass compared to the host quartz.…”

Section: Microthermometrymentioning

confidence: 94%

Magmatic-Hydrothermal Evolution in the “Bottoms” of Porphyry Copper Systems: Evidence from Silicate Melt and Aqueous Fluid Inclusions in Granitoid Intrusions in the Gyeongsang Basin, South Korea

Yang

Bodnar

1994

International Geology Review

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The Gyeongsang Basin of southeastern Korea contains numerous Cretaceous-early Tertiary (120-40 Ma) granitoid intrusions formed at a convergent plate boundary. The geotectonic setting is similar to that associated with porphyry-type mineralization elsewhere in the Circumpacific region. However, erosion has removed higher-level economic mineralization and exposed deeper levels of the granitoids, representing the poorly mineralized "bottoms" of porphyry copper systems. The intrusions of the Gyeongsang Basin thus provide a unique opportunity to advance our understanding of magmatic-hydrothermal evolution in the roots of porphyry-type systems, below the level of economic mineralization.The physical and chemical environment during crystallization of the magmas has been characterized through studies of silicate melt and aqueous fluid inclusions in the granitoids. Two different types of silicate melt inclusions were recognized based on occurrence and roomtemperature appearance. Type-I inclusions contain one or more crystalline phases and vapor; type-II inclusions consist of a cluster of small crystals, partially devitrified glass, and vapor. Petrographic and Raman analyses indicate that most silicate melt inclusions contain muscovite daughter crystals. Some also contain feldspar. Solidus temperatures of type-I inclusions in quartz phenocrysts range from '^SO to 650 ° C, whereas solidus temperatures of type-I and type-II inclusions in vug quartz are slightly higher (640-670° C). Liquidus temperatures span a much wider range compared to solidus temperatures, with maximum liquidus temperatures of melts in phenocrysts being slightly higher (<930° C) than those in vug quartz (<910° C).Three types of aqueous inclusions were observed based on occurrence and room temperature phase proportions. Type-A inclusions are liquid rich and low to moderate in salinity; type-B inclusions are vapor rich and low in salinity; type-C inclusions are liquid rich and contain a halite daughter mineral. Some type-A inclusions with a salinity of approximately 25 wt% NaCl equivalent are spatially associated with silicate melt inclusions in phenocrysts, where they occur as three-dimensional clusters of tiny inclusions surrounding the silicate melt inclusion. Type-A inclusions also occur along fractures in quartz phenocrysts. Non-fracture-controlled type-C inclusions are rare in phenocryst quartz, but are common in vug quartz, where they are associated with silicate melt inclusions. Type-C inclusions that coexist with silicate melt inclusions generally homogenize by halite dissolution after the vapor bubble and show a wide range in salinity, from about 30 to >60 wt% NaCl equivalent. Coexisting halite-bearing (Type-C) and vapor-rich (Type-B) inclusions in phenocryst quartz suggest local immiscibility in the lateor post-magmatic fluid.Pressure-temperature conditions during the final stages of magmatic-hydrothermal activity associated with the granitoid intrusions of the Gyeongsang Basin were approximately 630 ° to 670° C and 1.9 to 2.5 kbars. These resul...

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“…Estimates of the pressure at which miarole‐bearing granites have crystallised have also been made by estimating the depth from the local stratigraphy. For example, Hansteen and Lustenhouwer (1990) estimated that the pressure of crystallisation of a miarolitic granite near Oslo, Norway, was between 50 and 100 MPa.…”

Section: Water Contents Of Granite Magmasmentioning

confidence: 99%

Water, restite and granite mineralisation

White

2001

Australian Journal of Earth Sciences

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Dehydration (vapour absent) partial melting reactions in the Earth’s crust produce a hydrous granitic melt phase, new anhydrous minerals that are mostly pyroxenes, and new plagioclase more calcic than the initial plagioclase. These solid phases of the melt reaction are restite. If the restite is carried to high levels in the crust as a component of the magma, cooling and crystallisation to granite will result in back reactions in which the H2O in the melt phase is consumed and is not then available to form a hydrothermal solution. Even in magmas in which some restite has been removed there will be some back reaction and again less H2O. Only fractional crystallisation will enrich the H2O in the magma in sufficient amounts to form a substantial quantity of hydrothermal solution and possible mineralisation.

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Silicate melt inclusions from a mildly peralkaline granite in the Oslo paleorift, Norway

Cited by 17 publications

References 27 publications

Composition of fluids in quartz: discrimination of magma pulses in a Caledonian granitoid

Composition of fluids in quartz: discrimination of magma pulses in a Caledonian granitoid

Magmatic-Hydrothermal Evolution in the “Bottoms” of Porphyry Copper Systems: Evidence from Silicate Melt and Aqueous Fluid Inclusions in Granitoid Intrusions in the Gyeongsang Basin, South Korea

Water, restite and granite mineralisation

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