Topic
Grossular
About: Grossular is a research topic. Over the lifetime, 661 publications have been published within this topic receiving 22015 citations. The topic is also known as: grossularite & Grs.
Papers published on a yearly basis
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Papers
TL;DR: In this article, a series of experiments, between 100 and 2000 MPa, on the fluid-absent melting of a quartz-rich aluminous metagreywacke composed of 32 wt% plagioclase (Pl) (An22), 25 wt % biotite (Bt) (XMg45), and 41 wt percent quartz (Qtz), were carried out using a powder of minerals (≤5μm) and a glass of the same composition.
Abstract: Island arcs, active and passive margins are the best tectonic settings to generate fertile reservoirs likely to be involved in subsequent granitoid genesis. In such environments, greywackes are abundant crustal rock types and thus are good candidates to generate large quantities of granitoid magmas. We performed a series of experiments, between 100 and 2000 MPa, on the fluid-absent melting of a quartz-rich aluminous metagreywacke composed of 32 wt% plagioclase (Pl) (An22), 25 wt% biotite (Bt) (X
Mg45), and 41 wt% quartz (Qtz). Eighty experiments, averaging 13 days each, were carried out using a powder of minerals (≤5μm) and a glass of the same composition. The multivariant field of the complex reaction Bt+Pl+Qtz⇔Grt/Crd/Spl+ Opx+Kfs+melt limited by the Opx-in and Bt-out curves, is located between 810–860°C at 100 MPa, 800–850°C at 200 MPa, 810–860°C at 300 MPa, 820–880°C at 500 MPa, 860–930°C at 800 MPa, 890–990°C at 1000 MPa, and at a temperature lower than 1000°C at 1500 and 1700 MPa. The melting of biotite+plagioclase+ quartz produced melt+orthopyroxene (Opx) +cordierite (Crd) or spinel (Spl) at 100, 200 and 300 MPa, and melt+orthopyroxene+garnet (Grt) from 500 to 1700 MPa (+Qtz, Pl, FeTi Oxide at all pressures). K-feldspar (Kfs) was found as a product of the reaction in some cases and we observed that the residual plagioclase was always strongly enriched in orthoclase component. The P-T surface corresponding to the multivariant field of this reaction is about 50 to 100°C wide. At temperatures below the appearance of orthopyroxene, biotite is progressively replaced by garnet with increasing P. At 850°C, we observed that (1) the modal proportion of garnet increases markedly with P; (2) the grossular content of the garnet increases regularly from about 4 mol% at 500 MPa to 15 mol% at 2000 MPa. These changes can be ascribed to the reaction Bt+Pl+Qtz ⇔ Grt+Kfs+melt with biotite +plagioclase+quartz on the low-P side of the reaction. As a result, at 200 MPa, we observed the progressive disappearance of biotite without production of orthopyroxene. These experiments emphasize the importance of this reaction for the understanding of partial melting processes and evolution of the lower continental crust. Ca-poor Al-metagreywackes represent fertile rocks at commonly attainable temperatures (i.e. 800–900°C), below 700 MPa. There, 30 to 60 vol.% of melt can be produced. Above this pressure, temperatures above 900°C are required, making the production of granitoid magmas more difficult. Thin layers of gneisses composed of rothopyroxene, garnet, plagioclase, and quartz (±biotite), interbedded within sillimanite-bearing paragneisses, are quite common in granulite terrains. They may result from partial melting of metagreywackes and correspond to recrystallized mixtures of crystals (+trapped melt) left behind after removal of a major proportion of melt. Available experimental constraints indicate that extensive melting of pelites takes place at a significantly lower temperature (850°C±20) than in Al-metagreywackes (950°C±30), at 1000 MPa. The common observation that biotite is no longer stable in aluminous paragneisses while it still coexists commonly with orthopyroxene, garnet, plagioclase and quartz, provides rather tight temperature constraints for granulitic metamorphism.
552 citations
Journal Article•
TL;DR: In this article, two new geobarometers for the assemblage garnet + hornblende + plagioclase + quartz have been calibrated on the basis of the equilibrium 6 Anorthite + 3 Tremolite = 2 Grossular + 1 Pyrope + 3 Tschermakite + 6 Quartz and its Fe end-member equivalent.
Abstract: Two new geobarometers for the assemblage garnet + hornblende + plagioclase + quartz have been calibrated on the basis of the equilibrium 6 Anorthite + 3 Tremolite = 2 Grossular + 1 Pyrope + 3 Tschermakite + 6 Quartz and its Fe end-member equivalent. Data representing 37 natural samples that equilibrated at conditions of 2.5 to 13 kbar and 500 to 800°C were fitted to the general equation -RT In Keq= A - BT + (P - I)C by using a weighted least-squares method. Multiple correlation coefficients are high (0.98 and 0.97). Lines of constant Keqhave extremely shallow slopes in P- T space (- 2 to + 8 bars per degree), suggesting that pressures may be deduced precisely, even where temperatures are only poorly constrained. Typical analytical errors and temperature imprecisions propagate to very small errors in pressure (about ::!:500 bars). Caution is advised in applying the barometers outside the range of calibrant-mineral compositions. Application of the calibrations to samples from southeastern Vermont near the Strafford, Chester, and Athens domes documents relatively high pressure metamorphism (7 to 10 kbar) for these structures.
493 citations
TL;DR: In this article, partial melting of an eclogitic component of different modal compo- sitions may explain both subchondritic and super chondritic Zr/Hf ratios.
461 citations
TL;DR: In this article, a detailed analysis of separated phases of several Allende Ca-Al-rich inclusions is reported, which reveal a consistent pattern of large O-16 enrichments in spinel, pyroxene, and sometimes olivine, and small O- 16 enrichment in melilite, feldspathoids, and grossular.
459 citations
TL;DR: In this article, the chemical composition of the phases present in the experimental charges as determined by electron microprobe was reported, including biotite, plagioclase, orthopyroxene, garnet, cordierite, hercynite, staurolite, gedrite, oxide, and glass, over the range 100-1000"MPa, 780-1025"°C.
Abstract: A series of experiments on the fluid-absent melting of a quartz-rich aluminous metagreywacke has been carried out. In this paper, we report the chemical composition of the phases present in the experimental charges as determined by electron microprobe. This analytical work includes biotite, plagioclase, orthopyroxene, garnet, cordierite, hercynite, staurolite, gedrite, oxide, and glass, over the range 100–1000 MPa, 780–1025 °C. Biotites are Na- and Mg-rich, with Ti contents increasing with temperature. The compositions of plagioclase range from An17 to An35, with a significant orthoclase component, and are always different from the starting minerals. At high temperature, plagioclase crystals correspond to ternary feldspars with Or contents in the range 11–20 mol%. Garnets are almandine pyrope grossular spessartine solid solutions, with a regular and significant increase of the grossular content with pressure. All glasses are silicic (SiO2 = 67.6–74.4 wt%), peraluminous, and leucocratic (FeO + MgO = 0.9–2.9 wt%), with a bulk composition close to that of peraluminous leucogranites, even for degrees of melting as high as 60 vol.%. With increasing pressure, SiO2 contents decrease while K2O increases. At any pressure, the melt compositions are more potassic than the water-saturated granitic minima. The H2O contents estimated by mass balance are in the range 2.5–5.6 wt%. These values are higher than those predicted by thermodynamic models. Modal compositions were estimated by mass balance calculations and by image processing of the SEM photographs. The positions of the 20 to 70% isotects (curves of equal proportion of melt) have been located in the pressure-temperature space between 100 MPa and 1000 MPa. With increasing pressure, the isotects shift toward lower temperature between 100 and 200 MPa, then bend back toward higher temperature. The melting interval increases with pressure; the difference in temperature between the 20% and the 70% isotects is 40 °C at 100 MPa, and 150 °C at 800 MPa. The position of the isotects is interpreted in terms of both the solubility of water in the melt and the nature of the reactions involved in the melting process. A comparison with other partial melting experiments suggests that pelites are the most fertile source rocks above 800 MPa. The difference in fertility between pelites and greywackes decreases with decreasing pressure. A review of the glass compositions obtained in experimental studies demonstrates that partial melting of fertile rock types in the crust (greywackes, pelites, or orthogneisses) produces only peraluminous leucogranites. More mafic granitic compositions such as the various types of calk-alkaline rocks, or mafic S-type rocks, have never been obtained during partial melting experiments. Thus, only peraluminous leucogranites may correspond to liquids directly formed by partial melting of metasediments. Other types of granites involve other components or processes, such as restite unmixing from the source region, and/or interaction with mafic mantle-derived materials.
412 citations
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Performance Metrics
| Year | Papers |
|---|---|
| 2025 | 2 |
| 2024 | 7 |
| 2023 | 30 |
| 2022 | 42 |
| 2021 | 21 |
| 2020 | 12 |