Three-dimensional distribution of primary melt inclusions in garnets by X-ray microtomography

Parisatto, Matteo; Turina, Alice; Cruciani, Giuseppe; Mancini, Lucia; Peruzzo, Luca; Cesare, Bernardo

doi:10.2138/am-2018-6216ccbyncnd

Cited by 3 publications

(3 citation statements)

References 81 publications

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“…Unlike the discretely zoned garnet in the other studied samples, these garnet display continuous chemical zoning and variation in inclusion density (Figure 5m-p and Figure S2) characteristic of a single garnet growth event (e.g. Caddick et al, 2010;Parisatto et al, 2018;Tracy et al, 1976) and are interpreted as neoblasts formed at same time as the secondary garnet rims.…”

Section: Multi-stage Garnet Growthmentioning

confidence: 87%

Delineation of multiple metamorphic events in the Himalayan Kathmandu Complex, central Nepal

Johnson

Cottle

Larson

2020

Journal Metamorphic Geology

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Quartz-inclusion geothermobarometry of texturally and chemically zoned garnet, together with U-(Th)-Pb accessory phase petrochronology, phase equilibria modelling, and major element thermobarometry delineates two metamorphic events withinthe Kathmandu Complex in central Nepal. Combined titanium-in-quartz thermometry (TitaniQ) and quartz-in-garnet barometry (QuiG) of quartz inclusions in garnet cores yields temperatures and pressures (555-580°C, 0.89-0.91 GPa) statistically higher than those estimated for both garnet rims and secondary garnet neoblasts (535-545°C, 0.81-0.84 GPa). Comparison of these temperatures and pressures with the results from phase equilibria modelling indicates that the garnet cores nucleated after overstepping the equilibrium garnet isograd. Estimation of the degree to which overstepping may have occurred, however, is complicated by uncertainty in the estimated reactive bulk compositions. Major element thermobarometry of the garnet rims returns temperatures and pressures lower than those preserved by the garnet cores but are consistent with previous estimates of Cenozoic metamorphism in the frontal portion of Kathmandu thrust sheet. Two generations of titanite are recognized on the basis of mineral morphology, chemical zoning, and U-Pb date (c. 500 Ma versus 29 ± 5 Ma). Trace-element systematics of the two titanite populations indicate varying co-stability with allanite and are consistent with Th-Pb dates of allanite growth (c. 489 Ma) and breakdown to clinozoisite (c. 30 Ma). Inclusion patterns within titanite indicate that the younger group formed following breakdown of rutile that originally coexisted with the older generation of titanite at pressures and temperatures similar to those determined from the garnet cores. Application of the Zr-in-titanite and Zr-in-rutile thermometers yields temperatures 100-150°C in excess of those indicated by both TitaniQ-QuiG and major element thermobarometry. This discrepancy is interpreted to reflect disequilibrium partitioning of Zr and limited zircon reactivity during metamorphism. Collectively, these observations are consistent with previous estimates of the timing and conditions of metamorphism associated with the Palaeozoic Bhimphedian and Cenozoic Himalayan orogenies in central Nepal. The estimated temperatures and pressures for growth of the garnet cores are consistent with rapid burial during thrust stacking.

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Section: Multi-stage Garnet Growthmentioning

confidence: 87%

Delineation of multiple metamorphic events in the Himalayan Kathmandu Complex, central Nepal

Johnson

Cottle

Larson

2020

Journal Metamorphic Geology

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“…All garnet have an inclusion-free rim without any melt inclusions, as for the garnet located in the quartz-poor selvedge (Figure 5). This difference in the ability for garnet rims to entrap melt inclusions may be related to a slowdown of radial growth rate as garnet continuously grows (Parisatto et al, 2018). X-ray computed microtomography and sequential cuts through a single garnet crystal has been performed to highlight the volume, shape, and potential connectivity of the polyphase inclusions with the matrix.…”

Section: Evolution Of Garnet Morphology and Inclusionsmentioning

confidence: 99%

Garnet as a monitor for melt–rock interaction: Textural, mineralogical, and compositional evidence of partial melting and melt‐driven metasomatism

Gonçalves

Raimondo

Paquette

et al. 2021

Journal Metamorphic Geology

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In this study, we focus on a partially melted garnet-bearing granulite from the Salvador-Esplanade Belt (Salvador da Bahia, Brazil), and examine the behaviour of major and trace elements during partial melting and melt-driven metasomatism. Phase equilibria modelling and U-Th-Pb geochronology show that the sample underwent partial melting during the heating segment of the decompression path from ~1.2 GPa and 675-700°C to ~0.8 GPa and 790°C at c. 2.06 Ga. During the final stage of decompression, from 0.8 to ~0.5 GPa, physical segregation of melt resulted in the establishment of chemical potential gradients and mass transfer between the host granulite and the leucosome. Modelling shows that H 2 O, CaO, K 2 O, and Na 2 O diffused from the melt into the host residue, whereas SiO 2 was transferred from the host granulite into the adjacent leucosome. Opposed senses of diffusional transfer resulted in the formation of a quartz-rich anhydrous leucosome and a quartz-depleted selvedge in the host granulite. Compositional maps show that garnet exhibit contrasting major and trace element distributions depending on their textural position. The largest garnet located in the quartz-depleted selvedge preserve their original Ca and trace element growth zoning. A transition from bell-shaped profiles for Y and heavy rare earth elements to bowl-shaped profiles for light rare earth elements is consistent with a typical Rayleigh fractionation model, fast intergranular element mobility, and rock-wide equilibrium during prograde partial melting. In contrast, smaller garnet away from the leucosome show prograde growth zoning modified by intragranular diffusion, as evidenced by a network of open channels and healed cracks that act as connecting pathways between the matrix and garnet core. This results in either subtle modification of both major and trace elements adjacent to the inner core inclusions, or a complete re-equilibration. Recognition that the original Ca growth zoning was later modified by intragranular diffusion implies that misleading thermobarometric results and tectonic interpretations would be obtained if the core composition was used to fingerprint the early garnet nucleation stage. This study demonstrates that at high temperature (>750°C) and in the presence of melt, REE are not less vulnerable to diffusive resetting than divalent cations like Ca 2+ . K E Y W O R D S chemical potential, diffusion metasomatism, garnet zoning, LA-ICP-MS, partial melting 618 | GONCALVES Et AL.

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“…The µCT studies can be carried out by using conventional X-rays sources as well as a synchrotron radiation (SR) source, the latter providing several advantages in terms of quicker acquisition time, better sensitivity and contrast, higher voxel size resolution and a general reduction of image artifacts [33]. The synchrotron radiation X-ray micro-computed tomography (SR-µCT) is potentially a powerful tool to study the effects induced by inorganic consolidating treatments on the stone microstructure, as they penetrate by capillarity in the pore network, impregnate the voids and modify the 3D pore system at the microscale [30].…”

Section: Introductionmentioning

confidence: 99%

Consolidation of building materials with a phosphate-based treatment: Effects on the microstructure and on the 3D pore network

Possenti

Colombo

Conti

et al. 2019

Materials Characterization

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Three-dimensional distribution of primary melt inclusions in garnets by X-ray microtomography

Cited by 3 publications

References 81 publications

Delineation of multiple metamorphic events in the Himalayan Kathmandu Complex, central Nepal

Delineation of multiple metamorphic events in the Himalayan Kathmandu Complex, central Nepal

Garnet as a monitor for melt–rock interaction: Textural, mineralogical, and compositional evidence of partial melting and melt‐driven metasomatism

Consolidation of building materials with a phosphate-based treatment: Effects on the microstructure and on the 3D pore network

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