Internally consistent gahnitic spinel-cordierite-garnet equilibria in the FMASHZn system: geothermobarometry and applications

Nichols, Geoffrey T.; Berry, Ron F.; Green, David H.

doi:10.1007/bf00311197

Cited by 207 publications

(135 citation statements)

References 33 publications

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“…The effect of Cr 2 O 3 is not significant in the present case because the spinel contains very low concentration of Cr 2 O 3 . Only the effect of ZnO in the spinel, therefore, is considered in the reaction (3) and shown in Figure 4, using observed compositions of garnet and spinel (Table 1), and thermodynamic data of Nichols et al (1992). Spl + Qtz assemblage is stabilized to lower temperature by the addition of 2.77 3.39 wt% ZnO to the spinel for about 50 degrees.…”

Section: Discussionmentioning

confidence: 99%

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Timing of attainment of the spinel+quartz coexistence in garnet-sillimanite leucogneiss from Skallevikshalsen, Luetzow-Holm Complex, East Antarctica

Kawakami

Motoyoshi

2004

Journal of Mineralogical and Petrological Sciences

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Spinel in direct contact with quartz is newly found in the Grt Sil leucogneiss from Skallevikshalsen, Lützow Holm Complex, East Antarctica. It is included in the outermost core of the garnet porphyroblast and is characterized by low ZnO content (2.77 3.83 wt%) and very low Cr 2 O 3 content (0 0.09 wt%). Incorporation of 2.77 3.39 wt% ZnO stabilized the Spl + Qtz assemblage to lower temperatures for about 50 degrees. As a result, their coexistence can be attained around the peak P T conditions of Skallevikshalsen. The occurrence of relic staurolite, kyanite and breakdown texture of staurolite to spinel and kyanite included in the garnet core suggests that prograde stage is preserved in the garnet core and breakdown of staurolite itself was attained in the kyanite stability field. The Spl + Qtz assemblage is included at outermost part of the garnet core, suggesting that outermost core of the garnet was formed near the peak metamorphic conditions. Decrease in anorthite content of plagioclase included in the garnet core from that found in the rock matrix suggests that decompression took place during garnet formation. Attainment of these reaction sequences requires clockwise P T path as previously proposed for the Lützow Holm Complex.

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Section: Discussionmentioning

confidence: 99%

“…Bohlen et al, 1986;Nichols et al, 1992;Ikeda, 1998;Shimura et al, 2002). It is important, therefore, to evaluate the effect of ZnO and Cr 2 O 3 in spinel when we try to draw some information out from this assemblage.…”

Section: Introductionmentioning

confidence: 99%

Timing of attainment of the spinel+quartz coexistence in garnet-sillimanite leucogneiss from Skallevikshalsen, Luetzow-Holm Complex, East Antarctica

Kawakami

Motoyoshi

2004

Journal of Mineralogical and Petrological Sciences

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“…However, the phase relations cannot be directly applied to our spinel + quartz assemblage as the spinels contain Zn (up to 0.30 X Zn ). As Zn in spinel extends the stability field of the spinel + quartz toward higher pressure and/or lower temperature (Nichols et al, 1992), we attempted to apply Zn -inspinel geobarometer of Nichols et al (1992) for the spinel + quartz assemblages from the TGB. The results yielded pressure values of ~ 12 kbar at 900 -1000 °C from the eTGB, while slightly lower pressure of ~10 kbar was obtained from the wTGB (Fig.…”

Section: P-t Estimatesmentioning

confidence: 99%

Metamorphic P-T path of the eastern Trivandrum Granulite Block, southern India: implications for regional correlation of lower crustal fragments

Tadokoro

Tsunogae

Santosh

2008

Journal of Mineralogical and Petrological Sciences

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We report here the metamorphic P -T path for granulite -facies metapelites from the eastern part of the Trivandrum Granulite Block (TGB), southern India, and compare with the paths from the western part of the block as well as from other granulite blocks and shear zones in this region for understanding of exhumation history of the southern granulite terrane. The peak temperature condition of the eastern part (900 -1000 °C) is almost consistent with that from the western part, suggesting regional ultrahigh -temperature (UHT) metamorphism throughout the TGB. However, there is a slight difference in peak pressure conditions between the eastern part (12 kbar) and the western part (10 kbar) estimated from different Zn content within spinel in equilibrium with quartz. Such P ~ 12 kbar high -pressure event is consistent with that obtained from granulite -facies rocks further north in the Palghat -Cauvery Shear Zone system (PCSZ) and Madurai Granulite Block (MGB). The results therefore suggest that the TGB, MGB, and PCSZ underwent similar prograde high -pressure metamorphism followed by peak UHT event along a clockwise P -T trajectory, related to the collisional orogeny during the assembly of the Gondwana Supercontinent.

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“…The simplifications that are necessary to model phase equilibria in naturally complex chemical systems are also a limiting factor. The model chemical system used in this study does not take into account minor components, such as chlorine and fluorine in biotite and ZnO and Cr 2 O 3 in spinel, which are present in minor amounts, see Table 1, [58,59]. Although the effects of these minor components are unlikely to greatly influence the outcomes of the modelling, they are real and will slightly modify of the positions of reactions in P-T space [5].…”

Section: Limitations Of the Modellingmentioning

confidence: 99%

Melt Reintegration Modelling: Testing against a Subsolidus Reference Assemblage

et al. 2017

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Phase equilibria modelling incorporating melt reintegration offers a methodology to create hypothetical rock compositions that may have existed prior to melt loss, allowing the potential prograde evolution of rocks to be explored. However, melt reintegration modelling relies on assumptions concerning the volume of melt that was lost and is generally restricted by the absence of direct constraints on the pre-anatectic mineral assemblages. Mg-rich granulite in the 514-490 Ma Delamerian Orogen in southern Australia contains spinel-cordierite symplectic intergrowths that surround rare, coarse blocky domains of sillimanite. These sillimanite cores, as well as the widespread presence of andalusite in lower grade areas of the southern Delamerian Orogen, suggest that the subsolidus precursor to the granulite contained andalusite. This provides the opportunity to test if melt reintegration modelling of the granulite predicts subsolidus andalusite.Stepwise down-temperature melt reintegration modelling produces a water-saturated solidus after the addition of 12 mol% melt. When modelled at subsolidus conditions, the resulting rock composition produces andalusite-bearing assemblages with andalusite modes similar to the abundance of the sillimanite-cored spinel-cordierite intergrowths. The modelling results from this case study suggest that melt reintegration modelling is a valid method to recreate prograde subsolidus bulk rock compositions.

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Internally consistent gahnitic spinel-cordierite-garnet equilibria in the FMASHZn system: geothermobarometry and applications

Cited by 207 publications

References 33 publications

Timing of attainment of the spinel+quartz coexistence in garnet-sillimanite leucogneiss from Skallevikshalsen, Luetzow-Holm Complex, East Antarctica

Timing of attainment of the spinel+quartz coexistence in garnet-sillimanite leucogneiss from Skallevikshalsen, Luetzow-Holm Complex, East Antarctica

Metamorphic P-T path of the eastern Trivandrum Granulite Block, southern India: implications for regional correlation of lower crustal fragments

Melt Reintegration Modelling: Testing against a Subsolidus Reference Assemblage

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