Garnet–clinopyroxene intermediate granulites in the St. Leonhard massif of the Bohemian Massif: ultrahigh‐temperature metamorphism at high pressure or not?

Ráček, Martin; Štípská, Pavla; Powell, R.

doi:10.1111/j.1525-1314.2007.00754.x

Cited by 41 publications

(43 citation statements)

References 43 publications

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“…with subordinate amount of orthopyroxene, rutile and magnetite. The peak granulite assemblage is represented by garnetclinopyroxene-plagioclase-quartz-ilmenite with/without orthopyroxene which is characteristic of many high-pressure rocks (O'Brien, 2008;Racek et al, 2008). This assemblage could have evolved through dehydration melting of hornblende-bearing assemblage.…”

Section: Textural and Mineralogical Evolutionmentioning

confidence: 99%

Tectonic juxtaposition of crust and continental growth during orogenesis: Example from the Rengali Province, eastern India

Bose¹,

Guha²,

Ghosh³

et al. 2015

Geoscience Frontiers

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a b s t r a c tThe southern boundary of the Singhbhum Craton witnessed multiple orogenies that juxtaposed thin slice of granulite suite of the Rengali Province against the low-grade granite-greenstone belt of the craton along the EeW trending Sukinda Thrust. The strong southerly dipping mylonitic foliation within the granulites along with the prominent down-dip mineral lineation, suggest a northerly-verging thrusting. Mylonitized charnockite at the contact zone contains enclaves of mafic and ultramafic granulite, whereas granitoid gneiss contains enclaves of pelitic granulite. Mafic granulite enclaves preserve an early (S 1M ) foliation that formed during D 1M deformation. This rock, along with the host charnockite, were intensely deformed by the D 2M thrusting event and resulting S 2M foliation development in both rock suites. Geothermobarometric and pseudosection analyses show that the garnet-clinopyroxene-plagioclaseorthopyroxene-ilmenite-quartz assemblage in mafic granulite was stabilized at high-pressure and temperature conditions (10À12 kbar, 860 C) and was overprinted by a fine-grained assemblage of clinopyroxene-plagioclase AE hornblende that developed during decompression (down to 5.5e7.5 kbar). Matrix hornblende shows incipient breakdown to garnet-clinopyroxene-quartz intergrowth due to a granulite facies reworking. A contrasting P-T history is preserved in the pelitic granulite. The peak assemblage garnet-orthopyroxene-cordierite-quartz-rutile was stabilized at w6.0 kbar, 730 C which resulted from heating of the mid crust magma during the D 2M thrusting. The contrasting P-T histories could result from the tectonic juxtaposition of lower-and mid-crustal section during the D 2M event. Evidences of an early orogenic imprint within the mafic granulite imply involvement of deep continental crust during southward growth of the Singhbhum Craton.Ó 2014, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/3.0/).

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Section: Textural and Mineralogical Evolutionmentioning

confidence: 99%

Tectonic juxtaposition of crust and continental growth during orogenesis: Example from the Rengali Province, eastern India

Bose¹,

Guha²,

Ghosh³

et al. 2015

Geoscience Frontiers

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“…Calibrations The calibration and pressure dependence of Zr-in-rutile presented in Tomkins et al (2007) has proven reliable in a number of studies (e.g., Racek et al 2008;Kooijman et al 2012;Ewing et al 2013;Štípská et al 2014). The Ti-in-quartz calibration (Thomas et al 2010) has, however, been discussed by Huang and Audétat (2012) who inferred that quartz which grew at slow rates and relatively "low" temperatures (600-800 °C) might result in an underestimation of T, and presented a recalibration of the Ti-inquartz geothermometer.…”

Section: Factors Affecting Ti In Quartz and Zr In Rutilementioning

confidence: 99%

Tracking the prograde P–T path of Precambrian eclogite using Ti-in-quartz and Zr-in-rutile geothermobarometry

Tual

Möller

Whitehouse

2018

Contrib Mineral Petrol

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A Fe-Ti-rich garnet, clinopyroxene, and quartz eclogite sample from the 1.0 Ga Sveconorwegian orogen, SW Sweden, contains abundant quartz, rutile, and zircon in distinct micro-textural sites: garnet core, garnet rim, and matrix, constituting an ideal case for investigation of the behavior of Zr-in-rutile and Ti-in-quartz at high-pressure and temperature. A P-T path, peaking at 16.5-19 kbar and 850-900 °C, has been constrained independently for the same rock by pseudosection modelling; input pressures from this model were used for trace element geothermometry of each garnet micro-textural domain. Trace element thermo(baro)metry, based on in situ Secondary Ion Mass Spectrometry analyses of Ti contents in quartz and Zr contents in rutile, yields P-T estimates of progressive crystallization of quartz and rutile along the prograde metamorphic path. For inclusions in the garnet cores, Zr-in-rutile geothermometry yields 700-715 °C and Ti-in-quartz 620-640 °C at 7 kbar. For inclusions in the garnet rims, temperature estimates are 760-790 °C (Zr-in-rutile) and 740-920 °C (Ti-in-quartz) at 12-18 kbar. Finally, matrix rutile records 775-800 °C and locally ~ 900 °C, and quartz records temperatures up to 900 °C at 18 kbar. Ti-in-quartz estimates for the metamorphic peak (inclusions in the garnet rims and matrix) conform to the pseudosection, but appear too low for the early prograde stage (garnet cores), possibly due to lack of equilibrium at T < 700 °C. The pseudosection shows that rutile was produced by continuous ilmenite breakdown during the early stages of prograde metamorphism, a reaction that was completed at ~ 730 °C. Rutile grains in the garnet rims and the matrix grew subsequently larger by recrystallization of previously produced rutile. However, recrystallized rutile does not predominantly record peak temperatures, but instead yield 745-840 °C between 12 and 18 kbar. In the pseudosection, this temperature range broadly coincides with a stage during which (Ti-bearing) hornblende was consumed and clinopyroxene produced (i.e., dehydration); the Zr contents thus appear to reflect the last stage of efficient rutile recrystallization, catalysed by fluids released by the dehydration of hornblende preceding the metamorphic peak. Concurrently, combination of the isopleths for Ti content in quartz and Zr content in rutile (i.e. independent from pseudosection modelling) yields pressure and temperature conditions in almost perfect agreement with the P-T path as deduced from the pseudosection. The variation in Ti concentration in quartz is small regardless of crystal size, and the Ti-in-quartz geothermometer provides both precise and accurate peak temperatures of 875-920 °C, without a significant diffusional reequilibration. The lack of significant Ti diffusion in quartz is consistent with an inferred short residence time at high temperature. This study illustrates that Zr-in-rutile and Ti-in-quartz geothermobarometry can robustly constrain prograde P-T conditions and yield further insights into recrystallization proc...

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“…The P-T conditions of regional metamorphism in the Gföhl Unit were significantly higher, estimated at 850 to 1000 °C and 1.5 to 2.3 GPa (e.g. Carswell and O'Brien 1993;O'Brien and Rötzler 2003;Racek et al 2006Racek et al , 2008. Conditions of the subsequent retrograde metamorphism were calculated at ~600 to 800 °C and ~0.6 to 0.8 GPa (e.g Racek 2006;Tajčmanová et al 2006).…”

Section: Regional Geological Settingmentioning

confidence: 99%

Geochronology and petrology of pyroxene-garnet skarns (eastern Bohemian Massif): implications for the source and evolution of the Variscan continental crust

Pertoldová¹,

Kosulicova²,

Verner³

et al. 2014

J. Geosci.

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Zircon ages (U-Pb, LA-ICP-MS) obtained from skarns in the Kutná Hora and Svratka units and in the Moldanubian Zone (Bohemian Massif) show significant variations between the lithotectonic units as well as among samples from individual localities. The ages fall between 310 Ma and 3.1 Ga. We suggest that such large spread is a result of both different zircon clastic grain sources and subsequent metamorphic histories. The oldest Neoarchaean to Neoproterozoic ages are interpreted as detrital zircon grains from pre-Cadomian basement. Pronounced age maxima between 600 and 520 Ma (late Neoproterozoic to early Cambrian) were found in skarn samples from the Moldanubian Zone, Svratka and Kutná Hora units. We interpret these as maximum ages of skarn precursor deposition. Apparent Cambrian-OrdovicianSilurian to early Devonian zircon ages were obtained from non-mineralized samples of the Moldanubian Zone and also in the Kutná Hora Unit. This wide temporal interval could reflect maximum ages of skarn precursors related to disintegration of abundant early Palaeozoic magmatic rocks, provided the zircons were not modified by later metamorphism or fluid circulation. The early Carboniferous ages are interpreted to result from strong Variscan HT metamorphism and subsequent circulation of post-metamorphic fluids. Zircons of this age are dominant in skarns with massive magnetite mineralization, while the non-mineralized samples preserve the older ages.

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Garnet–clinopyroxene intermediate granulites in the St. Leonhard massif of the Bohemian Massif: ultrahigh‐temperature metamorphism at high pressure or not?

Abstract: International audienc

Cited by 41 publications

References 43 publications

Tectonic juxtaposition of crust and continental growth during orogenesis: Example from the Rengali Province, eastern India

Tectonic juxtaposition of crust and continental growth during orogenesis: Example from the Rengali Province, eastern India

Tracking the prograde P–T path of Precambrian eclogite using Ti-in-quartz and Zr-in-rutile geothermobarometry

Geochronology and petrology of pyroxene-garnet skarns (eastern Bohemian Massif): implications for the source and evolution of the Variscan continental crust

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