High-pressure and ultrahigh-temperature metamorphism at Komateri, northern Madurai Block, southern India

2008 ◽  
Vol 33 (5-6) ◽  
pp. 395-413 ◽  
Author(s):  
Toshiaki Tsunogae ◽  
M. Santosh ◽  
Hiroyuki Ohyama ◽  
Kei Sato
Keyword(s):  
High Pressure ◽  
Southern India ◽  
Ultrahigh Temperature

An unusual high-Mg garnet–spinel orthopyroxenite from southern India: evidence for ultrahigh-temperature metamorphism at high-pressure conditions

2006 ◽  
Vol 143 (6) ◽  
pp. 923-932 ◽  
Author(s):  
K. SAJEEV ◽  
M. SANTOSH
Keyword(s):  
High Pressure ◽  
Final Stage ◽  
Close Association ◽  
Southern India ◽  
Al Content ◽  
Multi Stage ◽  
Gondwana Supercontinent ◽  
Ultrahigh Temperature ◽  
Uht Metamorphism ◽  
High Al Content

We report here a garnet–spinel orthopyroxenite in close association with an ultrahigh-temperature (UHT) granulite from the central part of the Madurai Granulite Block in southern India. The garnet–spinel orthopyroxenite is almost entirely composed of orthopyroxene, spinel and rare garnet in a granular texture. Spinels in the rock are characterized by high Mg (XMg = 0.69–0.71) with low Cr and Fe3+, consistent with compositions reported from spinels occurring within xenoliths in kimberlites and high pressure–temperature (P–T) Alpine complexes. The orthopyroxenes have high Al content (Al2O3 up to 4.85 wt%), typical of equilibration under high P–T conditions. The P–T estimates derived for the garnet–spinel orthopyroxenite indicate temperatures of around 1000°C and pressures exceeding 17 kbar. The data indicate that UHT metamorphism in this locality traversed from above 17 kbar to 11 kbar prior to the final stage of isothermal decompression. Our study reports the highest pressures obtained by far, for extreme crustal metamorphism in southern India and elsewhere in Gondwana. The multi-stage decompression observed in the UHT rocks associated with the high P–T garnet–spinel orthopyroxenite could be correlated to extension of the crust and possibly of the lithospheric mantle and/or its delamination, with the asthenospheric mantle as the ultimate heat source, during the final stage of amalgamation of the Gondwana supercontinent.

Ultrahigh-temperature metamorphism and decompression history of sapphirine granulites from Rajapalaiyam, southern India: implications for the formation of hot orogens during Gondwana assembly

2009 ◽  
Vol 147 (1) ◽  
pp. 42-58 ◽  
Author(s):  
T. TSUNOGAE ◽  
M. SANTOSH
Keyword(s):  
Southern India ◽  
Stability Field ◽  
Fine Grained ◽  
History Of ◽  
Peak Metamorphism ◽  
Gondwana Supercontinent ◽  
Isothermal Decompression ◽  
Ultrahigh Temperature ◽  
Late Neoproterozoic ◽  
Uht Metamorphism

AbstractSapphirine-bearing Mg–Al granulites from Rajapalaiyam in the southern part of the Madurai Block provide critical evidence for Late Neoproterozoic–Cambrian ultrahigh-temperature (UHT) metamorphism in southern India. Poikiloblastic garnet in quartzo-feldspathic and pelitic granulites contain inclusions of fine-grained subidioblastic to xenoblastic sapphirine associated with quartz, suggesting that the rocks underwent T > 1000°C peak metamorphism. Quartz inclusions in spinel within garnet are also regarded as clear evidence for a UHT condition. Inclusions of orthopyroxene within porphyroblastic garnet in the sapphirine-bearing rocks show the highest Al2O3 content of up to 10.3 wt%, suggesting T = 1050–1070°C and P = 8.5–9.5 kbar. Temperatures estimated from ternary feldspar and other geothermometers (T = 950–1000°C) further support extreme thermal metamorphism in this region. Xenoblastic spinel inclusions in sapphirine coexisting with quartz suggest that the spinel + quartz assemblage pre-dates the sapphirine + quartz assemblage, probably implying a cooling from T ~ 1050°C or an anticlockwise P–T path. The FMAS reaction sapphirine + quartz + garnet → orthopyroxene + sillimanite indicates a cooling from the sapphirine + quartz stability field after the peak metamorphism. Corona textures of orthopyroxene + cordierite (± sapphirine), orthopyroxene + sapphirine + cordierite, and cordierite + spinel around garnet suggest subsequent near-isothermal decompression followed by decompressional cooling toward T = 650–750°C and P = 4.5–5.5 kbar. The sapphirine–quartz association and related textures described in this study have an important bearing on the UHT metamorphism and exhumation history of the Madurai Block, as well as on the tectonic evolution of the continental deep crust in southern India. Our study provides a typical example for extreme metamorphism associated with collisional tectonics during the Late Neoproterozoic–Cambrian assembly of the Gondwana supercontinent.

scholarly journals Response of the U–Pb chronometer and trace elements in zircon to ultrahigh-temperature metamorphism: The Kadavur anorthosite complex, southern India

2011 ◽  
Vol 290 (3-4) ◽  
pp. 177-188 ◽  
Author(s):  
Ellen Kooijman ◽  
Dewashish Upadhyay ◽  
Klaus Mezger ◽  
Michael M. Raith ◽  
Jasper Berndt ◽  
...  
Keyword(s):  
Trace Elements ◽  
Southern India ◽  
Ultrahigh Temperature ◽  
Anorthosite Complex

Petrological, geochronological, and geochemical potential accounting for continental subduction and exhumation: A case study of felsic granulites from South Altyn Tagh, northwestern China

2020 ◽  
Vol 132 (11-12) ◽  
pp. 2611-2630
Author(s):  
Yunshuai Li ◽  
Jianxin Zhang ◽  
Shengyao Yu ◽  
Yanguang Li ◽  
Hu Guo ◽  
...  
Keyword(s):  
High Pressure ◽  
Rare Earth ◽  
Rare Earth Element ◽  
Earth Element ◽  
Granitic Rocks ◽  
Geodynamic Evolution ◽  
Altyn Tagh ◽  
Rare Earth Element Distribution ◽  
Ultrahigh Temperature

Abstract Deciphering the formation and geodynamic evolution of high-pressure (HP) granulites in a collisional orogeny can provide crucial constraints on the geodynamic evolution of subduction-exhumation. To fully exploit the geodynamic potential of metamorphic rocks, it is necessary to constrain the metamorphic ages, although it is difficult to link zircon and monazite ages to metamorphic evolution. A good case study for understanding these geodynamic processes is felsic granulites in the Bashiwake area, South Altyn Tagh. Petrographic observations suggest that the studied felsic granulites have suffered multi-stage metamorphism, and the distinct metamorphic events were documented by compositional zoning and high Y + heavy rare earth element (HREE) concentrations in the large garnet porphyroblast. Zircon U-Pb dating yielded two major age clusters: one age cluster at ca. 900 Ma represents the age of the protolith for the felsic granulite, and another age cluster at ca. 500 Ma represents the post-UHT (ultrahigh temperature) stage based on the rare earth element distribution coefficients between zircon and garnet. Meanwhile, in situ monazites U-Pb dating yielded a weighted mean 206Pb/238U age of 482 ± 3.5 Ma, and the monazite U-Pb age was interpreted to be in agreement with the metamorphic zircon rims data, which together with zircon recorded the cooling time after the UHT stage. Whole-rock major and trace elements as well as Sr-Nd isotopes suggest that the protolith of the felsic granulite derived from partial melting of ancient crustal materials with the addition of mantle materials. Integrating these results along with previous studies, we propose that the felsic granulites metamorphosed from the Neoproterozoic granitic rocks, and the granitic rocks with associated mafic-ultramafic rocks suffered a common high-pressure–ultrahigh temperature (HP-UHT) metamorphism and subsequent granulite-facies metamorphism. A tentative model of subduction-relamination was proposed for the geodynamic evolution of the Bashiwake unit, South Altyn Tagh.

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