scholarly journals Petrogenesis of granitoid rocks at the northern margin of the Eastern Ghats Mobile Belt and evidence of syn-collisional magmatism

2004 ◽  
Vol 113 (4) ◽  
pp. 543-563
Author(s):  
S. Bhattacharya ◽  
Rajib Kar ◽  
S. Moitra
Keyword(s):  
Eastern Ghats ◽  
Mobile Belt ◽  
Northern Margin ◽  
Granitoid Rocks ◽  
Eastern Ghats Mobile Belt

Geochemistry and original nature of Precambrian khondalites in the Eastern Ghats, Orissa: a discussion

1991 ◽  
Vol 82 (1) ◽  
pp. 87-88 ◽  
Author(s):  
J. K. Nanda ◽  
U. C. Pati
Keyword(s):  
Major Part ◽  
Eastern Ghats ◽  
Geochemical Data ◽  
Mobile Belt ◽  
Indian Peninsula ◽  
Eastern Ghats Mobile Belt

While congratulating the authors for the wealth of geochemical data on a very important Precambrian lithological assemblage of India, known commonly as khondalites, which constitute a major part of the Eastern Ghats mobile belt bordering the eastern fringes of the Indian Peninsula, we have a few comments to offer on the hypothesis propounded by the authors (Dash et al. 1987).

Mantle deformation patterns and signatures of rift, beneath Eastern Ghats Mobile Belt

2019 ◽  
Vol 289 ◽  
pp. 20-33
Author(s):  
Niptika Jana ◽  
Arun Singh ◽  
Ashwani Kant Tiwari ◽  
Chandrani Singh ◽  
Rahul Biswas
Keyword(s):  
Eastern Ghats ◽  
Mobile Belt ◽  
Eastern Ghats Mobile Belt ◽  
Deformation Patterns

Orthogonal Tectonic and Magmatic Fabrics in a Layered Granite-Gneiss at Remal Dam Site, India: Implications for Fabric Generation and Superposition

2020 ◽  
Author(s):  
Ritabrata Dobe ◽  
Saibal Gupta
Keyword(s):  
Subsequent Development ◽  
Granite Gneiss ◽  
Greenschist Facies ◽  
Eastern Ghats ◽  
Mobile Belt ◽  
Mafic Intrusions ◽  
Shear Sense ◽  
Deformation Event ◽  
Eastern Ghats Mobile Belt ◽  
Shear Sense Indicators

<p>The Remal granite-gneiss is situated close to the tectonic boundary between the Singhbhum Craton and the Rengali Province in the state of Odisha, eastern India. This granite-gneiss contains two prominent fabric elements - a sub-horizontal to gently dipping felsic fabric S<sub>ign</sub>, believed to be of igneous origin that predates a sub-vertical gneissosity S<sub>1</sub> which is of tectonic origin. S<sub>ign</sub> layers have a non-uniform, arcuate geometry and grain-size within the layers show systematic variations. S<sub>1</sub> is defined by metre-scale segregations of biotite-poor and biotite-rich domains whose orientations are constant. S<sub>ign</sub> layers are arranged rhythmically in cross-section and either curve into parallelism with or truncate against layers above and below; the entire assembly resembles cross beds developed in sediments. Some of the layers develop trough cross-bedding similar to those seen in mafic intrusions such as the Skaergaard Complex, indicative of slumping of a crystallizing mush along an inclined depositional plane at the time of crystallization. The S<sub>ign</sub> layers are composed of quartz, K-feldspar and plagioclase with abundant graphic intergrowths and myrmekite, and lack any evidence of compaction. Plagioclase grains are often zoned, and dihedral angles between mineral grains is significantly different from the equilibrium value of 120°, testifying to the preservation of the igneous nature of this fabric without significant solid state modification. In contrast, S<sub>1</sub> is sub-parallel to localized mylonite zones within the granite-gneiss composed of chlorite and epidote, indicative of deformation under greenschist facies conditions. The mylonitized zones contain prominent dextral shear sense indicators and is believed to have originated due to the amalgamation of the Rengali Province with the Eastern Ghats Mobile Belt along the east-west trending, sub-vertical Brahmani Shear Zone further to the south. The S<sub>1</sub> gneissosity appears to have developed as a result of this deformation event. EBSD analyses of quartz grains within the granite-gneiss reveal distinct variations in the distribution of <c> axes in different domains. Close to the mylonite zones, deformation of quartz has been dominantly accommodated by basal <a> slip with a dextral shearing overprint while away from these zones and S<sub>1, </sub>the <c> axes are distributed in clusters without any systematic pattern. The persistence of an earlier igneous layering, despite the subsequent development of a gneissosity concomitant with localised mylonitisation, indicates that the later deformation event has not obliterated the earlier formed igneous fabric. The study also demonstrates that development of a gneissosity does not necessarily require deformation operating at moderate to high temperature, and can stabilize even under greenschist facies conditions.</p>

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