scholarly journals Mafic granulite xenoliths in the Chilka Lake suite, Eastern Ghats Belt, India: evidence of deep-subduction of residual oceanic crust

2012 ◽  
Vol 4 (2) ◽  
pp. 1379-1410
Author(s):  
S. Bhattacharya ◽  
A. K. Chaudhary ◽  
A. K. Saw ◽  
P. Das ◽  
D. Chatterjee
Keyword(s):  
Oceanic Crust ◽  
Mantle Peridotite ◽  
Mafic Granulite ◽  
Eastern Ghats ◽  
Chilka Lake ◽  
Isotopic Signatures ◽  
Eastern Ghats Belt ◽  
Melting Event ◽  
Subducted Oceanic Crust ◽  
Granulite Xenoliths

Abstract. Granulite xenoliths preserve key geochemical and isotopic signatures of their mantle source regions. Mafic granulite and pyroxinite xenoliths within massif-type charnockitic rocks from the Eastern Ghats Belt have recently been reported by us. The mafic granulite xenoliths from the Chilka Lake granulite suite with abundant prograde biotite are geochemically akin to Oceanic Island Basalt (OIB). They can be distinguished from the hornblende-mafic granulite xenoliths with signatures of Arc-derived basalt occurring in the other suites of the Eastern Ghats Belt. These two groups of xenoliths in the Paleoproterozoic Eastern Ghats Province have quite distinct Nd-model ages- 1.9 Ga and 2.5 Ga respectively, which may be interpreted as their crustal residence ages. Strong positive Nb anomalies, indicating subducted oceanic crust in the source, LREE enrichment and strongly fractionated REE pattern are key geochemical signatures attesting to their origin as OIB-type magma. Also low Yb and Sc contents and high (La / Yb)N ratios can be attributed to melting in the presence of residual garnet and hence at great depths (> 80 km). The variable enrichment in radiogenic 87Sr, between 0.70052 and 0.71092 at 1.9 Ga and less radiogenic 143Nd between ε-1.54 and 7.46 are similar to those of the OIBs compared to MORBs. As OIBs commonly contain some recycled oceanic crust in their sources, we suggest that the residue of the oceanic crust from a previous melting event (~ 2.5 Ga) that produced the Arc-derived basalts (protoliths of hornblende-mafic granulite xenoliths) could have subducted to great depths and mechanically mixed with the mantle peridotite. A subsequent re-melting event of this mixed source might have occurred at ca. 1.9 Ga as testified by the crustal residence ages of the biotite-mafic granulite xenoliths of the Chilka Lake granulite suite.

Origin of orthopyroxene-bearing felsic gneiss from the perspective of ultrahigh-temperature metamorphism: an example from the Chilka Lake migmatite complex, Eastern Ghats Belt, India

2020 ◽  
Vol 84 (5) ◽  
pp. 712-737 ◽  
Author(s):  
Sankar Bose ◽  
Kaushik Das ◽  
Junji Torimoto ◽  
Daniel Dunkley
Keyword(s):  
Partial Melting ◽  
Tectonic Setting ◽  
Granulite Facies ◽  
Time Frame ◽  
Eastern Ghats ◽  
Chilka Lake ◽  
Granulite Facies Metamorphism ◽  
Eastern Ghats Belt ◽  
Facies Metamorphism ◽  
Show Evidence

AbstractOrthopyroxene-bearing felsic gneiss occurs as foliation-parallel layers and bands together with aluminous granulite, mafic granulite, and quartzofeldspathic granulite in the Chilka Lake migmatite complex of the Proterozoic Eastern Ghats Belt, India. The rock was classified previously as charnockite which underwent granulite-facies metamorphism. Field and textural features of this rock show evidence of the partial melting of a biotite-bearing greywacke protolith. Orthopyroxene with/without garnet and cordierite were produced with K-feldspar as peritectic phases of incongruent melting of presumed metaluminous sediments. Fluid-inclusion data suggest the presence of high-density CO2-rich fluids during peak metamorphism, which are similar to those found in associated aluminous granulite. Whole-rock major and trace element data show wide variability of the source materials whereas REE distributions show enriched LREE and flat HREE patterns. Zircon grains from representative samples show the presence of inherited cores having spot dates (SHRIMP) in the range c. 1790–3270 Ma. The overgrowth on zircon was formed predominantly during c. 780–730 Ma and sporadically during c. 550–520 Ma. Some neoblastic zircons with c. 780–730 Ma ages are also present. U-rich dark zones surrounding cores appear partially metamictised, but spot ages from this zone vary within c. 1000–900 Ma. The <1000 Ma ages represent metamorphism that mirrors the events in associated aluminous granulite. The sources of metaluminous sediments are speculative as the rock compositions are largely modified under granulite-facies metamorphism and partial melting. Considering the accretionary tectonic setting of the Eastern Ghats Belt during the c. 1000–900 Ma time frame, a greywacke-type protolith for the migmatite complex has been proposed.

On the origin of ‘arrested’ charnockitization in the Chilka Lake area, Eastern Ghats Belt, India: a reappraisal

2000 ◽  
Vol 137 (1) ◽  
pp. 27-37 ◽  
Author(s):  
CHRISTOPH DOBMEIER ◽  
MICHAEL M. RAITH
Keyword(s):  
Large Scale ◽  
Pure Shear ◽  
Eastern Ghats ◽  
First Episode ◽  
Fluid Migration ◽  
Lake Area ◽  
High Grade ◽  
Chilka Lake ◽  
Eastern Ghats Belt

Arrested-type charnockite formation occurs in an assemblage of high-grade gneisses at several localities of the Chilka Lake area that belongs to the Proterozoic Eastern Ghats Belt of India. The isolated ellipsoidal domains are found exclusively in leucogranite (leptynite) bands that intruded lit-par- lit interbanded granulite-grade supracrustal and intermediate igneous rocks (khondalite–enderbite). Macrostructures and microfabrics document a multiple deformation of the rock assemblage under high-grade conditions. The intrusion of the leucogranitic melts separates a first episode of deformation, D1, from a younger progressive deformation, D2–D4. A transpressive regime and inhomogeneous deformation is indicated for D2–D4 by the associated structures and fabrics. But quartz c-axis patterns show that pure shear prevailed during the closing stages of deformation. The spatial distribution and orientation of the ellipsoidal charnockite domains within the host leptynite and the orientation pattern of orthopyroxene c-axes inside the domains provide evidence for a synkinematic in situ formation of the domains during D3, through partial breakdown of the leptynite assemblage (Bt+Grt+Qtz+Fl1[rlhar ]Opx+Fsp+Ilm+Fl2/L). Local fluid migration along steep foliation planes associated with large-scale D3 folds triggered the reaction. Orthopyroxene blastesis was confined to the centre of the domains, and an envelope formed in which the residing fluid caused secondary intergranular formation of chlorite, ore and carbonate, imparting the domains' typical greenish-brown charnockite colour. The shape of the envelope, which varies from prolate in limbs to oblate in hinges of D3 folds, is responsive to the local stress field. Comparison of chemical rock compositions supports the in situ formation of charnockite in leptynite. Subtle compositional differences are controlled by the changing mineralogy. Compared to the host leptynite, the charnockite domains are enriched in K2O, Ba, Rb and Sr, but depleted in FeO*, MnO, Y and Zr. The data obtained in this study provide conclusive evidence that the ellipsoidal charnockite domains do not represent remnants of stretched enderbite layers as proposed by Bhattacharya, Sen & Acharyya, but formed in situ in the leptynite as a result of localized synkinematic fluid migration late in the deformation history.

Granitic magmas: possible and impossible sources, water contents, and crystallization sequences

1976 ◽  
Vol 13 (8) ◽  
pp. 1007-1019 ◽  
Author(s):  
Peter J. Wyllie ◽  
Wuu-Liang Huang ◽  
Charles R. Stern ◽  
Sven Maaløe
Keyword(s):  
Continental Crust ◽  
Oceanic Crust ◽  
Mantle Wedge ◽  
Regional Metamorphism ◽  
Mantle Peridotite ◽  
Ocean Crust ◽  
Crustal Rocks ◽  
Subducted Oceanic Crust ◽  
Water Contents ◽  
Phase Relationships

The calc-alkalic rocks of batholiths or their precursors may be generated in deep continental crust, in subducted oceanic crust, in the mantle wedge above, or in processes involving material from all three sources. For the series gabbro–tonalite–granite, we have phase relationships with excess H2O to 35 kbar (3500 MPa), and the H2O-undersaturated liquidus surfaces mapped with contours for H2O contents and with fields for near-liquidus minerals. Isobaric diagrams with low H2O contents provide grids potentially useful in defining limits for the H2O content of magmas, based on the sequence of crystallization. Conclusions from the experimental framework include: (1) The H2O content of large granitic bodies is less than 1.5%. (2) Primary granite magmas can not be derived from the mantle or subducted ocean crust. (3) Primary granite magmas with low H2O content are generated in the crust, and erupted as rhyolites. (4) Primary tonalite and andesite are not generated from mantle peridotite; the H2O contents required are unrealistically high. (5) Primary tonalite and andesite are not generated in the crust unless temperatures are significantly higher than those of regional metamorphism. (6) Subducted ocean crust yields magmas with intermediate SiO2 content, but not primary tonalite and andesite. (7) Batholiths are produced from crustal rocks as a normal consequence of regional metamorphism, with the formation of H2O-undersaturated granite liquid and mobilized migmatites. Some batholiths receive in addition contributions of material and heat from mantle and subducted ocean crust.

Structural evidence supporting a remnant origin of patchy charnockites in the Chilka Lake area, India

1993 ◽  
Vol 130 (3) ◽  
pp. 363-368 ◽  
Author(s):  
S. Bhattacharya ◽  
S. K. Sen ◽  
A. Acharyya
Keyword(s):  
Eastern Ghats ◽  
Lake Area ◽  
Chilka Lake ◽  
Eastern Ghats Belt ◽  
The Third ◽  
Rock Types ◽  
Third Phase ◽  
Metapelitic Granulites ◽  
Three Phases

AbstractDark patches of charnockitic rocks characterized by orthopyroxene occur within garnetiferous granite gneisses (leptynites) in a granulite-migmatite suite around the Chilka Lake, Orissa, within the Eastern Ghats belt in the Indian Precambrian. Analysis of structures of different scales observed in this terrain establishes the presence of three phases of deformation. S1 is pervasive in the metapelitic granulites (mainlykhondalite), while in the migmatite complex composed of leptynites, charnockites and quartzofeldspathic veins, S1 is present exclusively within the charnockite lenses and bands, and shows different stages of obliteration in the associated leptynites. Thus, the charnockite patches must be earlier than the surrounding migmatitic rocks. The charnockite patches and the surrounding leptynitic gneisses are chemically quite different and the two rock types are not related by any prograde or retrograde transformation. The shapes and disposition of charnockite patches in the mixed exposures are found to be largely controlled by the third phase of folding and locally associated shearing. The kinematics of this late deformation are not favourable for fluid ingress from deeper levels.

Geochronology of the 983‐Ma Chilka Lake Anorthosite, Eastern Ghats Belt, India: Implications for Pre‐Gondwana Tectonics

2008 ◽  
Vol 116 (2) ◽  
pp. 105-118 ◽  
Author(s):  
Nilanjan Chatterjee ◽  
James L. Crowley ◽  
Amalbikash Mukherjee ◽  
Subhasish Das
Keyword(s):  
Eastern Ghats ◽  
Chilka Lake ◽  
Eastern Ghats Belt
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