P–T estimates from the Nellore schist belt (India) and evidence for superimposed metamorphic events

Moeen, S.

doi:10.1002/(sici)1099-1034(199801/03)33:1<1::aid-gj761>3.0.co;2-h

Cited by 29 publications

(5 citation statements)

References 18 publications

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“…) were recognized as a distinct lithostratigraphic unit juxtaposed with older continental crust consisting of high‐grade schistose to gneissic metapelites, metapsammites, and amphibolite by Vasudevan and Rao () and Vasudevan (). These volcanics rocks underwent lower amphibolite‐facies metamorphism at temperatures of 520–570 °C and pressures of 6–7 kbar (Moeen, ). Overlying this sequence, in the southern part, is the greenschist‐facies Udayagiri domain, a group of metasediments represented by metagreywacke with beds of orthoquartzite and chloritic grits and thin, impersistent beds of oligomictic quartz–pebble conglomerate.…”

Section: Geological Settingmentioning

confidence: 99%

Zircon evaporation ages and geochemistry of metamorphosed volcanic rocks from the Vinjamuru domain, Krishna Province: evidence for 1.78 Ga convergent tectonics along the southeastern margin of the Eastern Dharwar Craton

et al. 2012

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Palaeoproterozoic intermediate to potassic felsic volcanism in volcano‐sedimentary sequences could either have occurred in continental rift or at convergent magmatic arc tectonic settings. The Vinjamuru domain of the Krishna Province in Andhra Pradesh, SE India, contains such felsic and intermediate metavolcanic rocks, whose geochemistry constrains their probable tectonic setting and which were dated by the zircon Pb evaporation method in order to constrain their time of formation. These rocks consist of interlayered quartz–garnet–biotite schist, quartz–hematite–baryte–sericite schist as well as cherty quartzite, and represent a calc‐alkaline volcanic sequence of andesitic to rhyolitic rocks that underwent amphibolite‐facies metamorphism at ~1.61 Ga. Zircons from four felsic metavolcanic rock samples yielded youngest mean 207Pb/206Pb ages between 1771 and 1791 Ma, whereas the youngest zircon age for a meta‐andesite is 1868 Ma. A ~2.43 Ga zircon xenocryst reflects incorporation of Neoarchaean basement gneisses. Their calc‐alkaline trends, higher LILE, enriched chondrite‐normalized LREE pattern and negative Nb and Ti anomalies on primitive mantle‐normalized diagrams, suggest formation in a continental magmatic arc tectonic setting. Whereas the intermediate rocks may have been derived from mantle‐source parental arc magmas by fractionation and crustal contamination, the rhyolitic rocks had crustal parental magmas. The Vinjamuru Palaeoproterozoic volcanic eruption implies an event of convergent tectonism at the southeastern margin of the Eastern Dharwar Craton at ~1.78 Ga forming one of the major crustal domains of the Krishna Province. Copyright © 2012 John Wiley & Sons, Ltd.

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Section: Geological Settingmentioning

confidence: 99%

Zircon evaporation ages and geochemistry of metamorphosed volcanic rocks from the Vinjamuru domain, Krishna Province: evidence for 1.78 Ga convergent tectonics along the southeastern margin of the Eastern Dharwar Craton

et al. 2012

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“…Whereas temperature estimates from garnet-bearing metabasalt of Vinjamuru group give a temperature range of 540 • -600 • C and pressure estimate of 5.9-6.3 kb. Moeen (1998) estimated a temperature range of 715 • -765 • C and pressure range of 8.6-9.2 kb for the M1 phase of metamorphism and a temperature range of 520 • -570 • C and pressure range from 6.1-6.8 kb for the M2 phase of metamorphism from the metapelites of Vinjamuru group. This thrusted contact also explains the sudden increase of metamorphic grade from Udayagiri group (greenschist facies) to Vinjamuru group (amphibolite facies) across the contact.…”

Section: Resultsmentioning

confidence: 99%

“…Geological map of the study area. (Moeen 1998). (GSI unpublished report) reported a shear zone between the two groups of rocks and a possible thrust contact between them.…”

Section: Geological Settingmentioning

confidence: 99%

Evidences of inclined transpression at the contact between Vinjamuru group and Udayagiri group of Nellore Schist Belt, Andhra Pradesh, India

2016

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The Nellore Schist Belt (NSB) is a curvilinear Archaean schist belt, approximately 350 km long and 8-50 km wide. The Nellore Schist Belt is considered to be Neoarchean in age and stratigraphically NSB is classified as the western Udayagiri group (dominated by metasediments) and underlying eastern Vinjamuru group (dominated by metabasalts). There is a long controversy regarding the contact relationship between Udayagiri and Vinjamuru groups. Earlier researchers regarded the contact between two groups as tectonic on the basis of metamorphism. A shear zone and a possible thrust contact between the two groups have also been reported. On the basis of present study, an NNW-SSE trending, westerly dipping inclined transpressional zone is found at the contact between Udayagiri and Vinjamuru groups in the central western part of the NSB. Kinematic analysis of both the hanging wall and foot wall of the westerly dipping thrust zone shows presence of strong S1 schistosity, shear bands and S-C fabric in both strike and dip section along with east-verging overturned fold, westerly dipping inverted beds, suggesting partitioning of non-coaxial deformation in strike-slip and dip-slip component along with a pure shear component. Strike-slip is more prominent in the northern part of the contact than the southern part. The presence of steep to moderate northerly plunging non-orthogonal stretching/mineral elongation lineation all along the contact and clockwise shift of plot of the same in stereo net from its orthogonal position and presence of other kinematic indicators in plan suggests a right lateral strike-slip component. As a whole, it is suggested that Udayagiri group is thrusted over Vinjamuru group along a westerly dipping thrust plane with a right lateral strike-slip motion and simultaneous E-W contraction.

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“…The Udaigiri Group is composed of predominantly greenschist facies metasedimentary rocks, whereas the Vinjamuru Group is dominantly an amphibolite facies volcano-sedimentary assemblage (Moeen 1998;Dobmeier and Raith 2003). There are two ophiolite complexes reported from the schist belt, namely the Kandra ophiolite complex (Vijaya Kumar et al 2010) in the southern part and the Kanigiri ophiolite melange (Dharma Rao et al 2011a) in the central part of the NKSB.…”

Section: Nellore-khammam Schist Beltmentioning

confidence: 99%

Reassembly of the Dharwar and Bastar cratons at ca. 1 Ga: Evidence from multiple tectonothermal events along the Karimnagar granulite belt and Khammam schist belt, southern India

et al. 2018

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The northern part of the Nellore-Khammam schist belt and the Karimnagar granulite belt, which are juxtaposed at high angle to each other have unique U-Pb zircon age records suggesting distinctive tectonothermal histories. Plate accretion and rifting in the eastern part of the Dharwar craton and between the Dharwar and Bastar craton indicate multiple and complex events from 2600 to 500 Ma. The Khammam schist belt, the Dharwar and the Bastar craton were joined together by the end of the Archaean. The Khammam schist belt had experienced additional tectonic events at ∼1900 and ∼1600 Ma. The Dharwar and Bastar cratons separated during development of the Pranhita-Godavari (P-G) valley basin at ∼1600 Ma, potentially linked to the breakup of the Columbia supercontinent and were reassembled during the Mesoproterozoic at about 1000 Ma. This amalgamation process in southern India could be associated with the formation of the Rodinia supercontinent. The Khammam schist belt and the Eastern Ghats mobile belt also show evidence for accretionary processes at around 500 Ma, which is interpreted as a record of Pan-African collisions during the Gondwana assembly. From then on, southern India, as is known today, formed an integral part of the Indian continent.

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P–T estimates from the Nellore schist belt (India) and evidence for superimposed metamorphic events

Cited by 29 publications

References 18 publications

Zircon evaporation ages and geochemistry of metamorphosed volcanic rocks from the Vinjamuru domain, Krishna Province: evidence for 1.78 Ga convergent tectonics along the southeastern margin of the Eastern Dharwar Craton

Zircon evaporation ages and geochemistry of metamorphosed volcanic rocks from the Vinjamuru domain, Krishna Province: evidence for 1.78 Ga convergent tectonics along the southeastern margin of the Eastern Dharwar Craton

Evidences of inclined transpression at the contact between Vinjamuru group and Udayagiri group of Nellore Schist Belt, Andhra Pradesh, India

Reassembly of the Dharwar and Bastar cratons at ca. 1 Ga: Evidence from multiple tectonothermal events along the Karimnagar granulite belt and Khammam schist belt, southern India

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