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New SHRIMP Age and Microstructures from a Deformed A-Type Granite, Kanigiri, Southern India: Constraining the Hiatus between Orogenic Closure and Postorogenic Rifting

Sain, Arnab; Saha, Dilip; Joy, Sojen; Jelsma, Hielke; Armstrong, Richard

Description

A new U-Pb zircon SHRIMP age of 1284 Ma from the Kanigiri granite, India, is reported to help constrain the middle to late Mesoproterozoic tectonic evolution of the Nellore schist belt (NSB). The Kanigiri granite has whole-rock chemical characteristics of A-type granites and is marked by light rare earth element enrichment, a strong negative Eu anomaly, and negative Ba, Sr, P, Ti, and Yb anomalies, indicating feldspar, apatite, and ilmenite/magnetite fractionation. Samples show Y/Nb versus...[Show more]

dc.contributor.authorSain, Arnab
dc.contributor.authorSaha, Dilip
dc.contributor.authorJoy, Sojen
dc.contributor.authorJelsma, Hielke
dc.contributor.authorArmstrong, Richard
dc.date.accessioned2017-03-28T00:49:39Z
dc.identifier.issn0022-1376
dc.identifier.urihttp://hdl.handle.net/1885/113999
dc.description.abstractA new U-Pb zircon SHRIMP age of 1284 Ma from the Kanigiri granite, India, is reported to help constrain the middle to late Mesoproterozoic tectonic evolution of the Nellore schist belt (NSB). The Kanigiri granite has whole-rock chemical characteristics of A-type granites and is marked by light rare earth element enrichment, a strong negative Eu anomaly, and negative Ba, Sr, P, Ti, and Yb anomalies, indicating feldspar, apatite, and ilmenite/magnetite fractionation. Samples show Y/Nb versus Yb/Ta ratios in the range for granites associated with ocean island basalts. This two-mica granite is peraluminous and alkali-calcic to calc-alkalic, and it has high annite to phlogopite proportions (92%–98%). Strong alignment of flattened mafic microgranular enclaves in the granite, together with relatively high- to moderate-temperature crystal plastic deformation fabric in shear zones within the granite, suggest overprinting of subsolidus deformation over a relict magmatic fabric, a feature not very common in true anorogenic granites but reported in late- to postorogenic granites elsewhere. An intrusive relationship with the 1334 MaKanigiri ophiolitic mélange, within the NSB, indicates that there is a ≤50 m.yr. gap between the Mesoproterozoic subduction-accretion, represented by the ophiolite mélange and late- to postorogenic granite emplacement. Although the Kanigiri granite occurs in close proximity to mafic and felsic alkaline plutons belonging to the 1250–1400 Ma Prakasam alkaline province (PAkP) in the northern NSB and there is overlap in age, the A type granitic magma source is apparently unrelated to PAkP alkaline magmatism. Our work further substantiates the observation that A-type granites originate in varied tectonic settings, not necessarily only in a rift-related (intraplate) setting.
dc.description.sponsorshipThis work is funded by the Indian Statistical Institute
dc.format19 pages
dc.format.mimetypeapplication/pdf
dc.publisherUniversity of Chicago Press
dc.rights© 2017 by The University of Chicago.
dc.sourceThe Journal of Geology
dc.subjectU-Pb
dc.subjectzircon
dc.subjectSHRIMP
dc.subject1284 Ma
dc.subjectKanigiri
dc.subjectgranite
dc.subjectIndia
dc.subjectMesoproterozoic
dc.subjecttectonic
dc.subjectevolution
dc.subjectNellore schist belt
dc.titleNew SHRIMP Age and Microstructures from a Deformed A-Type Granite, Kanigiri, Southern India: Constraining the Hiatus between Orogenic Closure and Postorogenic Rifting
dc.typeJournal article
local.identifier.citationvolume125
dcterms.dateAccepted2016-10-26
dc.date.issued2017-03
local.publisher.urlhttp://www.press.uchicago.edu/
local.type.statusPublished Version
local.contributor.affiliationArmstrong, Richard, RSES General, CPMS Research School of Earth Sciences, The Australian National University
local.identifier.essn1537-5269
local.bibliographicCitation.issue2
local.bibliographicCitation.startpage241
local.bibliographicCitation.lastpage259
local.identifier.doi10.1086/690196
dcterms.accessRightsOpen Access
dc.provenancehttp://www.sherpa.ac.uk/romeo/issn/0022-1376/ Publisher's version/PDF may be used in open access repositories only, after 12 months embargo (Sherpa/Romeo as of 28/3/2017).
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