Late Archean mantle metasomatism below eastern Indian cration

Evidence from trace elements, REE geochemistry and Sr Nd-O isotope systematics of ultramafic dykes

A. Roy, A. Sarkar, S. Jeyakumar, S. K. Aggrawal, Mitsuru Ebihara, H. Satoh

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

Trace, rare earth elements (REE), Rb-Sr, Sm-Nd and O isotope studies have been carried out on ultramafic (harzburgite and lherzolite) dykes belonging to the newer dolerite dyke swarms of eastern Indian craton. The dyke swarms were earlier considered to be the youngest mafic magmatic activity in this region having ages not older than middle to late Proterozoic. The study indicates that the ultramafic members of these swarms are in fact of late Archaean age (Rb-Sr isochron age 2613 ± 177 Ma, Sri ∼ 0.702 ± 0.004) which attests that out of all the cratonic blocks of India, eastern Indian craton experienced earliest stabilization event. Primitive mantle normalized trace element plots of these dykes display enrichment in large ion lithophile elements (LILE), pronounced Ba, Nb and Sr depletions but very high concentrations of Cr and Ni. Chondrite normalised REE plots exhibit light REE (LREE) enrichment with nearly flat heavy REE (HREE; (σmHREE)N ∼ 2-3 times chondrite, (Gd/Yb)N ∼ 1). The εNd(t) values vary from +1.23 to -3.27 whereas δ18O values vary from +3.16‰ to +5.29‰ (average +3.97‰ ± 0.75‰) which is lighter than the average mantle value. Isotopic, trace and REE data together indicate that during 2.6 Ga the nearly primitive mantle below the eastern Indian Craton was metasomatised by the fluid (± silicate melt) coming out from the subducting early crust resulting in LILE and LREE enriched, Nb depleted, variable ε Nd, low Sri(0.702) and low δ 18O bearing EMI type mantle. Magmatic blobs of this metasomatised mantle were subsequently emplaced in deeper levels of the granitic crust which possibly originated due to the same thermal pulse.

Original languageEnglish
Pages (from-to)649-665
Number of pages17
JournalProceedings of the Indian Academy of Sciences, Earth and Planetary Sciences
Volume113
Issue number4
Publication statusPublished - 2004 Dec 1
Externally publishedYes

Fingerprint

metasomatism
Archean
rare earth element
geochemistry
trace element
isotope
mantle
craton
dike swarm
chondrite
crust
harzburgite
ion
lherzolite
silicate melt
diabase
Proterozoic
stabilization
fluid

Keywords

  • Eastern Indian craton
  • Rb-Sr & Sm-Nd
  • Source enrichment
  • Ultramafic dykes

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)

Cite this

@article{a34fbecc44e2492f8f22ab78b8bcf43f,
title = "Late Archean mantle metasomatism below eastern Indian cration: Evidence from trace elements, REE geochemistry and Sr Nd-O isotope systematics of ultramafic dykes",
abstract = "Trace, rare earth elements (REE), Rb-Sr, Sm-Nd and O isotope studies have been carried out on ultramafic (harzburgite and lherzolite) dykes belonging to the newer dolerite dyke swarms of eastern Indian craton. The dyke swarms were earlier considered to be the youngest mafic magmatic activity in this region having ages not older than middle to late Proterozoic. The study indicates that the ultramafic members of these swarms are in fact of late Archaean age (Rb-Sr isochron age 2613 ± 177 Ma, Sri ∼ 0.702 ± 0.004) which attests that out of all the cratonic blocks of India, eastern Indian craton experienced earliest stabilization event. Primitive mantle normalized trace element plots of these dykes display enrichment in large ion lithophile elements (LILE), pronounced Ba, Nb and Sr depletions but very high concentrations of Cr and Ni. Chondrite normalised REE plots exhibit light REE (LREE) enrichment with nearly flat heavy REE (HREE; (σmHREE)N ∼ 2-3 times chondrite, (Gd/Yb)N ∼ 1). The εNd(t) values vary from +1.23 to -3.27 whereas δ18O values vary from +3.16‰ to +5.29‰ (average +3.97‰ ± 0.75‰) which is lighter than the average mantle value. Isotopic, trace and REE data together indicate that during 2.6 Ga the nearly primitive mantle below the eastern Indian Craton was metasomatised by the fluid (± silicate melt) coming out from the subducting early crust resulting in LILE and LREE enriched, Nb depleted, variable ε Nd, low Sri(0.702) and low δ 18O bearing EMI type mantle. Magmatic blobs of this metasomatised mantle were subsequently emplaced in deeper levels of the granitic crust which possibly originated due to the same thermal pulse.",
keywords = "Eastern Indian craton, Rb-Sr & Sm-Nd, Source enrichment, Ultramafic dykes",
author = "A. Roy and A. Sarkar and S. Jeyakumar and Aggrawal, {S. K.} and Mitsuru Ebihara and H. Satoh",
year = "2004",
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T1 - Late Archean mantle metasomatism below eastern Indian cration

T2 - Evidence from trace elements, REE geochemistry and Sr Nd-O isotope systematics of ultramafic dykes

AU - Roy, A.

AU - Sarkar, A.

AU - Jeyakumar, S.

AU - Aggrawal, S. K.

AU - Ebihara, Mitsuru

AU - Satoh, H.

PY - 2004/12/1

Y1 - 2004/12/1

N2 - Trace, rare earth elements (REE), Rb-Sr, Sm-Nd and O isotope studies have been carried out on ultramafic (harzburgite and lherzolite) dykes belonging to the newer dolerite dyke swarms of eastern Indian craton. The dyke swarms were earlier considered to be the youngest mafic magmatic activity in this region having ages not older than middle to late Proterozoic. The study indicates that the ultramafic members of these swarms are in fact of late Archaean age (Rb-Sr isochron age 2613 ± 177 Ma, Sri ∼ 0.702 ± 0.004) which attests that out of all the cratonic blocks of India, eastern Indian craton experienced earliest stabilization event. Primitive mantle normalized trace element plots of these dykes display enrichment in large ion lithophile elements (LILE), pronounced Ba, Nb and Sr depletions but very high concentrations of Cr and Ni. Chondrite normalised REE plots exhibit light REE (LREE) enrichment with nearly flat heavy REE (HREE; (σmHREE)N ∼ 2-3 times chondrite, (Gd/Yb)N ∼ 1). The εNd(t) values vary from +1.23 to -3.27 whereas δ18O values vary from +3.16‰ to +5.29‰ (average +3.97‰ ± 0.75‰) which is lighter than the average mantle value. Isotopic, trace and REE data together indicate that during 2.6 Ga the nearly primitive mantle below the eastern Indian Craton was metasomatised by the fluid (± silicate melt) coming out from the subducting early crust resulting in LILE and LREE enriched, Nb depleted, variable ε Nd, low Sri(0.702) and low δ 18O bearing EMI type mantle. Magmatic blobs of this metasomatised mantle were subsequently emplaced in deeper levels of the granitic crust which possibly originated due to the same thermal pulse.

AB - Trace, rare earth elements (REE), Rb-Sr, Sm-Nd and O isotope studies have been carried out on ultramafic (harzburgite and lherzolite) dykes belonging to the newer dolerite dyke swarms of eastern Indian craton. The dyke swarms were earlier considered to be the youngest mafic magmatic activity in this region having ages not older than middle to late Proterozoic. The study indicates that the ultramafic members of these swarms are in fact of late Archaean age (Rb-Sr isochron age 2613 ± 177 Ma, Sri ∼ 0.702 ± 0.004) which attests that out of all the cratonic blocks of India, eastern Indian craton experienced earliest stabilization event. Primitive mantle normalized trace element plots of these dykes display enrichment in large ion lithophile elements (LILE), pronounced Ba, Nb and Sr depletions but very high concentrations of Cr and Ni. Chondrite normalised REE plots exhibit light REE (LREE) enrichment with nearly flat heavy REE (HREE; (σmHREE)N ∼ 2-3 times chondrite, (Gd/Yb)N ∼ 1). The εNd(t) values vary from +1.23 to -3.27 whereas δ18O values vary from +3.16‰ to +5.29‰ (average +3.97‰ ± 0.75‰) which is lighter than the average mantle value. Isotopic, trace and REE data together indicate that during 2.6 Ga the nearly primitive mantle below the eastern Indian Craton was metasomatised by the fluid (± silicate melt) coming out from the subducting early crust resulting in LILE and LREE enriched, Nb depleted, variable ε Nd, low Sri(0.702) and low δ 18O bearing EMI type mantle. Magmatic blobs of this metasomatised mantle were subsequently emplaced in deeper levels of the granitic crust which possibly originated due to the same thermal pulse.

KW - Eastern Indian craton

KW - Rb-Sr & Sm-Nd

KW - Source enrichment

KW - Ultramafic dykes

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