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, M. Ebihara, H. Satoh

*この研究の対応する著者

研究成果: Article査読

33 被引用数 (Scopus)

抄録

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.

本文言語English
ページ(範囲)649-665
ページ数17
ジャーナルProceedings of the Indian Academy of Sciences, Earth and Planetary Sciences
113
4
DOI
出版ステータスPublished - 2004 12月
外部発表はい

ASJC Scopus subject areas

  • 地球惑星科学(その他)

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