Geochemistry of mid-ocean ridge mafic intrusives from the Manipur Ophiolitic Complex, Indo-Myanmar Orogenic Belt, NE India

Mafic intrusives emplaced within the mélange zone of the Manipur Ophiolitic Complex are subalkalinetholeiitic affinity with Fe-enrichment. Based on the field occurrences, textures-mineralogy and whole-rock compositions, these mafic intrusives can be identified as type-I (gabbro intrusives) and type-...

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Bibliographic Details
Published in:Journal of the Geological Society of India 2012-08, Vol.80 (2), p.231-240
Main Authors: Krishnakanta Singh, A., Ibotombi Singh, N., Debala Devi, L., Bikramaditya Singh, R. K.
Format: Article
Language:English
Subjects:
Basalt
Depletion
Earth and Environmental Science
Earth Sciences
Enrichment
Fragments
Geochemistry
Geology
Hydrogeology
Local area networks
Mantle
Marine
Mid-ocean ridges
Mineralogy
Oceanic crust
Petrology
Plate tectonics
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Summary:Mafic intrusives emplaced within the mélange zone of the Manipur Ophiolitic Complex are subalkalinetholeiitic affinity with Fe-enrichment. Based on the field occurrences, textures-mineralogy and whole-rock compositions, these mafic intrusives can be identified as type-I (gabbro intrusives) and type-II (basalt-dolerite dykes). The type-I resembling enriched-type mid-ocean ridge basalt (E-MORB) shows moderate LREE enrichment (La N /Sm N = 2.5–2.6), slightly enriched MORB normalized HFSE patterns possibly represent melts derived from enriched MORB sub-oceanic mantle sources by small degree of partial melting. The other type-II has normal-type mid-ocean ridge basalt (N-MORB) geochemical features, as it exhibits nearly flat to depleted LREE (La N /Sm N = 1.0–0.6), flat MORB normalized HFSE patterns with slight LREE/HREE depletion (Ce N /Yb N = 1.37–0.46). It might have been derived from depleted MORB type sub-oceanic mantle source. The MORB signature displayed by these mafic intrusives indicates that they are dismembered fragments of oceanic crust generated at mid-ocean spreading ridge system and support the hypothesis that the Manipur ophiolites was initially formed in the divergent plate margin.
ISSN:0016-7622
0974-6889
DOI:10.1007/s12594-012-0133-9