We found a match
Your institution may have rights to this item. Sign in to continue.
- Title
Arc-nascent back-arc signature in metabasalts from the Neoarchaean Jonnagiri greenstone terrane, Eastern Dharwar Craton, India.
- Authors
Manikyamba, C.; Ganguly, Sohini; Santosh, M.; Singh, M. Rajanikanta; Saha, Abhishek
- Abstract
The Neoarchaean Jonnagiri greenstone terrane (JGT) is located at the centre of the arcuate Hutti-Jonnagiri-Kadiri-Kolar composite greenstone belt in the eastern Dharwar Craton. High MgO (MgO = ~14 wt.%; Nb = 0.2 ppm), low Nb (LNB) (MgO = 7.8-12 wt.%; Nb = 0.1-5.1 ppm) and high Nb basalts (HNB) (MgO = 5.6-10.1 wt.%; Nb = 9.0-10.6 ppm) metamorphosed to lower amphibolite facies are identified based on their geochemical compositions. These metabasalts exhibit depleted HFSE (Nb-Ta, Zr-Hf), pronounced LREE and LILE enrichments suggesting contribution from subduction-related components during their genesis. Th and U enrichment over Nb-Ta indicates influx of fluids dehydrated from subducted oceanic lithosphere. The high MgO basalts with higher Mg# (51) than that of the associated LNB and HNB (Mg# = 34-47) represent early fractionated melts of subduction-modified mantle peridotite. The LNB were produced by partial melting of mantle wedge metasomatized by slab-dehydrated fluids, whereas the HNB represents melts of subducted oceanic crust and hybridized mantle wedge. Lower Dy/Yb and variable La/Yb ratios suggest their generation at shallower depth within spinel peridotite stability field. The low Ce-Yb trend of these metabasalts reflects intraoceanic type subduction which straddles the fields of arc and back-arc basin basalts, resembling the Mariana-type arc basalts. The Jonnagiri metabasalts were derived in a paired arc-back-arc setting marked by nascent back-arc rift system that developed in the proximity of an intraoceanic arc. Copyright © 2014 John Wiley & Sons, Ltd.
- Subjects
GREENSTONE belts; METAMORPHIC rocks; BASALT; NEOARCHAEAN; ARCHAEAN
- Publication
Geological Journal, 2015, Vol 50, Issue 5, p651
- ISSN
0072-1050
- Publication type
Article
- DOI
10.1002/gj.2581