Physical volcanology and geochemistry of Palaeoarchaean komatiite lava flows from the western Dharwar craton, southern India: implications for Archaean mantle evolution and crustal growth

dc.contributor.author Jayananda, M.
dc.contributor.author Duraiswami, R. A.
dc.contributor.author Aadhiseshan, K. R.
dc.contributor.author Gireesh, R. V.
dc.contributor.author Prabhakar, B. C.
dc.contributor.author Kafo, Kowe U.
dc.contributor.author Tushipokla,
dc.contributor.author Namratha, R.
dc.date.accessioned 2022-03-26T23:49:38Z
dc.date.available 2022-03-26T23:49:38Z
dc.date.issued 2016-10-02
dc.description.abstract Palaeoarchaean (3.38–3.35 Ga) komatiites from the Jayachamaraja Pura (J.C. Pura) and Banasandra greenstone belts of the western Dharwar craton, southern India were erupted as submarine lava flows. These high-temperature (1450–1550°C), low-viscosity lavas produced thick, massive, polygonal jointed sheet flows with sporadic flow top breccias. Thick olivine cumulate zones within differentiated komatiites suggest channel/conduit facies. Compound, undifferentiated flow fields developed marginal-lobate thin flows with several spinifex-textured lobes. Individual lobes experienced two distinct vesiculation episodes and grew by inflation. Occasionally komatiite flows form pillows and quench fragmented hyaloclastites. J.C. Pura komatiite lavas represent massive coherent facies with minor channel facies, whilst the Bansandra komatiites correspond to compound flow fields interspersed with pillow facies. The komatiites are metamorphosed to greenschist facies and consist of serpentine-talc ± carbonate, actinolite–tremolite with remnants of primary olivine, chromite, and pyroxene. The majority of the studied samples are komatiites (22.46–42.41 wt.% MgO) whilst a few are komatiitic basalts (12.94–16.18 wt.% MgO) extending into basaltic (7.71 – 10.80 wt.% MgO) composition. The studied komatiites are Al-depleted Barberton type whilst komatiite basalts belong to the Al-undepleted Munro type. Trace element data suggest variable fractionation of garnet, olivine, pyroxene, and chromite. Incompatible element ratios (Nb/Th, Nb/U, Zr/Y Nb/Y) show that the komatiites were derived from heterogeneous sources ranging from depleted to primitive mantle. CaO/Al2O3 and (Gd/Yb)N ratios show that the Al-depleted komatiite magmas were generated at great depth (350–400 km) by 40–50% partial melting of deep mantle with or without garnet (majorite?) in residue whilst komatiite basalts and basalts were generated at shallow depth in an ascending plume. The widespread Palaeoarchaean deep depleted mantle-derived komatiite volcanism and sub-contemporaneous TTG accretion implies a major earlier episode of mantle differentiation and crustal growth during ca. 3.6–3.8 Ga.
dc.identifier.citation International Geology Review. v.58(13)
dc.identifier.issn 00206814
dc.identifier.uri 10.1080/00206814.2016.1172350
dc.identifier.uri https://www.tandfonline.com/doi/full/10.1080/00206814.2016.1172350
dc.identifier.uri https://dspace.uohyd.ac.in/handle/1/2523
dc.subject emplacement dynamics
dc.subject geochemistry
dc.subject Komatiite
dc.subject lava flows
dc.subject mantle plume and Archaean
dc.subject physical volcanology
dc.subject spinifex
dc.title Physical volcanology and geochemistry of Palaeoarchaean komatiite lava flows from the western Dharwar craton, southern India: implications for Archaean mantle evolution and crustal growth
dc.type Journal. Article
dspace.entity.type
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