Komatiite from Eastern Iron Ore Group, Singhbhum Craton, India: Implication for Mantle Plume - Arc Tectonic Setting

In this paper, the field, petrographic and geochemical data of Patka komatiite belonging to the Badampahar Group of rocks in the Badampahar - Gorumahisani Greenstone Belt of the eastern Iron Ore Group of the Singhbhum Craton are presented for the first time which is mapped to the south of Patka village, Jharkhand. It is showing a similar history of sedimentation and volcanism in other contemporary Archaean greenstone belts of the world. Komatiites recently reported in some of them may hold key to the understanding of the early history of the evolution of the craton. The komatiite body (~600 m X ~250 m) trending N10ºW - S10ºE shows the concordant relationship with phyllites, amphibolite, and metachert which is underlain by phyllites, talc-tremolite-serpentine schist, and amphibolite and is overlain by metachert and quartzite. Spinifex, platy, and cumulate zones have been recorded in these komatiites. Petrographic study reveals that these komatiites contain tremolite, serpentine, magnetite, chlorite, and talc besides glass and rare skeletal olivine, clinopyroxene, and orthopyroxene. Alteration of the primary mineralogy (olivine and pyroxene) and relict glass to tremolite, serpentine, magnetite, chlorite, and talc is also observed. The igneous mineralogy has been altered during post-magmatic hydrothermal alteration processes corresponding metamorphism under greenschist to lower amphibolite facies. These komatiites are quit enriched in SiO2: 37.56 - 42.79 wt. %, MgO: 24.78 - 33.36 wt. %, TiO2: 0.18 - 0.49 wt. %, Al2O3/TiO2: 8 - 30 and CaO/Al2O3: 0.49 - 1.79 and their Al2O3 contents (3.25 - 8.24 wt. %), (Gd/Yb) N (greater than 1.0), CaO/Al2O3 (greater than 1.0), Al2O3/TiO2 (mostly less than 18) and lower LREE and flat HREE fractionation patterns are comparable with those of the Al-depleted komatiites. In the Nb/Th vs. Zr/Nb diagram, these komatiites cluster away from the other volcanics, and in the Nb/Y vs. Zr/Y diagram they cluster between deep depleted mantle (DEP) and primitive mantle (PM). Biva