Shallow marine to pelagic sediments from a dismembered ophiolite,Kandra, southern India – Glimpses of ancient subduction zone related sedimentation |
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| Institution: | 1. Geological Studies Unit, Indian Statistical Institute, 203 B.T. Road, Kolkata 700108, India;2. Department of Applied Geology, Faculty of Engineering and Science, Curtin University of Technology Sarawak, CDT 250, Miri 98009, Sarawak, Malaysia;3. Department of Geology, University of Calcutta, Kolkata 700019, India;1. Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 129, Hobart, Tasmania 7001, Australia;2. ARC Centre of Excellence for Core to Crust Fluid Systems (CCFS)/GEMOC, Department of Earth and Planetary Sciences, Macquarie University, NSW 2109, Australia;1. Martin-Luther-Universität Halle-Wittenberg, Institut für Geowissenschaften und Geographie, von Seckendorff-Platz 3, 06120 Halle, Germany;2. Johann-Wolfgang-Goethe-Universität Frankfurt, Institut für Geowissenschaften, Altenhöferallee 1, 60438 Frankfurt am Main, Germany;3. Stellenbosch University, Department of Earth Sciences, Private Bag X1, Matieland 7602, South Africa;1. Kalkulo AS, Simula Research Laboratory, P.O. Box 134, 1325 Lysaker, Norway;2. Department of Earth and Environmental Sciences, Geophysics, Munich University, Theresienstr. 41, 80333 Munich, Germany;1. Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1, O-okayama, Meguro-ku, Tokyo 152-8550, Japan;2. Graduate School of Environmental Studies, Tohoku University, Sendai, Miyagi 980-8579, Japan;3. Department of Earth and Planetary Science, Tokyo Institute of Technology, 2-12-1, O-okayama, Meguro, Tokyo 152-8550, Japan;4. Department of Solid Earth Geochemistry, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka 237-0061, Japan;5. State Key Laboratory for Continental Tectonics and Dynamics, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;6. Department of Earth Science and Astronomy, The University of Tokyo, 3-8-1, Komaba, Meguro-ku, Tokyo 153-8902, Japan |
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| Abstract: | A suprasubduction zone oceanic back-arc setting for the Paleoproterozoic Kandra ophiolite complex (KOC) in southern India has been suggested from geochemical signatures. The telescoped segments of thin deformed sedimentary successions of shallow marine to pelagic affinity, overlying a basaltic substrate and preserved within thrust slices of the KOC, are tectonically juxtaposed against the Eastern Dharwar craton margin. In the northern thrust slice (Kandra village succession), about 150 m of sedimentary strata show intercalation of quartz arenite and basaltic flow in the lower part, grading upwards to heterolithic sandstone-mudstone deposited above the storm wave base. In the southeastern part of the KOC (Gurramkonda succession), deep-water greywacke turbidite, pelagic chert, mafic tuff and volcaniclastics, and quartz arenite deposited below the storm wave base, are preserved as thrust bound packets. Intermittent basaltic outpourings punctuated deeper water deposition as evidenced by alternate metachert and metabasalt layers, and emplacement of basaltic rocks along small thrusts which transpose stratification. Craton margin sediments consists of immature, coarse terrigenous clastics intercalated with thin mafic tuff, suggesting influence of mass flow processes giving way to fluvial sedimentation in the lower part of the Udaigiri Group. Further up, fine grained plane laminated siltstone-shale with rippled sandstone lenses grade upward to compositionally mature quartz arenite deposited close to the craton margin, with signatures of tidal- and wave reworking. The association of stratigraphic successions of two contrasting depositional environments in the KOC adds to the spectrum of variation of sedimentary collage of the ocean plate stratigraphy. The Kandra village and Gurramkonda successions of the KOC, possibly represent ancient arc-trench milieu, and shallower part of oceanic marginal basin respectively. Paleoproterozoic subduction-accretion process led to collapse of these basins and tectonic emplacement of the KOC against the Eastern Dharwar craton margin which hosted near shore sedimentary succession of the Udaigiri Group, occurring west of the KOC. |
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