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摘要
The present study aims at tracking sediment provenance for a Mesoproterozoic craton-margin basin in eastern India, i.e. the Ampani Basin. Occurring on the eastern flank of the Archean Bastar Craton, the basin occupies a very strategic geographic position coinciding with the boundary between Archean craton and a Proterozoic orogenic belt with spatially varied tectonothermal history. The studied basin succession includes unmetamorphosed siliciclastic sediments deposited under three different environmental set-up viz. fluvial, shoreface and shelf. The basin sediment package defines a fining-upward succession with fluvial products at its base, shoreface deposits in the middle and shelf sandstone-siltstone-shale sediments at the top. In this study sandstone-siltstone and shale units encompassing the entire basin succession are analyzed geochemically and with U-Pb detrital zircon geochronology in order to characterize the sediment source/s. The basin was fed mainly by the Paleoarchean to late Paleoproterozoic granitoid source with minor contribution from mafic source particularly at the closing part of its depositional history. Except for relative enrichment, REE and trace element patterns of the three arenaceous units, viz. fluvial, shoreface, shelf sandstone are quite similar. U-Pb analysis of detrital zircon grains from the three units indicate that in the initial phase of basin deposition, sediments were sourced from Paleo- to Neoarchean and Palaeoproterozoic (with an age spread from ca. 3700 to 2400 Ma) provenance. From the middle shoreface part upwards, the Paleo- to Neoarchean sources fade away and a new Mesoproterozoic source (Co. 2000 -1700 Ma) was added with the continued Paleoproterozoic source/s. The youngest zircon populations of the three analyzed units yield an upper age limit of sedimentation at 2079 +/- 44 Ma (lower being close to 1446 +/- 21 Ma, as evident from the age of tuffaceous rocks on the middle shoreface part of the basin). The change in detrital zircon age spectra from the middle part of the stratigraphy might be due to some basin-adjacent tectonic activities.
- 出版日期2016-8
