ABSTRACT

The Chhattisgarh Basin is one of the most important Proterozoic basins of peninsular India. Owing to its deposition in the Mesoproterozoic, the largely undeformed and unmetamorphosed sedimentary sequence of this basin is believed to hold vital clues to our understanding of the evolution of the Indian craton subsequent to the disintegration of the supercontinent Columbia. Despite its importance, only limited studies have been carried out to decipher the depositional history of the basin and to correlate various litho-units in it. Here, we present results of quantitative provenance analysis of the sediments in the basin using trace element and Nd isotopic ratios and discuss their implications for the evolution of the basin in the context of regional tectonics. The sediment provenance analysis reveals that the spatially extensive ~2.5 Ga old granitoids of the Bastar craton were the major contributors (45% to 65%) of the total sediment budget into the basin during its initial stage of evolution. As sedimentation progressed the contribution from the Bastar granitoids was restricted to less than 30% of the total budget with the remaining supplied by younger 1.6–1.7 Ga magmatic rocks. The overall provenance of sediments appears to have remained constant throughout the evolutionary history of the basin; however, the relative contributions of various sources did change with time. The latter is highly conspicuous across the stratigraphic boundary between the Singhora and Chandarpur groups, in the lower part of the Chhattisgarh Supergroup. The geochemical data suggest that the basin developed as a result of either rift or sag into which the sea incursion occurred through the adjacent grabens during the Mesoproterozoic marine transgression.

摘要

恰蒂斯加尔邦盆地是印度半岛最重要的元古代盆地之一。由于其沉积在中元古代，该盆地的大部分未变形和未变质的沉积层序为我们理解超大陆哥伦比亚解体后印度克拉通的演化提供了重要线索。尽管具有重要意义，但仅进行了有限的研究来解密该盆地的沉积历史并关联该盆地中的各种岩石单元。在这里，我们介绍了使用痕量元素和Nd同位素比率对盆地沉积物进行定量来源分析的结果，并讨论了它们在区域构造学背景下对盆地演化的影响。泥沙物源分析表明，其空间范围约为2。在演化初期，Bastar克拉通的5 Ga旧花岗岩是盆地沉积物总预算的主要贡献者（45％至65％）。随着沉积的进行，来自Bastar花岗岩的贡献被限制在总预算的30％以下，其余的则由年轻的1.6–1.7 Ga岩浆岩提供。在整个盆地的演化历史中，沉积物的总来源似乎保持不变。但是，各种来源的相对贡献确实随着时间而变化。后者在恰蒂斯加尔邦超群下部的Singhora组和Chandarpur组之间的地层边界上非常明显。