Abstract

Surma Basin in Northeast India is characterized by a thick Cenozoic sedimentary succession that initiated due to the collision between Indian and Burmese plates. Variability in the litho-association of a thick sedimentary column in this robust terrain represents the distribution and deposition of enormous sediments that supplied throughout the entire basin evolution, especially during the Middle Miocene. This makes Middle Bhuban sandstone as the best aspirant for this study. Miocene Bhuban sandstones collected from parts of Aizawl and Champhai Districts of Mizoram, NE India have been studied for the whole rock geochemistry to understand the nature of source rocks, probable source areas and paleoclimatic conditions. The geochemical behavior of studied sandstones represent a felsic nature (TiO₂/Zr: 15.03–37.09; La/Sc: 1.80–6.52, La/Co: 0.39–5.48, Th/Sc: 0.56–2.05; Cr/Th: 4.19–28.00; Al₂O₃/TiO₂: 13.13–28.09), fractionated granitoid provenance [(La/Lu)_N: 15.06–22.25; (La/Yb)_N: 14.09–19.96; (La/Sm)_N: 3.17–3.99; (Gd/Yb)_N: 2.00–2.84] and moderately weathered sediments (CIA: 65; CIW: 73; PIA: 69; WIP: 41; ICV: 0.87; Rb/Sr: 1.07). The deposition of these sediments took place in an oxic condition (sharp positive Ce anomaly) during a regressive phase with contribution from various granitoid plutons. Synthesizing the data available for different plutons around the Himalayan and Indo-Burmese Ranges (IBR), they show close similarity with Middle Bhuban geochemical signatures. Ladakh granite, Yangbajin granite and Jirong Granodiorite of Himalaya along with Wuntho-Mt. Popa and Banmauk granitoids are the most influential sources of the Surma sediments before the cessation of Paleo-Irrawaddy and then Paleo-Brahmaputra River courses. This is also evident by the paleo-current directions of sediments from various parts of the Surma Basin. Rise of Shillong plateau, Mikir massif and Naga hills in the north and IBR in the east caused the flow migration and lithological changes. Therefore, the present study ultimately invokes a significant supply of the sediments from the granitoids of neighbouring Indo-Burmese arc in the east in addition to their contribution from the Himalayan ranges in the north.

中文翻译：

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中弧新世苏尔马盆地作为两个弧形沉积模型的重建：来自物源，烃源岩风化和古环境条件的证据

摘要

印度东北部的苏尔马盆地的特征是由于印度板块和缅甸板块之间的碰撞而形成了厚的新生代沉积层序。在这个坚固的地形中，厚沉积柱的岩石联合的变化性代表了整个盆地演化过程中，特别是中新世中期所提供的大量沉积物的分布和沉积。这使得不丹中部砂岩成为这项研究的最佳选择。对印度东北部米佐拉姆邦Aizawl和Champhai地区部分收集的中新世布班砂岩进行了整个岩石地球化学研究，以了解烃源岩的性质，可能的烃源区和古气候条件。所研究的砂岩的地球化学行为代表了一种长英质的性质（TiO ₂/ Zr：15.03–37.09; La / Sc：1.80–6.52，La / Co：0.39–5.48，Th / Sc：0.56-2.05；Cr / Th：4.19–28.00；Al ₂ O ₃ / TiO ₂：13.13-28.09），分级的花岗岩来源[（La / Lu）_N：15.06-22.25；（La / Yb）_N：14.09–19.96；（La / Sm）_N：3.17–3.99；（Gd / Yb）_N：2.00–2.84]和中等风化的沉积物（CIA：65; CIW：73; PIA：69; WIP：41; ICV：0.87; Rb / Sr：1.07）。这些沉积物的沉积是在有氧条件下（Ce呈正的正异常）在回归阶段发生的，这是由各种花岗岩类云母造成的。综合喜马拉雅山脉和印度缅甸山脉（IBR）周围不同岩体的可用数据，它们显示出与中部布班族地球化学特征极为相似。喜马拉雅山的拉达克花岗岩，羊八金花岗岩和吉荣花岗闪长岩以及文索山。Popa和Banmauk花岗岩是苏美沉积物最有影响力的来源，在古伊拉瓦底河和随后的古布拉马普特拉河航道停止之前。苏尔马盆地各部分沉积物的古流向也证明了这一点。西隆高原的崛起，北部的Mikir地块和纳迦丘陵，东部的IBR引起了流体运移和岩性变化。因此，除了北部喜马拉雅山脉的贡献外，本研究最终还从东部邻近的印度-缅甸弧的花岗岩中提取了大量的沉积物。