Sandstones belonging to the Oligocene Barail Group and Miocene Surma Group of the Mizoram Foreland Basin have been studied geochemically to constrain their provenances,tectonic setting,and other sedimentary processes(...Sandstones belonging to the Oligocene Barail Group and Miocene Surma Group of the Mizoram Foreland Basin have been studied geochemically to constrain their provenances,tectonic setting,and other sedimentary processes(weathering and mineral sorting etc.).Based on their mineralogical compositions,these sandstones are classified as quartzarenite and sublithic-arenite.The sandstones of Barail and Surma Groups have similar contents of most of the major elements except for SiO2 and A12O3.The Barail sandstones are relatively more siliceous and less aluminous compared to the Surma sandstones.Barail and Surma sandstones were plotted in a singular array on different geochemical discrimination diagrams.The CIA and CIW values of the sandstones of Barail(69 and 77 respectively)and Surma Groups(68 and 77 respectively)suggest that the sandstones were derived from moderately weathered source rocks.In the A-CN-K diagram,the studied samples plotted along a roughly singular trend that originates from granodiorite as well as Trans-Himalayan granitoids and also confined within the field of Siwalik sediments.Chondrite・normalized REE patterns for the Surma and Barail sandstones are identical and are similar to upper continental crust,with moderate to high LREE enrichment and prominent negative Eu anomalies(*Eu/Eu for both Barail and Surma sandstone=0.69),indicating their derivation from a felsic magmatic source.The values of,*Eu/Eu(LaN/LuN),La/Sc,La/Co,Th/Sc,Th/Co,and Cr/Th ratios of Surma and Barail sandstones are also not significantly different,and the values are similar to finefractions derived from the weathering of felsic rocks.In the K2O/Na2O versus SiO2,Th-Sc-Zr/10 and Ti/Zr versus La/Sc tectonic discrimination diagrams the studied samples of Barail and Surma sandstones plot within the fields of greywacke from continental island arcs and active continental margin.The geochemical characteristics of the studied sedimentary rocks and their similarity with the Siwalik foreland sediments thus suggest were sourced from different felsic magmatic lithounits of Himalaya and were deposited in an active continental margin.展开更多
基金the financial support from UGC-NERO, Govt. of India [No. F.5-44/2013-14/(MRP/NERO)/281] to carry out the work
文摘Sandstones belonging to the Oligocene Barail Group and Miocene Surma Group of the Mizoram Foreland Basin have been studied geochemically to constrain their provenances,tectonic setting,and other sedimentary processes(weathering and mineral sorting etc.).Based on their mineralogical compositions,these sandstones are classified as quartzarenite and sublithic-arenite.The sandstones of Barail and Surma Groups have similar contents of most of the major elements except for SiO2 and A12O3.The Barail sandstones are relatively more siliceous and less aluminous compared to the Surma sandstones.Barail and Surma sandstones were plotted in a singular array on different geochemical discrimination diagrams.The CIA and CIW values of the sandstones of Barail(69 and 77 respectively)and Surma Groups(68 and 77 respectively)suggest that the sandstones were derived from moderately weathered source rocks.In the A-CN-K diagram,the studied samples plotted along a roughly singular trend that originates from granodiorite as well as Trans-Himalayan granitoids and also confined within the field of Siwalik sediments.Chondrite・normalized REE patterns for the Surma and Barail sandstones are identical and are similar to upper continental crust,with moderate to high LREE enrichment and prominent negative Eu anomalies(*Eu/Eu for both Barail and Surma sandstone=0.69),indicating their derivation from a felsic magmatic source.The values of,*Eu/Eu(LaN/LuN),La/Sc,La/Co,Th/Sc,Th/Co,and Cr/Th ratios of Surma and Barail sandstones are also not significantly different,and the values are similar to finefractions derived from the weathering of felsic rocks.In the K2O/Na2O versus SiO2,Th-Sc-Zr/10 and Ti/Zr versus La/Sc tectonic discrimination diagrams the studied samples of Barail and Surma sandstones plot within the fields of greywacke from continental island arcs and active continental margin.The geochemical characteristics of the studied sedimentary rocks and their similarity with the Siwalik foreland sediments thus suggest were sourced from different felsic magmatic lithounits of Himalaya and were deposited in an active continental margin.
