This study presents the results of geochemical investigations of early to middle Eocene sandstones belonging to the Dalbuing Formation of Yinkiong Group, occurring in and around Yamne valley of Arunachal Pradesh. Geochemically, these sandstones are wacke and lithic arenite, with the former being dominant than the other. The various indices of weathering (CIA, CIW, PIA) suggest intense chemical weathering of the source rock. Moreover, the average Th/U ratio (mean = 6.97) also indicates intense chemical weathering in the source areas and derivation of the sediments from the upper continental crust. However, the plot of chemical index of alteration (CIA) vs. index of compositional variability (ICV) shows that most of the sandstones are geochemically mature and were derived from intensively weathered source rock. The sandstones were deposited dominantly in semi-arid condition. Tectonically, these sandstones are found to have affinities towards both the passive margin (PM) and the active continental margin (ACM) settings, which further implies existence of multiple tectonic activities during their deposition. Moreover, the elemental ratios of Eu/Eu*, La/Sc, Th/Sc, La/Co, Th/Co, Th/Cr and chondrite normalized REE distribution pattern suggest their derivation from sources of felsic composition. The high ratio of Zr/Sc indicates the enrichment of heavy mineral zircon supplemented by sediment recycling.

这项研究提供了阿鲁纳恰尔邦亚姆纳河谷及其周围地区Yinkiong群Dalbuing组的始新世至中期始新世砂岩的地球化学研究结果。从地球化学上讲，这些砂岩是瓦克岩和石质砂岩，前者比其他砂岩更占优势。各种风化指数（CIA，CIW，PIA）表明源岩发生强烈的化学风化。此外，平均Th / U比（平均值= 6.97）也表明源区发生了强烈的化学风化作用，并从上陆壳中衍生出了沉积物。但是，化学变化指数（CIA）与成分变异性指数（ICV）的关系图表明，大多数砂岩是地球化学成熟的，并且来自强烈风化的烃源岩。砂岩主要以半干旱条件沉积。从构造上看，发现这些砂岩既对被动边缘（PM）也对主动大陆边缘（ACM）设置都具有亲和力，这进一步暗示了它们沉积过程中存在多种构造活动。此外，Eu / Eu *，La / Sc，Th / Sc，La / Co，Th / Co，Th / Cr和球粒晶归一化REE分布图的元素比表明它们源自长英质成分来源。Zr / Sc的高比值表示重矿物锆石的富集，并辅以沉积物再循环。此外，Eu / Eu *，La / Sc，Th / Sc，La / Co，Th / Co，Th / Cr和球粒晶归一化REE分布图的元素比表明它们源自长英质成分来源。Zr / Sc的高比值表示重矿物锆石的富集，并辅以沉积物再循环。此外，Eu / Eu *，La / Sc，Th / Sc，La / Co，Th / Co，Th / Cr和球粒晶归一化REE分布图的元素比表明它们源自长英质成分来源。Zr / Sc的高比值表示重矿物锆石的富集，并辅以沉积物再循环。