Sedimentology and Geochemistry of Siliciclastic Sediments (Tertiary-Quaternary) in the Eastern Coasts of Chabahar, SE Sistan and Baluchistan

In this study, geochemical and sedimentological assessment was carried out on mudstone and sandstone deposits of Eastern coasts of Chabahar. Fifty samples were taken five sectione of Tiss, Ramin, Lipar, Gorankesh and Garindar estuary and subjected to grain size analysis and chemical analysis using XRF and ICP AES methods. Positive sorting and skewness (with the frequency of fine grain particles) of samples indicate deposition in a low energy environment. Plotting geochemical data of major elements Late Miocene- Pleistocene age 10 mudstone and sandstone samples in east coasts of Chabahar in Makran zone, on siliciclastic rocks classification diagrams, showed that the sandstones are wacky and Mudstones are shale. The mean calculated chemical indexes of alteration (CIA) and weathering (CIW) for siliciclastic sediments, confirm low level weathering of source rocks of this sediments. The average index of combinational variety (ICV) for the studied sediments was 1.57, which indicates that these deposits have a moderate chemical maturity and are derived the first cycle of sediments. Distribution pattern of rare earth elements on spider diagrams shows the enrichment of light rare earth elements (LRRE) relative to heavy rare earth elements (HRRE) in the rocks. High ratios of LILE/HFSE and LRRE/HRRE in the rock samples and similarity of their chemical composition with subduction zone facies, indicates that siliciclastics of Chabahar coasts have formed in a subduction zone. The diagrams of tectonic setting associated with patterns of multivariate charts also shows that the studied rocks have been developed in an active continental margin.