The Relationship Between Chemical Index of Alteration andSome Major and Trace Elements Content in Rocksof Injana Formation of Northern Iraq

Abstract

The average CIA value for the Injana Formation (Late Miocene) sampled across a section consisting of alternating mudstones, siltstones and sandstones deposited mainly in fresh water environment is rather low value (45.6) indicating the very low level of chemical alteration which the source rocks have suffered which is mainly due to semi-arid to arid climate of weathering and also due to nearby position of the basin of deposition. No overall variation in climatic condition was observed along the section from bottom to top .The variation of major and trace elements involved in this study with mean values of CIA for the sandstone, siltstone and mudstone lithologies was attributed to either mobility of the element concerned (Na, K and Rb) or to gravity fractionation of minerals that host the element or to climate of weathering and deposition (P2O5, Ni, Co & TiO2). Major contribution of recycled argillaceous or clay rich sediments to the Injana Formation do not agree with the results reached in the present study.