HEAVY MINERAL ANALYSIS OF THE QUATERNARY SEDIMENTS IN THE SOUTHERN PART OF THE MESOPOTAMIA PLAIN, IRAQ

Abstract

Heavy mineral data of 87 samples from 51 fully cored boreholes, penetrated the Quaternary fluvial successions of the southern part of the Mesopotamia Plain, have been evaluated using numerical methods. Interpretation relied on the presumption that Quaternary physiography and geological settings of the source regions are comparable to those of today.Comparative analyses of the present study with the previous work show that the concentration of heavy minerals in the sediments of the studied area coincides with the concentration of heavy minerals in the sediments of the Euphrates and the Tigris Rivers, which have brought pyroxene, hornblende, epidote and garnet-rich sediments from the north and north-east (Turkey and Syria). There is an abnormal increase of concentration of ultrastable minerals (ZTR) in the west bank of the Euphrates River suggesting different sources for the supplied sediments, such sources may be the surrounding formations whose sediments were derived from the Western Desert.The result of the study reveals volcanogenic hornblende and pyroxene as well as metamorphic epidote and garnet as the dominant minerals of the Quaternary sands. The diversity of the heavy minerals suggests derivation from basic igneous rocks, metamorphic rocks and minor contribution from older sedimentary rocks.Study of heavy minerals using ZTR index, Ternary diagram and Pie-Diagram revealed that the sediments of the studied area are immature; affected more by mechanical than by chemical weathering. Variations in heavy mineral distributions also reflect tectonically-controlled fluvial channel switching.Appearance of pyrite in the heavy mineral assemblages at depth 22 – 22.2 m may record the evolution in reducing environments and confirm its authigenic origin.