الملخص

The present study focuses on mineralogy of the middle to upper Jurassic Sargelu, Naokelekan and Barsarin formations form northeastern Iraq to elucidate the implications of mineralogical variation for interpretation of provenance and climatic condition. The results from X-ray diffraction supported by scanning electron microscopy has revealed the presence of calcite and dolomite as dominating minerals followed by quartz and feldspars in addition to pyrite, anatase and natrolite. The clay minerals are dominated by illite-mica, kaolinite and mixed layers of illite/smectite (I/S), illite and kaolinite are of detrital origin while I/S is of diagenetic origin. Variation in mineralogical constituents reflects the effect of source area composition, depositional environment and diagenesis and the prevailing climatic conditions. Calcite commonly was formed in restricted evaporative conditions. Felsic igneous rocks from Zagros ophiolites and related igneous rocks, and/or Arabian Shield are suggested for the presence of detrital quartz and feldspars in addition to weathering from older clastic sedimentary rocks. Illite-mica and kaolinite as common clay minerals which also reflect the contribution from felsic igneous rocks and the prevailing hot dry and humid climatic conditions which coincided with a global paleoclimatic conditions. Pyrite forms under reducing environmental conditions. The presence of illite/smectite, natrolite and pyrite suggest the effect of diagenetic events on the studied rocks.