MINERALOGY AND GEOCHEMISTRY OF THE MIDDLE EOCENE (LUTETIAN) EL-MINYA CLAY, EGYPT

抄録

Recognizing mineralogy and geochemistry of the clay minerals is very important in order to utilize these deposits in ceramic manufacturing heavy and lightweight ceramic clay products. The objective of the study was to find mineralogical and geochemical characteristics of El-Minya clay deposits. El-Minya clay deposits are Middle Eocene (Lutetian) in age belonging to the Qarara Formation. The clay fractions were determined using X-ray diffraction analysis and were composed mainly of montmorillonite and kaolinite with minor illite. The crystallinity index measured for montmorillonite revealed that it was well crystallized, whereas that measured for kaolinite ranges from well crystallized to slightly disordered. The morphology of the clay particles was determined using a scanning electron microscope (SEM) which revealed that montmorillonite exhibited particles with regular outlines that appeared crushed edges as well as thin webby slightly crenulated flakey aggregates. Kaolinite, on the other hand, appeared as flakes with poorly developed hexagonal ragged outlines crudely seen, and as verm composed of books arranged face-to-face. These books were cracked by ribbons or shades of filamentous montmorillonite. The index of compositional variability (ICV) used to deduce the source rocks and its ratios indicated that, most of the samples were accumulated in cratonic environments and are compositionally mature. The chemical index of alteration (CIA) was proposed as an indication of the chemical weathering of the source rocks implying extreme weathering of the original source. Tectonic settings showed that all samples were in the oceanic Island Arc.