Symptoms of
diagenesis in some Miocene evaporite clays, Gulf of Suez, Egypt
Gamal M. Attia
Dept. Geology, Fac. Sciences; Menoufia Univ., Egypt |
The minerals and chemical composition of clays
in the Miocene evaporites,. Gulf of Suez, can be used to determine the type and extent of
weathering and explore the persistence of clays in changing - chemical environments. The
clay-sized fractions studied contain predominantly illite and irregularly inter-layered
chlorite/vermiculite/montmorillonite.
Detrital illite, biotite, chlorite and montmorillonite are probably the parent of the clay
minerals. Inductive coupled plasma analyses of clay-size fractions show that the
diagenetic clay minerals are enriched in Mg relative to the detrital ones. The chemical
composition of clay minerals, and the geologic history of Gulf of Suez suggest that
alteration of clays occurred in the hypersaline marine evaporite brine.
Clay minerals encased in primary marine halite, and clays from sites where halite had been
dissolved by fresh water (indicated by stable isotope study) are structurally and
chemically similar. The clay minerals are found to record paleohydric and
paloenvironmental conditions such as warmer temperature, high salinity and other
physico-chemical evaporite conditions.
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