Clay mineral variation in Tertiary sediments from the eastern flank of the Niger Delta

Abstract

Detailed clay mineralogical and chemical analyses of well cuttings of Tertiary sediments from two wells, Uruan-1 and Uda-1, on the eastern flank of the Niger delta, have been made in an attempt to investigate clay mineral burial diagenesis. The clay mineralogy indicates a transformation of smectite to an interstratified illite-smectite (I/S) phase. The relationship between ordered and random interlayering, however, is nonsystematic. The chemistry of the <0·1 µm size fraction shows some tendency towards a net gain in K2O and Al2O3 and a net loss in SiO2 with depth, but the relationship does not correlate well with the thermal gradient. The distribution of kaolinite and chlorite in both wells appears to be unrelated in any regular way to smectite transformation and these two minerals are considered to be either the products of other diagenetic reactions affecting various stratigraphic levels, or the result of primary sediment deposition. In well Uda-1, kaolinite decreases in relative abundance with depth. This trend has been interpreted elsewhere as indicative of a transition from nonmarine to marine facies. The results of this study indicate that lack of ion mobility, rather than availability, is a significant factor in retarding the formation of ordered I/S with depth, and that lithology, overpressuring, carbonate cement, and original smectite layer charge may be controlling factors in the smectite → illite transformation.

Palaeoenvironmental approach to the geology, mineralogy and geochemistry of an Early Miocene alluvial-fan to cyclic shallow-lacustrine depositional system in the Aktoprak Basin (central Anatolia), Turkey

“…Mg, Si and Al were supplied during wet seasons, and palygorskite formed during evaporatic dry seasons (Inglès & Anadón, 1991;Colson et al, 1998). Also, the coexistence of accessory illite and chlorite with smectite along the profiles may indicate either that illite and chlorite were detrital, or that illite was precipitated authigenically by conversion of smectite to illite/smectite following release of Al and K during degradation of feldspar and hornblende (by aqueous solutions in sediments either during burial processes or diagenesis in the lower parts, or of plant-and root-rich palaeosol levels in the upper parts of section P2) (Braide & Huff;Gürel, 1991). Conversion of smectite to illite may have occurred via substitution of tetrahedral Si by Al and uptake of K in the interlayer space (Pusch, 2006).…”

Analysis of illite-smectite interstratification

“…Impetus for the present interest in the geology of interstratified clay minerals can be attributed largely to the influence of the experimental studies of Hower and his colleagues, beginning with Perry & Hower (1970, 1972, and to Reynolds (Reynolds & Hower, 1970) for providing useful methods of X-ray diffraction (XRD) analysis which have added new insight. Experimental evidence is accumulating which shows that the smectite (S) to illite (I) transformation is affected by a variety of factors such as temperature and burial depth, residence time, ion mobility, and the amount and identity of competing cations (Perry & Hower, 1970;Ramseyer & Boles, 1986;Braide & Huff, 1986;Roberson & Lahann, 1981, respectively). More recently, lattice imaging has suggested a somewhat different picture of I/S interstratification (Ahn & Peacor, 1986), and theories, e.g.…”

Genesis of smectite in siliciclastics and pyroclastics of the Eocene İslambeyli Formation in the Lalapaşa region, NW Thrace, Turkey

“…In addition, local concentration of K (along with Al) resulted in the in situ precipitation of accessory illiteedging smectite flakes under alkaline environmental conditions (Braide & Huff;1986;Ziegler, 2006;Elliott et al, 1999). The local increase in Ca, K and Na associated with Al, resulted in the precipitation of heulandite-clinoptilolite-type zeolite under more alkaline conditions in the upper part of the İslambeyli Formation.…”