Diagenesis of trioctahedral clays in a Miocene to Pleistocene sedimentary–magmatic sequence in the Dead Sea Rift, Israel

Abstract

The diagenetic evolution of clay minerals in a 4249 m sedimentary-magmatic sequence of the Zemah-1 drillhole in the Dead Sea Rift, Israel, was studied, mainly by X-ray diffraction (XRD). The parallel maturation of the organic matter was estimated by the thermal alteration index (TAI) method. Both parameters follow a progressive diagenesis with depth. The original clays, now encountered only at shallow depths, were dioctahedral, and mostly detrital. They transformed into Mg-rich trioctahedral clays starting with a saponite-dominated assemblage, followed by a saponite, ordered chlorite-smectite (C-S), and chlorite assemblage, and finally by a saponite, corrensite, chlorite and talc assemblage. Significant mineralogical composition gaps occur between saponite to corrensite and corrensite to chlorite. Short-range variations within the most evolved assemblage are controlled by bulk-rock composition. Depths of first occurrence and disappearance of minerals indicate a much higher geothermal gradient in the past whereas the TAI values suggest an even higher palaeogradient of ∼708C km–1.

Mineralogical constraints on the paleoenvironments of the Ediacaran Doushantuo Formation

“…The local chemical environment is also probably an important control on the degree of diagenesis of saponite (e.g., ref. 21). The variation in the amounts of saponite, corrensite and chlorite observed at different stratigraphic horizons in the lower part of the Doushantuo Formation may be governed by the lithology of the host rock influencing fluid composition.…”

Mobilization of ore fluids during Alpine metamorphism: evidence from hydrothermal veins in the Variscan basement of Western Carpathians, Slovakia

“…Ages of the Gemeric hydrothermal veins are indirectly constrained by thermal gradients, which are substantially lower than those in typical volcanic rifts (Burrus & Foucher 1986; Whieldon et al. 1994; Sandler et al. 2001).…”

“…Ages of the Gemeric hydrothermal veins are indirectly constrained by thermal gradients, which are substantially lower than those in typical volcanic rifts (Burrus & Foucher 1986;Whieldon et al 1994;Sandler et al 2001). Estimated palaeodepths (6-14 km in north and 11-16 km in south) are in conflict with a possible Permo-Triassic age for the mineralization, because of a need for an additional rock pile overlying the autochthonous Permo-Triassic sedimentary cover.…”

Mobilization and retardation of reduced manganese in sandy aquifers: Column experiments, modeling and implications

“…The clay mineral content of the sediment was determined from the mineralogical and chemical composition with an estimated error of ±15% according to the method of Sandler et al (2001). The CaCO 3 content was determined with an estimated error of ±5% by measuring the CO 2 pressure produced by dissolving a known weight of sediment with 1:5 HNO 3 .…”