Transformation of Iron-Bearing Kaolinite to Iron-Free Kaolinite, Goethite, and Hematite

Abstract

Abstract--Ferruginous clay partings in limestones of the marine, largely evaporitic, Upper Triassic Mohila Formation (Makhtesh Ramon, Israel) contain hexagonal plates and cube-like bodies up to one millimeter across. Analyses by electron microscopy, infrared and Mrssbauer spectroscopy, and X-ray powder diffraction indicate that the matrix contains Fe-rich anhedral kaolinite, up to 100/zm in size; the hexagonal plates are composed of euhedral, Fe-free kaolinite covered with well-developed acicular goethite and platy hematite (0.5 to 2/zm in size), and the cubes consist of fine-grained goethite with minor amounts of kaolinite.The anhedral kaolinite appears to be detrital, the hexagonal plates to be authigenic, and the cubes to be pseudomorphs after pyrite. Oxidation appears to have altered Fe-rich kaolinite and pyrite to Fe-free kaolinite, goethite, and hematite and was accompanied by recrystallization and pseudomorphic replacement. The alteration process was slow and was probably induced by a small increase in pH and in the Al/Fe ratio, resulting from oxidation of reduced components (pyrite, ferrous carbonate, organic matter) in a semiclosed, sediment-mud system. Overlying kaolinitic flint clay deposits may be the final product of a similar process.

Goethite Morphologies Investigated Via X-Ray Diffraction of Oriented Samples

“…The effect most often observed is a change in the relative intensity of the (110) and (111) Bragg reflections compared to that predicted for a random sample (Schulze and Schwertmann 1984;Schwertmann et al 1985). In addition, preferred orientation in some natural goethites is expected based on published electron micrographic images (Rozenson et al 1982;Schwertmann 1990). In an attempt to derive the maximum amount of information from limited sample quantities, we have employed a method for powder XRD analysis which takes advantage of the preferred orientation phenomenon.…”

Purely Inorganic Highly Efficient Ice Nucleating Particle

“…This process includes the elimination of various cations and the product with contaminants . Fe is a common contaminant of kaolin and often leaches from kaolin to precipitate as oxide or oxyhydroxide . The laminated limestones of the Late Triassic Mohila Formation (Makhtesh Ramon, Israel) are interbedded with dolomite, gypsum, and some illite, kaolinite (mostly Fe-rich), and mixed-layer clay. , Various mining and fossil fuel power generation activities have also shown the concurrent emission of dusts containing iron and various clay minerals like kaolin, as well as trace metals, such as mercury…”

Structural and palynomorph evidence for Early Palaeogene‐Neogene conglomerate series in Peninsular Malaysia: Implication for basin development and tectonic history

“…The presence of haematite along with iron cement in Chenderoh conglomeratic series which is composed of authigenic goethite and associative magnetite (Figure 14a–f) implies a diagenetic process of iron oxyhydroxide in a near‐surface oxidizing environment (Shogenova et al, 2009). It is believed to originate from the transformation of iron‐rich kaolinite of a shale unit, which releases goethite and haematite (Langmuir, 1971; Rozenson et al, 1982). Authigenic magnetite indicates an increasing temperature by pyrogen or by burial with presence of organic matter under reducing condition (Till & Nowaczyk, 2018).…”