Element mobility during the formation of the Uzunisa-Ordu bentonite, NE Turkey, and potential applications

Abstract

Dacitic andesitic calc-alkaline lavas and their pyroclastic rocks of Upper Cretaceous age are widespread in the Ordu area, eastern Black Sea Coast of Turkey. Ca-bentonite and Ca/Nabentonite deposits with significant economic potential formed in the broader region. The mineralogy and geochemistry of these deposits were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and chemical analyses. The parent rocks (PR) and bentonite samples were analysed for the major and trace element contents, including rare-earth elements, to understand the effect of differential alterations on element mobility. The bentonites contain mainly di-octahedral Ca-montmorillonite with minor amounts of illite, quartz, calcite, dolomite and feldspar. Primary K-feldspar and plagioclase phenocrysts were altered in the bentonite horizons, and were completely leached at greater depth. For this reason, the higher quality bentonites are found at deeper zones. Bentonite horizons are characterized by relatively high loss on ignition (LOI: 9.8–20.8%) and MgO content (3–5%) and low K2O (<0.5%) and Na2O (<2%) contents compared with the least altered parent rocks. Silicon, Ca, Mg, Mn and P are markedly enriched whereas Fe, Na, K and Ti are depleted in the bentonite samples. The chondrite-normalized rare earth element (REE) patterns show identical trends characterized by strong light rare earth element (LREE) enrichment in both the PR and bentonite samples. The LREE contents are higher than those of their heavy counterparts (HREE) in the samples. Alteration of the PR to bentonite is associated with intense chemical leaching and subsequent removal of K and Na in open-system conditions.

Mineralogical and geochemical characteristics of K‐bentonites from the Late Ordovician to the Early Silurian in South China and their geological significance

“…The concentrations of these immobile elements and their ratios (Nb/Y‐Zr/TiO 2 ) vary systematically with differentiation in magma series, and as a result, different rock types and magma series may be distinguished (Winchester & Floyd, ). Some trace element discrimination diagrams (Nb/Y‐Zr/TiO 2 , Y‐Nb, Y + Ta‐Rb, and Y + Nb‐Rb) have been used as a means of determining the original rock types and the tectonic setting of the source volcanic rocks (Abedini, Calagari, & Akbari, ; Berkley & Baird, ; Christidis, ; Christidis & Huff, ; Floyd & Winchester, ; Hints, Kirimae, Somelar, Kallaste, & Kiipli, ; Huff, , ; Huff, Bergström, Kolata, Cingolani, & Astini, ; Huff et al, 1997; Kolarikova & Hanus, ; Muchangos, ; Özdamar et al, ; Pearce, ; Pearce & Cann, ; Pearce, Harris, & Tindle, ; Pellenard et al, ; Roberts & Merriman, ; Shervais, ; Spears, Kanaris‐Sotirios, Riley, & Krause, ; Teale & Spears, ; Winchester & Floyd, ; Wood, ). The determination of the type of parent rock in K‐bentonite occurrences may provide important information on ancient tectonic settings (Laviano & Mongelli, ).…”

Occurrence of anatase in reworking altered ash beds (K-bentonites and tonsteins) and discrimination of source magmas: a case study of terrestrial Permian–Triassic boundary successions in China

“…The hydrological setting of an ash deposit influences leaching intensity and transport ( e.g. with strong leaching and downward flushing in ombrogenous paludal environments; Kiipli et al , 2010; Özdamar et al , 2014). In marine environments, ashes are subject to reworking and redistribution by currents, which can change the ratios of immobile elements as the separation of minerals of various densities is closely related to ambient environmental energy (Ver Straeten, 2008).…”

Mineralogy and geochemistry of rare earth elements in the Moyil Valley alteration zones, Meshkinshahr (northwest Iran)

“…Other causes of the Eu anomaly in these alteration zones are the high activity of complex ligands, the highly acid pH of the hydrothermal solution and the increase in the ƒO 2 of the hydrothermal system, because Eu transfer is easy under such conditions (Sverjensky, 1984;Elderfield & Sholkovitz, 1987;Karakaya et al, 2012;Özdamar et al, 2014). However, due to very slight variations in Eu negative anomalies in the alteration zones, it can be concluded that pH changes were very small during the mation of these zones.…”