Distribution and Origin of Analcime in Marginal Lacustrine Mudstones of the Green River Formation, South-Central Uinta Basin, Utah

Abstract

X-Ray powder diffraction and thin section analyses indicate that marginal lacustrine mudstones of the Green River Formation in the south-central Uinta basin, Utah, contain abundant analcime. The analcime has a low Si/A1 ratio (<2.31) and occurs as very fine grained disseminated crystals and, to a lesser extent, as coarser-grained pore-filling cement. Analcime-rich mudstones and associated sandstones, siltstones, and carbonates lack volcanic detritus and zeolites other than analcime, thus making it diflicult to support the concept that the analcime formed from precursor zeolites derived from volcanic glass altered in saline, alkaline-lake water. Abundant dolomite, syneresis cracks, and the absence of freshwater pelecypods and gastropods suggest that the lake (Lake Uinta) was moderately saline and alkaline. The restricted illite-illite/smectite clay mineral suite in the analcime-rich mudstones suggests that detrital clays significantly altered in a moderately saline and alkaline environment, thereby providing a source of Si and A1 for the formation of analcime. Red mudstones contain twice as much analcime as green mudstones (14 vs. 7 wt. %). Green mudstones have a day mineral suite consisting of illite (44 wt. %), mixed-layer illite/smectite (35 wt. %), smectite (12 wt. %), and minor kaolinite (4 wt. %) and chlorite (5 wt. %), whereas red mudstones have a more restricted day mineral suite consisting ofillite (68 wt. %) and mixed-layer illite/smectite (26 wt. %) with very minor smectite, chlorite, and kaolinite. Periodic minor fluctuations in lake level probably exposed large areas of shallow lacustrine-interdistributary green mud. Evaporative pumping on the exposed mudfiats concentrated the moderately saline and alkaline-lake water, thereby producing Na-rich brines that enhanced the formation of analcime by accelerating the alteration of detrital clays and, perhaps, other minerals. Oxidation of iron from altered iron-bearing minerals stained the analcime-rich mud red with iron hydroxide or oxide (perhaps hematite). The overall reaction from green to red mud (mudstones) was probably: detrital phyllosilicates + Na-brine + iron-bearing minerals + oxygen ~ analcime + iron hydroxide or iron oxide.

Integrated multi-stratigraphic study of the Coll de Terrers late Permian–Early Triassic continental succession from the Catalan Pyrenees (NE Iberian Peninsula): A geologic reference record for equatorial Pangaea

“…The sizable decrease of quartz contents in the upper URU is possibly related to reduced chemical weathering (see also Williams et al, 2012), as this mineral is more resistant than feldspars and rock fragments (Coney et al, 2007). In turn, analcime occurs both as a primary mineral in alkaline igneous rocks but can also be authigenically formed (Remy and Ferrell, 1989;Schneider et al, 2006). The latter is the most possible origin of this mineral in Coll de Terrers, as no signals of igneous rocks have been found in the succession.…”

Clay mineral assemblages and analcime formation in a Palaeogene fluvial–lacustrine sequence (Maíz Gordo Formation Palaeogen) from northwestern Argentina

“…While volcanic glass is the most frequent precursor of zeolites in saline-alkaline lakes (Surdam and Sheppard, 1978;Boles and Surdam, 1979), these minerals can also form at the expense of other materials, such as clay minerals, feldspars, and feldspathoids (Hay and Sheppard, 2001). Analcime in particular has been recorded in several cases in lacustrine sediments free of associated volcaniclastic material (Hay, 1966;Gall and Hyde, 1989;Remy and Ferrell, 1989;Renaut, 1993;English, 2001).…”

Mineralogical and Chemical Properties and the Origin of Two Types of Analcime in SW Ankara, Turkey

“…Iijima and Hay (1968) reported that the Si/Al ratio of the analcime ranged from 1.95 to 2.81 and suggested that this variation might be caused by the reaction of analcime to authigenic feldspar, and may also indicate that analcime associated with authigenic feldspar has a lower Si/Al ratio than in analcime without feldspar with a Si/Al ratio in excess of 2.30. Researchers have suggested that analcime may form as an alteration product of clays deposited in saline and highly alkaline lakes (Hay and Moiola, 1963;Hay, 1970;Ataman and Gü ndog du, 1982;Hay and Guldman, 1986;Remy and Ferrell, 1989;English, 2001;Sheppard and Hay, 2001). Detrital clay minerals are known to react extensively in a saline, alkaline environment (Hay and Moiola, 1963;Hay, 1966;Brobst and Tucker, 1973;Hay and Guldman, 1986).…”

“…composition of the volcanic material, water temperature (30À45ºC), and pH (between 8 and 9) (Hay, 1966;Sheppard and Gude, 1969;Ataman and Beseme, 1972;Surdam and Parker, 1972;Gü ndog du et al, 1996, Temel and. In several cases analcime has been identified in lacustrine sediments free of associated volcaniclastic material (Hay, 1966;Sheppard and Gude, 1969;Gall and Hyde, 1989;Remy and Ferrell, 1989;Renaut, 1993;English, 2001; Karakas°a nd Kadir, 2006;Kadir et al, 2008). The physicochemical conditions necessary to form analcime from non-volcanic materials in lacustrine sediments have been studied (Ataman and Gü ndog du, 1982;English, 2001;Campo et al, 2007).…”