Early formation of K‐feldspar in shallow‐marine sediments at near‐surface temperatures (southern Israel): evidence from K‐Ar dating

Abstract

Authigenic K-feldspar was investigated in two Albian to Turonian sections in Israel using K-Ar and Ar-Ar dating, X-ray diffraction, scanning electron microscopy and chemical analysis. Both sections comprise a similar succession of shallow-marine limestones, dolomites and marls, with some sandstone and shale beds of continental origin. The HCl-insoluble residue fraction of the studied samples consists of clays, quartz, feldspars, goethite and trace amounts of heavy minerals. Most of the insoluble residues have a relatively high K-feldspar content that has an adularia habit and is concentrated in the 4-7 lm size fraction. The authigenic origin of the K-feldspar in the fine silt fraction is indicated by its high content relative to quartz, the uniform and idiomorphic shape of the crystals and its limited size range. Of the fine silt (4-7 or 4-10 lm) separates, 40% have ages that are similar to stratigraphic ages within the analytical and biostratigraphic errors. Ar-Ar dating of a fine silt fraction with 94% K-feldspar (4-10 lm, sample GYP 7) yields a plateau age identical to the total gas age and similar to the stratigraphic age. These results indicate that the K-Ar age is not a mixture between detrital and late diagenetic K-feldspar ages, but is rather an age of formation within a few million years after deposition. It is suggested that the early formation of the K-feldspar was associated with dolomitization and was induced by residual brines as part of a reflux process.

Post‐impact alteration of surficial suevites in Ries crater, Germany: Hydrothermal modification or weathering processes?

“…Moreover, secondary clays and zeolites, as well as feldspars, can form directly under ambient conditions or diagenetically by devitrification of silicate glasses (e.g., Kastner and Siever 1979;Sandler et al 2004;Meunier 2005).…”

K–Ar dating of authigenic minerals in siliciclastic sequences: an example from the south Sanfranciscana Basin (Western Minas Gerais, Brazil)

“…Baskin, ; Ali and Turner, ; Milliken, ; Girard and Onstott, ; Hagen et al ., ; Lee and Parsons, ; Mark et al ., , ). However, its formation under surface conditions is less common (Maraschin et al ., ; Sandler et al ., ).…”

“…The application of the K–Ar dating method for potassic authigenic minerals to determine the age of deposition or diagenetic events in sandstones is reported widely in the literature (Thomas, ; Hamilton, ; Banner, ; Maraschin and Mizusaki, ). The potassic authigenic minerals commonly used for age determinations are illite and mixed‐layer illite–smectite (Lee et al ., , ; Aronson and Douthitt, ; Macchi, ; Burley and Flisch, ; Hamilton et al ., , ; Mizusaki et al ., ; Barnes et al ., ; Clauer et al ., , ; Hogg et al ., ; Robinson et al ., ; Zwingmann et al ., , ; Pevear, ; Liewig and Clauer, ; Franks and Zwingmann, ; Maraschin et al ., ; Aubet et al ., ; Clauer, ; Clauer and Liewig, ), K‐feldspar overgrowths (Halliday and Mitchell, ; Girard et al ., ; Sandler et al ., ; Maraschin et al ., ) and glauconite (Montag and Seidemann, ; Amireh et al ., ; Kelly et al ., ; Duarte and Martínez, ; Rousset et al ., ; Gopalan, ).…”

“…The application of the K-Ar dating method for potassic authigenic minerals to determine the age of deposition or diagenetic events in sandstones is reported widely in the literature (Thomas, 1986;Hamilton, 2003;Banner, 2004;Maraschin and Mizusaki, 2008). The potassic authigenic minerals commonly used for age determinations are illite and mixed-layer illite-smectite (Lee et al, 1985(Lee et al, , 1989Aronson and Douthitt, 1986;Macchi, 1987;Burley and Flisch, 1989;Hamilton et al, 1989Hamilton et al, , 1992Mizusaki et al, 1990;Barnes et al, 1992;Clauer et al, 1992Clauer et al, , 2012Hogg et al, 1993;Robinson et al, 1993;Zwingmann et al, 1998Zwingmann et al, , 1999Pevear, 1999;Liewig and Clauer, 2000;Franks and Zwingmann, 2010;Maraschin et al, 2010a;Aubet et al, 2012;Clauer, 2013;Clauer and Liewig, 2013), Kfeldspar overgrowths (Halliday and Mitchell, 1976;Girard et al, 1988;Sandler et al, 2004;Maraschin et al, 2010b) and glauconite (Montag and Seidemann, 1981;Amireh et al, 1998;Kelly et al, 2001;Duarte and Martínez, 2002;Rousset et al, 2004;Gopalan, 2008). However, before it is possible to constrain the timing of deposition or diagenetic phases in sandstones through radiometric methods, it is necessary to investigate rock samples ...…”

Temperature–composition–time (T–X–t) data from authigenic K-feldspar: An integrated methodology for dating fluid flow events

“…Complete physical separation of authigenic and detrital phases has proved problematic, significantly hindering the analysis of bulk separates (Lee and Savin, 1985). Although some investigations have yielded sensible ages for authigenesis (Sandler et al, 2004), sample preparation is complex and unreliable. Complete separation of detrital and authigenic feldspar is difficult to verify.…”