Implications of trace element composition of syntaxial quartz cements for the geochemical conditions during quartz precipitation in sandstones

Abstract

A petrographic investigation revealed polyphase quartz cementation in the Finefrau Sandstone (Upper Carboniferous, Western Germany) and the Solling Sandstone (Lower Triassic, Central Germany). Three different cements could be distinguished in each sandstone based on their cathodoluminescence and trace element composition. The first quartz generation is suggested to have been formed during eogenesis due to dissolution and replacement of feldspar. The mesogenetic paragenesis comprises two generations of quartz and illite, which are accompanied by albite in the Solling Sandstone. Sharp luminescence zoning in quartz overgrowths points to distinct episodes of cementation in both sandstones. Significant amounts of Al, Li and H and traces of Ge and B have been detected in the quartz overgrowths. The Al-content of the quartz cements in the Finefrau Sandstones exceeds that in the quartz cements in the Solling Sandstone by a factor of five. It is suggested that this compositional variation reflects the conditions in the pore-water, such as temperature and pH. The Al-concentration is generally correlated to the Li-content with the exception of the latest quartz generation in the Finefrau Sandstones which is also most enriched in trace elements. The ratio of Li/Al varies between 0Á11 and 0Á25 in the two sandstones. The Li/H-ratio, which ranges from 0Á12 to 0Á3, is controlled by the activity ratio of Li and H in the pore fluid. Clay minerals are the most important source for Li and high salinities favour the mobilization of Li during diagenesis. Thus, a relatively low salinity and low pH are responsible for the low Li/H-ratio in the Finefrau Sandstone, while high salinity and neutral to alkaline pH results in a high Li/H-ratio for the Solling Sandstone. The Gecontents are generally near the average of detrital quartz and indicate that pressure dissolution is a major source for quartz cementation. Different chemical compositions of distinct quartz generations indicate changes in the physico-chemical conditions and point to mobilization of silica from different sources (for example, pressure solution and clay mineral transformations).

Cathodoluminescence, fluid inclusions, and trace element data for the syntaxial quartz cementation in the sandstones of the Ora Formation, northern Iraq

“…This is an indication of the availability of sufficient amounts of both Al and Li. Such a correlation was documented by Demars et al (1996) for quartz cement that precipitated at a temperature <150 °C; a similar Li/Al ratio was observed in sandstones elsewhere in the world (Demars et al, 1996;Lehmann et al, 2011;Götte et al, 2013). Since illite is the main clay mineral affecting the sandstones of the Ora Formation, the major source of Li is considered to be detrital clays, primarily smectite and illite; this element may be released as a result of interaction of pore water with smectite-illite and illite ripening (Williams and Hervig, 2005).…”

Trace elements in quartz shed light on sediment provenance

“…Quartz crystallizing from nonmagmatic systems generally exhibit low Ti content, variable Al and are often chemically indistinguishable from one another. Low‐Ti quartz can be generated through hydrothermal vein formation [ Allan and Yardley , ; Tanner et al ., ] dynamic recrystallization during low‐grade metamorphism [ Grujic et al ., ; Kidder et al ., ], dissolution‐precipitation during sedimentary diagenesis [ Götte et al ., ] or pegmatite formation [ Huang and Audétat , ]. Pegmatitic quartz can sometimes be distinguished from other low‐Ti populations due to its elevated Ge content [ Müller et al ., ; Breiter and Müller , ; Beurlen et al ., ] and elevated Ti has been observed in high‐T hydrothermal systems [ Rusk et al ., ].…”

“…Time-resolved LA-ICPMS analysis allows for removal or quantification of transient inclusions in the analytical signal, and several studies have measured fluid and melt inclusions Geochemistry, Geophysics, Geosystems 10.1002/2015GC005896 compositions in minerals using these ephemeral inclusion signals [McCandless et al, 1997;Aud etat et al, 2000;Guillong et al, 2008]. The large laser spot used during analysis, high fluid inclusion density in quartz, and demonstrably higher concentrations of Na, Ca, and K in fluid inclusions [Gagnon et al, 2004;Kostova et al, 2004;Guillong et al, 2008] makes separating the fluid inclusion signal from the lattice signal infeasible and diminishes the utility of these elements to province studies.…”

The Chemistry of Quartz in Granitic Pegmatites of Southern Norway: Petrogenetic and Economic Implications

“…However, comparatively little of this type of work has been carried out on the chemistry of pegmatite quartz. The limited number of publications is in contrast to the abundant studies dealing with trace elements of hydrothermal (e.g., Rusk et al 2006Rusk et al , 2008Rusk et al , 2011Rusk, 2012Rusk, , 2014Tanner et al, 2013;Maydagán et al, 2015), volcanic (e.g., Watt et al, 1997;Wark et al, 2007;Audétat, 2013), plutonic (e.g., Müller et al, 2000Müller et al, , 2010bWiebe et al, 2007;Jacamon and Larsen, 2009;Breiter et al, 2013), metamorphic (e.g., Van den Kerkhof et al, 2004;Spear and Wark, 2009;Kidder et al, 2013), and sedimentary quartz (e.g., Götze and Plötze, 1997;Götze, 2012;Götte et al, 2013;Müller and Knies, 2013).…”