Size distribution of quartz in mudrocks

Abstract

Sixteen penecontemporaneously deposited mudrock‐sandstone pairs ranging in age from Devonian to Cretaceous were treated chemically to isolate the quartz and chert fraction from the other constituents of the rocks. The amount of crystalline silica was determined from the chemical treatments; its size distribution was determined using a combination of normal and Micro Mesh sieving and settling tube analysis; the crystalline silica coarser than 10 μu was examined petrographically to determine the amount of chert. Percentages of crystalline silica in the mudrocks range from 6·7 to 46·7 % and average 27·6 (σ= 10·7). Mean grain size ranges from 4·4 φ to 7·3 φ and averages 6·1 φ. The crystalline silica fraction is a poorly sorted medium to fine silt consisting of one‐eighth sand, six‐eighths silt, and one‐eighth clay size sediment. Percentage of crystalline silica and mean size of crystalline silica in the thirty‐two mudrocks and sandstones are positively correlated; r= 0·685, which is significant at the 99 % level. The best fit linear regression line is: Y= 102·7–11·3X. Extrapolation of the regression line indicates that, on the average, crystalline silica is lacking in mudrocks in grain sizes finer than 9·1 φ (1·μm), a result consistent with observations by clay mineralogists. The crystalline silica fraction of both the mudrocks and associated sandstones averages 4% chert in the >10 μm portion. There is no correlation between the mean grain size of the crystalline silica and the percentage of chert in it.

Quartz cementation in Late Cretaceous mudstones, northern North Sea: Changes in rock properties due to dissolution of smectite and precipitation of micro-quartz crystals

“…On the other hand, the origin, authigenic or detrital, of silt-sized quartz (Blatt and Schultz, 1976;Milliken, 1994;Schieber et al, 2000;Williams et al, 2001) not identifiable as biogenically derived has been an issue of long-standing controversy (e.g., Milliken, 1994). Consistent with the findings of this study, silt-sized quartz verified by SEM/CL as authigenic, has been interpreted as re-crystallized siliceous planktonic organisms (Milliken, 1994;Schieber et al, 2000;Peltonen et al, 2009).…”

Molecular transport of methane, ethane and nitrogen and the influence of diffusion on the chemical and isotopic composition of natural gas accumulations

“…The results of the mineralogical and geochemical analyses are reported in Table 1. The quartz content varies between 12 and 66% and covers the entire range of mudrocks and siltstones from different sedimentological environments (Blatt & Schulz 1976). A general distinction between the sample subsets from the Norwegian shelf and the Lower Saxony Basin is not possible.…”

Dependence of quartz wettability on fluid density

“…An alpha-quartz crystal was selected as it is the most common constituent mineral found in mudrocks and sandstone storage rocks [Blatt and Schultz, 1976;Hawkes et al, 2005;Chiquet et al, 2007;Qi et al, 2009;Linstrom and Mallard, 2011;Grate et al, 2012;Wang et al, 2012;Broseta et al, 2012;Al-Yaseri et al, 2015;Sarmadivaleh et al, 2015;Gallé, 2000;Iglauer et al, 2015aIglauer et al, , 2015bAl-Yaseri et al, 2016]. The smooth sample (root-mean-square surface roughness is 56 nm ) was cleaned with acetone and then exposed to air plasma for a period of 15 min to remove surface contaminants prior to each test [Love et al, 2005;Mahadevan, 2012;Bikkina, 2012;Iglauer et al, 2014].…”