Feldspar albitization and feldspar cementation in the Albert Formation reservoir sandstones, New Brunswick, Canada

The Albitization of K-Feldspar in Organic- and Silt-Rich Fine-Grained Rocks of the Lower Cambrian Qiongzhusi Formation in the Southwestern Upper Yangtze Region, China

“…The results show that the Qiongzhusi Formation in the study area is rich in organic matter and silt, and the rock is mainly supported by silt-sized detrital grains ( Figure 2). XRD analysis shows that the minerals are mainly composed of quartz (ranging from 32.7% to 73.3%), clays (ranging from 9.7% to 37%), plagioclase (ranging from 3% to 28.3%; calcium-bearing plagioclase was not found in our test by EDS, which may indicate that all or most of the plagioclase has been albitized because of its thermodynamic instability [9]), carbonate minerals (including calcite and dolomite, ranging from 0% to 10.6%), K-feldspar (ranging from 1.2% to 7%), and pyrite (ranging from 0% to 13.9%) (Table 1, Figure 3). Clay minerals are composed of illite, illite/montmorillonite mixed-layer minerals, chlorite, and chlorite/montmorillonite mixed-layer minerals (Table 1, Figure 3).…”

“…Calcite cements in organic-rich mudstone successions have been widely regarded as the result of bacterial metabolic activity during the syngenetic period [5] (and references therein). Calcite can also result from albitization of plagioclase [9,14]. According to the observation of SEM images, we cannot determine whether the plagioclase albitization process took place because no plagioclase was found.…”

“…Ab and yellow arrow = albite, Q and red arrow = quartz, Ap = apatite. According to previous studies [9,14,16,[30][31][32][35][36][37][38] and the positional relationship between diagenetic minerals, the following diagenetic sequences can be established: framboidal pyrite, pyrite crystals (? ), and calcite cements formed during deposition and feldspar dissolution, which likely occurred during eogenesis, predates the pore-filling anhedral pyrite (Figure 5d-h) and euhedral apatite crystals in the albite grains ( Figure 5g).…”

“…This coincidence is very likely to indicate that all or most of the plagioclase and Ca 2+ had been removed from the rocks because of dissolution. Otherwise, calcite formed during deposition (cements) or from plagioclase albitization in the subsequent diagenesis stages [9,14] would be preserved well, because the pH of pore water is buffered by feldspar rather than calcite during mesogenesis [40]. Previous studies have also suggested that, in early eogenesis, strong diagenesis processes can take place because the rocks are in an open system [41].…”

Basin-scale distribution of authigenic clay minerals in the Late Maastrichtian-Early Paleocene fluvial strata of the Alberta foredeep: implications for burial depth

“…Although the process of formation of albite cements (i.e. 23 a) (Lerbekmo, 1963;Chowdhury and Noble, 1993). 23 a) (Lerbekmo, 1963;Chowdhury and Noble, 1993).…”