Mineralogical composition and organic matter characteristics of lacustrine fine-grained volcanic-hydrothermal sedimentary rocks: A data-driven analytics for the second member of Permian Lucaogou Formation, Santanghu Basin, NW China

Microcrystalline dolomite in a middle Permian volcanic lake: Insights on primary dolomite formation in a non‐evaporitic environment

“…It averages 200 m in thickness but locally can be up to 600 m thick. Recent studies have reported volcanic–hydrothermal sediments in the formation (Jiao et al ., 2018a,b, 2020; Liu et al ., 2020; Pan et al ., 2020; Zhang et al ., 2021). For example, tuffaceous grains are common in most lithofacies.…”

“…The predominant lithofacies is a shale, composed mainly of angular alkaline feldspars, some quartz and dolomite, and minor or no clay minerals (smectite) and are identified as tuffaceous shale. They are interpreted to be of a volcanic origin with hydrothermal alteration (Jiao et al ., 2020; Pan et al ., 2020; Zhang et al ., 2021). In summary, regional volcanism was intensive before and after the deposition of the Lucaogou Formation, but relatively weak during its deposition as a continuation of Haerjiawu and Kalagang volcanism and/or precursor to the Tiaohu volcanism.…”

“…Furthermore, volcanic and hydrothermal activities in both modern and ancient records commonly show a strong relationship with microbial blooms (Fouquet, 1999; Xie et al ., 2010; Procesi et al ., 2019), and provide the elements (for example, CO 2 , Mg 2+ and Ca 2+ ), and modify the temperature and pH values that facilitate dolomite precipitation. Recently, some organic‐rich lacustrine dolomitic shales have been interpreted as products of volcanic eruption and hydrothermal exhalation, including: (i) the middle Permian Lucaogou Formation in the Santanghu and Junggar basins of north‐west China (Liu et al ., 2012; Jiao et al ., 2018a,b, 2020; Pan et al ., 2020; Li et al ., 2021; Zhang et al ., 2021); (ii) the Cretaceous Tengger Formation in the Erlian Basin of northern China (Yang et al ., 2020, 2021); and (iii) the Cretaceous Xiagou Formation in the Jiuquan Basin of south‐west China (Zheng et al ., 2006; Wen et al ., 2013). These studies describe complex depositional and diagenetic environments affected by volcanic–hydrothermal, authigenic and biological processes, which may have promoted the formation of primary dolomitic formation related to hydrothermal activities (Zheng et al ., 2006; Liu et al ., 2012; Yang et al ., 2020).…”

Mineralogy and geochemistry of the Middle Permian Pingdiquan Formation black shales on the eastern margin of the Junggar Basin, north‐west China: Implications for palaeoenvironmental and organic matter accumulation analyses

“…The Middle Permian black shales are widely distributed in the northern Xinjiang region (including Junggar, Turpan‐Hami and Santanghu basins), and they have been proven as excellent nonmarine hydrocarbon source rocks (Carroll, Brassell, & Graham, 1992; Liu, Bechtel, Gross, et al, 2018, Liu, Bechtel, Sachsenhofer, et al, 2017; Tian, Liu, Zhang, & Cong, 2017). Several studies, including lithology, mineralogy, palaeontology, organic petrology, and organic and inorganic geochemistry, have been conducted to elucidate the palaeoenvironmental conditions and organic matter accumulation mechanism of these Middle Permian black shales (Hackley, Fishman, Wu, & Baugher, 2016; Huang et al, 2021; Tao et al, 2012; Xie et al, 2015; Zhang et al, 2021). These studies collectively suggested that warm‐humid climate, high salinity, volcanic‐hydrothermal activities, anoxic conditions, and high productivity contributed to the accumulation of organic matters during the deposition of the Middle Permian black shales in northern Xinjiang (Carroll, 1998; Ding et al, 2019; Xie et al, 2015; Zhang et al, 2021, Zhang et al, 2018).…”

“…Several studies, including lithology, mineralogy, palaeontology, organic petrology, and organic and inorganic geochemistry, have been conducted to elucidate the palaeoenvironmental conditions and organic matter accumulation mechanism of these Middle Permian black shales (Hackley, Fishman, Wu, & Baugher, 2016; Huang et al, 2021; Tao et al, 2012; Xie et al, 2015; Zhang et al, 2021). These studies collectively suggested that warm‐humid climate, high salinity, volcanic‐hydrothermal activities, anoxic conditions, and high productivity contributed to the accumulation of organic matters during the deposition of the Middle Permian black shales in northern Xinjiang (Carroll, 1998; Ding et al, 2019; Xie et al, 2015; Zhang et al, 2021, Zhang et al, 2018). However, palaeoenvironmental conditions and controlling factors of organic matter accumulation in different parts of the lacustrine basin are often highly varied (Talbot, 1988).…”