Geochemical characteristics, depositional environment, and provenance attitude of the Middle Jurassic Yangye Formation lacustrine mudstones in Kashi Sag, south‐western Tarim Basin

Abstract

Middle Jurassic mudstones from the Yangye Formation are widely exposed in the Kashi Sag and regarded as significant potential source rocks. Geochemical characteristics of mudstones in the Keziletao Depression have been analysed to decipher their source‐area weathering, provenance, tectonic setting, and depositional environment that have received significantly little attention. Mudstones are characterized by high Ca, U, Th, and REE contents when compared to those of PAAS. Their total REE abundances range from 155.2 to 234.2 ppm, with the enrichment of LREEs and distinct negative Eu anomalies, implying a principal felsic provenance. Various indicators (e.g., CIA, Th/Sc, ICV, and Rb/Sr) and A‐CN‐K ternary diagram suggest parental rocks experienced a moderate to intense chemical weathering degree and simple recycling and sorting. Furthermore, paleoenvironmental indexes (e.g., B, “S,” Sr/Ba, “C,” Sr/Cu, and V/(V + Ni)) indicate that they were likely deposited in a suboxic to anoxic freshwater setting, with semi‐arid to semi‐humid paleoclimatic conditions during the deposition of Yangye Formation. The geochemical data also demonstrate that the provenances were derived predominantly from the unroofing of felsic rocks with a minor intermediate supply. These parental rocks were commonly formed in the continental island arc, active continental margin, and/or collision tectonic settings. The results of this study, combined with published data, suggest the West Kunlun Orogen and thrusting zone to the west and south‐west of the basin were probably arrested to provide substantial detritus for sediments, stimulating a better understanding for the formation mechanism of the Yangye Formation sediments (especially for potential source rocks) in the Kashi Sag.

Geochemical characteristics, palaeoenvironment, and provenance of marine mudstone in Shanxi Formation of Huaibei Coalfield, southern North China Plate

“…However, compared with Lower Silurian black shales and Mississippian Barnett Shale (Figure 4), marine mudstones in the southern North China Plate have a lower carbonate content (Loucks & Ruppel, 2007;Tian et al, 2013). (Wang, He, et al, 2020;Xie, Cai, Dong, Zhai, & Li, 2019). Fe content is lower than Si and Al, with an average value of 5.54%, mainly in the form of haematite and siderite.…”

“…For example, the solubility and valence state of some trace elements change with the redox state of the depositional environment (i.e., U, V, Mo, Cr, Co), and are referred to as the redox sensitive elements (RSE) (Fonseca, Mendonça Filho, Lézin, de Oliveira, & Duarte, 2020;Tribovillard, Algeo, Lyons, & Riboulleau, 2006). Therefore, we can use the geochemical indicators such as the correlation and ratio of major and trace elements, as well as the triangulation diagram, element distribution patterns and other geochemical methods to complete the inversion of its depositional environment and provide evidence for further research (Awan et al, 2020;Bhatia, 1983;El-Bialy, 2013;Jones & Manning, 1994;Wang, Chen, Liang, Chang, & Deng, 2020;Wang, He, Zhu, & Ding, 2020).…”

Response of a continental fault basin to the global OAE1a during the Aptian: Hongmiaozi Basin, Northeast China

“…Trace element data of the Xiahuapidianzi Formation samples and relevant ratios (e.g., V/(V + Ni), Cu/Zn, and Sr/Ba) are list in Table 3 . These elements (e.g., V, Sr, Ba, B, Rb, and Ni) and their ratios are always useful in various studies to decipher the paleoclimate, paleosalinity, and redox conditions during the deposition of sedimentary rocks in basins 14 , 29 – 33 . Terrigenous debris are common components in sediments or sedimentary rocks.…”

“…This study aims to understand the influence of OAE1a on the terrestrial sediment and might also provide a reference for the impact of current lakes on the greenhouse effect through comprehensive indices (e.g., stable isotope geochemistry, element geochemistry, organic geochemistry, etc.). Organic stable carbon isotope and pyrite sulfur isotope methods are widely used for explaining environmental changes (including climate change), bottom-water anoxia and sedimentary environment conditions 1 , 12 , 13 , and trace elements are essential in deciphering the depositional environment 14 .…”

Organic-Inorganic Geochemical Characteristics of the Upper Permian Pusige Formation in a High-Saline Lake Basin, Tarim Basin: Implications for Provenance, Paleoenvironments, and Organic Matter Enrichment

“…Previous studies have documented that Fe, Mn, V, Cr, Co, and Ni are relatively enriched under the humid condi-tions, whereas Ca, K, Sr, Na, Mg, and Ba, being associated with saline mineral precipitates, are comparatively concentrated under arid climatic conditions [67][68][69][70]. Taken into consideration of their geochemical behaviors, the C-value was then proposed as an indicator for inferring the paleoclimate [7,67,71]. The C-value was defined as follows:…”