Tracing the provenance of volcanic ash in Permian–Triassic boundary strata, South China: Constraints from inherited and syn-depositional magmatic zircons

Provenance of the Permian–Triassic boundary volcanic ash beds in South China

“…More importantly, SCB experienced a clockwise rotation of 73.6 relative to the South Qinling Belt (SQB) during the interval of the Early Triassic to Middle Jurassic (Figure 9b) (Dong & Santosh, 2016;Zhao et al, 2020). In accordance with that, decreases in cumulative volcanic ash beds thickness and average zircon size from upper Yangtze to lower Yangtze region in South China indicate a palaeo-northward or palaeo-northeastward direction of ash transport (Zhao et al, 2019). Hence, the PTB ash beds in South China may not have originated from the convergent margin of Kunlun and Qinling in the north of South China.…”

“…According to the direction of the PTB ashes transport and a large quantity of data analysis, the basement rocks in the eastern margin of the Lanping Basin (Misha regions) consists of two tectono-stratigraphic units: the lower volcanic, and the upper Late Triassic fine-F I G U R E 9 (a) Distribution of principal continental blocks and sutures of Southeast Asia (modified after Metcalfe, 2002;Chung et al, 2005;Zheng et al, 2010;Deng et al, 2014;Liang et al, 2015;Liu et al, 2018), with Jomda-Weixi volcanic belt as the volcanic source; (b) Palaeogeography of South China at the PTB (~252 Ma) (after Shangyou, 1991;Bao, 1998;Algeo et al, 2013;Wang et al, 2019). White dashed arrow indicates the inferred direction of ash transport in South China and Indochina area (Zhao et al, 2019). J = Jiangnan Uplift, K = Khamdian Uplift, N = Nanpanjiang Basin, Y-Z = Yunkai-Zhemin Uplifts [Colour figure can be viewed at wileyonlinelibrary.com] F I G U R E 8 Discriminant diagrams of tectonic settings for zircons selected from five volcanic ash samples at Mao'ershan and Tielukou.…”

“…A felsic nature, negative Eu anomalies, most zircons of age c. 255-248 Ma, and negative ε Hf (t) values, are the common characteristics of the volcanic ash beds (Gao et al, 2013(Gao et al, , 2015He et al, 2014;Hu et al, 2018;Wang et al, 2019;Zhao, Algeo, Feng, Zi, & Xu, 2019;. Convergent continental margins in the eastern Palaeotethys region (Wang et al, 2019), or rather, the convergent margin between the South China and Indochina blocks Zhao et al, 2019), the Simao-Indochina convergent continental margin (Zheng, Mou, Zhou, et al, 2020), the Palaeotethys continental arc magmatism in the Kunlun area (He et al, 2014), or the Qinling convergent continental margin (Zheng, Mou, Zhou, et al, 2020) all might be the possible source of the ash beds, based on major and trace element contents of the ashes, U-Pb ages, trace elements, and Hf isotopes of zircons.…”

Neoarchean and Paleoproterozoic K-rich granites in the Phan Si Pan Complex, north Vietnam: Constraints on the early crustal evolution of the Yangtze Block

“…It comprises two continental blocks, the Yangtze Block and the Cathaysia Block, which amalgamated along the Jiangnan Belt in the Neoproterozoic ( Fig. 1; Cawood et al, 2013bCawood et al, , 2018bZhao et al, 2018Zhao et al, , 2019aZhang et al, 2019;Yao et al, in press). The South China Craton is separated from the North China Craton by the Qinling-Dabie-Sulu orogenic belt and from the Indochina Block by Song-Ma Suture (Fig.…”

Revisiting Glauconite Geochronology: Lessons Learned from In Situ Radiometric Dating of a Glauconite-Rich Cretaceous Shelfal Sequence

“…The physical, mineralogical, and chemical/isotopic characteristics of sedimentary sequences document the co-evolution of life and the earth system through time and space, but the precise dating and correlation of geographically distant localities are often challenging, which limits the applicability of most sedimentary archives for paleo-environmental reconstructions [1,2]. Indeed, the scarcity of precisely datable volcanic ash deposits [3] and organic-rich black shales [4] in the geological record as well as their close association with specific tectonic and environmental settings, such as active continental margins or anoxic deep-marine basins [5,6], currently limit the accurate dating of marine sediments and the establishment of high-resolution element/isotope records [7,8]. A directly dateable, widespread, and robust mineral archive, which forms at or immediately after the time of sediment deposition, is needed to resolve details on proxy signal evolution (e.g., magnesium, calcium, silicon, sulfur, or oxygen isotopes) in marine sediments throughout the rock record.…”