Petrography, geochemistry, and geochronology of Lower Jurassic sedimentary rocks from the Northern Tianshan (West Bogda area), Northwest China: Implications for provenance and tectonic evolution

Abstract

The Bogda Mountains, situated in the southern part of the Central Asian Orogenic Belt (CAOB), is an important intraplate orogenic belt for studying the Mesozoic tectonic evolution mechanism of the CAOB. The detailed palaeogeographic evolution process of the Bogda area during Early Jurassic times remains poorly understood. The sandstone petrography, sedimentary rock geochemistry, and detrital zircon U–Pb geochronology were integrated to research the provenance of the Lower Jurassic Badaowan and Sangonghe formations clastic rocks from the northern flank of the Bogda Mountains and further constrain the palaeogeographic evolution of Bogda Mountains. The petrological and geochemical data in this study indicate that the Lower Jurassic sediments were derived from a felsic source area. Compared with the Badaowan Formation, the source rocks for the Sangonghe Formation show more mafic characteristics. U–Pb age patterns of the Badaowan Formation have multiple age groups, and most of the zircon ages are concentrated in the Carboniferous and Late Permian–Early Triassic ages. The Late Permian–Early Triassic age group disappears in the U–Pb age spectrum of the Sangonghe Formation, and every peak age is 20–50 Ma younger than those of the Badaowan Formation. Combined with the compiled sedimentary facies and paleocurrent data, the felsic‐intermediate volcanic rocks and granitoid intrusions in the Harlik arc and the east of the Jueluotage belt were the predominant sources of the Badaowan Formation, and then the dominant source changed to the bimodal volcanic rocks in the Eastern Bogda Mountains during the Sangonghe Formation deposition period. Early Mesozoic palaeogeographic evolution of the Northern Tianshan belt is speculated: (1) the paleotopography of the Jueluotage belt had a differential uplift along its strike, transforming from high in the west during Triassic times to high in the east during early Early Jurassic times and (2) the Eastern Bogda Mountains initiated uplift during late Early Jurassic times.

Tectonic Evolution of the West Bogeda: Evidences from Zircon U-Pb Geochronology and Geochemistry Proxies, NW China

“…Geochemical data suggests that it was not an island arc as proposed by Sébastien Laurent-Charvet et al [81] but could have been a continental rift during the Carboniferous and Early Permian. Geochemical investigations of volcanic rocks and turbiditic deposits as well as gravimetric and magnetic data suggest that Turpan Block and Junggar Block were separated in the end of the Early Permian due to extension and rift of the Bogeda area [56,58,82]. The rift setting was also demonstrated by a series of coarse clastic rocks with intercalations of pillow lava-vesicular basalt [57].…”

“…This could also be demonstrated by poorly-sorted and rounded conglomerate and pebbly sandstone of Late Permian age, suggesting that the deposits were near the source area without long distance of transporting (Figure 3f). [8,44]; Data for Triassic are from [56]. (c) Paleocurrent of Lower Permian [57], Middle Permian [58] and Upper Permian to Lower Triassic [15].…”

Late Mesozoic intracontinental deformation and magmatism in the Chinese Tianshan and adjacent areas, Central Asia

“…The Jurassic to Quaternary lacustrine to alluvial fan sedimentary sequences are well preserved and widely distributed along the southern and eastern margins of the Junggar Basin (Hendrix, 2000;Fang et al, 2005Fang et al, , 2006Fang et al, , 2015Charreau et al, 2009;Yang et al, 2013). Based on available detrital geochronological data, late Mesozoic (i.e., Jurassic-Cretaceous) magmatic zircons constitute a significant population of the clastic sediments from the southern and eastern Junggar Basin (Yang et al, 2013;Tang et al, 2014;Fang et al, 2015Fang et al, , 2019Ji et al, 2018Ji et al, , 2019Ji et al, , 2020. In this regard, the origin of these zircons is an essential issue in understanding late Mesozoic magmatic events in the Tianshan and Kalamaili Ranges.…”

“…The late Paleozoic magmatic rock from the South Kalamaili Range provided primary sources for the eastern Junggar Basin. At the same time, the eastern Bogda Range also was subjected to episodic uplifts (Ji et al, 2019), whereas the western Bogda area was a depositional region and received detrital materials from the latter mountain range (Fang et al, 2019;Ji et al, 2019). In addition, both northward and southward paleocurrents in Middle to Lower Jurassic sequences in the western Bogda area indicate that the North Tianshan Arc and Kalamaili Range were other vital source areas (Fang et al, 2019).…”

Detrital zircon U–Pb geochronology and geochemistry of the Riachuelos and Palma Sola beach sediments, Veracruz State, Gulf of Mexico: a new insight on palaeoenvironment

“…Zircon is a common accessory mineral in clastic sediments, which retains U-Pb isotopic signatures during erosion, recycling, and transport; differences in zircon age populations in sediments are linked to the nature and age of source terranes (Ji et al 2019;Joy et al 2019;Liu et al 2019;Chaudhuri et al 2020). Hence, detrital zircon U-Pb age geochronology is reliable to infer provenance, as well as helpful to discriminate sediments derived from various source terranes and to understand their sediment-transport pathways (An et al 2016;Madhavaraju et al 2018;Wang et al 2018a).…”