Integrated Provenance Analysis of a Complex Orogenic Terrane: Mesozoic Uplift of the Bogda Shan and Inception of the Turpan-Hami Basin, NW China

Abstract

We employ petrographic and advanced geochemical techniques to better document the evolution of the Turpan-Hami basin based on the unique geologic histories of the arc terranes that served as potential sources of Turpan-Hami deposits. First, a provenance study of Permian through Cretaceous sandstone of the Turpan-Hami basin reveals temporal and spatial changes in dominant source terranes that provided detritus to the basin. points to the initial uplift and unroofing of the largely andesitic Bogda Shan to the north, which first shed its sedimentary cover as it emerged to become the partition between the Turpan-Hami and southern Junggar basins.Second, geochronological, trace-element, and Sm-Nd isotopic variations among granitoids in the late Paleozoic Tian Shan orogenic belt provide a further test of Mesozoic uplift of the Bogda Shan. On the basis of previous models of crustal compositions throughout the South, Central, and North Tian Shan, Bogda Shan, and East and West Junggar terranes, we infer that isotopically enriched granitic cobbles (average ⑀Nd i ‫؍‬ Ϫ0.50, n ‫؍‬ 6) contained in Lower Triassic deposits in the north-central Turpan-Hami basin were derived from the continental crustal Central Tian Shan terrane, south of Turpan-Hami, and not from the more oceanic North Tian Shan, Bogda Shan, and East and West Junggar terranes, north of the Turpan-Hami basin. We therefore infer that the ancestral Bogda Shan had not been uplifted by the Early Triassic, and that prior to this time, a unified Junggar-Turpan-Hami basin existed during Late Permian deposition of extensive lacustrine deposits.

Late Early Permian (266 Ma) N–S compressional deformation of the Turfan basin, NW China: the cause of the change in basin pattern

“…6a); (2) alternatively, in the Gangou area, where there is an Early Paleozoic ophiolite mélange (Che et al 1994), greenish basalt, pink radiolarian chert, and even pale rodingite pebbles are common. These observations suggest that the pebbles of the conglomerates came from the Central Tianshan to the south, and this polarity is consistent with palaeocurrent studies (Greene et al 2005) and sandstone provenance analyses (Wartes et al 2002) of the Permian strata of the Turfan basin. These relations also suggest that lateral displacement along the NTF is not significant, which is consistent with our structural observations (below), but inconsistent with the conclusion of Laurent-Charvet et al (2003).…”

“…1). At present, the Turfan basin can be regarded as an intermontane basin that consists mainly of Cenozoic sediments and that started in the Jurassic (Hendrix et al 1992;Greene et al 2005;Wartes et al 2002). The widespread, although isolated, distribution of Permian organic-rich deep lake deposits (Chen et al 1985) suggests that the southern border of the unified Junger-Turfan basin was Fig.…”

“…Integrated provenance analyses (Greene et al 2005) confirm that a unified Junger-Turfan basin existed during Early Permian to Late Triassic time (Carroll et al 1990. Available stratigraphic and sedimentary data from the unified Junger-Turfan Basin Wartes et al 2002;Greene et al 2005) further demonstrate a sedimentary break between the Lower and Upper Permian, and suggest an important transition in basin pattern from extensional to flexural foreland.…”

“…Available stratigraphic and sedimentary data from the unified Junger-Turfan Basin Wartes et al 2002;Greene et al 2005) further demonstrate a sedimentary break between the Lower and Upper Permian, and suggest an important transition in basin pattern from extensional to flexural foreland. Obviously this transition implies variations in tectonic setting, the cause of which is still open (Wartes et al 2002).…”

“…In the north of the Chinese Tianshan, integrated geologic data suggest that subduction-collision processes ceased in the Late Carboniferous. Subsequently extensional basins, such as the unified Junger-Turfan, developed and overlapped the subductioncollision complexes (Allen et al 1991;Wartes et al 2002;Greene et al 2005). In the Late Carboniferous the Tarim plate collided with the Altaids from the south, resulting in a complicated deformation pattern in the Chinese Tianshan to the north (320-300 Ma, Yang et al 2007).…”