The Serpukhovian–Bashkirian Amalgamation of Laurussia and the Siberian Continent and Implications for Assembly of Pangea

Abstract

The final assembly of Pangea is thought to be marked by the Siberia‐Laurussia amalgamation during the Late Carboniferous–Permian, but there are large uncertainties on the timing of the amalgamation in the previous paleogeographic reconstructions because there are no high‐quality Carboniferous–Permian paleomagnetic data available from the Siberian continent. The Zharma‐Saur area in the junction between the Siberia‐Laurussia amalgamation, involving the Zharma‐Saur arc on the northern margin of the Kazakhstan microcontinent, the South Chinese Altai terrane in the southern margin of the Siberian continent and the Irtysh‐Zaisan suture in between, can provide crucial geological constraints for the assembly of Pangea. In the Zharma‐Saur arc, the Tournaisian–Visean marine sequences are interbedded with thick pillow lavas, which were formed during southward subduction of the Irtysh‐Zaisan Ocean and unconformably covered by the Moscovian terrestrial bimodal volcanic associations and sedimentary successions, in which the basalts are columnar‐jointed in structure and the sandstones also contain the detritus derived from the South Chinese Altai terrane. The Serpukhovian–Bashkirian unconformity was coeval with the transition from the Tournaisian–Visean calc‐alkaline to the Moscovian–Early Permian high alkaline and bimodal volcanism. These dramatic changes in sedimentary environments, provenances and volcanism together indicate the Siberia‐Laurussia amalgamation during the Serpukhovian–Bashkirian and this event was almost simultaneous with the Laurussia‐Gondwana collision and the welding of Laurussia with the Kazakhstan microcontinent, but slightly earlier than the Laurussia‐Tarim collision. Therefore, the final assembly of Pangea could be completed in the Late Carboniferous.

Paleozoic Episodic Magmatism in Western Tianshan: Insight Into Assembling the Northeastern Pangea

“…In consequence, the southern limb of Kazakhstan experienced the early Paleozoic welding of multiple microcontinents with arcs, the late Paleozoic maturation of a united continental arc, and the late Carboniferous collision of Kazakhstan with two blocks. Combined with a recent study indicating that the collision of the northern limb of Kazakhstan with Siberia and Baltica occurred in the late Carboniferous (Y. Xu et al., 2022), we propose that Kazakhstan, acting as a bridge connecting Siberia, Baltica, and Tarim, ceased its orogenesis in the late Carboniferous.…”

“…The closure of the Uralian Ocean and the Ob-Zaisan Ocean was confirmed to have occurred in the late Carboniferous, resulting in the collision of Kazakhstan with Siberia and Baltica (Y. Xu et al, 2022) (Figure 1a). Consequently, by reconstructing the orogenic duration of the Junggar Ocean and/or the South Tianshan Ocean, it is viable to constrain the time at which Kazakhstan assembled northeastern Pangea (Figure 1b).…”

Structural and Geochronological Constraints on the Collision Between the Chinese Altai and the West Junggar in Central Asia: Implication for Deformation Response and Geodynamic Evolution of Arc‐Arc Collision in 4D

“…It is worth mentioning that Y. Xu et al. (2022) interpreted the Ob‐Zaisan Ocean to be closed before the deposition of the Late Carboniferous Qiaqihai Formation based on the occurrence of a few Early Paleozoic and Precambrian zircon grains in this formation. Alternatively, these zircon grains could recycle from the Bozshakol‐Chingiz Arc farther south as discussed above.…”

“…The southward paleocurrent orientation was locally observed in one outcrop within the Qiaqihai Formation by Y. Xu et al (2022), which indicates a minor provenance contribution possibly recycling from the Nalinkala Formation farther north (Figure 3).…”

Zircon U-Pb-Hf Isotopes and Whole-Rock Geochemistry of the “Kulumudi Formation” from the Laofengkou Area (West Junggar): Implications of the Construction of a Juvenile Arc in the Junggar–Balkhash Ocean

“…The northern WJT is composed of the Zharma-Saur arc and Boshchekul-Chingiz arc from north to south, which are separated by the EW-trending Kujibai-Hebukesaier-Hongguleleng ophiolitic mélanges [36,38]. The Zharma-Saur arc (346-321 Ma [24]) formed during the southward subduction of the Irtysh-Zaisan Ocean [2,24,39,40], while the Boshchekul-Chingiz arc is supposed to be related to the northward subduction of the Junggar-Balkhash Ocean [2,41] or the southward subduction of the Irtysh-Zaisan Ocean [42,43] during the Late Silurian-Early Devonian period.…”