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Widely distributed Mid-Neoproterozoic mafic rocks of the Qilian – Qaidam – East Kunlun region record the tectonic evolution of the northeastern Tibetan Plateau. This study presents whole-rock geochemistry, zircon U–Pb geochronology and Hf isotopes for the Xialanuoer gabbros of the central South Qilian Belt (SQB). Zircon laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS) U–Pb dating indicates that the gabbros were emplaced at ca. 738 Ma, indicating they are contemporaneous with mafic magmatism elsewhere in the northeastern Tibetan Plateau. The gabbros have low SiO2, Cr and Ni contents and Mg# values, are relatively enriched in light rare-earth elements (LREEs) and depleted in high-field-strength elements (HFSEs; e.g. Nb and Ta), have no positive Zr or Hf anomalies and have relatively high Nb/Ta but low Nb/La ratios. These data indicate that the Xialanuoer gabbros formed from calc-alkaline basaltic magmas that were originally generated by the partial melting of an enriched mantle of type-I (EMI-type) enriched region of the lithospheric mantle, underwent little to no crustal contamination prior to their emplacement, and have within-plate basalt geochemical affinities. Combining these data with the presence of widespread contemporaneous continental rift-related magmatism and sedimentation in the North Qilian, Central Qilian, South Qilian, Quanji, North Qaidam and East Kunlun regions suggests that the northeastern Tibetan Plateau underwent Mid-Neoproterozoic continental rifting, which also affected other Rodinian blocks (e.g. Tarim, South China, Australia, North America and Southern Africa). [ABSTRACT FROM AUTHOR]

This study presents new integrated stratigraphic, sedimentary, and geochronological data for Silurian to Devonian sedimentary rocks in the central North Qilian Belt (NQB), NW China. These data constrain the timing and processes involved in the Palaeozoic tectonic transition from compression to extension in the NQB. This study indicates that the Angzanggou Formation probably formed in a foreland basin setting during 439–430 Ma compression associated with the closure of the North Qilian Ocean. The terrestrial sedimentary rocks overlying the formation were most likely deposited in a superimposed basin at 409–388 Ma as a result of the post‐orogenic extension of the NQB, an event that involved initial post‐orogenic extension‐related sedimentation. Silurian–Devonian sediments were derived from multiple sources, including the NQB, Central Qilian Block (CQB), and Alxa and Dunhuang blocks. Convergence between the CQB and the Alxa Block propagated westward, leading to the scissor‐like closure of the North Qilian Ocean during the Middle to Late Silurian and the oblique docking and collision of these two blocks. This is evidenced by a lack of middle–upper Silurian sedimentary rocks in the middle and eastern NQB compared with the well‐developed and well‐preserved sedimentary strata in the western segment. Devonian retrogradation and intracontinental extension‐related magmatism in the NQB also provide evidence of long‐lived tectonic extension of the lithosphere. Combining these new data with previously published data for the NQB and the wider region suggests that the Devonian terrestrial strata were deposited in a post‐orogenic extensional setting similar to that in the North Qaidam and East Kunlun belts, indicating that the Palaeozoic large‐scale tectonic transition from compression to extension in these three belts most likely started during the Early Devonian. [ABSTRACT FROM AUTHOR]

The arid northwestern China is the most vulnerable region to climate change, where the variability of seasonally extreme temperature events has profound implications for both its hydrological, ecological, and human systems. In this study, we applied 15 indicators of extreme temperature to analyze the spatial and temporal variation of its occurrence in arid northwestern China for a recent 40-year period (1979 to 2018). These extreme temperature event dynamics were then combined with atmospheric and oceanic circulation to explore their response mechanisms. Our results revealed the following: (1) Over the 40-year period, the annual average temperature in this arid zone increased at a rate of 0.4 °C/decade (p = 0.09), exceeding the national average rate (0.28 °C/decade). Apart from a few indicators, extreme temperature events (TXx, TNx, TXn and TNn) generally increased at least twice as fast as average temperature during the four seasons, especially in spring, when TNn (0.98 °C/decade) rose five times faster than did the average temperature (0.2 °C/decade). (2) Spatially, except for the Kunlun Mountains and Tarim Basin, seasonal warming occurred in most parts of the studied arid zone, being most prominent in the summer. In this season, the average number of warm nights increased (3.23 days/decade), while the average number of cold nights decreased (2.69 days/decade). (3) After the 1990s, extreme temperature events accelerated significantly. The Cold Spell Duration Indicator decreased 42% in spring and the Warm Spell Duration Indicator increased 300% in summer, from 1979 –1998 to 1999–2018, which may hasten the formation of snow and glacier melt flooding events in the spring and summer. Spatiotemporal variability in seasonally extreme temperature events was closely related to atmospheric and oceanic circulation, particularly for the AMO (r = 0.8). Altogether, these findings enhance our understanding of how to better assess shifts in extreme temperature events in response to a changing climate in arid zones. • The strongest extreme temperature events have generally increased at least twice as fast as average temperature. • Seasonal extreme temperatures accelerated in arid northwestern China, particularly for the cold and warm nights in summer. • The escalation of annual and seasonal average temperatures denotes a substantial warming trend in the region. • CSDI's decreasing in spring and WSDI's increasing in summer may hasten melting of glaciers and snow cover. • Extreme temperatures are strongly tied to circulation patterns, particularly the Atlantic Multidecadal Oscillation. [ABSTRACT FROM AUTHOR]