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The NE-trending Longmen Shan (LMS) thrust belt, located between the Songpan-Garze terrane and the Yangtze craton, is one of the steepest topographic margins around the Tibetan Plateau. However, the exhumation history and the fault activity of the southern segment of the LMS have remained poorly constrained, particularly in the range front, where little thermochronology ages have been reported. Herein, we report 17 apatites (U-Th)/He (AHe) ages from the southern LMS along the Qingyi River across the Dachuan–Shuangshi Fault (DSF), the Yanjing–Wulong Fault (YWF), and the Gengda–Longdong Fault (GLF). The AHe ages in the hanging-wall of the DSF are ca. 6–11 Ma, which increase to ca.19–23 Ma in the footwall of the DSF. New AHe ages reveal that exhumation rates across the DSF increased significantly from 0.05 to 0.1 km/Myr in the footwall to 0.2–0.4 km/Myr in the hanging-wall since the Late Miocene. The width of the high exhumation rate (0.4–0.6 km/Myr) belt concentrated between the DSF and the GLF, and towards DSF eastward and GLF westward, the exhumation rates decrease rapidly. The results show that continuous crustal shortening along the DSF. Our results support the upper crustal thrusting model that emphasizes crustal shortening deformation along the eastern Tibetan Plateau margin. [ABSTRACT FROM AUTHOR]

Jurassic coal-bearing strata are widely distributed in the North China Craton (NCC) and other areas of northern China. These coal-bearing strata were previously considered to be Early-Middle Jurassic in age based on plant fossils, particularly the fossil assemblage of Coniopteris-Phoenicopsis. Since coal-bearing strata are interbedded with volcanic units in the basins of the Yanshan Fold-and-Thrust Belt (YFTB), northern NCC, isotopic dating of the volcanic units can therefore provide age constraints on the coal-bearing strata and the Coniopteris‒Phoenicopsis assemblage. In this paper, we performed a systematic geological survey and present the results of zircon U-Pb dating of the volcanic units and a pluton in typical basins of the YFTB. These data, combined with the results of previous studies, indicate that the ages of the Nandaling/Xinglonggou, Haifanggou, Jiulongshan, and Tiaojishan/Lanqi formations are 180-168, 169-161, 161-157, and 161-153 Ma, respectively. The ages of the interbedded coal-bearing Yaopo and Beipiao formations are constrained to be 169-161 and 177-169 Ma, respectively. Our results demonstrate that both the coal-bearing strata and the Coniopteris‒Phoenicopsis assemblage are Middle Jurassic in age, which is younger than that previously considered. This fossil assemblage plays a critical role in age constraints on the Jurassic coal-bearing strata. The refinement of its age permits a more precise dating of the coal-bearing strata, especially in northwestern China, where datable interbedded volcanic units are lacking. Stratigraphical framework for the Jurassic strata of Yanshan region is established. The fossil assemblage of Coniopteris‒Phoenicopsis occurred in Middle Jurassic. The Jurassic coal-bearing strata in northern China are mainly Middle Jurassic. [ABSTRACT FROM AUTHOR]

Carboniferous volcanic rocks are widely distributed in the Jueluotage belt of eastern Tianshan, located in the southern Central Asian Orogenic belt. The petrogenesis and tectonic history of this region have long been a matter of debate. These volcanic rocks erupted in two episodes, with zircon U–Pb ages of ca. 336 Ma and ca. 320 Ma. The ca. 336 Ma volcanic rocks are dominated by arc-like igneous rocks. They show enrichment of light rare earth elements (LREEs) and large-ion lithophile elements (LILEs), and depletion of high field-strength elements (HFSEs) according to the N-MORB-normalized and chondrite-normalized diagrams. However, the ca. 320 Ma volcanic rocks mainly consist of MORB-like igneous rocks that show nearly flat REE patterns. They are also slightly enriched in LILEs and LREEs according to the N-MORB-normalized and chondrite-normalized diagrams. These Carboniferous volcanic rocks are geochemically similar to the back-arc basin basalt (BABB) from the Mariana and Okinawa troughs. The inherited zircon ages of volcanic rocks from the Jueluotage belt show similar trends and features to those of the Central Tianshan Block, suggesting they shared the same basement, at least before the early Carboniferous. The evolution from arc-like volcanic rocks to MORB-like volcanic rocks reflects the development of the back-arc basin in the northern Central Tianshan Block during the Carboniferous. The Palaeo-Asian oceanic plate subducted beneath the Central Tianshan Block. The position of one of the major sutures of the Palaeo-Asian Ocean should be in the north of the Jueluotage belt. The Jueluotage belt may have the same basement as the Central Tianshan Block. The back-arc basin formed above the Central Tianshan ‘whole’ Block due to the subduction-exhumation of the Palaeo-Asian oceanic plate. [ABSTRACT FROM AUTHOR]

The article presents a study on a three-point boundary value problem singular pertubation for a third-order nonlinear equation through the use of differential inequality techniques and Volterra type integral operator.