The Mesozoic to Cenozoic intraplate deformation of the North China Craton (NCC) is an intriguing phenomenon that led to different evolutions of the Ordos Basin and the eastern part of the NCC. Located in the central part of the NCC, the Lüliangshan is regarded as a boundary between the Ordos Basin and the eastern NCC, but the exact location of this boundary is still debated. Our field investigations suggest that the Lüliangshan anticline is a classical Mesozoic basement-involved anticline. The Lishi fault on the west of the southern part of the Lüliangshan anticline is argued to be a large fault and the east boundary of the Ordos Basin. However, our investigations show that it is not a continuous single fault but a deformation zone composed of several segments without connection along the strike. In front of the western Lüliangshan, this tectonic zone is a top-to-the-west breakthrough thrust placing the western Lüliangshan basement-involved anticline in the hanging wall with limited displacement. Field investigations show that the traditional view of the northern segment of the Lishi fault as a boundary between blocks is not clear. With a similar deformation style, the southern Lishi fault passes Lishi City, extends northeastward, connects to the Ximafang fault, and then extends to link with the Kouquan fault as the west boundary of the Datong Basin. All these faults show a map pattern of relay array. The eastern margin of the Ordos Basin was deformed by a series of thrusts that controlled the basement-involved folds. The Lüliangshan anticline and its boundary faults were formed in the Late Jurassic, and the driving force of the intraplate deformation is inferred to the westward low-angle subduction of the Paleo-Pacific plate from the east.
The cultivation of energy plants (Pennisetum hybrid) from anaerobic fermentation residues has become an important phytoremediation approach in ionic rare earth elements (REEs) tailings because of its advantages in low cost and sustainability recently. Interactions among microbial taxa contribute significantly to the soil ecological function and material cycling. However, it is not clear how the interaction pattern and key ecological clusters in microbial community respond to phytoremediation. Hence, we carried out a 2-year comparative pot experiment including control treatment (NCK), no fertilization treatment (PHCK), biogas slurry treatment (PHBS) and biogas residue treatment (PHBR). Results showed that the application of biogas residues or biogas slurry could effectively mitigate soil acidification, increase soil nutrients and promote plant growth. Without fertilization, the acidification and nutrients deficiency would be further aggravated. This effect was associated with the assembly pattern of seven ecological clusters (Modules #1-7) in co-occurrence network of rhizosphere soil, which determined by the environmental preference (e.g. pH, REEs), nutrient demand and interaction among clusters. Modules #1-2 participated in nutrient cycling in all treatments, which affected majority of clusters simultaneously. Modules #3-7 increased in specific context and exerted diversified functions (e.g. nutrient cycling, plant growth promoting and REEs bioavailability alteration). Among them, Module #4 was dominant in soil with acidity and low nutrient (NCK and PHCK), while Module #3 tended to thrive under high pH and nutrients status (PHBR). In case of the soil context with acidity and high nutrient (PHBS), Modules #5-7 occupied the main ecological niche. Application of anaerobic fermentation residues could promote remediation plant growth by replacing ecological niche of Module #4 with Modules #3 or #5. These findings provided new evidences for anaerobic fermentation residues application, and offered insights into assembly pattern of ecological clusters for guiding phytoremediation.
Abstract Strike-slip faults are widely developed throughout the Central Asian Orogenic Belt (CAOB), one of the largest Phanerozoic accretionary orogenic collages in the world, and may have played a key role in its evolution. Recent studies have shown that a large number of Late Paleozoic–Early Mesozoic ductile shear zones developed along the southern CAOB. This study reports the discovery of a NW–SE striking, approximately 500 km long and up to 2 km wide regional ductile shear zone in the southern Alxa Block, the Southern Alxa Ductile Shear Zone (SADSZ), which is located in the central part of the southern CAOB. The nearly vertical mylonitic foliation and subhorizontal stretching lineation indicate that the SADSZ is a ductile strike-slip shear zone, and various kinematic indicators indicate dextral shearing. The zircon U-Pb ages and the 40Ar/39Ar plateau ages of the muscovite and biotite indicate that the dextral ductile shearing was active during Middle Permian to Middle Triassic (ca. 269–240 Ma). The least horizontal displacement of the SADSZ is constrained between ca. 40 and 50 km. The aeromagnetic data shows that the SADSZ is in structural continuity with the coeval shear zones in the central and northern Alxa Block, and these connected shear zones form a ductile strike-slip duplex in the central part of the southern CAOB. The ductile strike-slip duplex in the Alxa Block, including the SADSZ, connected the dextral ductile shear zones in the western and eastern parts of the southern CAOB to form a 3000 km long E-W trending dextral shear zone, which developed along the southern CAOB during Late Paleozoic to Early Mesozoic. This large-scale dextral shear zone was caused by the eastward migration of the orogenic collages and blocks of the CAOB and indicates a transition from convergence to transcurrent setting of the southern CAOB during Late Paleozoic to Early Mesozoic.
The Alxa Block is a significant tectonic unit in the middle part of the southern Central Asian Orogenic Belt that was affected by multiple Paleozoic and Meso-Cenozoic deformation events. In this study, the results from detailed mapping and structural analysis coupled with new U-Pb zircon ages indicate that the northeastern Alxa Block has experienced ten deformation events since the late Paleozoic. Four separate structural domains are identified in the study area, and these domains contain intrusive and structural crosscutting relationships that allow the complex deformational history to be determined. Each deformation phase can be related to regional tectonic events associated with the consolidation of Central Asia's crust and subsequent intraplate reactivation. The first three events are tied to convergence between the Alxa Block, the North China and the Yangtze Cratons prior to and during closure of the Paleo-Asian Ocean in the Mid-Late Permian. Subsequently, sinistral displacement occurred between the Alxa Block and the North China Craton during the Triassic. Since the late Mesozoic, reactivation of the northeastern Alxa Block occurred repeatedly as an intraplate response to the subduction of the Paleo-Pacific Plate, the closure of the Mongol-Okhotsk Ocean, the collision between the Qiangtang and Lhasa blocks and the later collision between India and Eurasia. The Alxa Block provides a superb case study of how continental interior regions that evolve from plate boundaries to intraplate settings may remain susceptible to reactivation in different kinematic modes in response to distant plate margin-derived forces and internal gravitational forces that evolve through time.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)
