GEODYNAMICS OF THE KAZAKHSTAN OROCLINE, CENTRAL ASIA

Curved mountain belts, commonly referred as to oroclines that result from bending of quasi-linear orogenic belts, have fascinated generations of geologists. Such structures are widely recognized in modern and ancient orogens, and are fundamentally important for understanding geodynamics of convergent plate boundaries. However, how and why orogenic belts become bent has been in debate. Here we investigate the Kazakhstan Orocline in the Central Asian Orogenic Belt with an aim at understanding the geodynamics of oroclinal bending in accretionary orogens.Curved mountain belts, commonly referred as to oroclines that result from bending of quasi-linear orogenic belts, have fascinated generations of geologists. Such structures are widely recognized in modern and ancient orogens, and are fundamentally important for understanding geodynamics of convergent plate boundaries. However, how and why orogenic belts become bent has been in debate. Here we investigate the Kazakhstan Orocline in the Central Asian Orogenic Belt with an aim at understanding the geodynamics of oroclinal bending in accretionary orogens

Structural evolution of the Irtysh Shear Zone (northwestern China) and implications for the amalgamation of arc systems in the Central Asian Orogenic Belt

The NW-SE Irtysh Shear Zone is a major tectonic boundary in the Central Asian Orogenic Belt (CAOB), which supposedly records the amalgamation history between the pen-Siberian orogenic system and the Kazakhstan/south Mongolia orogenic system. However, the tectonic evolution of the Irtysh Shear Zone is not fully understood. Here we present new structural and geochronological data, which together with other constraints on the timing of deformation suggests that the Irtysh Shear Zone was subjected to three phases of deformation in the late Paleozoic. D-1 is locally recognized as folded foliations in low strain areas and as an internal fabric within garnet porphyroblasts. D-2 is represented by a shallowly dipping fabric and related similar to NW-SE stretching lineations oriented sub-parallel to the strike of the orogen. D2 foliations are folded by similar to NW-SE folds (F-3) that are bounded by a series of mylonite zones with evidence for sinistral/reverse kinematics. These fold and shear structures are kinematically compatible, and thus interpreted to result from a transpressional deformation phase (D-3). Two samples of mica schists yielded youngest detrital zircon peaks at similar to 322 Ma, placing a maximum constraint on the timing of D-1-D-3 deformation. A similar to NE-SW granitic dyke swarm (similar to 252 Ma) crosscuts D-3 fold structures and mylonitic fabrics in the central part of the shear zone, but is displaced by a mylonite zone that represents the southern boundary of the Irtysh Shear Zone. This observation indicates that the major phase of D-3 transpressional deformation took place prior to similar to 252 Ma, although later phases of reactivation in the Mesozoic and Cenozoic are likely. The late Paleozoic deformation (D-1-D-3 at similar to 322-252 Ma) overlaps in time with the collision between the Chinese Altai and the intra-oceanic arc system of the East Junggar. We therefore interpret that three episodes of late Paleozoic deformation represent orogenic thickening (D-1), collapse (D-2), and transpressional deformation (D3) during the convergence between the Chinese Altai and the East Junggar. On a larger scale, late Paleozoic sinistral shearing (D3), together with dextral shearing farther south, accommodated the eastward migration of internal segments of the western CAOB, possibly associated with the amalgamation of multiple arc systems and continental blocks during the late Paleozoic. (C) 2015 Elsevier Ltd. All rights reserved

SAR2EO: A High-resolution Image Translation Framework with Denoising Enhancement

Synthetic Aperture Radar (SAR) to electro-optical (EO) image translation is a fundamental task in remote sensing that can enrich the dataset by fusing information from different sources. Recently, many methods have been proposed to tackle this task, but they are still difficult to complete the conversion from low-resolution images to high-resolution images. Thus, we propose a framework, SAR2EO, aiming at addressing this challenge. Firstly, to generate high-quality EO images, we adopt the coarse-to-fine generator, multi-scale discriminators, and improved adversarial loss in the pix2pixHD model to increase the synthesis quality. Secondly, we introduce a denoising module to remove the noise in SAR images, which helps to suppress the noise while preserving the structural information of the images. To validate the effectiveness of the proposed framework, we conduct experiments on the dataset of the Multi-modal Aerial View Imagery Challenge (MAVIC), which consists of large-scale SAR and EO image pairs. The experimental results demonstrate the superiority of our proposed framework, and we win the first place in the MAVIC held in CVPR PBVS 2023

Magmatism and tectonic evolution of the Chinese Altai, NW China: insights from the paleozoic mafic andfelsic intrusions

published_or_final_versionEarth SciencesDoctoralDoctor of Philosoph

Accretionary and collisional orogenesis in the south domain of the western Central Asian Orogenic Belt (CAOB) Preface

The Central Asian Orogenic Belt (CAOB) was the result of long-lived multi-stage tectonic evolution, including Proterozoic to Paleozoic accretion and collision, Mesozoic intracontinental modification, and Cenozoic rapid deformation and uplift. The accretionary and collisional orogenesis of its early history generated a huge orogenic collage consisting of diverse tectonic units including island arcs, ophiolites, accretionary prisms, seamounts, oceanic plateaus and micro-continents. These incorporated orogenic components preserved valuable detailed information on orogenic process and continental crust growth, which make the CAOB a key region to understanding of continental evolution, mantle-crust interaction and associated mineralization. The western CAOB refers to the west region in North Xinjiang of China and circum-Balkash of Kazakhstan, with occurrences of the spectacular Kazakhstan orocline and its surrounding mountain belts. Because orogenic fabrics of this part mostly preserve their original features caused by the interactions among the southern Siberian active margin in the north and the Tarim Craton in the south, the western CAOB can be regarded as an ideal region to study the processes of the accretionary and collisional orogenesis and associated mineralization. Since a large number of researchers have been working on this region, research advances bloom strikingly in a short-time period. Therefore, we, in this special issue, focus on these new study advances on the south domain of the western CAOB, including the Kazakhstan collage system, Tianshan orogenic belt and Beishan region, and it is anticipated that this issue can draw more attention from the international research groups to be interested in the studies on orogenesis of the CAOB

Transpressional deformation, strain partitioning and fold superimposition in the southern Chinese Altai, Central Asian Orogenic Belt

Transpressional deformation has played an important role in the late Paleozoic evolution of the western Central Asian Orogenic Belt (CAOB), and understanding the structural evolution of such transpressional zones is crucial for tectonic reconstructions. Here we focus on the transpressional Irtysh Shear Zone with an aim at understanding amalgamation processes between the Chinese Altai and the West/East Junggar. We mapped macroscopic fold structures in the southern Chinese Altai and analyzed their relationships with the development of the adjacent Irtysh Shear Zone. Structural observations from these macroscopic folds show evidence for four generations of folding and associated fabrics. The earlier fabric (S-1), is locally recognized in low strain areas, and is commonly isoclinally folded by F-2 folds that have an axial plane orientation parallel to the dominant fabric (S-2). S-2 is associated with a shallowly plunging stretching lineation (L-2), and defines similar to NW-SE tight-close upright macroscopic folds (F-3) with the doubly plunging geometry. F-3 folds are superimposed by similar to NNW-SSE gentle F-4 folds. The F-3 and F-4 folds are kinematically compatible with sinistral transpressional deformation along the Irtysh Shear Zone and may represent strain partitioning during deformation. The sub-parallelism of F-3 fold axis with the Irtysh Shear Zone may have resulted from strain partitioning associated with simple shear deformation along narrow mylonite zones and pure shear-dominant deformation (F-3) in fold zones. The strain partitioning may have become less efficient in the later stage of transpressional deformation, so that a fraction of trans current components was partitioned into F-4 folds. (C) 2016 Elsevier Ltd. All rights reserved

Changes of provenance of Permian and Triassic sedimentary rocks from the Ailaoshan suture zone (SW China) with implications for the closure of the eastern Paleotethys

Tectonic evolution of the Ailaoshan Ocean (eastern Paleotethys), especially on the timing of opening and closure, has long been debated. Published works on the Paleotethyan evolution were mainly dedicated to structural tectonics and magmatic and metamorphic rocks, whereas studies on sediment chemistry are rare. In this study, we present new chemical data on the Permian and Middle-Upper Triassic elastic sedimentary rocks from the Ailaoshan suture zone in southwestern Yunnan (SW China). Compared with the Post-Archean Australian Shale (PAAS) and the average upper continental crust, these Ailaoshan elastic rocks are generally depleted in LILEs (e.g. K and Rb) and HFSEs (e.g. Nb and Zr), and show varying LREE/HREE enrichments ((La/Yb)(N) = 1.32-11.86), flat HREE pattern and negative Eu anomalies (Eu/Eu* = 0.3-0.9). In spite of these similarities, the Permian samples have relatively low SiO2 (avg. 71.4 wt%) contents, K2O/Na2O (avg. 0.65) and Eu/Eu* (avg. 0.65) ratios, but high Al2O3 (avg. 14.1 wt%), TiO2 (avg. 0.60 wt%), (Fe2OT 3 + MgO) (avg. 6.96 wt%) contents, Al2O3/SiO2 (avg. 0.20) and (La/Yb)(N) (avg. 6.9) ratios, similar to greywackes from typical continental arcs. In contrast, the Upper Triassic samples have relatively high SiO2 (avg. 81.9 wt%) contents, K2O/Na2O (avg. 8.48) and La-N/Yb-N (avg. 9.74) ratios, but low Al2O3 (avg. 9.98 wt%), TiO2 (avg. 0.54 wt%), (Fe2OT 3 + MgO) (avg. 5.26 wt%) contents, Al2O3/SiO2 (avg. 0.12) and Eu/Eu* (avg. 0.64) ratios, similar to greywackes from typical passive continental margin. Moreover, the Permian samples have lower CIA values (Chemical Index of Alteration: 47-74, avg. 59) but higher ICV values (Index of Compositional Variability: 0.70-1.29, avg. 1.03) than those of PAAS, indicating relatively weak chemical weathering of the source rocks with low sediment maturity. In contrast, the Upper Triassic samples have relatively high CIA (77-84, avg. 80) but low ICV values (0.52-1.12, avg. 0.79), suggesting intense chemical weathering of the source rocks with high sediment maturity. The wide range of CIA (52-84, avg. 69) and ICV (0.50-1.14, avg. 0.88) values for the Middle Triassic samples suggest multiple detrital sources with varying degree of chemical weathering and diverse sediment maturity, as also supported by their wide range of detrital contents and chemical compositions. Based on the distinct chemical contrast between the Permian and Triassic sedimentary rocks, we infer that a significant change in detrital provenance and depositional setting may have occurred across the Middle and Late Triassic boundary, which was likely caused by the closure of the Ailaoshan Ocean

Petrogenesis and tectonic implications of early Devonian mafic dike-granite association in the northern West Junggar, NW China

Mafic dike-granite associations are common in extensional tectonic settings and important and pivotal in reconstructing crust-mantle geodynamic processes. We report results of zircon U-Pb and hornblende Ar-40-Ar-39 ages and major-element and trace-element data for mafic dike-granite association from the northern West Junggar, in order to constrain their ages, petrogenesis, and geodynamic process. The mafic dike-granite association was emplaced in the early Devonian. The Xiemisitai monzogranites have high SiO2 contents and low MgO, Cr, and Ni concentrations, suggesting that they were mainly derived from crustal sources and were probably generated by partial melt of the juvenile mid-lower crust. The mafic dikes have low Mg-# and Cr and Ni abundances, suggesting that they have experienced significant fractional crystallization. The Xiemisitai mafic dikes contain hornblende and biotite and display negative Nb-Ta-Ti anomalies, enrichment of LREEs and LILEs, and depletion of HREEs and HFSEs, consistent with an origin from a lithospheric mantle metasomatized by subducted slab-derived fluids. In addition, the Xiemisitai mafic dikes are plotted within melting trends with little to no garnet (Cpx: Grt=6:1) in their source. The La/Yb versus Tb/Yb plot also indicates the presence of less than 1% residual garnet in the source region for the Xiemisitai mafic dikes. Therefore, it can be inferred that the Xiemisitai mafic dikes were generated at a correspondingly shallow depth, mostly within the spinel stability field. The Xiemisitai mafic dikes were most probably generated by the partial melting of the metasomatized lithospheric mantle at relatively shallow depths (<80km). The Xiemisitai mafic dike-granite association could have been triggered by asthenospheric upwelling as a result of the rollback of the subducted Irtysh-Zaysan oceanic lithosphere