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[Objective] The study of the sedimentology, geochemistry and zircon U-Pb dating of sand-gravel sediments is highly significant for determining stratigraphic division, river system evolution, mountain tectonic uplift history and regional tectono-magmatic events. However, little is understood regarding the Hulun Buir Bayan Tara sand-gravel profile, which has restricted its stratigraphic division and in-depth understanding of the regional surface process. [Methods] For this reason, analyses of the sedimentology, heavy mineral, geochemical (macronutrients, trace and rare earth elements) and zircon U-Pb chronology were performed on this section to determine the chemical weathering characteristics and sedimentary cycles, as well as the material sources, and to explore the stratigraphic delineation attribution as well as the tectonic context and indications of regional magmatic-tectonic events. This has provided a new basis for discussion of areas of sedimentary environment and stratigraphic division and correlation. [Results] The following results were obtained. (1) The gravels are poorly sorted and rounded, and have undergone a non-weak degree of weathering, with quartzaceous material (61.2%) and tuff (34.9%) dominating the gravel composition, followed by terrigenous clastics (2.6%) and rhyolite (1.3%). The heavy mineral composition is clearly dominated by white titanium (32.54%) and ilmenite (33.01%c), followed by magnetite (12.11%), zircon-tourmaline- rutile (ZTR) (6.53%), hematite (5.47%) and anatase (1.34%), with less than 1% chlorite, rutile and garnet. There are very few, if any, unstable minerals in the sediments, indicating that they have undergone strong chemical weathering. Combined with geochemical characteristics and geomorphological evidence, the comprehensive analysis shows that the maturity of the sediment in the Bayan Tara sand-gravel profile is low, and is the product of the first weathering cycle, with moderate chemical weathering after accumulation. Comparison with the age spectrum of detrital zircons in the northern section of the Greater Khingan Mountains indicates that this is the provenance area. (2) Combined with macro- and micro-perspectives (heavy minerals and geochemical indicators, etc.), it is considered that the sediments of the Bayan Tala sand-gravel profile are alluvial-proluvial deposits formed in a warm, dry oxidizing environment. Combined with the new research findings, various methods (sedimentology, mineral petrology and geochronology) were integrated and analyzed and compared with the standard sections of the Baitushan Formation in Longjiang county and Ping'an town at the eastern foot of the Greater Khingan Mountains. This indicated that the stratigraphic units are part of the Baitushan Group. (3) The discriminant diagram of the tectonic background indicates a passive continental margin, which is consistent with the fact that the Greater Khingan Mountains are located within the tectonic plate and their structure is relatively stable. Peak U-Pb ages of clastic zircons at 100-200 Ma and 250-350 Ma record multi-stage magmatic tectonic events triggered by the closure of the Paleo-Asian Ocean and subduction and retrogression of the Paleo-Pacific Ocean in the northern segment of the Greater Khingan Mountains. [Conclusions] The study provides new evidence for division and further categorization of Quaternary strata and for reconstructing regional surface processes in the Greater Khingan Mountains during the early Pleistocene. [ABSTRACT FROM AUTHOR]

Rock weathering, an important geological process on the earth's surface, plays a key role in shaping surface morphology, providing nutrients needed by the ecosystem, and regulating the global climate. However, the regimes for controlling rock weathering in different regions are still controversial. In this respect, the heavy minerals, elements, Sr-Nd isotope, magnetic susceptibility, and chromaticity of the granite weathering profile in Harbin, a high latitude area of China, were analyzed for understanding the weathering characteristics and mechanisms of the granite weathering profile in the cold area. The results indicate that the profile underwent strengthened physical weathering (large volumes of cracks in the granite parent rock) and low–moderate chemical weathering (CIA = 56~68). However, the chemical weathering does not clearly affect the composition of the weathering products, making the weathering products a good inheritance from the parent rocks, as evidenced by the binary diagram (e.g., TiO2-Zr, and La/Sc-Co/Th) and geochemical genes (LG01 and LG03). The development process of the weathering profile has been affected by the input of external materials and biological activities, as evidenced by the Sr-Nd isotopic composition, Th/Zr values, chemical depletion fractions, ΔAl/Ti ratios, χfd%, and geochemical genes (LG03). Notably, a progressively decreasing weathering degree with a reduced depth is observed in the profile, which is likely to be related to an addition of external materials and/or effects of biological activities. In addition, the weathering regime of the profile does not vary in geology time, characterized by a kinetic-limited weathering regime with a limited supply. [ABSTRACT FROM AUTHOR]

The provenance and aeolian–fluvial interaction are essential for understanding the formation and evolution of sandy land. However, the dune sediment source in the Horqin Sandy Land (HQSL), the largest semi‐stable sandy land in China, has been debated. Here, we collected 900 coarse (i.e., >63 μm) and 750 fine (i.e., <63 μm) detrital zircon (DZ) grains from surface sand in different spatial locations for U–Pb age analysis. The visual comparison largely shows remarkably similar zircon age characteristics throughout the HQSL, and the quantitative results of the inverse Monte Carlo modelling show the primary detrital contribution of the Central Asian orogenic belt (~50.5%–61.3%) to the HQSL. In contrast, the southeast of the HQSL is characterized by the absolute dominance of the North China Craton (~75.8%). The DZ age spectra in the western and northern HQSL are extremely similar but significantly different from the south, indicating the spatial heterogeneity of the HQSL. The DZ ages are largely unaffected by particle size sorting, except in the southeastern HQSL (e.g., the dramatically different detrital contribution of the North China Craton to the fine [52.4%] and coarse fractions [75.8%]). We argue that the aeolian–fluvial interaction and the resulting sedimentary sorting and recycling are responsible for the DZ age characteristics of the HQSL. We confirm that the DZ ages of the HQSL are a faithful record of the tectonic‐magmatic events, for example, the North China Craton massif collision and collusion, the Paleo‐Asian Ocean subduction and closure, the Mongolian‐Okhotsk Ocean plate subduction and the paleo‐Pacific Ocean subduction and retreat. Finally, this study suggests that caution must be exercised in interpreting the paleoclimatic record and the aeolian deposit source investigations due to the spatial heterogeneity and the complex wind‐fluvial interactions in the HQSL. [ABSTRACT FROM AUTHOR]

The Harbin loess is located in the easternmost part of the Eurasian loess belt. It is an ideal material for reconstructing the history of aridification of the Songnen Plain and determining the eastward advance of inland Asia. However, research on aridification of the climate in the Songnen Plain is quite weak. The relationships between aridification, tectonism, climate and drainage evolution in the area are currently poorly understood. In this study, these sedimentary characteristics, grain-size, magnetic susceptibility, total organic carbon and Sr-Nd isotopes are presented, combined with grain size end-member and wavelet analysis, to examine the history and driving mechanism of climate aridification in the Songnen Plain. It was found that due to the high-latitude cold climate, deposition of the Harbin loess-paleosol sequence was significantly different from that in other regions. The gleization sedimentary environment is the main controlling factor for the low magnetic susceptibility of the paleosol layer; the appearance of the Harbin loess indicates the climate aridification of the Songnen Plain. The Songnen sandy land began to develop at about 460 ka; loess >63 im and the EM3 end member component together clearly indicate the occurrence of two aridification and sandy expansion events at 380 ka and 300 ka. The Sr and Nd isotopes and TOC indicators reveal that the aridification phenomenon continued until 180 ka, after which the climate of the Songnen Plain gradually became warmer and wetter. Global climate cooling (enlargement of ice areas), regional tectonism (uplift of the Songliao watershed), and drainage change (altered Songliao water system) were collectively responsible for aridification in the Songnen Plain. This study is of great significance to the sustainable developmentof the ecology and social economy of the Songnen Plain. [ABSTRACT FROM AUTHOR]

• The loess in NE China has a weak weathering and simple sedimentary recycling history. • The Onqin Daga, Horqin and Songnen Sandy Land are dust source of XW, KL and HS loess, respectively. • The loess accumulation in NE China is in response to the geomorphic-climatic regime in the region. The study of the loess deposits is the key for understanding the linkage between dust accumulation, tectonics, landform and climate change. However, little is known about loess accumulation in NE China. Loess deposits at the easternmost edge of the Eurasian loess belt are represented by those in the Xinwopu (XWP), Kulungou (KLG) and Huangshan (HS) sections of NE China. These loess deposits are much coarser than the loess in the southern Chinese Loess Plateau, with a sand (>63 μm) content of 6–39% in the loess deposits, and show distinct grain-size distribution with a trimodal or bimodal pattern. There are markedly different geochemical compositions between the studied loess deposits: the XWP loess is characterized by the highest content of CaO (9.81%) and MgO (2.06%), and the highest 87Sr/86Sr ratios (0.713119); the KLG loess is highlighted by the lowest content of the element Sc (7.68 ppm), V (54.1 ppm), Cr (36.4 ppm), Co (6.32 ppm), Ni (15.6 ppm), Cu (16 ppm), Zn (38.8 ppm), Ga(12.8 ppm) and ∑REE (113 ppm); the HS loess is of the lowest content of CaO (1.15%), and the highest content of the element Y (84.8 ppm), Zr (242 ppm), Nb (18.1 ppm), Hf (7.2 ppm), Ta (1.45 ppm), Th (12.7 ppm) and ∑REE (185 ppm); the XWP and KLG loess samples have similar ε Nd (0) values (−7.9), moderately higher than those (−8.9) of the HS loess. The comparison between various geochemical indicators (e.g., low values of SiO 2 /Al 2 O 3 , Zr/Sc and CIA, and high ICV values) shows that these loess deposits have undergone a different and low degree of chemical weathering with a low maturity and recycling history. Integrated methods including grain size, elemental and isotopic composition, multidimensional scaling as well as physical geographical elements (including the geomorphic and climatic features), clearly revealed the Onqin Daga Sandy Land, the Horqin Sandy Land and the Songnen Sandy Land as main dust provenances of the XWP, KLG and HS loess, respectively. [ABSTRACT FROM AUTHOR]