Abstract. The thermal state of permafrost in the present and future is fundamental to the ecosystem evolution, hydrological process, carbon release, and infrastructure integrity in cold regions. From 2011, we began to establish a permafrost monitoring network along the China-Russia crude oil pipelines (CRCOPs) route at the eastern flank of the northern Da Xing'anling Mountains in Northeast China. Based on meteorological data near the southern limit of latitudinal permafrost (SLLP), ground temperature data in 20 boreholes with the depths of 10–60.6 m, soil volumetric liquid water contents and 2-D electrical resistivity tomography (ERT) data, we compiled an integrated dataset of the ground thermal state along the CRCOPs route. Study results demonstrate that permafrost in the vicinity of SLLP has experienced marked warming (2011–2020) to climate change, manifested as the rising permafrost temperatures at depth. Local thermal disturbances triggered by the construction and operation of CRCOPs have resulted in significant permafrost warming and subsequent thawing on the right-of-way (ROW) of the pipeline. This permafrost thaw will persist, but it can be alleviated by adopting mitigative measures, such as insulation layer and thermosyphons. The in-situ observational dataset is of great value for assessing the variability of permafrost under the linear disturbances of the CRCOPs and related environmental effects, for understanding hydro-thermal-mechanical interactions between the buried pipelines and permafrost foundation soils, and for evaluating the operational and structural integrity of the pipeline systems in the future. The dataset is available at the Third Pole Environment Data Center (http://doi.org/10.11888/Cryos.tpdc.272357 (Li, 2022)).
The thermal state of permafrost in the present and future is fundamental to the ecosystem evolution, hydrological process, carbon release, and infrastructure integrity in cold regions. From 2011, we began to establish a permafrost monitoring network along the China-Russia crude oil pipelines (CRCOPs) route at the eastern flank of the northern Da Xing'anling Mountains in Northeast China. Based on meteorological data near the southern limit of latitudinal permafrost (SLLP), ground temperature data in 20 boreholes with the depths of 10–60.6 m, soil volumetric liquid water contents and 2-D electrical resistivity tomography (ERT) data, we compiled an integrated dataset of the ground thermal state along the CRCOPs route. Study results demonstrate that permafrost in the vicinity of SLLP has experienced marked warming (2011–2020) to climate change, manifested as the rising permafrost temperatures at depth. Local thermal disturbances triggered by the construction and operation of CRCOPs have resulted in significant permafrost warming and subsequent thawing on the right-of-way (ROW) of the pipeline. This permafrost thaw will persist, but it can be alleviated by adopting mitigative measures, such as insulation layer and thermosyphons. The in-situ observational dataset is of great value for assessing the variability of permafrost under the linear disturbances of the CRCOPs and related environmental effects, for understanding hydro-thermal-mechanical interactions between the buried pipelines and permafrost foundation soils, and for evaluating the operational and structural integrity of the pipeline systems in the future. The dataset is available at the Third Pole Environment Data Center (http://doi.org/10.11888/Cryos.tpdc.272357 (Li, 2022)).
Using the triaxial shear or compressive strength as a single index of the resistance of frozen soils to failure does not always meet frozen soil engineering requirements for the comprehensive evaluation of the resistance. In this study, triaxial compression experiments were carried out on undisturbed ice-rich frozen clay samples with various levels of water content under different confining pressures to study the characteristics of the failure strain energy density of the samples. The results indicate that as the confining pressure increased, the failure strain energy density first increased and then decreased. The failure strain energy density reached a maximum at a critical confining pressure of 2.00 MPa for 13.25–25.76% water content and 1.00 MPa for 26.02–45.82% water content. The failure strain energy density increased as the water content increased at low confining pressures (0.05–0.50 MPa) but then declined slightly at intermediate confining pressures (1.00–2.00 MPa). At a high confined pressure of 3.00 MPa, the failure strain energy density decreased overall as the water content increased. There were similarities and differences between the change characteristics of the compressive strength and the failure strain energy density. The failure strain energy density can be used as a supplementary reference index of the resistance of frozen soils to damage. The variation characteristics of the failure strain energy density of undisturbed frozen clay are essentially consistent with those of remolded frozen sandy soils. However, there are also clear differences between the characteristics of the failure strain energy density of these two types of frozen soil.
A new Rb–Be rare metal deposit has been discovered in the northern margin of the North China Craton in Fuxin City, western Liaoning Province, China. The Daxiyingzi Rb–Be deposit is a granitic pegmatite-type deposit and composed mainly of biotite granite, albite granite, and amazonite granitic pegmatite. Amazonite and beryl are the main ore minerals containing Rb and Be, and occur in the amazonite granitic pegmatite. We present integrated biotite 40Ar/39Ar geochronology, mineralogy, whole-rock geochemistry, and Nd–Pb isotope analyses of the Daxiyingzi ore-bearing granites to better understand their petrogenesis and geodynamic setting. Biotite separates in biotite granite and albite granite yield 40Ar/39Ar ages of 223.27 ± 2.39 and 223.37 ± 2.45 Ma, which we interpret as the metallogenic age of the deposit. The Daxiyingzi granites have high A/CNK ratios (1.01–1.11) and sufficient contents of SiO2 (74.68–79.42 wt%), total alkali (K2O + Na2O, 7.89–9.49 wt%), Li (64.0–300 ppm), Be (6.85–10.95 ppm), Nb (38.2–144 ppm), Ta (12.6–109 ppm), and Rb (60.8–1426 ppm). Depletion in Eu, Ba, Sr, P, and Ti and enrichment in Rb, Th, Nb, Ta, Nd, and Hf indicate that the granites are highly fractionated I-type granites. The Nd–Pb isotopic compositions [εNd(t) = −2.5 to −4.1; TDM2 = 1320–1202 Ma] of these granites suggest that they were derived from a single magma reservoir in an extensional orogenic setting at ∼223 Ma via high-temperature partial melting of Mesoproterozoic–Neoproterozoic basement and the injection of mantle derived magma. As a peraluminous magmatic polymetallic deposit formed in an orogenic setting, the Daxiyingzi Rb–Be deposit represents a potential new direction for prospecting along the northern margin of the North China Craton.
As a major parameter in the energy balance of the ground surface, temperature represents the level of exchange of energy and moisture between the ground and air. The Qinghai-Tibet Plateau (QTP) has the permafrost region with the highest altitude and the largest area in low–middle latitude of the world. The variation in ground surface temperature has an impact on the existence and development of the permafrost. Therefore, the analysis of the ground surface temperature in the QTP is significant to reflect the energy exchange in permafrost regions. This paper collected solar radiation data and calculated the conversion coefficient from total solar radiation to long-wave radiation of the ground surface on different underlying surfaces. The ground surface temperature was inversely calculated and modified based on the reception of solar radiation on different underlying surfaces. A simplified calculation model of ground surface temperature was built to reflect the ground surface temperature on different underlying surfaces of the QTP. The calculation results were compared with MODIS and showed good fitness, providing a systematic and reliable method for calculating the ground surface temperature on the QTP. The above model plays a significant role in the estimation of soil moisture, ground surface energy and water balance.
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