The geological structures on both banks of the Yarlung Zangbo river and the Niyang river are active,and landslides occur frequently.The landslide susceptibility assessment can effectively reduce the damage to hu-man life and property caused by disasters.This paper studies the performances of Weighted Random Forests,XGBoost and LightGBM algorithms based on Gini coefficient in landslide susceptibility.Select 188 landslide samples and 7 influencing factors,and use the 50-fold cross-validation method to train the model.During the training process,the feature selection algorithm is considered at the same time,and the Bayesian method is used to optimize the hyperparameters.Analysis of forecast results at the level.The results show that landslide is most likely to occur within the elevation of 32～1544 m and 2722～3752 m,the gradient of 30°～40°,and the dis-tance of 200 m from the fault zone,river and road.The extremely high and high landslide prone areas account for 12.14%and 12.41%respectively,and the low and extremely low landslide prone areas account for 26.47%and 29.55%respectively.More than half of the areas in Nyingchi prefecture are not prone to landslide disasters.Among all models,LightGBM model performs best,with AUC value of 0.8432,accuracy of 0.8531,and F1 score of 0.8345.Damu township and Bangxin township in Motuo county,Danniang,Lilong,Zhaxi Raodeng township in Linzhi county,Long village in Lang county,and Jiangda township in Gongbujiangda county are po-sitioned in extraordinarily high-risk areas,with a excessive likelihood of landslides.Corresponding prevention and control measures should be taken in these areas.
As a major component of the western segment of the Central Orogenic System, the East Kunlun Orogeny is characterized by the largely exposed of Triassic magmatic rocks. Based on the collected zircon U–Pb geochronological data of 96 Triassic magmatic rocks in the eastern segment of the East Kunlun orogeny, the Triassic magmatic activity is limited to 212～252 Ma, and can be further divided into three stages: early– (238～252 Ma), middle– (226～238 Ma) and late–stage (212～226 Ma). Among them, the peak magmatic period is the early stage (238～252 Ma). The statistical results of 106 Nd isotopes of Triassic magmatite in the eastern segment of the East Kunlun Orogeny show that εNd(t) values range from –9.4 to –1.7, mainly concentrated between –6.5 and –3.0, and the Nd model ages (TDM(Nd)) range from 0.72 to 1.88 Ga, mainly concentrated between 1.00 and 1.80 Ga. The statistical results of 41 Hf isotopes (whole rock, zircon) of Triassic magmatite show that εHf(t) values vary greatly (–8.4 to +12.4), mainly concentrated between –4.5 and +2.0, and the crustal model ages (TDMC(Hf)) range from 0.49 to 1.80 Ga, mainly concentrated between 1.15 and 1.55 Ga. Overall, the Triassic magmatic rocks are mainly derived from the reworking of Mesoproterozoic crustal materials, with minor involvement of juvenile crust (＜ 1.0 Ga) and Paleoproterozoic crustal materials. From the early stage (237～250 Ma) to middle stage (226～238 Ma) and then to late stage (212～226 Ma), the Nd–Hf isotopic parameters seems exhibit a certain evolutionary trend. In the early stage especially in the early Triassic, the εNd(t) values are higher, and positive εHf(t) values occupy a large proportion, indicating the presence of more juvenile material in the source. In the middle stage, lower εNd(t) values and negative εHf(t) values dominate the major proportion, and Hf model ages (TDMC(Hf)) reveals the presence of Paleoproterozoic crustal material. In the late stage, the Nd–Hf model ages reveal an increase in older crustal source components. This magmatic source evolutionary trend is consistent with the tectonic evolution setting of subduction to collision and then to post–collision in the eastern segment of the East Kunlun orogeny in Triassic period.
Aqiyin gold deposit is a newly discovered gold deposit in the western section of East Kunlun in recent years.In order to explore the genesis of the deposit, the characteristics of ore−forming fluid and the source of ore−forming materials, and establish the metallogenic model, the fluid inclusion analysis of pyrite bearing quartz fine mesh vein type gold ore in the metallogenic period was carried out, and the isotopic analysis of fluid H−O, pyrite and arsenopyrite S−Pb in quartz vein was carried out. The results show that the homogenization temperature of inclusions is 167～356.9℃, the salinity is mainly concentrated between 3.21～9.99 wt% NaCleqv, and the density is 0.65～0.94 g/cm3. The ore-forming fluid has the characteristics of medium temperature, low salinity and low density. The fluid inclusions in ore bearing quartz vein have δDv-smow values of −90.3‰～−98.7‰, δ18O of 9.4‰～11.3‰ and δ34S of 11.6 ‰～13.9 ‰. The Pb isotopes of Au−bearing pyrite vary from 38.067 to 38.651, from 15.598 to 15.681, and from 18.122 to 18.533 for 208Pb/204Pb, 207Pb/204Pb and 206Pb/204Pb ratios, respectively. The values of μ are from 9.49 to 9.61. Combined with the geological background of the Aqiyin gold deposit, the author hold that the ore–bearing hydrothermal fluid is a mixture of metamorphic water and meteoric water, sulfur is mainly derived from dynamic metamorphism, and lead shows the characteristics of lead source in orogenic belt. The genetic type is orogenic (tectonic altered rock type) gold deposit.
Ordos Basin is rich in geothermal energy at moderate and low temperature. By studying the occurrence state of geothermal resources in Yanchang oil and gas area, it is found that there are mainly two sets of thermal reservoirs: Cretaceous clastic rocks in the west and Carboniferous and Jurassic clastic rocks in the east; The thermal conductivity of rock is closely related to the degree of diagenesis and porosity of formation rock; The geothermal gradient is 2.73–3.50 ℃/100 m, which is higher in the north and lower in the south; The earth heat flow value is 57.28–86.18 mW/m2, with obvious east–west distribution characteristics. The comprehensive analysis shows that the geothermal resources in the eastern part of the region are better than those in the western part, and can be divided into three types: shallow low temperature favorable area, middle–low temperature favorable area and middle-deep medium temperature favorable area. Combined with the exploitation and utilization examples of geothermal resources in oil fields, it is considered that the transformation and utilization of abandoned Wells in these favorable areas can reduce the cost of geothermal development projects and realize the stepwise utilization of geothermal resources in geothermal power generation, industrial utilization and three–production and aquaculture, it is expected to establish an energy internet framework of "Source network load storage integration".
The subduction−collision (accretion)−post−collision stages in the ocean−continent transition process have different magmatisms, among which the slab subduction and lithosphere delamination−thinning mechanisms have received special attention. The East Kunlun orogenic belt is located in the northern part of the Qinghai−Tibet Plateau, and is an important part of the Qin−Qi−Kun central orogenic belt, which has experienced the transformation process of the Proto−Tethys Ocean and Continent in the Early Paleozoic. Based on the geochronology, whole−rock geochemistry and Sr−Nd−Hf isotope studies of the Paleozoic granites in the Dulan area, eastern Kunlun, this paper suggests that the Langmuri Middle Silurian (429±4 Ma) granites were formed in the subduction stage of the oceanic crust. It has the property of adakitic island arc magma, which is related to the partial melting of oceanic crust under the mechanism of thermal subduction. The Xiwanggou and Harizha Early Devonian (416 ~ 403 Ma) granites were formed in the post−collision stage, showing the characteristics of I−type and A−type granites, respectively, which are related to the partial melting of the young lower crust and thinning of the lithosphere. The comprehensive regional Paleozoic granite geochemical data indicate that the difference of magmatic rocks in the east and west of East Kunlun may be caused by ocean ridge subduction.
