Abstract Based on the CCD images, IIM data and DEM data of China's lunar exploration project (Chang'E‐I) and related processed and analytic results, an integrated study of regional geology of Sinus Iridum and its adjacent area was conducted, and a series of relevant researches and analyses were carried out, including analysis of impact craters and their extrusive and accumulative materials, division of stratigraphic and tectonic units and classification of rock types, integrated analysis of chronology and lunar evolution history. In consideration of crater's shape features, quantity and preserving status of filling materials, the lunar impact craters can be divided into 7 types and 11 subtypes, and the accumulative materials of craters are divided into 6 types and 9 accumulative groups. According to the content and distribution of TiO 2 and image characteristics, the basalts are divided into high‐TiO 2 , medium‐TiO 2 and low‐TiO 2 basalts. Discussion was made on division of tectonic units and evolution features in the study area. The geological map of the Sinus Iridum Quadrangle (LQ‐4) at a scale of 1:2.5 M was preliminarily compiled with the ArcGIS system, and the spatial database of the map was established. Related technical specification, procedure and method for lunar geological mapping have been worked out, so as to lay a foundation for the forthcoming geological mapping of the global Moon in China by using the data of Chang'E‐II and also for comprehensive study and geological mapping of other celestial bodies in the future.
Geological Map Database Management System has been developed based on component GIS in this paper. It integrated the DEM and the National basic geological map. It can realize real-time transformation of two-dimensional plane and three- dimensional display on the geological map, extraction data by custom area, and geological analysis of slope, aspect, section lines. It can improve the map's information, administrative levels and accuracy, and also widely used in geological prospecting, water, earthquake, engineering geology, etc. Therefore, the developed system will provide a scientific basis in the respect of optimizing geological environment, the early warning of geological disasters zoning, utilization of underground space and planning for urban construction and development.
Abstract The migration, accumulation and dispersion of elements caused by tectonic dynamics have always been a focus of attention, and become the basis of tectono‐geochemistry. However, the effects of faulting, especially strike‐slip faulting, on the adjustment of geochemical element distribution, are still not clear. In this paper, we select the West Junggar Orogenic Belt (WJOB), NW China, as a case study to test the migration behavior of elements under tectonic dynamics. The WJOB is dominated by NE‐trending large‐scale sinistral strike‐slip faults such as the Darabut Fault, the Mayile Fault, and the Baerluke Fault, which formed during the intracontinental adjustment under N–S compression during ocean‐continental conversion in the Late Paleozoic. Geochemical maps of 13 elements, Al, W, Sn, Mo, Cu, Pb, Zn, As, Sb, Hg, Fe, Ni, and Au, are analyzed for the effects of faulting and folding on element distribution at the regional scale. The results show that the element distribution in the WJOB is controlled mainly by two mechanisms during tectonic deformation: first is the material transporting mechanism, where the movement of geological units is consistent with the direction of tectonic movement; second is the diffusion mechanism, especially by tectonic pressure dissolution driven by tectonic dynamics, where the migration of elements is approximately perpendicular or opposite to the direction of tectonic movement. We conclude that the adjustment of element distributions has been determined by the combined actions of transporting and diffusion mechanisms, and that the diffusion mechanism plays an important role in the formation of geochemical Au blocks in the WJOB.
The West Junggar of the western Central Asian Orogenic Belt is one of the typical regions in the term of ocean subduction, contraction and continental growth in the Late Paleozoic. However, it is still controversial on the exact time of ocean‐continent transition so far. This study investigates rhyolites with columnar joint in the West Junggar for the first time. Based on zircon U‐Pb dating, we determined that the ages of the newly‐discovered rhyolites are between 303.6 and 294.5 Ma, belonging to Late Carboniferous–Early Permian, which is the oldest rhyolite with columnar joint preserved in the world at present. Geochemical results show that the characteristics of the major element compositions include a high content of SiO 2 (75.78–79.20 wt%) and a moderate content of Al 2 O 3 (12.21–13.19 wt%). The total alkali content (K 2 O + Na 2 O) is 6.14–8.05 wt%, among which K 2 O is 2.09–4.72 wt% and the rate of K 2 O/Na 2 O is 0.38–3.05. Over‐based minerals such as Ne, Lc, and Ac do not appear. The contents of TiO 2 (0.09–0.24 wt%), CaO (0.15–0.99 wt%) and MgO (0.06–0.18 wt%) are low. A/CNK=0.91–1.68, A/NK=1.06–1.76, and as such, these are associated with the quasi‐aluminum‐weak peraluminous high potassium calc‐alkaline and some calc‐alkaline magma series. These rhyolites show a significant negative Eu anomaly with relative enrichment of LREE and LILE (Rb, Ba, Th, U, K) and depletion of Sr, HREE and HFSE (Nb, Ta, Ti, P). These rhyolites also have the characteristics of an A2‐type granite, similar to the Miaoergou batholith, which indicates they both were affected by post‐orogenic extension. Combining petrological, zircon U‐Pb dating and geochemical characteristics of the rhyolites, we conclude that the specific time of ocean‐continent transition of the West Junggar is the Late Carboniferous–Early Permian.
Abstract The continental Asia is mainly composed of three major tectonic regimes, the Tethys, Paleo Asian Ocean, and West Pacific. It underwent multi‐stage plate convergences, ocean‐continent transformations, and subductions, collisions and/or collages, and post collisional (orogenic) extensions in Phanerozoic. Tectonic evolution of the Asia brings up a unique fault system and tectonic geomorphological features in the mainland China. Also, it provides a geodynamic background for the formation and evolution of metallogeneses and mineral systems, resulting in nonuniform distribution of tectono‐metallogenic systems and metallogenic belts. The spatiotemporal distribution of mineral deposits in China and adjacent areas exhibits periodic variation under controlling of the full life Wilson cycle and tectonic evolution, forming the plate convergence‐related mineral system in East Asia. Porphyry Cu deposits are mainly related to compressional systems in Paleozoic and early Mesozoic, and more closely related to post‐collision extensional settings in late Mesozoic and Cenozoic. Orogenic Au deposits mainly formed in post‐orogeny extensional setting. Alkaline rock related rare earth element deposits formed mainly at margins of the North China and Yangtze cratons. Granite‐pegmatite Li and other rare metal deposits formed mainly in early Mesozoic, related to Indosinian post‐orogeny extension. Tectono‐metallogenic systems provide important basis for the prospecting of mineral resources.
Abstract This is a review of the formation and tectonic evolution of the continental Asia in Phanerozoic. The continental Asia has formed on the bases of some pre‐Cambrian cratons, such as the Siberia, India, Arabia, North China, Tarim, South China, and Indochina, through multi‐stage plate convergence and collisional collages in Phanerozoic. The north‐central Asia had experienced the expansion and subduction of the Paleo‐Asian Ocean (PAO) in the early Paleozoic and the closure of the PAO in the late Paleozoic and early Mesozoic, forming the PAO regime and Central Asian orogenic belt (CAOB). In the core of the CAOB, the Mongol‐Okhotsk Ocean (MOO) opened with limited expansion in the Early Permian and finally closed in the Late Jurassic–Early Cretaceous. The south‐central Asia had experienced mainly multi‐stage oceanic opening, subduction and collision evolution in the Tethys Ocean, forming the Tethys regime and Himalaya‐Tibetan orogenic belt. In eastern Asia, the plate subduction and continental margin orogeny on western margin of the Pacific Ocean, forms the West Pacific regime and West Pacific orogenic belt. The PAO, Tethys, and West Pacific regimes, together with Precambrian cratons among or surrounding them, made up the major tectonic and dynamic systems of the continental Asia in Phanerozoic. Major tectonic events, such as the Early Paleozoic Qilian, Uralian, and Dunhuang orogeneses, the late Paleozoic East Junggar, Tianshan and West Junggar orogeneses, the Middle to Late Permian Ailaoshan orogeny and North‐South Lhasa collision, the early Mesozoic Indochina‐South China and North‐South China collisions, the late Mesozoic Mongolia‐Okhotsk orogeny, Lhasa‐Qiangtang collision, and intra‐continental Yanshanian orogeny, and the Cenozoic Indo‐Asian, Arab‐Asian, and West Pacific margin collisions, constrained the formation and evolution of the continental Asia. The complex dynamic systems have left large number of deformation features, such as large‐scale strike‐slip faults, thrust‐fold systems and extensional detachments on the continental Asia. Based on past tectonics, a future supercontinent, the Ameurasia, is prospected for the development of the Asia in ca. 250 Myr.
Mountainous areas have become among the most developed areas of geological hazards due to special geological environmental conditions and intensive human engineering activities. Geological hazards are a main threat to urbanization, rural revitalization, and new rural construction in complex mountainous areas. It is of great strategic significance to conduct large-scale geological hazard investigation and risk assessment in urban areas, control the risk of geological hazards at the source and propose risk control measures. In this paper, we established the technical methods of geologic hazard risk assessment and control in complex mountain towns by taking Longlin Town in the mountainous region of Gansu Longnan, China as the study area, with the Quanjia bay debris flows and Panping Village landslides as the typical pilot investigation and assessment. The methods consist of six stages—risk identification, hazard disaster model investigation, risk analysis, vulnerability assessment, risk evaluation and risk management and control measures and proposals. On this basis, the results of geological hazards with different precipitation frequencies (5%, 2%, 1%) are presented. The results show that 75.23% of the regions remained at low risk levels; 24.38% of the regions increased a risk level with decreasing precipitation frequency, and 0.39% of the regions remained at extremely high risk levels under different precipitation frequency conditions. For the Quanjia bay debris flows and Panping Village landslides case, we discussed the geological hazards risk source control contents, management and control technologies, engineering and non-engineering measures of disaster prevention and control for urban disasters and specific disaster areas. This research can provide technical support and reference for disaster prevention and mitigation, and territorial spatial planning.
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