As one of the largest Phanerozoic orogens in the world,the Central Asian Orogenic Belt (CAOB) is a natural laboratory for studies of continental dynamics and metallogenesis.This paper summarizes the research progresses of the accretionary processes and metallogenesis of the CAOB since the Peopled Republic of China was founded,and puts forward the prospect for future research.During the early period (1950s-1970s),several geological theories were applied to explain the geological evolution of Central Asia.In the early period of China's reform and opening-up,the plate tectonics theory was applied to explain the evolution of the northern Xinjiang and Xingmeng regions,and the opinion of subduction-collision between Siberian Kazakhstan and China-North Korea-Tarim plates was proposed.The idea of the Solonker-Yanbian suture zone was established.In the 1990s,the study of the CAOB entered a period of rapid development.One school of scholars including geologists from the former Soviet Union proposed a multi-block collision model for the assemblage of the CAOB.In contrast,another school of scholars,led by a Turkish geologist,Celal Sengor,proposed that the Altaids was formed through the growth and strike-slip duplicates of a single island arc,and pointed out that the Altaids is a special type of collisional orogen.During this period,Chinese geologists carried out a lot of pioneering researches on ophiolites and high-pressure metamorphic rocks in northern China,and confirmed the main suture zones accordingly.In 1999,the concept of"Central Asian metallogenic domain"was proposed,and it became one of the three major metallogenic domains in the world.Since the 21st century,given the importance for understanding continental accretion and metallogenic mechanism,the CAOB has become the international academic forefront.China has laid out a series of scientific research projects in Central Asia.A large number of important scientific research achievements have been spawned,including the tectonic attribution of micro-continents,timing and tectonic settings of ophiolites,magmatic arcs,identification and anatomy of accretionary wedges,regional metamorphism-deformation,(ultra)high-pressure metamorphism,ridge subduction plume-plate interaction archipelagic paleogeography and spatio-temporal framework of multiple accretionary orogeny,continental growth accretionary metallogenesis,structural superposition and transformation etc.These achievements have made important international influences.There still exist the following aspects that need further study:(1) Early evolution history and subduction initiation of the Paleo-Asian Ocean;(2) The accretionary mechanism of the extroversion Paleo-Asian Ocean;(3) The properties of the mantle of the Paleo-Asian Ocean and their spatiotemporal distribution;(4) The interaction between the Paleo-Asian Ocean and the Tethys Ocean;(5) Phanerozoic continental growth mechanism and its global comparison;(6) Accretionary metallogenic mechanism of the Central Asian metallogenic domain;and (7) Continental transformation mechanism. 相似文献
The failures of surface vertical wells (SVWs) for methane extraction during mining are known to be the main causes of the shortening of the highly efficient drainage periods of the SVWs. Therefore, in order to improve the stability of the SVWs, it is of great significance to accurately investigate the failure characteristics when SVWs are severely destroyed and can no longer extract methane. In this research, a physical simulation experiment was carried out for the purpose of investigating the most possible failure periods, as well as the highest possible failure locations and failure modes of SVWs. This study’s results showed that the displacements of the SVW were constantly changing under the influences of mining stress. After the mine working faces had past the SVWs by more than 157 m, the total displacements reached the maximum, and the SVWs were in the most possible failure periods. During those periods, failure positions of the SVWs are prone to occur at the interfaces between the hard and soft strata; within the thick rock layers; and within the thick-thin-thick strata combination. Among these, the SVWs may suffer from shear slippage at the interface of the hard-soft combined rock layers with relatively large thickness differences; the SVWs may suffer from horizontal shear at the interfaces of the hard-soft combined rock layers with small thickness differences; the SVWs within the thick rock layers may become destroyed by shear slippage actions; and the SVWs in the thick-thin-thick combined rock layers may become distorted by shearing at the interface between the rock layers or blocking within the intermediate thin rock. The results of this research study were verified through the field tests which were conducted in China’s Sihe Coal Mine.
Coronal Mass Ejections (CMEs) are important sources of Solar Proton Events (SPEs). Their speeds and source region locations have significant effects on the occurrence of SPEs. In this paper, all the halo CMEs observed in recent five years are statistically analyzed. The results show that the fast halo CMEs with small angular distances are more likely to produce SPEs, especially, those halo CMEs with a speed greater than 1200 km s?1 and an angular distance less than 60°. Three fast halo CMEs with no SPEs caused are elaborately studied. The results show that the ejection direction of the CME's main body and the variation of interplanetary magnetic field also have important impacts on the occurrence of SPEs. Consequently, in the practical daily space environment forecasts, an accurate forecast for SPEs must take various factors into account, such as the eruption speed, source region location, the main-body ejection direction of CMEs, and the interplanetary environment, etc. 相似文献