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11.
The West Kunlun orogenic belt is located at the conjunction of the paleo-Asian tectonic system and the Tethys tectonic system.
Petrological and mineralogical studies of the Early Cambrian metamorphic surface crust in this region have shown that in case
the metamorphism reached low-temperature granulate facies, the typical mineral assemblage is biotite-garnet-silimanite-K feldspar-plagioclase-quartz.
The peak metamorphic temperatures are within the range of 720–740°C and the pressure is 0.6 GPa ±. Three types of metamorphic
zircon have been detected in the metamorphic rocks: the complex inclusion-bearing type ; the early relic zircon inclusion-bearing
type; and the inclusion-free type. SHRIMP age determination of these three types of metamorphic zircon have revealed that
these zircons were formed principally during 400–460 Ma, indicating that pre-Cambrian metamorphic surface crust rocks underwent
low-temperature granulite facies metamorphism during the Caledonian. In combination with the geological characteristics of
this region, it is considered that when the oceanic basin was closed, there occurred intense intracontinental subduction (type
A), bringing part of the Early Cambrian metamorphic basement in this region downwards to the lower crust. Meanwhile, there
were accompanied with tectonic deformation at deep levels and medium- to high-grade metamorphism. This study provided important
chronological and mineralogical evidence for the exploration of the evolutionary mechanism and process of the West Kunlun
Early Paleozoic.
Part of the results from the research project “ Research on the West Kunlun pre-Cambrian tectonic events” under the program
“ Research on the important geological problems of China’ s pre-Cambrian” (No. 200113900070) sponsored by the China National
Geological Surveying Bureau. 相似文献
12.
Zhao Kang Zhou Yun Yu Xiang Yan Yajing Song Yufeng Wang Junqiang Suo Tianyuan Guo Xiao 《Natural Resources Research》2021,30(5):3839-3852
Natural Resources Research - Depletion of shallow mineral resources caused by deep mining has become an inevitable trend, and deep mining can increase safety accidents and geological hazards.... 相似文献
13.
通过对郑州望京楼遗址出土的二里头文化时期石杵和石臼进行淀粉粒分析,发现了5类可鉴定的不同形态淀粉粒,主要为粟黍类、小麦族(Triticeae)、薏苡属(Coix)、栎属(Quercus)和豆科(Fabaceae)等,以及部分未知种属的淀粉粒。石臼和石杵的使用部位形态多样的淀粉粒表明此类工具在当时被用于加工处理多种植物种子或果实。望京楼遗址二里头文化时期石器上粟、黍以及小麦等多种农作物淀粉粒的发现,同时结合二里头、南洼、皂角树等二里头文化遗址植物浮选结果,表明二里头文化时期中原腹心地区已普遍存在多品种的农作物种植。 相似文献
14.
15.
GIS中多幅地图的缩放漫游及其数据组织 总被引:1,自引:0,他引:1
本文在分析现存GIS软件中处理多幅不同比例尺或相同比例尺地图的放缩漫游时的不足及其原因的基础上,提出了一种使用地理逻辑窗口动态裁剪快速而安全的多幅地图无级缩放和全区域自由漫游的方法,并对其数据组织和管理作了探讨。 相似文献
16.
本文介绍新滩滑坡后两岸边坡监测的工作,对边坡变形提出了趋势意见。认为新滩斜坡目前正处于整体稳定下的局部调整阶段,变形缓慢平稳,但要注视广家崖的危岩动态;链子崖仍有趋势性的倾江形变。5—6号缝围成的7万方危岩及江段的5万方危岩体尚有一触即崩之势,须加强监视。 相似文献
17.
用丰富的高质量数字强震记录对台湾集集大地震及余震的长周期地震动特性进行了研究. 本文主要研究了长周期地震动的强度随震级、距离及场地条件的变化情况;同时对近断层的长周期地震动特性进行了分析. 结果表明,集集大地震及余震的长周期地震动反应谱的形状主要受场地条件和震级控制(D+E类场地的反应谱要比B+C类的宽,震级大的反应谱要比震级小的宽),而受距离影响并不显著;近断层长周期地震动明显受断层活动特性影响:上盘的长周期地震动比下盘的强,北部的比南部的强. 相似文献
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20.
Christophe COLIN 《中国科学D辑(英文版)》2007,50(11):1674-1684
High-resolution clay mineral records combined with oxygen isotopic stratigraphy over the past 450 ka during late Quaternary from Core MD05-2901 off Middle Vietnam in the western South China Sea are re-ported to reconstruct a history of East Asian monsoon evolution. Variations in Illite, chlorite, and kaolinite contents indicate a strong glacial-interglacial cyclicity, while changes in smectite content present a higher frequency cyclicity. The provenance analysis indicates a mixture of individual clay minerals from various sources surrounding the South China Sea. Smectite derived mainly from the Sunda shelf and its major source area of the Indonesian islands. Illite and chlorite originated mainly from the Mekong and Red rivers. Kaolinite was provided mainly by the Pearl River. Spectral analysis of the kaolin-ite/(illite chlorite) ratio displays a strong eccentricity period of 100 ka, implying the ice sheet-forced win-ter monsoon evolution; whereas higher frequency changes in the smectite content show an ice sheet-forced obliquity period of 41 ka, and precession periods of 23 and 19 ka and a semi-precession period of 13 ka as well, implying the tropical-forced summer monsoon evolution. The winter monsoon evolution is generally in coherence with the glacial-interglacial cyclicity, with intensified winter monsoon winds during glacials and weakened winter monsoon winds during interglacials; whereas the summer monsoon evolution provides an almost linear response to the summer insolation of low latitude in the Northern Hemisphere, with strengthened summer monsoon during higher insolation and weakened summer monsoon during lower insolation. The result suggests that the high-latitude ice sheet and low-latitude tropical factor could drive the late Quaternary evolution of East Asian winter and summer monsoons, respectively, implying their diplex and self-contained forcing mechanism. 相似文献