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951.
Depositional Sequences of Yitong Graben (Eastern China) and Its Response to Transform-Extensional Processes 总被引:1,自引:0,他引:1
Lu Yongchao Ren Jianye Li Sitian Chen Ping Ye Hongpo Cui Xuezhou Li Bencai 《中国地质大学学报(英文版)》1999,10(2):170-177
INTRODUCTIONTheTancheng-Lujiangfaultbeltisthelargeststrike-slipfaultbeltinEastChina.Thisfaultbelthasundergoneacom-plicatedgeo... 相似文献
952.
953.
基于控制降温速率的动力结晶实验,对五大连池老黑山钾质玄武质熔岩的冷却结晶过程中橄榄石晶体形态随降温速率变化动力学演变进行了研究。实验研究表明,老黑山钾质玄武岩的熔融温度发生在1 022 ℃~1 260 ℃之间,峰值为1 166.3 ℃~1 186.5 ℃;实验产物主要由橄榄石和玻璃质组成,新生的橄榄石晶体形态差异较大,有针状骸晶、铁轨状骸晶、羽毛状雏晶、细长条状和粒状微晶。橄榄石晶体的生长、尺寸和形态、分布和实验产物的结晶程度与降温速率之间存在着密切关联。随着降温速率的变慢,橄榄石从针状(0.075 ℃ /min~0.5 ℃ /min)、铁轨状(0.075 ℃ /min~0.5 ℃ /min)、放射状与羽毛状(0.046 8 ℃ /min~0.075 ℃ /min)、细长条状(0.062 5 ℃ /min)等晶体演变为粒状微晶(0.03 ℃ /min);同时,岩石的结晶程度逐渐增强,橄榄石晶体尺寸逐渐变大、自形程度逐渐变高,玻璃相和气孔逐渐减少。这种新生橄榄石形态的变化与降温速率的内在关联性,对认识老黑山熔岩流固结的动力结晶机制、熔岩流的运动机制有一定科学意义。 相似文献
954.
在暴雨触发作用下,2006年5月18日贵州都匀马达岭发生滑坡,滑体随即形成的碎屑流,充填了坡下长达1km的沟谷。滑坡堆积物在空间上有明显的分区特征,由上至下可分为滑源区、滑体堆积区、碎屑流流通区、碎屑流堆积区四个区域进行研究。在对马达岭滑坡进行详细野外调查的基础上,从滑坡的地形条件、堆积情况及运动特征等方面探讨滑坡的发生机理及运动过程,结果表明:马达岭滑坡为一高速远程滑坡,滑坡迅速启动并在特殊的破坏模式和地形条件下,形成了"一快一慢"两种不同的运动方式,即大块岩体"坐着"下伏流体的缓慢运移以及碰撞、铲刮形成的碎屑物质的高速抛飞。 相似文献
955.
博格达与哈尔里克早泥盆世火山岩成因对比及其构造意义 总被引:1,自引:0,他引:1
本次研究在东天山博格达东段下涝坝南部新确认一套以安山岩为主的火山岩,为钙碱性系列,LA-ICP-MS锆石U-Pb年龄为397.5±4.7 Ma,属早泥盆世。该火山岩具有一致的轻稀土与重稀土分馏明显的右倾配分模式,K、Ba等大离子亲石元素显著富集,而Nb、Ta等高场强元素相对亏损,其原始岩浆可能来自于石榴石稳定域地幔橄榄岩2%~5%的部分熔融,同化混染程度较小。对应的哈尔里克南麓下泥盆统大南湖组火山岩为一套基性到酸性连续演化的钙碱性系列岩石,稀土丰度较下涝坝火山岩高,轻、重稀土之间分馏较弱,整体富集大离子亲石元素而亏损高场强元素。其岩浆可能来源于尖晶石稳定域地幔橄榄岩3%的部分熔融,受地壳物质混染明显,岩石后期蚀变较强。Hf/3-Th-Ta图解和Yb标准化的Th-Nb判别图解显示这两套泥盆纪火山岩均形成于与俯冲有关的活动陆缘环境,暗示博格达和哈尔里克地区在早泥盆世时期可能具有相同的大地构造环境。 相似文献
956.
957.
958.
二叠纪海相碳酸盐的锶同位素演化及其意义 总被引:4,自引:0,他引:4
本文从沫阳和熊家场剖面二叠纪海相碳酸盐和玄武岩的锶同位素变化出发,讨论了碳酸盐的锶同位素组成与峨嵋山玄武岩喷发之间的关系,以及玄武岩中海相碳酸盐的锶同位素贫化原因,指出海相碳酸盐的锶同位素组成可作为了解地球构造演化的工具。 相似文献
959.
The Seismic Induced Soft Sediment Deformation Structures in the Middle Jurassic of Western Qaidamu Basin 总被引:1,自引:0,他引:1
Intervals of soft-sediment deformation structures are well-exposed in Jurassic lacustrine deposits in the western Qaidamu basin. Through field observation, many soft-sediment deformation structures can be identified, such as convoluted bedding, liquefied sand veins, load and flame structures, slump structures and sliding-overlapping structures. Based on their genesis, soft-sediment deformation structures can be classified as three types: seismic induced structures, vertical loading structures, and horizontal shear structures. Based on their geometry and genesis analysis, they are seismic-induced structures. According to the characteristics of convoluted bedding structures and liquefied sand veins, it can be inferred that there were earthquakes greater than magnitude 6 in the study area during the middle Jurassic. Furthermore, the study of the slump structures and sliding-overlapping structures indicates that there was a southeastern slope during the middle Jurassic. Since the distance from the study area to the Altyn Mountain and the Altyn fault is no more than 10km, it can be also inferred that the Altyn Mountain existed then and that the Altyn strike-slip fault was active during the middle Jurassic. 相似文献
960.
The 12 May Wenchuan earthquake-induced landslide lakes: distribution and preliminary risk evaluation 总被引:17,自引:9,他引:17
The Wenchuan earthquake, measured at M
s 8.0 according to the China Earthquake Administration, occurred at 14:28 on 12 May 2008 in the Sichuan Province of China.
It brought overwhelming destruction to eight provinces and cities. Landslides and rock avalanches triggered by the earthquake
produced 257 landslide lakes which were distributed along the fault rupture zone and river channels. The authors traveled
to the disaster zone immediately after the earthquake to examine some of the features of the debris dams and performed a quick
evaluation of the potential for outburst of earthquake-induced landslide lakes for the purpose of disaster relief. The preliminary
analysis indicated that the landslide lakes could be classified as those exhibiting extremely high risk, medium risk, and
low risk according to field observations and remote sensing, to determine material composition, dam structure, dam height,
maximum water storage capacity, and size of the population potentially affected area. The failure risk of 21 debris dams were
evaluated as follows: one dam with an extremely high danger risk, seven dams with a high danger, five dams with a medium danger,
and eight dams of low danger. More concern was given to the Tangjiashan Lake and different scenarios for the potential sudden
failure of its dam were assessed. The risk evaluation result was accepted in full, by the earthquake disaster relief office.
A successful emergency dam treatment for risk reduction was planned, based on our assessments, and these measures were quickly
carried out. According to this research, the earthquake destabilized the surrounding mountains, resulting in a prolonged geohazard
for the area. Landslides and debris flows will continue to develop for at least 5 to 10 years after the Wenchuan earthquake
and will produce additional dammed lakes. Recommendations and plans for earthquake–landslide lake mitigation were proposed,
based on past successful practices. 相似文献