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青藏高原南羌塘荣玛晚侏罗世闪长岩:班公湖——怒江特提斯洋向北俯冲产物 总被引:3,自引:0,他引:3
班公湖—怒江特提斯洋的演化一直以来备受关注,对于其俯冲极性存在不同认识。报道在青藏高原南羌塘荣玛地区新发现的晚侏罗世闪长岩年代学、地球化学和锆石Hf同位素特征。LA-MC-ICP-MS锆石U-Pb年龄结果表明,岩石形成于149.7±0.8Ma,时代为晚侏罗世。岩石呈富碱,低Mg O、TFe O、Ca O,富集轻稀土元素和Rb、Th、U、K等元素,亏损Ta、Nb、P、Ti等元素。锆石εHf(t)值为正值,并且具有较大的变化范围(+4.26~+9.29),指示岩浆来源于幔源和壳源岩浆的混合。结合区域地质背景认为,荣玛地区晚侏罗世闪长岩为班公湖—怒江特提斯洋向北俯冲所引起的幔源和壳源岩浆混合作用的产物。 相似文献
173.
针对四川盆地北部上三叠统须家河组硅质砾岩外表单调的物理特性和物源难以明确区分的问题,利用阴极发光技术对米仓山—大巴山前缘9条须家河组砾岩剖面中采集的砂砾岩和胶结物共计36块样品,127片薄片进行砾石和砂级碎屑组分详细的对比分析。结果表明须家河组硅质砾岩中石英质砾石主要有两种阴极发光类型:1以紫光、蓝光为主,变化于蓝-紫、红-紫之间,占40.2%~84.5%,平均为67.97%,其中紫色光占3.2%~13.04%,红色光占3.8%~13%,蓝色光占16.7%~33.3%,蓝紫色光占8.7%~37.5%,紫红色光占17.5%~22.6%,主要来自于岩浆岩(1%~15%),变质岩(40%~80%),主要分布于万源-南江一带;2不发光,占15.49%~59.79%,平均为32.03%,主要来自于沉积-成岩成因的石英(燧石),主要分布于旺苍-金溪,呈现出由东到西递减的趋势。揭示须家河组硅质砾石尽管成分单一,但其硅质来源具有明显的差异,来源于岩浆岩、变质岩、沉积岩等不同的母源。综合分析认为四川盆地北部须家河组砾岩沉积时期存在三大源岩体系,具有明显的多源性。秦岭造山带是川北地区须家河组的主要物源供给区。研究结果亦证明,阴极发光分析方法可作为沉积岩物源分析的一种有效手段。 相似文献
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175.
Late Quaternary Large Earthquakes on the Western Branch of the Xiaojiang Fault and Their Tectonic Implications 总被引:1,自引:0,他引:1
The Xiaojiang fault is a major active left-lateral fault along the southeastern margin of the Tibetan Plateau.The largest historical earthquake in Yunnan Province, with a magnitude 8 and a mean coseismic left-lateral displacement of ~ 6.9 m, occurred on the western branch of the Xiaojiang fault.Studying this fault is important in understanding current deformation and kinematic characteristics of the Tibetan Plateau.Activities and stretches have been well undertaken on the Xiaojiang fault, while paleoseismic research work is always the weak link on this fault.To investigate the paleoseismic history and large earthquake activity of the Xiaojiang fault, we opened a large trench at the northern edge of Caohaizi sag pond on the western branch of the Xiaojiang fault.Six paleoseismic events have been identified, and named E1 through E6 from the oldest to the youngest.Charcoal and woods are abundant, 20 samples were dated to constrain the ages of the paleoseismic events at 40 000–36 300 BC, 35 400–24 800 BC, 9 500 BC–AD 500, AD 390–720, AD 1120–1620 and AD 1750–present.We associate the youngest event E6 with the 1833 M8 earthquake.Events E4, E5 and E6 show a continuous record of the western strand of the Xiaojiang fault in the late Holocene, with a average recurrence interval of 370–480 yr.Large earthquake recurrence in the late Holocene is far less than the recurrence of 2000–4000 yr posed in previous studies.Thus, the seismic hazard on the Xiaojiang fault should be reevaluated.Furthermore, the irregular recurrence of large earthquakes on the Xiaojiang fault and other faults in the Xianshuihe-Xiaojiang system, indicates the uneven southeastward extrusion of the Sichuan-Yunnan block along the southeastern margin of the Tibetan Plateau. 相似文献
176.
定居是人类从高度移动的游猎生活发展到全年固定于一处居住的漫长过程。定居的发生和发展对人类社会的生产方式、技术演化和文明起源具有深远影响,而定居的产生受到气候变化、人口增长、资源压力、技术革新等多种因素影响。青藏高原是研究人类适应和定居高寒缺氧极端环境的理想区域,对史前人类在青藏高原的定居过程关注较多亦争议颇多。通过梳理已发表的考古学、地理学、遗传学等相关学科文献,发现目前对于史前人类定居青藏高原的研究,侧重于讨论低海拔人群或者农作物扩散的影响,对动物资源在这一过程中的作用则关注较少,定居高原的年代和驱动机制仍存在争议。遗址使用的季节性分析,是判断古人是否全年定居的关键。本文总结了如何利用青藏高原鱼类、鸟类和哺乳类等动物遗存因地制宜进行遗址季节性分析以及建立高原遗址动物资源利用时间表的方法。本文认为,开展史前人类在青藏高原定居与动物资源利用研究,首先,应全面建立和完善青藏高原现生动物骨骼形态、全基因组和蛋白质组的数据库,为考古遗址动物遗存物种鉴定提供基础;其次,在物种鉴定的基础上,研究人—动物—环境之间的关系;最后,评估人类在遗址活动的季节性以及动物资源在人类定居青藏高原过程中的作用。 相似文献
177.
Influence of Mass and Radius of Ice Crystals on Hydrometeors,Internal Energy,and Kinetic Energy:A Numeric Model Study 下载免费PDF全文
Two cloud-scale experiments with two different ice-phase schemes were carried out for a precipitation event that occurred in eastern China in 2005.The results were analyzed to examine the influences of the change of ice-particle mass and radius on hydrometeors,internal energy,and kinetic energy,as well as the primary factors responsible.It was found that the ice content increases notably and the snow content decreases due to the change.This is the consequence of the modulation of cloud microphysical processes.In particular,the Bergeron process and the accretion of snow and cloud ice are markedly influenced.The differences of internal energy and kinetic energy between the two experiments are caused by adjustments to pressure-flux divergence,the coupling of temperature and divergence,and gravitational work,and the reason is that these three factors result in differences of local changes of internal and kinetic energy. 相似文献
178.
CE-1立体相机与激光高度计数据联合平差 总被引:1,自引:0,他引:1
CE-1三线阵立体相机和激光高度计主要用于获取月球形貌信息.CE-1沿轨运动过程中,可同时获取高分辨率的三线阵扫描影像和高精度的激光测高数据.在分析立体影像与激光高度计数据不一致性的基础上,为提高定位精度,将激光测距数据引入三线阵立体影像光束法平差处理.本文提出一种改进的外定向参数模型,采用3阶Lagrange多项式模型(LPM)建立外定向线元素内插模型,采用四元数球面线性内插建立外定向角元素模型,并根据改进模型建立激光高度计数据与影像数据的联合平差数学模型.试验表明,本文立体相机和激光高度计数据联合平差模型是有效的. 相似文献
180.
A moist thermodynamic advection parameter, defined as an absolute value of the dot product of hori- zontal gradients of three-dimensional potential temperature advection and general potential temperature, is introduced to diagnose frontal heavy rainfall events in the north of China. It is shown that the parameter is closely related to observed 6-h accumulative surface rainfall and simulated cloud hydrometeors. Since the parameter is capable of describing the typical vertical structural characteristics of dynamic, thermodynamic and water vapor fields above a strong precipitation region near the front surface, it may serve as a physical tracker to detect precipitable weather systems near to a front. A tendency equation of the parameter was derived in Cartesian coordinates and calculated with the simulation output data of a heavy rainfall event. Results revealed that the advection of the parameter by the three-dimensional velocity vector, the covariance of potential temperature advection by local change of the velocity vector and general potential temperature, and the interaction between potential temperature advection and the source or sink of general potential temperature, accounted for local change in the parameter. This indicated that the parameter was determined by a combination of dynamic processes and cloud microphysical processes. 相似文献