西秦岭南缘阳山金矿带磷灰石LA-ICP-MS裂变径迹热年代学研究     

杨忠虎  熊韬  勾宗洋  李虎  王亮 《地质学报》2022,96(11):3849-3866

位于西秦岭文县弧形构造带的阳山金矿,是勉略缝合带内已探明金资源最大的独立金矿,且金矿形成后经历多期次构造活动,因此阳山金矿是研究矿床热演化、变化与保存的理想选区,其研究成果可用来约束金成矿时限,同时定量的隆升剥蚀数据可为深部找矿及矿床储藏提供远景潜力评价依据。本文采集钻孔矿化接触带中英云闪长斑岩脉,利用LA-ICP-MS技术进行裂变径迹测年。3件样品磷灰石裂变径迹年龄中心值为124.3±6.4 Ma、146.4±6.3 Ma和117±13 Ma,其中一件样品磷灰石裂变径迹平均长度为12.11μm。热历史反演的时间-温度曲线表明,在146 Ma阳山金矿带内英云闪长斑岩脉体温度下降到磷灰石裂变径迹封闭温度区间(60～120℃),即在侏罗纪晚期或白垩纪早期之后,研究区几乎没有大规模岩浆活动或热液活动,缺乏与燕山期同时期区域性岩浆活动相对应的热事件。磷灰石裂变径迹年龄数据分析认为,即使金矿带在喜马拉雅期可能存在微弱的热事件扰动,但岩浆热液活动规模较小且对金成矿作用贡献微乎其微。结合磷灰石热历史时间-温度曲线,阳山金矿带大规模成矿事件的时间集中在210～195 Ma区间,且热历史反演曲线未显示有...  相似文献   

青藏高原中部五道梁-曲麻莱断裂系西段晚第四纪滑动速率厘定     

罗浩  郭广海  张斌  王继  缑亚森  徐伟  高战武 《震灾防御技术》2021,16(2):283-292

五道梁-曲麻莱断裂系位于青藏高原中部,关于其晚第四纪活动性迄今鲜有介绍.由高分辨率卫星影像解译和野外地质考察可知,断裂系西段由五道梁南山北缘断裂和五道梁南山南缘断裂组成,二者分别断错了五道梁南山两侧的各级洪积扇.通过洪积扇上的断错地貌分析和光释光测年方法得到南缘断裂缩短速率为(0.25±0.11)mm/a,北缘断裂缩短...  相似文献   

全息测量接收机系统     

王锦清  梁世光  王鹏  范庆元  虞林峰  苟伟  夏博  蒋甬斌  肖英  高辽荣  胡阿丽 《云南天文台台刊》2011,(3):242-247

简单介绍了微波全息测量的原理、用于微波全息测量的接收机系统,然后比较详细地叙述了对该接收机系统相位稳定性的测试,指出了当前接收系统的主要问题。并对接收系统的改进做了两种设计方案。  相似文献   

长江河口深层软土含盐特征及其沉积环境分析     

苟富刚  龚绪龙  张岩  杨露梅  刘彦 《海洋学报》2022,44(4):12-22

软土的含盐特征是地基设计的一个重要指标,含盐特征主要受沉积环境控制,往往具有较强的地域性.以长江河口北翼海陆交互相软土为研究对象,采集多组土样进行室内试验,进行土体含盐特征、参数相关性及沉积环境分析.研究结果表明,软土含盐特征为NaCl型,含盐量均值为0.613％,以弱盐渍土为主,占比85.4％.含盐量、Cl-含量、N...  相似文献   

Rejuvenated extension of the Philippine Sea plate and its effect on subduction dynamics in the Nankai Trough     

Gaku Kimura  Yasuyuki Nakamura  Kazuya Shiraishi  Gou Fujie  Shuichi Kodaira  Asuka Yamaguchi  Rina Fukuchi  Yoshitaka Hashimoto 《Island Arc》2021,30(1):e12402

The Nankai Trough, Japan, is a subduction zone characterized by the recurrence of disastrous earthquakes and tsunamis. Slow earthquakes and associated tremor also occur intermittently and locally in the Nankai Trough and the causal relationship between slow earthquakes and large earthquakes is important to understanding subduction zone dynamics. The Nankai Trough off Muroto, Shikoku Island, near the southeast margin of the rupture segment of the 1946 Nankai earthquake, is one of three regions where slow earthquakes and tremor cluster in the Nankai Trough. On the Philippine Sea plate, the rifting of the central domain of the Shikoku Basin was aborted at ~15 Ma and underthrust the Nankai forearc off Muroto. Here, the Tosa-Bae seamount and other high-relief features, which are northern extension of the Kinan Seamount chain, have collided with and indented the forearc wedge. In this study, we analyzed seismic reflection profiles around the deformation front of accretionary wedge and stratigraphically correlated them to drilling sites off Muroto. Our results show that the previously aborted horst-and-graben structures, which were formed around the spreading center of the Shikoku Basin at ~15 Ma, were rejuvenated locally at ~6 Ma and more regionally at ~3.3 Ma and have remained active since. The reactivated normal faulting has enhanced seafloor roughness and appears to affect the locations of slow earthquakes and tremors. Rejuvenated normal faulting is not limited to areas near the Nankai Trough, and extends more than 200 km into the Shikoku Basin to the south. This extension might be due to extensional forces applied to the Philippine Sea plate, which appear to be driven by slab-pull in the Ryukyu and Philippine trenches along the western margin of the Philippine Sea plate.  相似文献   

基于CNN海上钻井平台检测模型的构建及训练算法分析     

柳林  孙毅  李万武 《测绘通报》2022,(7):26

卷积神经网络(CNN)是深度学习(DL)中最具代表性的一种网络结构。合成孔径雷达(SAR)图像具有位置结构关系,CNN模型可以利用图像的位置结构关系,能够更好地提取图像特征,因此更适合采用CNN模型检测海洋目标。本文首先基于CNN框架构建了海上钻井平台检测的DL模型Ocean TDAx,并对模型进行训练和测试。试验结果表明,Ocean TDA9模型精度最高。然后针对Ocean TDA9模型,采用Adam、RMSprop、Stochastic gradient descent (SGD)、Adagrad、Momentum等7种模型训练算法进行试验,比较不同算法的训练损失和精度与训练批次的相关性。最后基于渤海海域的极化SAR数据,对提出的Ocean TDA9模型、已有的CNN模型及VGG模型进行海上钻井平台检测对比。结果表明,构建的Ocean TDA9模型在钻井平台检测中整体性能优良。  相似文献   

Estimating the criterion for determining water vapour sources of summer precipitation on the northern Tibetan Plateau     

Meixue Yang  Tandong Yao  Huijun Wang  Lide Tian  Xiaohua Gou 《水文研究》2006,20(3):505-513

According to the precipitation and δ¹⁸O data obtained during the GEWEX Asian Monsoon Experiment–Tibet Intensive Observation Period, based on the knowledge that δ¹⁸O is lower in precipitation formed from ocean air mass vapour than that from local evaporation vapour, the water vapour sources can be identified from the δ¹⁸O values in precipitation. We attempt to give the identification criterion of δ¹⁸O values in precipitation. The threshold values chosen to distinguish between ocean and local sources are δ¹⁸O < ?20‰ and δ¹⁸O > ?13‰ respectively. According to this criterion, the proportion of local evaporation‐formed precipitation and ocean air‐mass‐formed precipitation in total precipitation was estimated. The average value of precipitation at three sites (NODA, Amdo and AQB) is 249·76 mm. Among this, precipitation formed directly by the ocean air mass vapour is 80·08 mm at most. Precipitation formed by water vapour evaporated from local places is 117·05 mm at least. That is to say that precipitation formed directly by the ocean air mass vapour accounts for 32·06% of the total precipitation at most. Precipitation formed by water vapour evaporated from local places accounts for 46·86% of the total precipitation at least. At least 21·8% of the total precipitation came from water vapour that was evaporated on the way and transported by the monsoon circulation. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Self-potential and passive seismic monitoring of hydrothermal activity: A case study at Iodine Pool,Waimangu geothermal valley,New Zealand     

A. Legaz  A. Revil  P. Roux  J. Vandemeulebrouck  P. Gouédard  T. Hurst  A. Bolève 《Journal of Volcanology and Geothermal Research》2009,179(1-2):11-18

Iodine geyser, located in the Waimangu Geothermal Valley (New Zealand), has been studied by both passive electrical and seismic methods. The activity of the geyser was monitored at various distances from the vent using self-potential method. The self-potential signals display cyclic negative variations with respect to a baseline drawn when the geyser is quiet. The minimum in the self-potential signals coincides with the maximum overflow. We provide a numerical model able to explain both the polarity and magnitude of the observed signal. This model is based on the fluctuations of the hydraulic head in the conduit of the geyser; the divergence of the streaming current density is created at the interface between the pipe and the surrounding rock. Passive seismic experiments were used to localize ambient noise sources. These signals have been processed with the so-called Matched-Field Processing technique (MFP); a dominant source emerged from this processing, that we characterized in range and depth with a good accuracy.  相似文献   

A dendrochronological analysis of maximum summer half-year temperature variations over the past 700 years on the northeastern Tibetan Plateau     

X. Gou  J. Peng  F. Chen  M. Yang  D. F. Levia  J. Li 《Theoretical and Applied Climatology》2008,93(3-4):195-206

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城市化对长沙市两气象站气温记录的影响     

金凯  王飞  苟娇娇 《气候变化研究进展》2017,13(5):456-464

为深入认识城市对其附近气象站气温的影响,采用位于长沙市区东部和西部两个气象观测站的2007-2009年的逐日气温、风向和风速资料,结合地表覆盖特征数据,对比分析了两站气象记录差异,并通过改进的城市影响指数模型估算了气温资料中的城市影响偏差。分析显示：（1）2007-2009年东、西气象站逐月平均气温（T_mean）、最高气温（T_max）和最低气温（T_min）差异很大,最大差异分别可达0.90℃、0.83℃和1.34℃;（2）受城市及风向的影响,两气象站的逐月城市影响指数（K）差异较大,东、西站平均K值分别为2.01和1.50,年内同一台站的K值存在季节变化规律;（3）两站逐月△K与△T之间存在极显著正相关关系;（4）东、西两站2007年T_mean中的城市增温最大,分别达0.63℃和0.45℃。城市附近气象站气温记录受城市规模、风向和风速等因素影响明显,在分析长历时气候变化特征和利用站点记录数据进行空间分析时,有必要对气温数据进行订正。  相似文献