青藏高原东部黄河切开若尔盖湖盆的沉积证据与年代研究     

王娜  查小春  黄春长  张玉柱  周亚利  庞奖励  戎晓庆  尚瑞清  柴佳楠 《地理科学进展》2022,41(8):1453-1466

对青藏高原东部若尔盖盆地内外实地考察,在玛曲瓶颈段黄河二级阶地前沿陡坎,发现了含有古深湖相和古河床河漫滩相地层序列的典型沉积剖面。通过沉积物粒度特征分析和光释光(optically stimulated luminescence,OSL)测年,研究结果表明：① 剖面下部淡蓝灰色古深湖相沉积层为深水厌氧环境下形成的湖相沉积物,而覆盖其上的杂色卵石层夹淡黄橙色透镜状沙层则是古河床河漫滩相沉积物,指示了强动力流水作用过程。这2组地层的不整合接触关系,是黄河切开若尔盖湖盆导致古湖水外泄的直接证据。② 剖面古深湖相沉积层顶部和古滨浅湖相沉积层底部的OSL测年结果表明,古黄河在37 ka BP切开若尔盖湖盆,导致湖水外泄,35 ka BP湖水变浅消失,黄河沟通了若尔盖盆地水系。③ 晚更新世东昆仑大断裂强烈的新构造运动和37 ka 温暖湿润气候的综合影响使得尚处于玛曲断陷谷地草原的古黄河源溯源侵蚀加剧,由西向东在玛曲城南瓶颈段切开了若尔盖古湖盆,导致古湖水外泄,从而沟通了若尔盖湖盆的水系,使之成为黄河源。该研究结果对于深入理解青藏高原东北部河湖水系演变及黄河水系的形成具有重要的科学意义。  相似文献   

柴北缘大陆深俯冲板片折返过程中的深熔作用研究   总被引：3，自引：2，他引：1  

于胜尧  张建新  孙德有  李云帅  宫江华 《岩石学报》2014,30(8):2287-2296

柴北缘锡铁山地区长英质（花岗）片麻岩普遍经历了不同程度的部分熔融作用,常见新生的花岗质浅色体呈层状、脉状或网络状分布于长英质片麻岩中,并显示出混合岩化的特征。岩相学观察结果显示长英质片麻岩保留了关键的深熔作用显微结构证据:（1）石榴石内部发育有钾长石、石英和斜长石组成的矿物包裹体;（2）长石颗粒边界出现由石英+钾长石±斜长石±白云母组成的楔形矿物集合体;（3）云母颗粒边界发育尖锐的、不规则的微斜长石,而且云母边界溶蚀明显,形成锯齿状不规则的边界;（4）石英、斜长石或钾长石颗粒边界发育圆珠状（stringofbeads）结构,而且颗粒边界或三联点中尖锐状微斜长石与周围矿物的形成较小的二面角。阴极发光图像和锆石U-Pb定年结果表明花岗质浅色体中的锆石具有明显的核、幔、边三层结构,而且具有明显不同的年龄结果。发光较强的继承性锆石岩浆核部的²⁰⁶Pb/²³⁸U年龄约为~910Ma,而且具有高的Th/U比值;弱发光的变质锆石幔的²⁰⁶Pb/²³⁸U年龄结果约为~450Ma。新生的锆石增生边中等程度发光,并发育震荡环带和较低的Th/U比值,与世界典型地区混合岩中深熔锆石的特征十分相似,其²⁰⁶Pb/²³⁸U年龄结果为432±3Ma。野外关系、显微结构特征和年代学的研究结果显示柴北缘锡铁山地区花岗质浅色体可能是其寄主岩石长英质片麻岩在折返到高压麻粒岩相条件下深熔作用的产物,而且白云母的脱水熔融是引发岩石发生深熔作用的主要机制。柴北缘地区已有的资料综合研究表明,大陆深俯冲板片在俯冲/碰撞和折返过程中可能经历了多重深熔作用。  相似文献   

略论庭前供证的证明力与证据能力     

栗克元 《广东海洋大学学报》2006,26(2):21-25

庭前供证是指被告人或证人在庭审前向司法机关就案件事实所作的陈述,是与当庭供证相对应的概念。当庭前供证与当庭供证矛盾后如何采信,历来是司法理论界和实务界所关注的焦点。但由于庭前供证的及时和供证人的心理防线未完全建构的背景下,其获得的证明力不逊于当庭供证的品质,故在对庭前供证的证据能力进行严格的司法审查后,应当作为定案的根据。  相似文献   

Simulation of peri-urban growth dynamics using weights of evidence approach     

Sandeep Maithani  Arifa Begum  Pramod Kumar  A. Senthil Kumar 《国际地球制图》2018,33(9):957-976

The study aims to simulate the peri-urban growth dynamics in a growing region of India using Weights of Evidence (WOE) based cellular automata model. The growth process was expressed as a function of four causative variables corresponding to which seven data layers were generated in a Geographic Information Systems environment. The model was calibrated for the period 2000–2005 using Kappa indices and fuzzy set theory based two way comparison method. The Kappa value was 0.7, while the value of K_location and K_histo were 0.81 and 0.93, respectively. The fuzzy similarity values increased for small to large neighbourhood sizes which showed that the model was able to simulate the contiguous and dense growth. However, for dispersed and isolated growth the model showed less accuracy. The model was validated for period 2005–2010 and revealed a Kappa value of 0.88, while value of K_location and K_histo were 0.91 and 0.96, respectively.  相似文献   

一种基于DS理论的水库适应性调度规则          下载免费PDF全文

张玮  王旭  雷晓辉  刘攀  王浩 《水科学进展》2018,29(5):685-695

针对适应性管理研究领域中GCMs集合子情景的权重取值尚不统一问题,通过DS理论综合考虑了3种权重分配方式:等权重、考虑年径流统计特征参数值变化的权重和基于相对月径流变幅的权重。基于得到的综合权重,进一步提出了一种基于DS理论的水库适应性调度规则,以规避气候变化对水库调度造成的不利影响。该调度规则,以多情景多年的加权平均发电量最大化为水库优化调度的目标函数,采用模拟优化法提取规则参数。以锦西水库的研究案例可知:在不确定的气候变化环境下,与基于历史径流的调度规则和基于等权重分配的适应性调度规则相比,基于DS理论的水库适应性调度规则不仅能够获取更多的发电效益（多发电量:0.76亿kWh、0.61亿kWh）与发电可靠性（多增发电保证率:0.5%~11.17%、3.50%~9.34%）,还具有更高的水库决策稳健性。因此,基于DS理论的水库适应性调度规则是有助于水库管理者应对气候变化。  相似文献   

青海省天峻县疏勒河地区铜及多金属综合信息成矿预测          下载免费PDF全文

张文斌  张子鸣  杨延峰  郑德胜 《甘肃地质》2018,(1):43-50

研究区位于中—南祁连弧盆系中祁连岩浆弧区。区内以沉积地层分布最为广泛,地层时代跨度大,其中青白口系碎屑岩与碳酸盐岩组成的建造、奥陶系中基性火山喷出岩—碳酸盐岩—碎屑岩建造及二叠系碎屑岩系与成矿关系密切。区内断裂纵横交错,褶皱发育,总体构造线以NW、NWW向为主,近EW向、NNE、NNW向次之。区域岩浆活动主要表现在加里东期,岩浆从超基性—基性—中酸性—酸性都有不同程度的出露。区内主要成矿类型有岩浆热液型钨钼矿、砂岩型铜矿、中低温热液型铜矿及铅锌矿。本文从成矿地质背景分析入手,研究了与成矿有关的地质特征,应用MORPAS软件将研究区划分为3 km×3 km的单元格,提取变量,构置证据图层,计算单元找矿信息量,对研究区进行了铜及多金属矿的成矿预测,圈定并评价了6处找矿靶区,其中Ⅰ类靶区3处,Ⅱ类靶区3处。为该区今后部署铜、钨钼、铅锌等矿产勘查工作提供了重要依据,指出了进一步工作的方向。  相似文献   

Can citizen science contribute to the evidence-base that underpins marine policy?     

《Marine Policy》2015

Marine legislation is becoming ever more complex, so new cost-effective ways of obtaining and processing increasingly large data sets are required to support evidence-based policy making. Citizen science is one solution, but the uptake of the evidence generated by citizens among policy makers is often limited. Here, the importance of citizen science in delivery of the evidence-base that underpins marine policy was assessed using a series of case-studies. There was no consistent rationale for developing policy-relevant citizen science, but drivers included: lack of existing data, difficulty in collecting data by other means, the use of citizen science data by other organisations, and the capabilities of volunteers. Challenges to the uptake of marine citizen science were identified from policy-maker, scientist and citizen perspectives, and these related to data quality, data access, motivation of volunteers, and physical location. Citizen science has good potential to contribute to the evidence-base alongside traditional monitoring, remote sensing, and modelling, but only if outputs from citizen science projects are judged individually on quality. If this is the case, citizen science has an important role in delivery and understanding of future marine policy, but is only one part of an integrated solution.  相似文献   

Beyond PRISMA: Systematic reviews to inform marine science and policy     

《Marine Policy》2015

A recent article by Sierra-Correa and Cantera Kintz published in Marine Policy 51 2015 identifies the need for systematic reviews of evidence to inform marine policy and management. To guide their review, the authors apply the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) Statement as a methodology. We identified eighteen systematic reviews published on marine topics between 2008 and 2015. Of those which stated a methodology (N=12), 25% (N=3) applied the PRISMA Statement. PRISMA is a checklist designed by the medical community to improve reporting standards of systematic reviews and meta-analyses, rather than guidelines for their conduct. Relevant guidelines have already been produced by the Collaboration for Environmental Evidence. By using PRISMA as a methodology without referring to these guidelines, or worse, post hoc without conducting a full systematic review, authors may unintentionally give the impression of having undertaken a more rigorous review than is in fact the case. Given the apparent increase in systematic reviews of marine and coastal topics, it is vital that appropriate methodology be used. Authors undertaking future reviews should use existing environmental systematic review guidance to help plan and conduct their review. By following these guidelines, standards for marine reviews should increase, ultimately resulting in more rigorous reviews better able to inform future marine science and policy.  相似文献   

内蒙古白云鄂博群金矿综合地质信息预测     

张彤  许立权  闫洁  张婷婷 《吉林大学学报(地球科学版)》2013,43(4):1246-1253

白云鄂博群是内蒙古中西部稀土、铁、金等矿产的重要含矿层位,具有良好的成矿条件,在该层位发现铌、钽、铀、钍、钨、钼、锑、银、铜、铅、锌、锰等金属矿产30多种。在综合研究内蒙古白云鄂博地区地物化遥及其解译资料的基础上,提取了与金成矿密切相关的异常要素,建立了白云鄂博地区白云鄂博群层控型金矿矿床模型。在此基础上,利用基于GIS平台的证据权重法和矿床模型综合地质信息体积法对研究区进行了金矿的定位与定量预测,优选出57个最小预测区,预测资源量402 834kg。  相似文献   

基于MORPAS的证据权重法在沽源盆地铀成矿预测中的应用     

张恩  汪冰  王瑞军  卢辉雄 《地质找矿论丛》2013,28(4):540-545

文章在对沽源盆地内的地质、物化探等信息与铀成矿的关系进行深入分析的基础上,借助MORPAS平台,对区内各控矿要素定量化,利用GIS的空间分析功能提取了断裂Buffer、潜火山岩Buffer、航磁异常等在内的16个证据图层,并将研究区划分为1 km×1 km大小的9 562个单元,利用证据权重法对研究区铀矿进行预测,圈定了3级成矿远景,为该区进一步找矿指出了方向.  相似文献