基于ArcView3.2的证据权重法在层间氧化带型砂岩铀矿定量评价中的应用

介绍了证据权重法及其理论基础,根据层间氧化带型砂岩铀矿成矿理论,应用由ArcView3.2二次开发形成的砂岩铀矿勘查信息系统软件在克鲁伦盆地内提取控矿信息,最后通过证据权重分析综合证据因子,完成盆地内层间氧化带型砂岩铀矿的远景预测.     

A Combined Weight of Evidence and Logistic Regression Method for Susceptibility Mapping of Earthquake-induced Landslides: A Case Study of the April 20, 2013 Lushan Earthquake,China

The Ms 7.0 Lushan earthquake triggered a huge number of landslides. Landslide susceptibility mapping is of great importance. Weight of Evidence (WoE) and Logistic Regression (LR) methods have been widely used for LSM (Landslide Susceptibility Mapping). However, limitations still exist. WoE is capable of assessing the influence of different classes of each factor, but neglects the correlation between factors. LR is able to analyze the relationship among the factors while it is not capable of evaluating the influence of different classes. This paper proposes a combined method of LR and WoE for LSM, taking advantage of their individual merits and overcoming their limitations. An inventory of 1289 landslides was used: 70% were random-selected for training and the remaining for validation. 11 landslide condition factors were employed in the model and the result was validated using Receiver Operating Characteristic (ROC) curve. The results showed that the LR-WoE model had a better accuracy than the LR model, producing an area below the curve with values of 0.802 success and 0.791 predictive, higher than that of the LR model (0.715 success and 0.722 predictive). It is therefore concluded that the combined method of WoE and LR can provide a promising level of accuracy for earthquake-induced landslide susceptibility mapping.     

辽东沉积变质型铁矿找矿预测研究

辽东为华北地台5个重点成矿区之一,铁矿资源丰富,铁矿主要成因类型为沉积变质型。在对区域地质环境、成矿作用、矿床形成以及后期改造作用分析的基础上,探讨了辽东沉积变质型铁矿的成矿模式。在成矿模式指导下筛选出地质、化探、物探等多元找矿信息,建立适合本区域资源预测的找矿模型。依据已建立的辽东区域找矿模型,采用证据权重法对辽东地区进行铁矿资源预测与评价,根据预测的后验概率值圈定一级成矿远景区3个,二级成矿远景区5个。预测结果表明,辽东地区具有较大的找矿潜力,该矿产资源预测方法有效性较好。     

美国加利福尼亚海岸出水石锚的地质学考证

通过对加利福尼亚海岸出水石锚的岩石学和古生物学的研究,初步推断了其原岩的产地,并用14C同位素测年测定了保存于石锚内的现代贝壳的年龄,由此大致推断出石锚的入水年龄。以上研究结果表明:(1)这些石锚石料非采自美洲本土,就世界范围而言,其产地分布于环太平洋的新阿尔卑斯皱褶带内,包括日本、台湾、马来西亚、印度尼西亚及中东、西亚乃至地中海沿岸地区;(2)这些石锚至少在1500年前就已落入海中,也就是说这些石锚的主人要比哥仑布发现美洲新大陆早1000余年。     

金鸡岭产铀花岗岩体印支期侵位的岩浆动力学证据及其构造意义

通过对南岭西段金鸡岭花岗岩体地质-岩石地球化学特征研究,判明该岩体的侵位深度(7.5km)、围岩温度(270℃)及岩浆初始温度(950℃),建立起金鸡岭花岗岩体的数学计算模型,分别计算得出:金鸡岭花岗岩熔体侵位后,其初始温度降低至结晶温度所需的时间(Δtcol)为3.91Ma;由于结晶潜热释放而使结晶过程延长的时间(ΔtL)为2.92Ma;由于金鸡岭花岗岩体放射性元素含量(U——16.5×10-6,Th——51.3×10-6,K2O——4.82%)是世界平均花岗岩放射性元素含量(U——5×10-6,Th——20×10-6,K2O——2.66%)的3倍左右,金鸡岭花岗岩熔体侵位后产生的放射性成因热使结晶过程延长的时间(ΔtA)为34.5Ma,远长于按世界花岗岩平均放射性元素含量计算的ΔtA*(2.82Ma)。金鸡岭花岗岩体的侵位-结晶时差(ΔtECTD)为41.3Ma,结合锆石U-Pb年龄值(156Ma),通过反演计算得出金鸡岭花岗岩体侵位年龄值(tE)为197.3Ma,从而为该岩体属于印支期侵位提供了重要的岩浆动力学证据。     

胶东金矿形成期间地幔流体参与成矿过程的碳氧氢同位素证据

胶东地区发育有两种类型的金矿床，以玲珑，焦家，三山岛，乳山为代表的石英脉型-破碎蚀变岩型和以大庄子，蓬家夼为代表的胶莱盆地北缘滑脱破碎带内的角砾岩型金矿，本文选择了两种类型中的玲珑，三山岛和大庄子金矿床进行碳氧氢同位素测定。初步认为两类金矿属于同一成矿系统，它们形成于120Ma左右的华北克拉通岩石圈减薄和软流圈上涌期间，岩浆流体和地幔脱气与胶东世界级金矿的形成密切相关，在石英脉型-破碎蚀变岩型矿石中可见深刻的地幔流体和岩浆流体的“烙印”。形成于滑脱破碎带中的角砾岩金矿流体与中生代大气降水和海相碳酸盐岩发生了强烈的交换作用。     

Was the Younger Dryas (Loch Lomond Stadial) icefield on Rannoch Moor,western Scotland,deglaciated as early as c.12.5 cal ka BP?

The concept that Rannoch Moor, the centre of the Younger Dryas (YD), West Highland Icefield, was deglaciated as early as 12.5 cal ka BP is discussed in the light of radiocarbon dates and varve sequences from outlet glaciers of this icefield, and climate change during the YD. The maximum positions of three YD glaciers were reached after 11.6–11.8 cal ka BP (Lomond), and after 11.8–11.9 cal ka BP (Spean and Treig) indicating that ice remained on Rannoch Moor until long after c.12.5 cal ka BP, and possibly until the YD/Holocene transition at c.11.7 cal ka BP. Further, the Spean glacier dammed a proglacial lake in Lochaber for at least 495 varve years over a period that included the deposition of the Vedde Ash (c.12.1 cal ka BP) and a late YD ash layer (c. 11.7–11.2 cal ka BP), a thesis at variance with supposed early YD deglaciation. Recent examination of this issue using ¹⁰Be exposure age determinations from Rannoch Moor is equivocal. In view of the presence of hard water algae at the sampling site on Rannoch Moor it is recommended that the ‘early’ ¹⁴C dates from Rannoch Moor need to be further reassessed using chronological constraints provided by dated microtephra, and a collaborative radiocarbon dating programme.     

南岭花山和姑婆山花岗岩基属印支期侵位:来自花岗岩熔体冷却-结晶和放射成因热计算的依据

通过对南岭西段花山和姑婆山花岗岩基地质-岩石地球化学特征研究,判明它们的侵位深度(5.5km)、围岩温度(196℃)及岩浆初始温度(950℃),建立起花山和姑婆山岩基的数学计算模型,计算得出:花山-姑婆山花岗岩熔体侵位后,其初始温度降低至结晶温度所需的时间(△tco1)分别为4.14 Ma(花山)和4.36Ma(姑婆山...     

内蒙古中部地区太古宙绿岩带金矿找矿标志

内蒙中部地区金矿集中分布在太古界花岗岩──—绿岩带中，并受区域深大断裂带及韧性剪切变质带的控制，构成内蒙中部金的矿化集中区。尽管人们对金矿化的成因有不同认识，但找矿标志是有规律可寻的，因而，总结内蒙中部地区金矿化的找矿标志是有重要意义的。本文着重通过内蒙古中部区的含金建造、容矿构造、岩浆活动、载金矿物、围岩蚀变及地球物理、地球化学、遥感影象和重砂等方面，总结本区的金矿找矿标志。     

青藏高原东缘龙门山 晚新生代走滑-逆冲作用的地貌标志*

文章以青藏高原东缘龙门山活动构造的地貌标志为切入点,在汶川-茂汶断裂、北川断裂、彭灌断裂和大邑断裂等主干活动断裂的关键部位,对断错山脊、洪积扇、河流阶地、边坡脊、断层陡坎、河道错断、冲沟侧缘壁位错、拉分盆地、断层偏转、砾石定向带、坡中槽、弃沟和断塞塘等活动构造地貌和断裂带开展了详细的野外地质填图和地貌测量,利用精确的地貌测量数据和测年数据,定量计算了龙门山主干断裂的逆冲速率和走滑速率,结果表明在晚新生代时期龙门山构造带仅具有微弱的构造缩短作用,其中逆冲速率的速度值小于1.1mm/a,走滑速率的速度值小于1.46mm/a,表明走滑分量与逆冲分量的比率介于6 ∶ 1~1.3 ∶ 1之间,以右行走滑作用为主。在此基础上,对各主干活动断裂的逆冲速率和走滑速率进行了定量的对比研究,结果表明自北西向南东4条主干断裂的最大逆冲分量滑动速率具有变小的趋势,而走滑分量的滑动速率则具有逐渐变大的趋势,显示了从龙门山的后山带至前山带主干断裂的走滑作用越来越强。由此推测现今的龙门山及其前缘盆地不完全是由于构造缩短作用形成的,而主要是走滑作用和剥蚀卸载作用的产物。另外,根据沉积、构造、盆地充填体的几何形态、地貌、古地磁等标定和对比了龙门山在中生代和新生代的走滑方向,表明龙门山构造带在中生代与新生代之交走滑方向发生了反转,即由中生代时期的左行变为新生代时期的右行。