Zircon U-Pb and Hf isotope constraints on crustal melting associated with the Emeishan mantle plume

SHRIMP zircon U-Pb dates, combined with in-situ Hf isotopic data, provide new constraints on the petrogenesis and protolith of peralkaline, metaluminous and peraluminous intrusions and rhyolitic tuffs in the Emeishan large igneous province, with significant bearing on crustal melting associated with mantle plumes. Syenite and A-type granitic intrusions from Huili, Miyi and Taihe in the center of this large igneous province yield U-Pb dates at ∼260 Ma, consistent with the ages obtained for mafic layered intrusions in the same province. Zircon from these rocks exhibits a wide range of initial Hf isotope ratios (ε_Hf(t) = −1.4 to +13.4), with corresponding T_DM1 of 400-900 Ma. The highest ε_Hf(t) value is only marginally lower than that of depleted mantle reservoir at 260 Ma, suggesting that their source is primarily juvenile crust added during Emeishan volcanism, with incorporation of variable amounts of Neoproterozoic crust. The trigger of crustal melting is most likely related to advective heating associated with magmatic underplating. In contrast, the 255-251 Ma peraluminous granites from Ailanghe and 238 Ma rhyolitic tuff from Binchuan, have negative initial ε_Hf values of −1.3 to −4.4, and of −7.7 to −14, respectively. Hf isotopic model ages and presence of inherited zircons indicate their derivation from Mesoproterozoic and Paleoproterozoic crust, respectively. Given the time lag relative to the plume impact (∼260 Ma) and insignificant mantle contribution to 255-238 Ma magmatism, conductive heating is suggested as the trigger of crustal melting that resulted in formation of delayed felsic magmas. The involvement of older crust in younger felsic magmas is consistent with upward heat transfer to the lithosphere during plume impregnation, if the age of crust is inversely stratified, i.e., changes from Paleoproterozoic to Mesoproterozoic to Neoproterozoic to Permian with increasing depth. Such crust may have resulted from episodic, downward crustal growth during the evolution of the western Yangtze Craton.     

拉萨古城居民地方依恋及其影响因素研究

以拉萨为案例,对古城区居民地方依恋及其影响因素进行解读。研究发现:居民地方依恋水平整体较高,居民对古城的情感性依恋要大于功能性依恋;但由于依赖类型、居住时间、文化背景、宗教信仰以及"家"的归属感不同,原住居民的地方依恋水平要高于非原住居民;从地方因素来看,宗教信仰、环境状况、活动参与和社交关系是影响居民地方依恋的关键因素,原住居民排在第一位的影响因素是环境状况,而非原住居民排在第一位的则是宗教信仰,这为提升拉萨古城居民地方依恋水平提供了科学依据。     

旅游景区商业化层级结构研究:要素识别与矢量测度

旅游景区商业化现象已经成为影响游客满意度及景区健康发展的重要前置变量,进一步厘清民族村寨、历史文化城镇景区商业化现象的系统结构、功能与影响机理,有助于对景区商业化现象进行合理的引导及控制。以贵州雷山西江苗寨为例,通过德尔菲调查法对旅游商业化结构系统的驱动要素进行识别,运用集成DEMATEL的解释结构模型方法对旅游商业化影响要素间的层级结构、有向作用强度及身份信息进行分析。研究结果显示:旅游景区商业化系统分为7个层级,涉及商业、社会、环境、管理及旅游产品5个类别的18个构成要素,各要素间表现为非平衡的作用关系。最后提出民族村寨、历史文化城镇景区旅游商业化控制的建议。     

Deformation monitoring and analysis at two frost mounds during freeze–thaw cycles along the Qinghai–Tibet Engineering Corridor

This paper presents various deformation-monitoring technologies employed to monitor the frost heave and thaw settlement of two mounds along the Qinghai–Tibet Engineering Corridor(QTEC), China. The QTEC is known as a critical infrastructure and passage connecting inland China and the Qinghai–Tibet Plateau(QTP). Three technologies—global navigation satellite system(GNSS), terrestrial laser scanning(TLS), and unmanned aerial vehicle(UAV)—were used to estimate the freeze/thaw–induced 3D surface deformation of two frost mounds. Our results showed that (1) the two frost mounds exhibited mainly thaw settlement in thawing periods and frost heave in the freezing period, but frost heave dominated after repeated freeze–thaw cycles;(2) different zones of the mounds showed different deformation characteristics;(3) active-layer thickness(ALT) and elevation changes were highly correlated during thaw periods;(4) integrated 3D-measurement technologies can achieve a better understanding and assessment of hazards in the permafrost area.     

用深井观测的地震研究东川地区随深度变化的场地放大因子.

采用中日合作，分别布设于东川垂直竖井中地下200ｍ、100ｍ 和地面３个位置的高精度数字化地震仪记录的地方震资料（震中距8.5～95ｋｍ，震级ML1.3～5.1），用频谱比的分析方法计算了东川地区不同深度（－100ｍ 和地面）的场地放大因子．在８个频率（f ＝0.75，1.0，1.5，2，3，4，5和12Ｈｚ）上所对应的在-100ｍ 处的3个分向（N-S，E-W，U-D）的场地放大因子（与-200ｍ 处相比），当0.75Ｈｚ f 2Ｈｚ时，为1.0～1.49；当2Ｈｚ＜ f ＜12Ｈｚ时，为0.47～0.99；在地面，3个分向在8个频率上所对应的场地放大因子（与-200ｍ 处相比）均大于1，其值为1.6～7.63．-100ｍ 处的Ｓ波和尾波场地放大因子与地面的Ｓ波和尾波的场地放大因子的相关系数，当0.75Ｈｚ f 2Ｈｚ频段时，分别为0.82和0.81；当2Ｈｚ＜ f＜12Ｈｚ频段时，分别为0.47和0.45．      

西部山区CEMP采集方法技术试验研究

西部山区CEMP数据采集技术与其它地区相比具有其特殊性 ,如果采用常规方法往往难以实施 ,或采集数据质量难以保证。根据近年来结合生产开展的试验 ,对一些具体技术 ,如电极距如何灵活选择 ,采集记录时间如何掌握 ,测点位置对资料品质的影响 ,磁站布设的疏密程度以及远参考、近参考的作用等 ,作了对比分析。此外 ,还总结了西部山区CEMP施工的一些技术特点及规律 ,指出了西部山区CEMP采集方法研究的重要性     

额尔古纳超大型火山热液型铀成矿带地质特征及找矿前景

本文介绍了在额尔古纳超大型火山热液型铀成矿带中发现的超大型火山热液脉型铀矿末有５个，大型火山热液脉型铀矿床有６个，总共有铀金属储量３３万ｔ，在世界热液脉型铀矿资源量中占有重要地位。经研究认为，该成矿带内铀矿就成矿作用在时间上具有突发性特征，成矿时代集中在早白垩世，受统一中生代大陆裂陷－火山岩浆活动控制；成矿介质中深源的火山岩水，大气水和变质水三者相混合的具中低温的火山热液，成矿物质主要来自中生代深     

STUDY ON MIXED MODEL OF NEURAL NETWORK FOR FARMLAND FLOOD/DROUGHT PREDICTION*

The paper concerns a flood/drought prediction model involving the continuation of time series of a predictand and the physical factors influencing the change of predictand.Attempt is made to construct the model by the neural network scheme for the nonlinear mapping relation based on multi-input and single output.The model is found of steadily higher predictive accuracy by testing the output from one and multiple stepwise predictions against observations and comparing the results to those from a traditional statistical model.