峰丛洼地石漠化景观演化与土地利用模式

峰丛洼地石漠化景观格局是土壤分布空间格局的制约下,岩溶生态系统对植被强烈依附性条下,由不同类型人类活动决定的。农耕、放牧和砍伐是最主要的破坏峰丛植被的人类活动;缓坡耕地形成轻度石漠化景观;陡坡地形成中度石漠化景观,因坡面土壤流失,演化为更高等级石漠化景观;峰丛陡坡放牧和砍伐都可能直接形成峰丛上部大面积中-强度石漠化景观,出现峰丛坡面石漠化景观分异,产生不同的土地利用模式。     

Geochronology of the Xihuashan Tungsten Deposit in Southeastern China: Constraints from Re–Os and U–Pb Dating

Xihuashan tungsten deposit is one of the earliest explored tungsten deposits in southeastern China. It is a vein type deposit genetically associated with the Xihuashan granite pluton. Here we report new dating and zircon geochemistry results. Re–Os isotopic dating for molybdenite intergrowth with wolframite in the oldest generation of the Xihuashan pluton yielded an isochron age of 157.0 ± 2.5 Ma (2σ). Zircon U–Pb laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) dating shows that the pluton crystallized at 155.7 ± 2.2 Ma (2σ). This age is similar to the molybdenite Re–Os age for the ore deposit within error. This, together with published data, suggests that the major W(Mo)‐Sn mineralization occurred between 160–150 Ma in southeastern China. These deposits constitute a major part of the magmatic‐metallogenic belt of eastern Nanlin. The lower Re content in molybdenite of the Xihuashan tungsten deposit shows crustal origin for the ore‐forming material. The limited direct contributions from the subducting slab for the tungsten mineralization in the Nanling region suggest a change of the style of the paleo‐Pacific plate beneath southeastern China.     

岩脉多次侵入条件下斜坡变形破坏模式及稳定性分析

岩质斜坡受到花岗岩脉的多次侵入,坡体结构和岩体结构均有较大的改变,因此斜坡的变形破坏模式和稳定性均有可能发生变化。本文以雅砻江中游楞古水电站坝址区嘎夏帕斜坡为例,对多次花岗岩脉侵入条件下斜坡的变形破坏模式和稳定性进行分析。嘎夏帕斜坡原本为陡倾中薄层砂岩组成的逆向坡,岩体完整性较好,稳定性较高; 由于受到花岗岩脉的多次侵入,坡体变成砂岩和岩脉互层的结构,在岩脉挤压作用下,大部分岩体呈碎裂状,完整性差,坡体的变形模式由弯曲-倾倒式变为挡墙溃决式。中部完整性较好的砂岩成为挡墙,和前部岩脉一起阻止后部大方量碎裂状岩体下滑,但是随着前部脉体的失稳破坏,斜坡有可能发生挡墙溃决式整体滑坡。并通过数值模拟软件3DEC进行了验证,计算结果与定性分析一致。本文的结论可以为此类斜坡的稳定性分析和防治提供理论支持,具有一定的参考价值和实际意义。     

Dynamic features of near-inertial oscillations in the Northwestern Pacific derived from mooring observations from 2015 to 2018

Near-inertial oscillation is an important physical process transferring surface wind energy into deep ocean.We investigated the near-inertial kinetic energy(NIKE) variability using acoustic Doppler current profiler measurements from a mooring array deployed in the tropical western Pacific Ocean along130°E at 8.5°N,11°N,12.6°N,15°N,and 17.5°N from September 2015 to January 2018.Spatial features,decay timescales,and significant seasonal variability of the observed NIKE were described.At the mooring sites of 17.5°N,15°N,and 12.6°N,the NIKE peaks occurred in boreal autumn and the NIKE troughs were observed in boreal spring.By contrast,the NIKE at 11°N and 8.5°N showed peaks in winter and troughs in summer.Tropical cyclones and strong wind events played an important role in the emergence of high-NIKE events and explained the seasonality and latitudinal characteristics of the observed NIKE.     

The effects of dam construction and precipitation variability on hydrologic alteration in the Lancang River Basin of southwest China

This paper presents an evaluation of the spatio-temporal patterns of hydrologic alteration induced by dam construction and precipitation variability in the Lancang River Basin of southwest China from 1957 to 2000. Analyses were conducted using the linear regression method, the Mann–Kendall test, and the Range of Variability Approach. The results indicate that there was considerable variation in the average monthly precipitation between the pre- and post-dam periods in the Lancang River Basin. Second, the magnitude of monthly runoff was strongly related to precipitation, which showed an up-down annual variation, and was significantly altered by dam construction and precipitation variability. In the modified series (hydrologic series with the precipitation impacts removed), runoff deviations between the pre- and post-dam periods became larger. Third, the extreme runoff cycles were influenced by dam construction and precipitation variability downstream from the dam, and the monthly maximum runoff increased from the pre-dam to post-dam period at all hydrologic stations. Fourth, the degree of hydrologic alteration (DHA) indicates that the precipitation variability not only affected the hydrologic regime of unregulated river reach but also modified the negative impacts of dam construction, which could provide a modest mitigation of the hydrologic alterations induced by dam construction, possibly decreasing the level of DHA. Last, the overall degree of hydrologic alteration in the observed series reached 25.2, 25.3, and 29.1 % for the upstream, midstream, and downstream areas, respectively. These results show that the hydrologic regimes of the Lancang River during the 1957–2000 period were affected by damming and precipitation variability, but the hydrologic alteration was relatively low in the upstream areas of the river without a dam.     

双量子阱结构OLED效率和电流的磁效应

通过结构为ITO/NPB(60 nm)/ Alq₃ ∶1 wt% rubrene(20 nm)/ Alq₃(3 nm)/ Alq₃ ∶1 wt% rubrene(20 nm)/ Alq₃(20 nm)/LiF/Al的双量子阱的黄色有机电致发光器件,研究了不同磁场强度下的发光效率和电流变化特性. 研究结果表明该器件的电流是随着磁场强度的增加而单调下降的,显示了器件的电阻是随着磁场强度的增加而增加的. 同时也得到了该结构有     

上扬子区下古生界层序地层格架的初步研究

上扬子区下古生界在贵州及其邻区发育较为完整。在震旦纪与寒武纪之交的台地淹没事件之后,寒武系形成一个从深水盆地相黑色页岩系到大套台地碳酸盐的沉积序列,其中下寒武统包含5个三级层序而可以进一步归为一个二级层序,中上寒武统构成一个二级层序而且可以进一步划分为7个三级层序。奥陶纪艾家山世末期的都匀运动、奥陶纪末期的与冈瓦纳大陆冰期相响应的全球海平面下降事件以及志留纪末期广西运动的共同作用,造成扬子地台大幅度的古地理变迁以及残留不全的奥陶系和志留系。详尽追踪和对比的结果可以将奥陶系划分为8个三级层序且可以进一步归为一个二级层序,在残留不全的的志留系中可以划分出7个三级层序并可以进一步归为一个二级层序。层序地层格架的建立,可以大致解读许多有趣的地质现象,如寒武纪碳酸盐台地的生长过程,奥陶纪与志留纪之交的“浅海静水”型黑色页岩系的发育特点,志留纪由北而南的海侵所造成的复杂的志留系展布特征等等;同时也意味着许多有待于进一步研究的问题,早寒武世数次快速海侵事件与生物事件的关系,奥陶系顶部特殊的“观音桥灰岩”的成因,奥陶系红花园组海绵生物礁的基本沉积模式等等。     

黄山不同高度雨滴谱的演变特征

选取2011年6月黄山地区一次降水过程,利用测得的雨滴谱资料对不同高度上降水微物理量及雨滴谱分布特征进行分析,并讨论其中的差异。结果表明:此次降水较强,各直径微物理量在山腰最大、山底次之、山顶最小;山腰的雨强最大,而山顶数浓度最大。在雨滴谱分布中,小于1mm的雨滴数密度是山顶大于山腰大于山底,这与小雨滴的蒸发和碰并有关;大于1.5 mm的雨滴数密度则是山腰大于山顶和山底,这可能与地形抬升使得云系加强有关。由各微物理量的时间序列可将降水过程分为两个阶段,第一阶段各微物理量值明显大于第二阶段,其中第一阶段的降水量约为第二阶段的3倍。雨强与雷达反射率、数浓度、最大直径近似成幂函数关系,其中雨强与雷达反射率相关性最好。     

基于细粒岩石类型对玛湖凹陷下二叠统风城组烃源岩分类评价

准噶尔盆地玛湖凹陷风城组页岩油勘探取得巨大突破,但是按照普遍认可的页岩油烃源岩评价标准,本区的烃源岩品质并不理想。为了科学评价玛湖凹陷烃源岩品质特征,本文在系统的岩心观察和有机地球化学分析的基础上,揭示烃源岩的形成环境,并按照矿物组成对烃源岩分类评价。玛湖凹陷风城组细粒岩主要沉积于正常半深湖、咸化半深湖、半咸化半深湖、含热液半深湖和滨浅湖环境中,各环境中细粒岩的有机质特征存在一定区别,其中半咸化半深湖有机质较为富集,w(TOC)均值在1%左右。进一步结合有机质类型判别图解,表明咸化半深湖和含热液半深湖有机质来源以湖泊生物为主,而其他环境中存在湖泊和陆源混合有机质来源。基于有机质生烃潜力评价和成熟度(V_re=0.74%)估算,表明目前风城组烃源岩中有机质正处于大量排烃的成熟阶段,且确定了细粒岩中的烃类为原生烃。由于不同矿物组成的烃源岩吸附能力的差异,按照陆相泥质烃源岩和碳酸盐质烃源岩开展分类评价,结果表明风城组沉积了累计厚度近250 m的的有效烃源岩,且富含以藻类体为主的有机质。     

拉萨地块松多榴辉岩的变质演化过程:NCKMnFMASHTO体系中的相平衡关系

拉萨地块松多榴辉岩主要矿物组合为石榴子石、绿辉石、角闪石、多硅白云母、绿帘石、金红石。石榴子石环带不明显,核部成分均一,从核部到边部,镁铝榴石和钙铝榴石含量降低,可能分别记录了榴辉岩峰期及退变质过程信息。绿辉石显示微弱的成分环带,硬玉含量从核部到边部略有升高,部分绿辉石边部发育韭闪石退变质边,反映了在减压过程中外来流体进入体系的过程。多硅白云母具有高的Si含量(3.5~3.6),其中石榴石包体中的多硅白云母相对基质中的白云母有更高的Si值。本文利用Thermocalc变质相平衡模拟软件,结合详细岩相学观察,在NCKMn FMASHTO体系下,模拟松多含多硅白云母榴辉岩的变质演化过程。其中,榴辉岩峰期矿物组合为g+o+law+phn+ru,石榴石核部最大镁铝榴石值和石榴子石包体中多硅白云母最大Si值确定的榴辉岩峰期温压条件约为620℃,32×105Pa,榴辉岩经历了近等温降压的退变质过程。相平衡模拟结果表明拉萨地块松多榴辉岩经历了超高压变质作用过程,并经历了相对快速的折返过程到中部地壳层次。