Geochemistry, Geochronology, Sr-Nd Isotopic Compositions of Jiang Tso Ophiolite in the Middle Segment of the Bangong- Nujiang Suture Zone and Their Geological Significance

The Jiang Tso ophiolite,situated in the middle segment of the Bangong- Nujiang Suture Zone,is a part of the easternmost Qieli Lake ophiolite subzone and is close to the south of Pung Lake ophiolite. The rock association of Jiang Tso ophiolite is relatively complete and is mainly composed of metamorphic peridotite,gabbro and diabase. Comparing with N-MORB,the ophiolite is high in Mg and low in Ti,K,Na,P,and is depleted in Nb,Ta,Hf,Th and enriched in Rb,Sr and Ba. Geochemical characteristics of the Jiang Tso ophiolite indicate it is of a supra-subduction zone type formed in the spreading ridge of back arc basin. The SHRIMP U-Pb dating of zircons from the gabbro yielded a weighted average age of 188.1±4.1 Ma(MSWD=1.4),indicating the Jiang Tso ophiolite was formed in the late stage of early Jurassic. The Sr,Nd isotopic compositions show that the Tethyan mantle domain is the depleted mantle(DM),with enriched mantle domain II(EM II). They have the same Sr,Nd isotopic composition with the India Ocean MORB type.     

Lithospheric Electrical Structure across the Eastern Segment of the Altyn Tagh Fault on the Northern Margin of the Tibetan Plateau

Project INDEPTH (InterNational DEep Profiling of Tibet and the Himalaya) is an interdisciplinary program designed to develop a better understanding of deep structures and mechanics of the Tibetan Plateau. As a component of magnetotelluric (MT) work in the 4th phase of the project, MT data were collected along a profile that crosses the eastern segment of the Altyn Tagh fault on the northern margin of the plateau. Time series data processing used robust algorithms to give high quality responses. Dimensionality analysis showed that 2D approach is only valid for the northern section of the profile. Consequently, 2D inversions were only conducted for the northern section, and 3D inversions were conducted on MT data from the whole profile. From the 2D inversion model, the eastern segment of the Altyn Tagh fault only appears as a crustal structure, which suggests accommodation of strike slip motion along the Altyn Tagh fault by thrusting within the Qilian block. A large-scale off-profile conductor within the mid-lower crust of the Qilian block was revealed from the 3D inversion model, which is probably correlated with the North Qaidam thrust belt. Furthermore, the unconnected conductors from the 3D inversion model indicate that deformations in the study area are generally localized.     

Paleostress Reconstruction of Micangshan Anticlinorium on the Southern Margin of the Qinling Orogenic Belts, China

Brittle structures in rock of different ages can be used to establish the tectonic evolution of an orogenic belt through paleostress calculations. Micangshan is located at the southern margin of the Qinling orogenic belt,between the SE-trending Longmenshan fold-and-thrust belt and the arcuate Dabashan thrust-and-fold belt. Structural observations revealed that the dominant structures are reverse and strike-slip faults and folds with E–W and NE–SE trends. To increase knowledge of the tectonic evolution of the Micangshan anticlinorium,faults,joints,veins,and folds were measured at more than eighty sites. On the basis of structural analysis,it emerged that the multiphase paleostress fields became established after the oblique collision between the North and South China plates. The earliest stress field with N–S compression was established during the Micangshan uplift associated with the E–W trending faults and folds. Subsequently,a N–S extension occurred when the Qinling orogenic belt collapsed. Then NW–SE compression developed,with NE trending faults and folds forming in relation to Longmenshan thrusting toward southwest on the eastern margin of the Tibetan plateau. With the development of the arcuate Dabashan orogenic belt,the compression stress orientation of the Micangshan anticlinorium altered from NE–SW to E–W.     

The Geological Characteristics of Chengkou Type Shale Gas of Lower Cambrian in Dabashan

<正>1 Introduction After the successful implementation of large-scale shale gas exploration、development and utilization in United States,the domestic shale gas exploration and development is in a rapid development.However,the progress of exploration and understanding of the highEvolution shale gas in the complex structure zone of the outer basin are relatively slow,the evaluation method and     

西藏古堆—隆子地区Sb,Pb,Zn化探元素的分形研究及其地质意义

文章根据西藏古堆—隆子地区Sb,Pb,Zn化探元素品位分析结果,结合区域地质资料,基于分形几何学的理论基础,对研究区Sb,Pb,Zn的分布规律进行了定量研究。结果表明,4个研究区Sb,Pb都具有多重分维的性质,且与矿化有关的分维值D2ⅡD2Ⅲ,同一研究区同一元素的各组分维值差距较大,Ⅲ区和Ⅳ区的Zn只有一个维数值,说明典型矿床发育的地区成矿元素具有多重的分维结构和低分维值D2,基于此理论成功验证了恰嘎研究区具有寻找锑矿前景。通过研究Sb,Pb,Zn的分形特征,揭示出化探元素的分维结构和分维值的大小与矿化程度有关,并为找矿勘查工作提供一定的地质依据。     

长江与嘉陵江交汇区水流结构的数值模拟

针对天然河流交汇区域复杂的地形条件及水流运动特性,采用水气两相流三维数值模型,对长江与嘉陵江交汇区水流运动进行深入研究,分析了交汇区域分离区、剪切层、流速场及螺旋度的变化特性。研究结果表明:长江与嘉陵江交汇的水流分离区形状受地形影响明显,随着水位的增加向右岸移动,剪切层整体呈一个扭曲的曲面;干支流原有的环流在交汇之后重新汇合,左岸未出现明显的环流,右岸逆时针的环流有减弱趋势,交汇区域纵向流速呈现高速与低速带分布特征。此外,长江和嘉陵江在交汇口下游螺旋度呈现左侧为负、右侧为正的对称分布,水流结构表现出逐渐形成双螺旋流的趋势,其中左侧的螺旋流逆时针运动,右侧的螺旋流顺时针运动。     

鄂尔多斯盆地LFP区块长2段沉积相研究

储层的沉积相研究通常是油气藏勘探开发过程中一项十分重要的任务,它控制着储集砂体的成因类型及宏观分布。在岩芯观察的基础上,结合综合录井资料和野外露头剖面信息,运用沉积学、沉积构造、剖面结构、古生物及测井相等划分沉积相的标志,对研究区内钻井进行单井沉积相划分,对不同钻井之间的沉积相进行综合比对,结果认为LEP区块长2段主要从三角洲前缘高建设的水下分流河道骨架砂体沉积为主。     

可可西里盆地东部五道梁群热水湖相成因新认识

五道梁地区位于青藏高原北部可可西里盆地东部,其中新世发育一系列古湖泊,保存有大套碳酸盐沉积。本文通过对五道梁北山含叠层石剖面和南部剖面进行矿物学、元素地球化学研究,发现叠层石剖面主要矿物为方解石和少量石英,而南侧剖面则含有铁白云石、方解石、石英和钠长石。铁白云石和钠长石次生加大边的发现说明该区曾受热水活动的影响。元素分析结果也显示As、Sb、Ba、Fe等热水沉积标志元素含量较高,且Ni/Co、Mn/Sr、V/Cr、V/Sc等比值也较高;加之稀土元素配分模式和碳氧同位素特征均表明该地区为热水湖相沉积。另外叠层藻的出现也反映当时湖水温度至少为20~30℃。综合各种分析结果说明五道梁群为热水湖相成因,该区中新世发育有大量火山岩,因此可作为下一步寻找火山沉积型硼矿床重要线索。     

中天山地块暗色岩墙LA-ICP-MS锆石U-Pb年龄和岩石地球化学特征

中天山地块发育有大量的暗色岩墙,主要走向为北北西。对中天山暗色岩墙进行LA-ICP-MS锆石U-Pb测年,获得的年龄为304.8±1.5Ma,表明其形成于晚石炭世。这些暗色岩墙具有较高的Si O2,较低的Mg、Cr、Ni含量。它们富集大离子亲石元素(Rb、Ba、Th),亏损高场强元素(Nb、Ta、Ti),显示俯冲相关特征。上述特征暗示,中天山暗色岩墙可能是由俯冲板片流体交代的地幔楔部分熔融形成的。这一发现表明,准噶尔洋的闭合应该发生在晚石炭世之后。     

区域产学研体系下创新人才培养研究——以工科专业学位研究生为例

从人才创新机制下剖析区域产学研合作体系内涵,分析工科专业学位研究生培养现状及存在问题。以西南科技大学多年来区域产学研联合办学及专业学位发展为例,深入剖析产学研体系下工科专业学位研究生创新人才教育模式,探索总结区域产学研模式下创新型人才培养途径和思路,为进一步壮大工科专业学位研究生培养模式和发展规模提供参考。