Anticlockwise pressure–temperature paths record Variscan upper‐plate exhumation: Example from micaschists of the Porto Vecchio region,Corsica

To better understand the evolution of deep‐seated crust of the Variscan orogen in the Sardinia‐Corsica region, we studied garnet‐bearing micaschists which were sampled 3 km east and 15 km northeast of Porto Vecchio, south‐eastern Corsica. After a careful investigation of the textural relations and compositions of minerals, especially of zoned garnet, a P–T path was reconstructed using contoured P–T pseudosections. U–Th–Pb dating of monazite in the micaschists was undertaken with the electron microprobe. The micaschists from both localities were formed along similar anticlockwise P–T paths. The prograde branch of these paths starts at 3 kbar close to 600°C in the P–T field of sillimanite and reaches peak conditions at 7 kbar and 600 (15 km NE of Porto Vecchio) to 630°C (3 km E of Porto Vecchio). The metamorphism at peak P–T conditions happened c. 340 Ma based on low‐Y (<0.65 wt% Y₂O₃) monazite. Ages of monazite with high‐Y contents (>2 wt% Y₂O₃), which probably have formed before garnet, scatter around 362 Ma. The retrograde branch of the P–T paths passes through 4 kbar at ~550°C. We conclude that the micaschists belong to a common metasedimentary sequence, which extends over the Porto Vecchio region and is separated from other metamorphic rock sequences in the north and the south by major tectonic boundaries. This sequence had experienced peak pressures which are lower than those determined for metamorphic rocks, such as micaschist and gneiss, from north‐eastern Sardinia. At present, we favour a continent–continent collisional scenario with the studied metasedimentary sequence buried during the collisional event as part of the upper plate. The contemporaneous high‐P metamorphic rocks from NE Sardinia were part of the upper portion of the lower plate. The addressed rocks from both plates were exhumed in an exhumation channel.     

P–T evolution of glaucophane–omphacite bearing HP–LT rocks in the western Tianshan Orogen, NW China:new evidence for 'Alpine-type' tectonics

The late Palaeozoic western Tianshan high‐pressure /low‐temperature belt extends for about 200 km along the south‐central Tianshan suture zone and is composed mainly of blueschist, eclogite and epidote amphibolite/greenschist facies rocks. P–T conditions of mafic garnet omphacite and garnet–omphacite blueschist, which are interlayered with eclogite, were investigated in order to establish an exhumation path for these high‐pressure rocks. Maximum pressure conditions are represented by the assemblage garnet–omphacite–paragonite–phengite–glaucophane–quartz–rutile. Estimated maximum pressures range between 18 and 21 kbar at temperatures between 490 and 570 °C. Decompression caused the destabilization of omphacite, garnet and glaucophane to albite, Ca‐amphibole and chlorite. The post‐eclogite facies metamorphic conditions between 9 and 14 kbar at 480–570 °C suggest an almost isothermal decompression from eclogite to epidote–amphibolite facies conditions. Prograde growth zoning and mineral inclusions in garnet as well as post‐eclogite facies conditions are evidence for a clockwise P–T path. Analysis of phase diagrams constrains the P–T path to more or less isothermal cooling which is well corroborated by the results of geothermobarometry and mineral textures. This implies that the high‐pressure rocks from the western Tianshan Orogen formed in a tectonic regime similar to ‘Alpine‐type’ tectonics. This contradicts previous models which favour ‘Franciscan‐type’ tectonics for the southern Tianshan high‐pressure rocks.     

T Tauri Stars

The observable characteristics of young solar-mass stars (T Tauri stars) are reviewed. Modern theoretical concepts and models of these stars are discussed briefly.     

基于T2WELL的U型地热井供暖潜力数值模拟

为了了解U型井式闭循环地热系统的可持续利用能力,探究场地内利用U型井式闭循环地热系统开发地热能用于供暖的可行性,以及地热井长期运行下的产能状态和不同影响因素的作用规律,设计合理的地热能开采方案。采用数值模拟方法,以邯郸东部平原地区试验井的短期实测数据为基础,以多相多组分井筒-储层耦合流动模拟程序T2WELL为工具,开展场地尺度U型井长期换热数值模拟。研究结果显示：U型井式闭循环地热系统水平井段长度为400～500 m,循环流速和注入温度分别设置为80 m3/h和20 ℃左右时,可以实现地热能的可持续开采,20 a平均提热功率能满足供暖需求,采用该种方式进行供暖具备较高的可行性。      

构造活动影响下地质事件沉积序列——以鄂尔多斯盆地延长组长7油层组为例

中晚三叠世,印支运动I幕导致秦岭隆升,同期地震、火山活动频发,在鄂尔多斯湖盆中保存了大量地质事件沉积层。为了认识构造活动影响下地质事件沉积序列,探讨地质历史时期内各类地质事件的耦合关系,从全新的角度认识大型坳陷湖盆的形成和演化过程,笔者等以鄂尔多斯盆地内部及周缘的长7油层组野外露头及钻井岩芯中发育的关键事件沉积层为研究对象,对地震事件、浊流事件、火山事件、缺氧事件沉积特征和叠置关系进行研究。研究结果表明：在长7期,湖盆中多种事件沉积类型主要受控于中—晚三叠世秦岭造山运动,构造活动引起湖盆沉降,为事件沉积层的保存提供了条件;火山事件喷发的火山灰降落在湖盆中形成凝灰岩层,同时,也为湖盆缺氧事件创造了条件;沉积层因地震活动形成震积岩,而地震活动又是诱发浊流事件发生的关键因素;这些构造活动影响下的地质事件交替发生,共同构成长7油层组内各类事件沉积层的相互叠置关系。     

Mineralogical characteristics of continental shale: a case study in Yan-Chang Formation,Ordos Basin

The Chang 7 Member of the Yan-Chang Formation (Yan-Chang #7 Member), which is located in the central south of the Ordos Basin (China), is assessed for its potential as a shale gas resource. The characteristics and spatial variability of mineral components in this continental shale formation play a crucial role in evaluating and characterising the shale reservoirs. We collected 64 shale core samples from 30 representative sampling sites located in the central south of the Ordos Basin using X-ray diffraction and field emission scanning electron microscopy to study the mineral compositions, vertical/planar variations of minerals, and the major controlling factors that result in such variations. Based on the relative fractions of the dominant minerals, the shale rocks can be classified into four categories: quartz-rich (type #1), illite/chlorite-rich (type #2), illite–smectite mixed-layer-rich (type #3) and feldspar-rich (type #4). In general, type #1 is mainly located in the northwest of the study area, type #4 is mainly located in the south of the study area, and types #2 and #3 are sandwiched between types #1 and #4. In the centre of the basin, the illite content increases with burial depth and the conversion from smectite to illite, which is experimentally confirmed in this study, enhances the surface porosity of shale. The major factors influencing the properties and spatial variability of the mineral components include sedimentary environment, provenance and diagenesis. Compared with marine shales in China (e.g. Longmaxi marine shales), the Yan-Chang #7 Member continental shale has a higher clay content, but lower calcite, dolomite and pyrite contents. The brittleness indexes of type #1 shale in Wuqi and its surrounding areas are marginally higher than that of Longmaxi marine shales, which makes the type #1 shale in the Wuqi and its surrounding areas slightly easier to fracture than the Longmaxi marine shales.     

湖泊细粒沉积特征精细研究：以鄂尔多斯盆地延河剖面长7油层组为例

野外地质露头为精细刻画沉积体内部结构、建立准确地下地质模型发挥着重要作用。以鄂尔多斯盆地延河剖面长7段为例,采用岩石学、野外露头沉积学方法,详细剖析了湖泊细粒沉积的岩相类型、特征、垂向组合及沉积环境。研究结果表明,延河剖面长7段发育平行层理细砂岩相、流水交错层理细砂岩相、浪成交错层理粉砂岩相、沙纹层理粉砂岩相、变形层理粉砂岩相、水平层理(泥质)粉砂岩相、块状泥岩相、水平层理(砂质)泥岩相、水平纹层页岩相9种岩相类型。在结合区域地质特征基础上,研究认为长7段为远源的曲流河三角洲前缘和浅湖-半深湖沉积,进一步细分出7类沉积单元,其中水下分支河道、支流间湾较为发育,水下天然堤、远砂坝、席状砂发育规模较小,浅湖-半深湖沉积只在长72段下部发育,河口坝基本不发育,仅局部可见。对各沉积单元的垂向分布特征进行深入研究,识别出Ⅰ、Ⅱ、Ⅲ、Ⅳ 4类垂向分布形式,其中Ⅰ、Ⅱ组合主要分布在研究区长71、长73亚段,Ⅲ、Ⅳ组合主要分布在研究区长72亚段。剖面相分析表明,长7沉积期整体为一套先变细、再变粗的细粒沉积序列,为曲流河三角洲前缘沉积—浅湖-半深湖沉积—曲流河三角洲前缘沉积。     

HYD verifications using numerical methods

HYD, as described in Eurocode 7 (EC7), is related to the upward flow of water through the soil towards a free surface, such as in front of a retaining wall or in the base of an excavation. The HYD verification, using numerical analysis, can be performed with two different approaches. The first approach is the conventional soil block approach where safety may be checked by calculating the equilibrium of a rectangular block of soil. The second approach is the integration point approach where stability can be verified at every integration point in the numerical analysis by checking that the equilibrium is satisfied for a soil column of negligible width above each point. In this paper, the two approaches are described and their advantages and disadvantages are discussed. Comparisons made using benchmark geometries, extensively studied and discussed between the members of the EC7 Evolution Group 9, on Water Pressures, illustrate that the HYD verification using numerical methods seems very promising. Thorough comparisons between the factors from the two approaches allow designers to better understand the benefits of using more advanced and robust approaches for such stability verifications.     

非均质裂隙介质中重非水相流体运移

由于裂隙介质具有强烈非均质性,使得重非水相流体(DNAPLs)在裂隙介质中的运移行为较孔隙介质更为复杂.基于指示模拟算法模拟裂隙介质的二元变量(粗糙面接触和裂隙开口),综合模拟退火算法构建裂隙渗透率随机场.采用T2VOC模拟DNAPLs在裂隙介质的运移,探讨粗糙面接触的相关长度、各向异性比、倾角以及非均质性程度对DNAPLs运移分布的影响.数值分析结果表明,粗糙面接触的相关性越差,DNAPLs污染范围越大;粗糙面接触的各向异性比和倾角增大,将导致更多DNAPLs残留;而相关长度和各向异性比增大以及倾角减小,都会引起DNAPLs锋面运移速率增大;随着渗透率非均质性增强,会导致局部粗糙面接触上蓄积的DNAPLs饱和度增大,运移速率减小.     

基于 C＃的 CORS 数据预处理

针对CORS数据预处理的不可视性和繁琐性问题,综合 T EQC和QCVIEW的优势,用C＃编程实现了CORS数据预处理的可视化和便捷化。详细论述了程序的设计思路,并对预处理结果数据进行了对比分析,证明该程序可以有效改善CORS观测数据的质量,并有助于进行数据质量评价。