重庆地区地震震源机制解及动力环境分析

使用中国地震台网约100台原始观测波形数据,利用FOCMEC震相法确定了2017年11月23日5.0级重庆武隆和2016年12月27日4.9级重庆荣昌地震的震源机制解。同时搜集了重庆地区近年来其它震源机制资料。结果显示武隆地震属于走滑正断型,与2013年发生在七曜山断裂带中段的石柱地震活动性质相似,推断七曜山断裂以正断活动为主。发生在华蓥山断裂带南段的荣昌地震属于走滑逆冲型,推断华蓥山断裂(南段)以逆冲活动为主。从区域震源机制解结果看,华蓥山断裂南段所在的重庆西部主要受近东西向挤压构造应力控制,与华南区域构造应力场一致。七曜山断裂带所在的重庆中东部主要受近南北向挤压应力控制,与现今华南区域构造应力场不一致。推断重庆中东部处于一个与周围应力和构造活动方式不同的独特环境。综合新生代构造资料推断,青藏高原隆升基本没有影响华蓥山断裂带以东地区。重庆中东部至两湖平原地区处于特提斯构造域和环太平洋构造域的转换过渡区,其独特的应力环境表明该区现今似乎不受两大构造域的影响。     

郯庐断裂带(安徽段)及邻区的动力学分析与区域构造演化

依据区域构造层次划分,采用构造筛分法,层层深入,层层筛分,确定发生于各个不同时代地层/岩层内的断裂活动的同期及叠加的应力场特征。综合所有的同期应力场特征及辅以叠加的应力场特征来验证,从而确定了一个连续的、完整的断裂活动的应力场演化序列;结合区域构造变形特征分析,阐明郯庐断裂带(安徽段)的构造演化。应力场分析显示:晚三叠-早侏罗世应力场为北北西—南南东或近南北向挤压,属古特提斯构造域,断裂发生同造山走滑;早白垩世早期,应力场为北西—南东向挤压,断裂发生左行走滑运动,中国东部处于西环太平洋构造域;早白垩世晚期—古新世(始新世),区域发生北西—南东向伸展作用,断裂处于伸展断陷作用阶段;新生代,受区域上近东西向的挤压作用影响,断裂发生挤压逆冲兼右行走滑作用。     

冀东宽城-青龙-金厂峪金矿集中区早燕山期构造应力场及其对金矿化的控制作用

冀东宽城-青龙-金厂峪金矿集中区早燕山期地壳运动与构造-岩浆活动强烈,形成了区内NE向、EW向与NW向压扭性-扭性主干断裂构造-岩浆带与20多个金矿床。早燕山期构造应力场对这些断裂的形成演化与金矿的成矿作用有重要的控制意义。在野外调研与古构造应力测量的基础上,确定受力方式、位移方向与若干地点的差应力值,进而应用有限元计算模拟方法,剖析早燕山期区域平面构造应力场及其与金矿化的关系。结果表明,该金矿集中区早燕山期区域最大主压应力方向以NW-SE向为主,最小主压应力方向以NE-SW向为主;区域构造应力值变化于2.5-220MPa;构造应力方向、构造应力大小与应力梯度带对金矿化均有明显的控制作用。      

丽江地震区应力场研究

通过现场调查工作,研究了丽江地区主要活动断裂的特征及现代活动性,分析了该地区构造应力场演化历史及现今构造应力场特征,探讨了丽江地震产生的机制,然后用离散元方法对该地区现今应力场进行了二维模拟,并进而深化了对丽江地震区应力场的认识。丽江地区处于川滇菱形断块的西南部,巨甸-九子海断块二级断块中的玉龙雪山-九子海三级断块上,该断块介于近南北向的楚波-白汉场断裂、北东走向丽江-小金河断裂和北西向中甸-永胜断裂之间,平面上成一顶角向东的三角形。在近南北向现今应力场的作用下,北东向的丽江-小金河断裂左旋走滑,北西向的中甸一永胜断裂右旋走滑,使两者所夹持的巨甸-九子海断块的主体部分发生向西的位移,在两者的复合部位,即断块的尖端附近,形成了局部的近东西向的拉张应力环境,从而使处于该部位的南北向玉龙雪山东麓断裂于1996年2月3日因发生了正断错动而导致了7．0级地震的发生。该地震后第三天,在其震中的正南方又发生了一次6．0级余震,其地震破裂是由北向南的一种撕裂,进而说明,本次地震的发生是由于玉龙雪山东麓断裂与中甸一永胜断裂复合部位拉张应力的强烈集中造成的。     

鄂尔多斯盆地周边断裂运动学分析与晚中生代构造应力体制转换

基于对鄂尔多斯盆地西南缘构造带、中央断裂、东缘边界带和东北部地区的断裂几何特征、运动学及其活动期次的野外观察和测量,并根据断层面上滑动矢量的叠加关系和区域构造演化历史,确定了鄂尔多斯盆地周边地带晚中生代构造主应力方向、应力体制及其转换序列,提出了4阶段构造演化模式和引张-挤压交替转换过程。早中侏罗世,盆地处于引张应力环境,引张方向为N-S至NNE-SSW向。中侏罗世晚期至晚侏罗世,构造应力场转换为挤压体制,盆地周缘遭受近W-E、NW-SE、NE-SW等多向挤压应力作用。早白垩世,盆地构造应力场转换为引张应力体制,引张应力方向为近W-E、NW-SE和NE-SW向。早白垩世晚期至晚白垩世,盆地应力体制再次发生转换,从前期的引张应力体制转换为NW-SE向挤压应力体制。晚中生代构造应力体制转换和应力场方向变化不仅记录了不同板块之间汇聚产生的远程效应,同时记录了盆地深部构造-热活动事件,并对盆地原型进行了一定的改造。     

浙江新路火山岩盆地构造应力场及其对铀成矿的控制

构造因素分析是成矿过程分析的基本要素之一。本文通过对各古构造层中发育的共轭剪节理和褶皱测量统计,恢复了本区白垩纪以来的各期古构造应力场,发现各期古构造应力场的中间主应力轴均为近水平状态,其中建德期最大主压应力方向为NW向,衢江期最大主压应力方向为NNE向,始新世–渐新世期最大主压应力方向为近EW向。指出本区球川–萧山断裂等NE向区域大断裂构造开启的期次,决定了成矿期次,开启的时间决定了铀矿形成的年龄,其开启时序明显受古构造应力场发展演化控制。建德期晚期,随着NW向挤压应力场转为应力松弛状态,区域大断裂处于开启状态,火山喷发期后的深部含矿流体沿区域大断裂向上运移,形成了本区早期铀成矿(125~115 Ma),衢江期NNE向挤压构造应力场使本区区域大断裂再次开启,带来了深部成矿流体,形成了第二期铀成矿(90~70.2 Ma),两期铀成矿叠加最终形成了本区的铀矿化定位。     

信阳地区现今构造应力场数值模拟

研究活动断裂的构造格架，以震源机制解和现今位移测量资料为基础，采用非连续介质有限元法，对信阳地区现今构造应力场进行了数据模拟。结果表明，信阳地区现今区域构造应力场的特征反映出沿北西向游河-赐儿山、龟山-凉亭活动断裂和北东向张湾-平桥、南湾-湾Si河港活动断裂的端部和拐点应力集中；信阳市燃气混气站场址处于构造应力平缓区，构造应力集中区离燃气混气站场址的距离均在7km以上。这一结果为信阳燃气混气气站工程的建设提供了现今构造应力场方面的依据。     

甘肃北山旧井地区晚第四纪活动断裂分布及其构造意义

通过对甘肃北山地区遥感影像分析、地质填图和断裂活动性研究,探讨了北山地区晚第四纪以来的变形机制。结合青藏高原北部区域构造应变、应力场,认为北山地区现今构造格局是在印度板块与欧亚板块相碰撞形成的北东向挤压构造应力场的作用下,重新激活东西向的晚古生代、中生代断裂,并产生北东向新生断裂。说明印度板块与欧亚板块相碰撞并持续向北运移所产生的构造变形不仅局限于青藏高原内部及其边界,更影响到青藏高原以北的地区。     

塔里木盆地大北气田构造应力场解析与数值模拟

构造应力场研究对于塔里木盆地大北气田的开发具有重要理论与现实意义。通过区域断裂与背斜长轴走向、钻井诱导缝走向与井壁坍塌方位分别确定了古、今构造应力场的方向,采用测井资料计算了古、今构造应力场的大小。在此基础上,利用ANSYS有限元分析软件建立了大北气田主体气藏区大北102区块和大北201区块的地质模型,并通过测井资料计算及动静态转换确定岩石力学参数,利用构造应力场解析结果确定边界条件,进行了大北气田古今构造应力场的数值模拟,分析了构造应力场的分布规律以及构造应力场与构造裂缝和产能的关系。结果表明:大北气田古、今水平最大主应力方向分别约NNW336°和NWW305°,应力大小分别具有σHσhσv和σHσvσh的特征,分别属于Ⅱ类和Ⅲ类地应力;主应力和主差应力在平面上表现为背斜高部位为低值、翼部为高值,纵向上随深度增加而增大;构造裂缝的走向受控于水平最大古构造应力方向,与现今水平最大主应力方向近似平行或呈小角度相交,构造裂缝可沿走向继续延伸,开度也不会因构造挤压作用大幅降低,有效性可得到很好的保存,气藏区构造裂缝发育程度与主差应力的大小呈正相关关系;背斜高点是构造应力的低值区,油气在应力势差和浮力的共同驱动下聚集成藏,其中主差应力较大的井点构造裂缝较发育,无阻流量较高,因此在背斜高点主差应力较大的区域部署井位,有较大概率获得天然气的高产。     

川东南构造应力场地质分析及构造变形成因机制讨论

细致辨析构造应力对研究区域作用方式和转换形式,对页岩气保存条件评价具有重要的指导意义。通过研究直立褶皱、共轭节理等各种构造形迹,采用构造解析分析方法,研究川东南构造应力场演化特征。同时在构造应力场地质分析的指导下,运用构造形迹叠加分析的方法及定年分析,清晰刻画了川东南构造应力作用方式以及期次,认为川东南主要受到四期不同方向构造应力作用,其中NW向挤压应力最早影响到研究区,形成控制研究区主体构造特征的NE向构造;其次是近SN向挤压应力对研究区的作用,发育一系列及EW向构造;随后印—亚板块碰撞远程响应在川东南形成EW向挤压,形成近SN向构造;最后NE—SW向构造应力是渐新世晚期以来一直影响研究区活动的主要动力来源,并对早期油藏进行改造和调整。川东南龙马溪组页岩气受到多期构造联合作用的影响:燕山晚期NW向挤压应力作用,致使研究区褶皱变形;渐新世晚期以来的构造活动,导致研究区大范围隆升剥蚀,断层出露地表,影响了页岩气保存条件的有效性。     

The terrestrial fauna of the Late Triassic Pant-y-ffynnon Quarry fissures,South Wales,UK and a new species of Clevosaurus (Lepidosauria: Rhynchocephalia)

Pant-y-ffynnon Quarry in South Wales yielded a rich cache of fossils in the early 1950s, including articulated specimens of new species (the small sauropodomorph dinosaur Pantydraco caducus and the crocodylomorph Terrestrisuchus gracilis), but no substantial study of the wider fauna of the Pant-y-ffynnon fissure systems has been published. Here, our overview of existing specimens, a few described but mostly undescribed, as well as freshly processed material, provides a comprehensive picture of the Pant-y-ffynnon palaeo-island of the Late Triassic. This was an island with a relatively impoverished fauna dominated by small clevosaurs (rhynchocephalians), including a new species, Clevosaurus cambrica, described here from a partially articulated specimen and isolated bones. The new species has a dental morphology that is intermediate between the Late Triassic Clevosaurus hudsoni, from Cromhall Quarry to the east, and the younger C. convallis from Pant Quarry to the west, suggesting adaptive radiation of clevosaurs in the palaeo-archipelago. The larger reptiles on the palaeo-island do not exceed 1.5?m in length, including a small carnivorous crocodylomorph, Terrestrisuchus, and a possible example of insular dwarfism in the basal dinosaur Pantydraco.     

Définition d'une limite multicritère ; stratigraphie du passage Campanien–Maastrichtien du site géologique de Tercis (Landes,SW France)Definition of a multi-criteria boundary; stratigraphy of the Campanian–Maastrichtian interval of the geological site at Tercis (Landes,SW France)

Lithostratigraphy, physicochemical stratigraphy, biostratigraphy, and geochronology of the 77–70 Ma old series bracketing the Campanian–Maastrichtian boundary have been investigated by 70 experts. For the first time, direct relationships between macro- and microfossils have been established, as well as direct and indirect relationships between chemo-physical and biostratigraphical tools. A combination of criteria for selecting the boundary level, duration estimates, uncertainties on durations and on the location of biohorizons have been considered; new chronostratigraphic units are proposed. The geological site at Tercis is accepted by the Commission on Stratigraphy as the international reference for the stratigraphy of the studied interval. To cite this article: G.S. Odin, C. R. Geoscience 334 (2002) 409–414.     

The effect of water on accessory phase solubility in subaluminous and peralkaline granitic melts

The solubilities of columbite, tantalite, wolframite, rutile, zircon and hafnon were determined as a function of the water contents in peralkaline and subaluminous granite melts. All experiments were conducted at 1035 °C and 2 kbar and the water contents of the melts ranged from nominally dry to approximately 6 wt.% H₂O. Accessory phase solubilities are not affected by the water content of the peralkaline melt. By contrast, solubilities are affected by the water content of the subaluminous melt, where the solubilities of all the accessory phases examined increase with the water content of the melt, up to 2 wt.% H₂O. At higher water contents, solubilities are nearly constant. It can be concluded that water is not an important control of accessory phase solubility, although the water content will affect diffusivities of components in the melt, thus whether or not accessory phases will be present as restite material. The solubility behaviour in the subaluminous and peralkaline melts supports previous spectroscopic studies, which have observed differences in the coordination of high field strength elements in dry vs. wet subaluminous granitic glasses, but not for peralkaline granitic glasses. Lastly, the fact that wolframite solubility increases with increasing water content in the subaluminous melt suggests that tungsten dissolved as a hexavalent species.     

Quaternary stresses revealed by calcite twinning inversion: insights from observations in the Savonnières underground quarry (eastern France)

Calcite samples were extracted both from the rock matrix and the superficial coating of a karstified fault plane of an underground quarry, located in the eastern border of the Paris basin. The karstification is dated as Quaternary. Analysis of mechanical calcite twinning reveals that only the calcite matrix has also undergone a compression trending WNW that can be attributed to the Mio-Pliocene alpine collision. Both coating and matrix have undergone a strike-slip regime with σ₁ roughly trending north–south, that could correspond to the regional present-day state of stress, a strike-slip compression rather trending NNW, modified by local phenomena. To cite this article: M. Rocher et al., C. R. Geoscience 335 (2003).     

NONMETALS DEPOSITS

正20141520 Bo Ying(Key Laboratory of Metallogeny and Mineral Assessment,MLR,Beijing 100037,China);Liu Chenglin Saline Spring Hydrochemical Characteristics and Indicators for Potassium Exploration in Southwestern and Northern Tarim Basin,Xinjiang(Acta Geoscientica Sinica,ISSN1006-3021,CN11-3474/P,34(5),2013,p.594-602,5 illus.,3 tables,28 refs.)     

MATHEMATICAL GEOLOGY

正20141243Chen Ge(Hangzhou Research Institute of Petroleum Geology,PetroChina,Hangzhou 310023,China);Si Chunsong Study on Sedimentary Numerical Simulation Method of Fan Delta Sand Body(Journal of Geology,     

PROSPECTING EXPLORATION

正20142599Chen Sanming(Guangxi Key Laboratory of Concealed Deposits Exploration,Guilin University of Technology,Guilin541004,China);He Yuzhou Block Model and Reserves Estimation of Panzhihua Iron Deposit Based on 3D Geological Modeling(Journal of Guilin University of Technology,ISSN1674-9057,CN45-1375/N,33(4),2013,p.610-615,9illus.,1table,15refs.)     

STRUCTURAL GEOLOGY

正20140594 Bai Daoyuan(Hunan Institute of Geology Survey,Changsha 410016,China);Zhong Xiang Faults in the Jingzhou Basin and Their Tectonic Settings(Geotectonica et Metallogenia,ISSN1001-1552,CN44-1595/P,37(2),2013,p.173-183,6illus.,59refs.)Key words:basin evolution,tectonic setting,South China In the Upper Paleozoic and Jurassic se-     

STRUCTURAL GEOLOGY

正20141912Cao Hui(State Key Laboratory for Continental Tectonics and Dynamics,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China)Gravitational Collapse and Folding during Orogenesis:A Comparative Study of FIA Trends and Fold Axial Plane Traces(Geology in China,ISSN1000-3657,CN11-1167/P,40(6),2013,p.1818-1828,9illus.,35refs.,with