红河断裂带莺歌海段地质构造特征

红河入海后的地质构造特征研究是当前红河断裂带研究的薄弱环节.结合莺歌海地区重力和地震资料解释与前人研究成果,系统总结了红河断裂带莺歌海盆地内的几何学、运动学特征,并根据莺歌海盆地沉积中心迁移规律获得了红河断裂带的年代学数据.研究认为:红河断裂带在入海口附近分叉,其中Tien Lang断层折向NE,呈马尾状展布;在莺歌海盆地内红河断裂带分支为A(Ⅰ号断层)、B、C和D(莺西断层)4条断层,其中A断层是最主要的一条分支断层.莺歌海盆地内的分支断层均呈近NW-SE走向,延伸420～500km,其地震解释剖面上发育的典型花状构造和马尾状Tien Lang断层共同指示该断层具有走滑运动性质;红河断裂带对莺歌海盆地的沉积具有明显的控制作用,盆地沉积中心变化规律揭示红河断裂带在30～15.5Ma期间具有左行走滑运动性质,15.5～5.5Ma期间为左行向右行转换阶段,发生了强烈的构造反转作用,5.5Ma以来具有右行走滑运动特征.     

Silurian-Devonian and Jurassic Thermal Events in the Ordos Basin, China: Indications from K-Ar Dating on Illites

In the Ordos basin, two distinct thermal events of different ages have been identified for the first time by means of K-Ar dating combined with illite crystallinity analysis. For the Late Triassic and Late Permian samples, the K-Ar ages of the < 0.2μm fractions (159-173 Ma) reflect an illitization age related to the Yanshanian movement and indicate a short thermal event in the Middle Jurassic; the K-Ar ages of the <2 μm fractions (210-308 Ma) are interpreted as mixed ages of detrital material and authigenic illites. The K-Ar ages of both < 0.2μm and < 2μm fractions of a Middle Cambrian sample (368 Ma and 419 Ma) correspond to the ages of the metamorphism and earliest granite intrusion in the northern Caledonian Qinling fold zone (380-420 Ma) and show a thermal event during Silurian-Devonian time.     

钾长石K—Ar定年若干问题的讨论

现有的测试数据反映,钾长石在K—Ar定年中存在很多问题,最常见的情况是年龄值偏年轻,有时也出现比共存矿物年龄偏老的情况。钾长石在实验过程中不完全释氩是造成年龄值偏年轻的原因之一,对此前人已经提出几个解决方案,但在实际应用中都不够完善。钾长石的封闭温度低（130～150℃）是放射成因氩丢失的最主要因素,个别情况下也出现捕获围岩中的放射成因氩,从而出现过剩氩。低温钾长石（如冰长石）的氩保存能力和结构有关系,通常情况下随着三斜度的升高所保存的放射成因氩会相应减少。不同地质环境中产出的钾长石在K—Ar定年中适用性有所不同,侵入岩中的钾长石（微斜长石和条纹长石等）不适合于K—Ar定年,而喷出岩中的钾长石（透长石和歪长石等）是非常好的定年矿物;低温钾长石可有条件应用     

Dating Fault Activity Based on Surface Texture of Quartz Grains from the Bailong River Fault

Much important information referring to fault motion （e.g., fault activities period, intensity, frequency, and even dynamic background） can be revealed by resolving fault gouge, which is the result of fault motion while extruding or grinding. The field investigation encompassed sample collecting from the Bailong River fault system of the western segment of the Qinling Orogenic Belt （QOB）; 44 samples of fault gouges were collected for quartz micro-morphology analysis. These samples were analyzed using field emission scanning electron microscopy. In addition, 14 samples were tested for thermo-luminescence dating. The results showed that most of the surface textures of quartz grains are characterized by fish scale, moss-like texture, and stalactite. However, a small amount of orange peel-like fractures and worm-hole-like shaped surface texture were observed. Moreover, a few typical conchoids or subconchoidal fractures in quartz grains can be seen. This implies that the Bailong River Fault was active repeatedly during the Quaternary period, but the main motion period is the Pleistocene. The 14 thermo-luminescence dating values showed two age groups： 343.29-184.06 ka and 92.18-13.87 ka. These study data reveal that fault movement started during the Pliocene, occurred frequently in the early-middle period of the Pleistocene, and the peak frequency of the motion was reached in the early Pleistocene. The fault motions were stopped terminated in the early Holocene. The results are significant for the natural disaster risk evaluation in the western segment of the QOB.     

红河断裂带类微生物状纳米颗粒的发现及其构造意义

通过扫描电镜(SEM)观察,首次在红河断裂带内的花岗糜棱岩中发现类微生物状纳米颗粒.高分辨率平插能谱分析结果表明,该类微生物状纳米颗粒成分中的C元素平均含量约为10％,指示无机成因,并非某些菌类微生物,结合XRD分析结果表明该类纳米颗粒成分来自花岗糜棱岩的造岩矿物.通过对各种形貌特征的纳米颗粒观察、筛查和规律分析,探讨...     

红河断裂带中段北探槽古地震及其标志性地层佐证

探槽方法能够揭露地质记录中保存的古地震事件,可弥补仪器地震及历史地震记录的短暂性及局限性。文章通过数字影像分析、地质地貌调查,在红河断裂带中段北变形遗迹保存较好的德苴乡大丫口村段开挖了一个大型组合探槽。根据探槽剖面揭露的断裂信息以及断裂切、盖地层关系分析,组合探槽共揭露出了3次古地震事件,从老到新命名为E1、E2和E3。利用OxCal软件对古地震事件断错地层及覆盖地层中的炭屑样品AMS ¹⁴C测年结果进行校正分析,3次古地震事件分别限定在约1190 BC、341~126 BC和1460~1784 A.D.,最新一次事件E3应对应1652年弥渡M7地震。其中年龄限定较好的两次事件E2、E3的复发间隔约1800~2000 a表明,红河断裂中段北具有复发周期较长的特征。基于铁锰结核很可能是历史上新构造运动地质作用下,土壤环境巨大波动条件下形成的认识,以及组合探槽中揭露的标志性地层——铁锰结核层中多个炭屑样品年龄均为全新世,进一步佐证了红河断裂中段北在全新世期间曾有过多次强地震活动。

     

青川断裂带中段断层泥中石英颗粒表面微形貌特征及其年代学意义

断层泥作为断裂脆性剪切变形的产物,记录了断层滑动方式和活动时间等信息,尤其是断层泥中石英颗粒表面微形貌特征的识别和统计,可以为估算断层活动相对时间提供证据。青川断裂作为秦岭构造带的南界,晚新生代以来发生右旋走滑运动,沿断裂带出露完整的断层破碎带,断层泥非常发育。本文以该断裂带中段:木鱼—大安段发育的青灰色和紫红色断层泥为研究对象,在野外调查的基础上,重点对断层泥中石英颗粒表面的微形貌进行了扫描电子显微镜观察,发现两类(Ⅱ和Ⅲ类)中-深度溶蚀石英形貌和一类(Ia类)弱溶蚀石英形貌,未见Io类破裂微形貌。石英微形貌类型的统计结果指示青川断裂中段最新活动时间在晚更新世,全新世没有明显活动,与断裂带全新世河流阶地未发生构造扰动的现象一致。     

太行山东缘断裂南支断层性质及断层泥K-Ar同位素定年

太行山东缘断裂是华北盆地西边界的控制性断裂,对研究华北盆地中-新生代油气藏、地震分布及成矿作用具有重要意义。通过对太行山东缘断裂南支断层几何学、运动学的详细研究以及对断层泥的X射线衍射分析、K-Ar同位素年代学研究,确定了太行山东缘断裂为枢纽性质正断层,由一系列北北东走向正断层组成,呈左阶阶梯状展布,断层活动时间为113.42±2.31 Ma。断裂在新生代再次活动,形成多幕式的断陷盆地。     

K-Ar dating of episodic Mesozoic fluid migrations along the fault system of Gernsbach between the Moldanubian and Saxothuringian (Northern Black Forest,Germany)

Along the SW-NE trending fault zone of Gernsbach (northern Black Forest), over a distance of about 45 km between Baden-Baden and Pforzheim, basal series of the sedimentary cover are extensively altered by hydrothermal solutions. The fluids were conveyed in the fault zone and because of favourable permeabilities they spread out along the unconformity between the basement and sedimentary cover. K-Ar dates on authigenic white micas (illites) and hydrothermally altered detrital micas point to the occurrence of two major episodes of fluid migration. The extensive alteration along the entire fault system occurred about 150 Ma ago during the Jurassic. In relation to these hydrothermal activities, the epigenetic strata-bound uranium deposit of Müllenbach originated in Upper Carboniferous sediments near the fault and the fluorite-quartz vein-type mineralization of Käfersteige was formed along the fault about 100 Ma ago during the Cretaceous. The results indicate various geological processes of the fault system of Gernsbach, which is located between the Saxothuringian and Moldanubian zone. The mobilization of the fluids and the formation of the ore deposits were probably caused by and connected with tectonic activities in mid-Europe.     

红河断裂的GPS监测

红河断裂带(RRFZ)是一条大型的走滑断裂带,本文利用1999年和2003年的GPS观测,通过数据反演,获得在欧亚参考框架下的速度矢量图。结果表明:在欧亚框架下,东向分量平均速度为3.726mm/a;北向分量平均速度为-9.013mm/a;由北向南,各测站的北向分量速率值逐渐减小;由西向东,各测站的东向分量速率值逐渐减小;测区内呈现明显的右旋拉张走滑运动。分析表明云南红河地区地壳水平运动的特征以及断裂活动性质与构造地质相当一致。     

断层泥自生伊利石年龄分析及其在龙门山断裂带的应用

韧性剪切带的活动年龄及其相关的隆升/剥蚀速率可以通过各种同位素技术进行直接测定和计算。相比较而言,由于形成于浅部低温环境,老的碎屑物质和新的重结晶物质相互掺杂,脆性断裂的同位素年龄往往代表的是一个混合年龄,难以反映其真实的活动时间。近些年来,断层泥自生伊利石定年方法在地表脆性断裂的年代学研究中展现出了良好的应用前景。文中介绍了断层泥中自生伊利石的生成过程、形貌特征和定年原理,并简要介绍了样品的处理过程和伊利石多型相对含量的确定方法。近几年,这种方法逐渐被应用于龙门山断裂带及其山前飞来峰活动时代的确定,为青藏高原东缘早期的构造活动提供了直接的年代证据。     

从地震信息看红河—金沙江断裂带构造特征

红河—金沙江断裂带,根据地质结构的差异可分为北段羌塘向北叠瓦逆冲断裂带,中段三江—哀牢山向东叠瓦逆冲断裂带,南段河内—中建正反转走滑断裂带。北段和中段均由三组基本平行的叠瓦逆冲断层构成,显示以强烈挤压为特征,但后者相对较弱;南段则经历了古近纪由挤压反转为拉张,形成一些断陷构造,新近纪又反转为挤压,断陷转变为坳陷,形成河内、莺歌海及中建等坳陷。该南段的主断层为正反转构造逆冲带的前锋太平断裂带,与原先人们所认为的不相同。红河—金沙江断裂带的挤压特征总体上由北往南逐渐减弱,其演化受特提斯构造活动所控制。断裂带的油气勘探成果表明,在喜马拉雅期形成的断坳结构盆地中油气显示较好。     

从水系的分布形态探讨沂沭断裂带的运动特征

郯城-庐江断裂带是纵贯中国大陆东部,长达2 000 km以上的大断裂带。该研究利用DEM数据和ETM,以及谷歌卫星影像来分析郯城-庐江断裂带中段的沂沭断裂带周边的水系的几何分布形态特征。三维卫星图像解译和野外调查的结果显示：(1)沿断裂带周边发育的水系的几何分布形态主要受由F1-F4 4条主要断层所组成的沂沭断裂带构造所制约;(2)沿断裂带发育的水系不具有典型的走滑断层的系统化的同步转折和位错的变形特征;(3)沂沭断裂带东侧的F1和F2断裂是现今的活动断裂,而F3和F4断裂在第四纪基本没有明显的活动迹象;(4)F1和F2断裂以垂向运动为主,具有高角度的逆断层或正断层的运动特征。该研究结果显示沿断裂发育的水系地貌和几何分布特征可作为评价断裂的活动性和运动特征的地貌标志。     

活断层中断层泥分形与断裂活动关系

以长江三峡仙女山、九湾溪和天阳坪３条断裂为例,对断裂活动性与断层泥分维值（Ｄ）进行对比研究发现,Ｄ值受断裂活动性与断层泥粒度双因素制约。同一断裂带中细粒断层泥Ｄ值低且粒断层泥Ｄ值;不断断裂之间相对活动断裂Ｄ值低于弱活动断裂Ｄ值。在改进断层泥分形计算方法的基础上,通过变换得到了具有物理意义的判断断裂活动性的单因素参量（ｒＬ）。该方法克服了用断层泥分维值判断断裂活动性时粒径影响Ｄ值的困难,为利用分形理     

Dating pseudotachylyte of the Asuke Shear Zone using zircon fission-track and U–Pb methods

Zircon fission-track (FT) and U–Pb analyses were performed on zircon extracted from a pseudotachylyte zone and surrounding rocks of the Asuke Shear Zone (ASZ), Aichi Prefecture, Japan. The U–Pb ages of all four samples are  67–76 Ma, which is interpreted as the formation age of Ryoke granitic rocks along the ASZ. The mean zircon FT age of host rock is 73 ± 7 (2σ) Ma, suggesting a time of initial cooling through the zircon closure temperature. The pseudotachylyte zone however, yielded a zircon FT age of 53 ± 9 (2σ) Ma, statistically different from the age of the host rock. Zircon FTs showed reduced mean lengths and intermediate ages for samples adjacent to the pseudotachylyte zone. Coupled with the new zircon U–Pb ages and previous heat conduction modeling, the present FT data are best interpreted as reflecting paleothermal effects of the frictional heating of the fault. The age for the pseudotachylyte coincides with the change in direction of rotation of the Pacific plate from NW to N which can be considered to initialize the NNE–SSW trending sinistral–extensional ASZ before the Miocene clockwise rotation of SW Japan. The present study demonstrates that a history of fault motions in seismically active regions can be reconstructed by dating pseudotachylytes using zircon FT thermochronology.     

塔里木盆地典型砂岩油气储层自生伊利石K-Ar同位素测年研究与成藏年代探讨

塔里木盆地共发现 8套砂岩油气储层 ,对其中的 5套典型砂岩油气储层进行了自生伊利石K Ar同位素测年分析与研究。利用该项技术对其成藏史进行初步探讨是本次研究的主要目的。中央隆起下志留统沥青砂岩的自生伊利石年龄为 383.4 5～ 2 35 .17Ma ,表明志留系古油藏形成于加里东晚期—海西晚期 ;上泥盆统东河砂岩的自生伊利石年龄为 2 6 3.82～ 2 31.34Ma ,表明东河砂岩油气藏主要形成于海西晚期 ;库车坳陷依南 2气田 (依南 2井 )下侏罗统阳霞组砂岩的自生伊利石年龄为 2 8.0 8～ 2 3.85Ma ,表明油气充注发生在中新世以来 ;喀什凹陷阿克莫木气田 (阿克 1井 )下白垩统砂岩的自生伊利石年龄为 2 2 .6 0～ 18.79Ma ,表明中新世可能有古油气运移或古油藏形成 ;库车坳陷迪那 2气藏 (迪那 2 0 1井 )古近系砂岩中的伊利石主要为碎屑成因 ,不能用于进行油气成藏史研究 ,但该气藏白垩系砂岩的自生伊利石年龄为 2 5 .4 9～ 15 .4 7Ma ,表明可能为中新世成藏。本次研究表明 ,该项技术在塔里木盆地初步显示出较好的应用效果 ,具有较为广阔的应用前景。     

Hydrogeochemical characteristics of groundwater from the two main aquifers in the Red River Delta,Vietnam

In the Red River Delta, situated in the northern part of Vietnam, nearly its entire population depends solely on groundwater for daily water consumptions. For this reason, groundwater quality assessments must be carefully carried out using hydrogeochemical properties, to ensure effective groundwater resource planning for the Delta’s present and future groundwater use. In this study, the spatial and seasonal changes in the hydrogeochemical characteristics of groundwater in the two main aquifers of the RRD were investigated by analyzing the physicochemical data obtained in 2011 from 31 conjunctive wells in the Delta’s Holocene unconfined aquifer (HUA) and Pleistocene confined aquifer (PCA) using the Piper diagram and the Gibbs diagram. Results of the data analysis show that the groundwater in both aquifers in the upstream area of the delta is dominated by the [Ca²⁺–HCO₃⁻] water-type, while the [Na⁺–Cl⁻] dominates along the middle-stream and downstream areas. Seasonal changes in the hydrogeochemical facies in both aquifers, comparing the results for the dry and the rainy seasons, were detected in about one third of the sampling wells, which were mainly located at the upstream portion of the Delta. The hydrogeochemical facies of HUA were different from that of PCA by about 45% of the sampling wells in both the dry and the rainy seasons, which were found mostly in the upstream and middle-stream areas.     

肥东花岗质岩脉的变形及年代学特征对郯庐断裂带早白垩世构造活动的指示

郯庐断裂带肥东段位于大别造山带与苏鲁造山带之间。在肥东段西韦采石场内发育了大规模的北北东向左行走滑韧性剪切带和一条低角度的韧性滑脱正断层。走滑韧性剪切带为郯庐断裂带走滑活动的产物,低角度滑脱正断层则代表了伸展背景下的构造活动。低角度滑脱正断层上、下盘发育未变形和变形的岩脉,走滑韧性剪切带内外也发育有受剪切带活动而变形的岩脉。对采石场内岩脉的构造和同位素年代学研究表明,低角度韧性滑脱正断层在129~126Ma之间发生过剪切活动,走滑韧性剪切带的活动时间在125Ma之后。综合研究认为,郯庐断裂带的伸展活动可能开始于早白垩世早期(130Ma),但在早白垩世并非一直处于伸展活动之中,125Ma之后的左行走滑活动很可能发生在早白垩世的晚期。     

Early formation of K-feldspar in shallow-marine sediments at near-surface temperatures (southern Israel): evidence from K-Ar dating

Authigenic K‐feldspar was investigated in two Albian to Turonian sections in Israel using K‐Ar and Ar‐Ar dating, X‐ray diffraction, scanning electron microscopy and chemical analysis. Both sections comprise a similar succession of shallow‐marine limestones, dolomites and marls, with some sandstone and shale beds of continental origin. The HCl‐insoluble residue fraction of the studied samples consists of clays, quartz, feldspars, goethite and trace amounts of heavy minerals. Most of the insoluble residues have a relatively high K‐feldspar content that has an adularia habit and is concentrated in the 4–7 µm size fraction. The authigenic origin of the K‐feldspar in the fine silt fraction is indicated by its high content relative to quartz, the uniform and idiomorphic shape of the crystals and its limited size range. Of the fine silt (4–7 or 4–10 µm) separates, 40% have ages that are similar to stratigraphic ages within the analytical and biostratigraphic errors. Ar‐Ar dating of a fine silt fraction with 94% K‐feldspar (4–10 µm, sample GYP 7) yields a plateau age identical to the total gas age and similar to the stratigraphic age. These results indicate that the K‐Ar age is not a mixture between detrital and late diagenetic K‐feldspar ages, but is rather an age of formation within a few million years after deposition. It is suggested that the early formation of the K‐feldspar was associated with dolomitization and was induced by residual brines as part of a reflux process.     

念青唐古拉花岗岩的同位素年龄测定及其地质意义

念青唐古拉花岗岩体位于西藏当雄县境内,是拉萨地块中部出露的巨型侵入岩岩基,其面积超过1500km2,以大面积出露的黑云母二长花岗岩为主体。本文分别应用单矿物K-Ar法、全岩-单矿物Rb-Sr等时线法和高灵敏度高分辨率离子探针法(SHRIMP-)对念青唐古拉岩体不同位置上的代表性岩石样品进行同位素测年,得到中细粒黑云母二长花岗岩的K-Ar年龄为8.49±0.14Ma,Rb-Sr等时线年龄为8.07±0.35Ma和8.70±1.40Ma,SHRIMPU-Pb年龄为18.3±0.4Ma;中粗粒黑云母二长花岗岩的K-Ar年龄为9.80±0.35Ma,Rb-Sr等时线年龄为9.33±0.41Ma,SHRIMPU-Pb年龄为11.01±0.24Ma。不同方法测年结果均表明念青唐古拉花岗岩形成于中新世,属拉萨地块内部最年轻的巨型花岗岩岩基,其侵位结晶时代处于青藏高原地壳由南北向挤压增厚向东西向伸展的转变时期,岩浆来源于地壳局部熔融,属后碰撞构造-岩浆活动的产物。