长乐-南澳韧性剪切带中糜棱岩变形微构造研究

 长乐-南澳韧性剪切带糜棱岩的显微变形机制有粒间滑动、粒内滑动、位错及其滑移和蠕变、应变的局部恢复等。石英丰富的韧性变形和位错特征以及长石的脆一弹性变形说明糜棱岩形成于绿片岩相条件,变形时的温度约为300-350℃。石英塑性变形处于重结晶一软化阶段和热加工一恢复阶段。由位错密度和动态重结晶颗粒粒径计算了差异应力和应变速率,分别为56.8-99.7MPa,(0.35-1.61)×10^-13s^-1和175.8-406.9MPa,(0.7-7.2)×10^-12s^-1,二者较大的差值表明糜棱岩是缓慢上升至地表的,这一结论与应变局部恢复现象一致。该韧性剪切带是闽粤沿海早白垩世末碰撞造山的产物。     

满洲里南部白音高老组流纹岩锆石U-Pb定年及岩石成因

满洲里南部白音高老组火山岩主要由流纹岩组成,含少量珍珠岩和流纹质凝灰岩。LA-ICPMS锆石U-Pb定年结果显示,流纹岩形成于141~139Ma的早白垩世早期。岩石地球化学研究表明,火山岩具有高硅富碱、贫钙镁和高FeO^T/MgO比值的特征; 稀土丰度总量较高(∑REE介于103×10^-6~488×10^-6),轻重稀土分馏明显［(La/ Yb)_N=4.12~30.94)］,Eu负异常显著(δEu=0.12~0.46); 微量元素以富集Rb、Th、U、K,强烈亏损Ba、Sr、P、Ti,中等亏损Nb、Ta和高Ga/Al值为特征,与A-型花岗岩特征相似。锆石¹⁷⁶Hf/¹⁷⁷Hf比值介于0.282785~0.282970之间,ε_Hf(t)值均为正值,介于3.78~9.98之间。流纹岩岩浆来源于斜长石稳定区玄武质下地壳物质的部分熔融,形成于非造山板内伸展构造环境。     

佛子岭群逆时针P-T轨迹对大别碰撞造山带构造演化的探究

佛子岭群位于大别造山带最北缘，处于华北和扬子两大板块结合部位，构造位置十分关键，是解析两大板块精细耦合过程和探究大别造山带晚古生代构造事件的重要单元。然而，由于长期以来佛子岭群一直被视为"浅变质"复理石沉积单元，因而对其变质演化过程的解析较为薄弱，制约了对大别造山带形成过程的全面理解。本次通过对老虎场-龚店地质剖面细致的观测，石榴黑云母片麻岩精细的岩相学、矿物化学分析、热力学评价和年代学研究，建立了佛子岭群一个逆时针P-T变质演化型式。研究显示，佛子岭群记录了Ⅰ、Ⅱ、Ⅲ和Ⅳ四个变质阶段，温压变化依次为：①T=658~663℃、P=1.08~1.16GPa→②T=755~762℃、P=1.21~1.45GPa→③T=549~554℃、P=1.08~1.19GPa→④P_标定=0.3~0.6GPa、T=477~499℃，①至③为近等压升温和降温过程，③至④则表现为近等温降压型式。锆石U-Pb定年显示了1484±64Ma~1180±192Ma、995±35Ma~606±14Ma和370±14Ma~331±8Ma三组年龄，前两组代表了碎屑锆石年龄；第三组共计7颗锆石，年龄集中，Th/U比值0.01~0.03，加权平均年龄为344±11Ma，代表了主期变质年龄。结合此次地质剖面结构特征和岩石类型，以及前人白云母⁴⁰Ar-³⁹Ar的270~255Ma变质年龄，表明佛子岭群记录了两期变质事件，早期为晚古生代的拉张背景下的岛弧根部变质，晚期为晚古生代末的较为快速抬升构造热事件，并据此推测大别造山带可能为增生和碰撞复合型造山带。     

铁橄榄石高温高压流变性的实验研究

通过高温高压实验研究了铁橄榄石集合体的流变性.首先,利用高精度的Paterson气体介质变形装置对铁橄榄石集合体Fe2SiO4进行了高温三轴压缩蠕变试验.变形试验条件为:温度1273～1423K,围压300MPa,差应力10～250MPa,应变率10-7～10-4s-1,试件的最大变形量不超过20%.利用三维非线性拟合方法对蠕变试验数据进行分析,得到铁橄榄石集合体的微观变形机制为扩散域和位错域,扩散域的应力指数为1左右.位错蠕变域中,干燥铁橄榄石集合体的应力指数为5.4.活化能为781kJ/mol;含水铁橄榄石集合体的应力指数为3.4,活化能为516kJ/mol.实验结果表明,含水时铁橄榄石的流变强度比干燥时小一个数量级.将实验结果与铁橄榄石单晶的强度进行对比,发现铁橄榄石集合体的流变强度比铁橄榄石单晶的强度高.从而得到了铁橄榄石集合体高温高压流变性(强度)的初步试验结果.     

鲜水河断裂带康定段雅拉河断裂深部应力应变状态及其孕震环境

鲜水河断裂带位于青藏高原东缘,是中国大陆内部地震活动性最强的大型左行走滑断裂之一,揭示其深部应力状态与应变是认识孕震环境和评估断裂带地震危险性的重要依据。本文选择鲜水河断裂带未来强震危险性较高的康定段作为研究对象,聚焦雅拉河断裂带内的糜棱岩,通过光学显微镜和扫描电镜（SEM）的显微构造分析、粒度统计、石英组构和Ti含量测试,确定石英递进变形过程中差应力的变化和不同阶段的变形温度,构建鲜水河断裂带康定段的地壳强度剖面。观测结果显示,糜棱岩在抬升过程中石英发生颗粒边界迁移（GBM）、亚颗粒旋转（SGR）和膨凸重结晶（BLG）三种类型的变形机制。构建的地壳强度剖面显示,雅拉河断裂带应变速率约为6.08×10^-13~1.62×10^-11s^-1,脆韧性转化带发生在~12.5±2.5km深度,该处岩石极限强度~145.5MPa。实际岩石强度（μ=0.383）小于理论破裂摩尔圆（μ=0.85）的岩石强度发育应变弱化。当韧性变形阶段由位错蠕变形成的应变局部化以及细粒化等机制降低岩石的强度至临界条件时,会导致破裂频次的增强,应力释放发生地震。同时,位错蠕变引起的应变弱化导致岩石强度降低,使高应力无法积累。     

苏鲁超高压岩石部分熔融时间的准确限定：来自含黑云母花岗岩中锆石U-Pb定年、REE和Lu-Hf同位素的证据

在北苏鲁超高压变质带中,广泛分布强变形的新三叠纪含黑云母花岗岩和伟晶岩脉。锆石中矿物包体激光拉曼测试、阴极发光图像分析、不同性质锆石微区LA-(MC)-ICP-MS和SHRIMP U-Pb定年、REE及Lu-Hf同位素测试等综合研究结果表明,北苏鲁威海地区超高压正片麻岩在构造折返的 (高压)麻粒岩相升温减压阶段,发生部分熔融 (深熔)作用形成了花岗质岩浆,并在临近角闪岩相退变质作用之前结晶结束形成了含黑云母的花岗岩。该类含黑云母花岗岩中的锆石成因复杂,可划分为三类锆石微区。第一类为强发光效应 (白色)继承性岩浆锆石 (微区I),具有典型的岩浆结晶环带,矿物包体为Qtz+Kfs+Ap,记录的²⁰⁶Pb/²³⁸U年龄为790~782Ma;第二类为新生锆石微区 (微区II),发光强度相对较弱 (灰色-灰白色),也具有较明显的岩浆结晶环带,矿物包体为Qtz+Kfs+Ab+Ap,记录的²⁰⁶Pb/²³⁸U年龄为222~217Ma,加权平均年龄为219±2Ma,表明苏鲁超高压地体的部分熔融 (深熔)作用发生在新三叠纪,这组年龄比苏鲁地体超高压变质时代 (235~225Ma)明显偏新,指示部分熔融 (深熔)作用的时代要晚于苏鲁地体的超高压变质时代;第三类锆石微区 (微区III)围绕第二类锆石微区分布,发光强度最弱 (黑色),也具有典型的岩浆结晶环带,矿物包体十分少见,为Qtz+Ap,记录的²⁰⁶Pb/²³⁸U年龄集中于216~209Ma之间,加权平均年龄为214±2Ma,应代表部分熔融 (深熔)而成的岩浆结晶结束的年龄,这组年龄比苏鲁地体构造折返晚期角闪岩相退变质时代(210~200Ma)偏老,表明新生岩浆结晶结束的时间要早于角闪岩相退变质时代。继承性岩浆结晶锆石 (微区I) ¹⁷⁶Hf/¹⁷⁷Hf(t)=0.281975~0.281984,¹⁷⁶Hf/¹⁷⁷Hf=0.00196~0.00221,ε_Hf(t)=-11.6~-11.8,相应的t_DM2=2160~2170Ma,与研究区周围新元古代 (795~730Ma)正片麻岩继承性岩浆结晶锆石的Lu-Hf同位素特征十分相似,表明新元古代正片麻岩是新三叠纪部分熔融 (深熔)成因的含黑云母花岗岩的母岩。新三叠纪新生岩浆结晶锆石的核部 (微区II)和边部 (微区III)具有类似的¹⁷⁶Hf/¹⁷⁷Hf(t)、¹⁷⁶Hf/¹⁷⁷Hf比值和ε_Hf(t)值,¹⁷⁶Hf/¹⁷⁷Hf(t)=0.282110~0.282199,¹⁷⁶Hf/¹⁷⁷Hf=0.00041~0.00183,ε_Hf(t)=-15.8~-19.1,t_DM2=1980~2130Ma,表明新三叠纪由超高压正片麻岩部分熔融而成的岩浆自结晶开始到结束是在一个相对封闭体系条件下完成的。晚期角闪岩相退变质作用对其Lu-Hf同位素体系也未造成破坏。     

压力对橄榄石流变性的影响

本文给出细粒橄榄石集合体在位错蠕变域中压力效应的实验结果。对干燥、人工合成的橄榄石集合体进行了三轴压缩实验,试验在一台高分辨率的气体介质试验机上进行。典型的常载荷蠕变试验温度为1473K或1523K,围压为400MPa、200MPa、400MPa、200MPa。当差压力和温度给定时,试件在400MPa围压下,变形速度较200MPa围压下要慢。实验得出的细粒橄榄石集合体在位错蠕变域中的活化体积值为(23±3)×10~(-6)m~3/mol。最后,对实验结果在地幔动力学中的应用进行了讨论。     

湖南千里山花岗岩体的Nd-Sr同位素及岩石成因研究

本文利用Rb-Sr等时线方法测得第一阶段似斑状黑云母花岗岩、第二阶段等粒黑云母花岗岩和第三阶段花岗斑岩的成岩年龄分别为（152士9）×l0⁶ a、（137士7）×l0⁶ a ~（136士6）×10⁶ a和（131士1）×l0⁶ a。Sr-Nd同位素资料表明各阶段花岗质岩石均基本上源于地壳物质的重熔。与钨多金属矿化有关的似斑状黑云母花岗岩和等粒黑云母花岗岩属同一岩浆体系分异演化的产物，其钕模式年龄(t_DM= 2307×l0⁶ a)反映出成岩物质来自早元古宙地层的重熔。与铅，锌一银矿化有关的花岗斑岩的钕模式年龄(t_DM= 1284×l0⁶ ~ 1578×l0⁶ a)示意出其成岩物质来自中元古宙地层的重熔。     

江南钨矿带桂林郑富钼白钨矿稀土元素的富集机制及其地质意义

桂林郑钼钨多金属矿床位于江南钨矿带北部,其矿石矿物以富钼白钨矿为主。研究显示,该矿床富钼白钨矿中富集稀土元素。为探究其富集机制,文章对不同世代的富钼白钨矿进行原位LA-ICP-MS微量分析和面扫描分析。结果显示,富钼白钨矿的总稀土元素含量（∑REE）在28.59×10^-6~4863.82×10^-6之间,均值为789.21×10^-6（n=122）,从第一世代（Sch-Ⅰ）28.59×10^-6~1059.18×10^-6（平均值为203.19×10^-6,n=55）→第二世代（Sch-Ⅱ）533.54×10^-6~2536.51×10^-6（平均值=928.79×10^-6,n=30）→第三世代（Sch-Ⅲ）117.21×10^-6~4863.82×10^-6（平均值=1547.13×10^-6;n=37）逐渐增高。从Sch-Ⅰ→Sch-Ⅱ→Sch-Ⅲ,轻重稀土元素比值（LREE/HREE）13.99~143.90（平均值=53.53）→22.38~70.08（平均值=33.74）→7.44~69.86（平均值=27.54）逐渐降低。桂林郑富钼白钨矿形成于高氧逸度、富F的岩浆热液系统,REE主要以Ca²⁺+Mo⁶⁺=REE³⁺+(1-x) Mo⁵⁺+xNb⁵⁺(0≤x≤1）为主导方式进入富钼白钨矿中。成矿流体中Cl降低、F增高、氧逸度降低等是REE进入富钼白钨矿的有利条件。通过对江南钨矿带代表性矽卡岩型矿床综合对比分析显示,富钼白钨矿床相比贫钼白钨矿床具有更高的REE,说明桂林郑矿床富钼白钨矿在后续开采中具有稀土元素的综合利用前景。     

西藏南部冈底斯岩基曲林岩体渐新世-中新世高Sr/Y比岩浆作用及其对深部过程的启示

曲林岩体位于冈底斯带中段的南缘,为渐新世-中新世复合岩体,主体为粗粒花岗斑岩,被后期煌斑质、花岗闪长质和花岗质岩脉切割,是多期岩浆作用的产物,出露面积约8km²。花岗斑岩两组样品（T0849-PG和T0849-G）的锆石U-Pb定年结果分别为29.7±0.1Ma和30.0±0.2Ma。花岗斑岩为高钾,准铝质,低MgO,高度富集轻稀土元素（LREE）和大离子亲石元素（LILE）,亏损重稀土元素（HREE）和高场强元素（HFSE）。此外具有高Sr、Sr/Y、（La/Yb）_N;低Y和Yb,弱Eu负异常等特征。岩体内发育一系列近南北向展布的花岗闪长玢岩脉,其中两组样品的锆石U-Pb定年结果分别为15.5±0.1Ma（T0848-PY）和14.4±0.1Ma（T0850）。两条花岗闪长玢岩脉具有与岩体主体相似的稀土和微量元素分布模式,同样富集轻稀土及大离子亲石元素,亏损重稀土及高场强元素。花岗斑岩的⁸⁷Sr/⁸⁶Sr_（i）=0.706102~0.706202,ε_Nd（t）=-0.6~+0.6,锆石ε_Hf（t）=+4.9~+7.9;花岗闪长玢岩脉的⁸⁷Sr/⁸⁶Sr_（i）=0.705429~0.705474,ε_Nd（t）=-1.4~-0.2,锆石ε_Hf（t）=+2.6~+7.6。本文数据和文献数据结果表明：曲林花岗斑岩与花岗闪长玢岩脉均来源于加厚南拉萨下地壳的部分熔融,很可能与增厚的深部岩石圈的拆沉或俯冲印度岩石圈的撕裂诱发软流圈上涌有关。     

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