豫西地区熊耳群的地质年代学研究

在地质构造背景基础上分析单颗粒锆石U Pb稀释法年龄数据 ,以标志王屋山期热构造事件有关的穿切熊耳群焦园组、坡前街组岩浆侵入活动年龄 16 4 4Ma～ 175 0Ma和热扰动年龄 16 5 0Ma±为依据 ,确定熊耳群上限年龄为 16 5 0Ma～ 170 0Ma。熊耳群火山岩系第二喷发旋回眼窑寨组 (“龙脖组”)流纹斑岩成岩年龄为 196 0Ma±。第一喷发旋回上部焦园组流纹斑岩成岩年龄为 2 10 0Ma± ;下部张合庙组大斑安山岩成岩年龄为 2 2 0 0Ma～2 30 0Ma。熊耳群的下限年龄小于 2 4 0 0Ma。这与豫西地区地层情况大体吻合。     

内蒙古西乌珠穆沁旗本巴图组碎屑锆石LA—ICP—MSU—Pb年龄及其意义

在前人研究的基础上,对本巴图组的野外地质特征、岩石类型、岩石组合、锆石年代学等进行了研究。镜下特征显示本巴图组砂岩主体为岩屑晶屑含砾砂岩;碎屑锆石阴极发光图像显示,它们多具有震荡生长环带或条痕状吸收．Th／U比值为0．06～1．03（平均0．55）,具有岩浆锆石的典型特点。应用LA—ICP—MS测年技术对本巴图组进行了碎屑锆石分析．其^206Pb／^238U年龄可以分为5组：①319～451Ma,峰期年龄为363Ma;②457～543Ma,峰期年龄为513Ma;③724-996Ma,峰期年龄为945Ma：④1031～1836Ma,峰期年龄为1572Ma;⑤2469-2505Ma,峰期年龄为2487Ma。年龄分布的意义：研究区本巴图组沉积的时间下限应为319Ma之后;457-543Ma发生泛非期构造热事件,沉积物源主要来源于佳～蒙地块;另外几组峰值年龄945Ma、1572Ma和2487Ma主要反映了佳-蒙地块基底的年龄信息。     

北京云蒙山片麻状花岗岩锆石SHRIMP定年及其地质意义

应用锆石SHRIMP定年方法对云蒙山片麻状花岗岩进行年代学研究 ,得到 4组年龄 :14 4± 4Ma、16 0～ 16 3Ma、193～ 2 18Ma和 2 4 16Ma。其中 14 4± 4Ma代表了云蒙山岩体的侵位时间 ,16 0～ 16 3Ma和 193～ 2 18Ma两组年龄可能是岩浆侵位过程中捕虏锆石的年龄。 2 4 16Ma与Davis等的锆石U_Pb法上交点年龄 (190 0～ 2 4 0 0Ma)一致 ,可能反映了原岩的时代 ,说明该花岗岩来源于晚太古代片麻岩的局部熔融或者是岩浆侵位过程中捕获了晚太古代的锆石。     

萍乡东桥岩门寨组凝灰岩LA-ICP-MS锆石U-Pb年龄及南华冰期底界年代探讨

目前关于南华系底界年代存在早(780 Ma或760 Ma)、晚(725 Ma或720 Ma)两种不同观点。本文对萍乡东桥板溪期晚期岩门寨组顶部的凝灰岩进行了28颗锆石的LA-ICP-MS U-Pb年龄分析,由早至晚获得5组主要年龄,并分析探讨了各组年龄锆石形成的地质背景。第1组和第2组锆石均为继承性岩浆锆石,平均年龄分别为805.5±10.6 Ma和767.6±7.7Ma,分别与扬子东南缘810~800Ma期间的岛弧岩浆活动和板溪期中期760Ma前后的岩浆活动有关。第4组和第5组锆石为变质成因锆石,平均年龄分别为390.8±2.8 Ma和211.2±1.5 Ma,分别与加里东晚期和印支晚期的构造-热事件有关。第3组共11颗岩浆锆石的平均年龄为717.2±8.9 Ma,为凝灰岩的成岩年龄。该年龄为南华冰期底界720 Ma的年龄提供了约束。此外,本文讨论并提出前人在湘中碧溪获得的长安组下部760 Ma左右U-Pb年龄为继承性锆石年龄,且发现在误差范围内有50%锆石的年龄上限也为720 Ma左右,暗示成岩年龄实为720 Ma而非760 Ma。     

鲁西铜石岩体的锆石SHRIMP U-Pb年龄及其地质意义

首次报道了鲁西地区铜石岩体的锆石SHRIMPU Pb年龄结果。通过对斑状细粒闪长岩中单颗粒锆石 1 8个样品点的分析 ,获得了两组谐和年龄数据 ,其中有 1 0个分析点的2 0 6Pb/ 2 3 8U年龄为 1 6 7.9～ 1 83Ma ,加权平均值为 (1 75 .7± 3.8)Ma ;另外 8个分析点的2 0 7Pb/ 2 0 6Pb年龄为 2 5 0 2～ 2 5 5 4Ma ,加权平均值为 (2 5 1 8± 1 1 )Ma。二长斑岩样品仅获得 2个2 0 7Pb/ 2 0 6Pb年龄数据 ,在 2 4 85～ 2 5 1 2Ma之间。(1 75 .7± 3.8)Ma指示了铜石岩体的结晶年龄为中侏罗世 ,(2 5 1 8± 1 1 )Ma代表了岩体侵位过程中捕获的新太古代五台期锆石的年龄。根据SHRIMPU Pb年龄结果 ,认为鲁西地区存在燕山早期构造岩浆热事件 ,与之有关的归来庄金矿也在此时期形成     

内蒙古莲花山铜矿区花岗闪长斑岩LA-ICP-MS锆石U-Pb年龄

为了精确厘定莲花山铜矿的成矿时代,在前人研究的基础上,开展了与成矿关系密切的花岗闪长斑岩锆石U-Pb定年测定。实验结果共获得4组年龄数据,第1组有1个锆石,206Pb/238U年龄为343Ma±2Ma;第2组1个锆石,206Pb/238U年龄为264Ma±2Ma;第3组有1个锆石,206Pb/238U年龄为256Ma±2Ma;第4组有17个锆石,206Pb/238U年龄在240~249Ma之间,206Pb/238U年龄加权平均值为246.4Ma±1.2Ma(N=17)。结合所测锆石的CL图像特征,确定花岗闪长斑岩就位发生在晚二叠世—早三叠世。     

攀西古裂谷钠质碱性岩锆石SHRIMP U-Pb年龄及地质意义--以红格、白马和鸡街岩体为例

用SHRIMP测定攀西古裂谷内钠质碱性岩锆石的U Pb年龄 :红格酸性碱性岩 (钠闪石花岗岩 )锆石U Pb年龄为 2 39Ma,白马中性碱性岩 (碱长石英正长岩 )锆石U Pb年龄为 2 2 5Ma和鸡街超基性碱性岩 (霞辉岩 )锆石U Pb年龄为 2 0 4Ma等 ,其年龄变化范围在 2 39～ 2 0 4Ma ,相当于中三叠世—晚三叠世 ,属于印支期。在成岩时间上显示先酸性、后基性。结合近期对其裂谷作用有关的镁铁—超镁铁层状侵入体和峨眉山玄武岩等定年的结果 ,暗示其裂谷强烈的张裂时间是在晚二叠世—晚三叠世 (2 5 9～ 2 0 4Ma)。     

内蒙古西乌珠穆沁旗本巴图组碎屑锆石LA-ICP-MS U-Pb年龄及其意义

在前人研究的基础上,对本巴图组的野外地质特征、岩石类型、岩石组合、锆石年代学等进行了研究.镜下特征显示本巴图组砂岩主体为岩屑晶屑含砾砂岩;碎屑锆石阴极发光图像显示,它们多具有震荡生长环带或条痕状吸收,Th/U比值为0.06～1.03(平均0.55).具有岩浆锆石的典型特点.应用LA-ICP-MS测年技术对本巴图组进行了碎屑锆石分析,其206Pb/238U年龄可以分为5组:①319～451Ma,峰期年龄为363Ma;②457～543Ma,峰期年龄为513Ma;③724～996Ma,峰期年龄为945Ma;④1031～1836Ma.峰期年龄为1572Ma;⑤2469～2505Ma,峰期年龄为2487Ma.年龄分布的意义:研究区本巴图组沉积的时间下限应为319Ma之后:457～543Ma发生泛非期构造热事件,沉积物源主要来源于佳-蒙地块;另外几组峰值年龄945Ma、1572Ma和2487Ma主要反映了佳一蒙地块基底的年龄信息.     

滇东南瑶山群SHRIMP锆石U-Pb年代学及其地质意义

为探讨滇东南瑶山群的原岩年龄以及后期经历的岩浆-变质-构造事件年龄,开展了SHRIMP锆石U-Pb定年研究。结果表明,阴极发光(CL)分析和光学显微分析显示瑶山群的锆石组成比较复杂,可以分为继承锆石、变质锆石、深熔锆石/岩浆锆石等几大类。除少量测点207Pb/206Pb年龄为新元古代外,继承锆石206Pb/238 U表面年龄变化范围集中在235±1.7Ma~261±3.6Ma,加权平均值为250.8±9.8Ma(N=4,MSWD=4.1);深熔/岩浆锆石206Pb/238 U表面年龄显示出~85Ma和~75Ma两个峰值;变质增生锆石206Pb/238 U表面年龄为49~30Ma,且主要集中在32Ma、37Ma和42Ma左右。结合区域地质情况,初步推测:250.8±9.8Ma的继承锆石峰值年龄表明,瑶山群主体的原岩时代可能不早于二叠纪;变质锆石、深熔锆石/岩浆锆石的206Pb/238 U表面年龄可分为~85Ma、~75Ma、~42Ma、~37Ma和~32Ma等5组,可能代表了红河断裂南段自燕山晚期以来5期较强烈构造-岩浆-变质事件的时限。     

浙东南松阳县枫坪组沉积岩碎屑锆石年代学及地质意义

利用激光剥蚀电感耦合等离子质谱技术(LA-ICP-MS)对浙东南松阳县枫坪组地层底部的细砂岩进行了锆石U-Pb定年及稀土元素分析。样品中大部分碎屑锆石具有较好的振荡环带且Th/U值大于0. 1,表明其为岩浆成因。碎屑锆石中稀土元素含量变化范围较大,(La/Yb)_N值为0～0. 29,LREE/HREE值为0. 003×10~(-6)～0. 977×10~(-6),表明样品中锆石的轻、重稀土元素分异程度较小且重稀土元素相对富集,具有轻稀土元素含量低、重稀土元素含量高的左倾模式且具有负Eu异常、正Ce异常的特征,表明碎屑锆石主要以岩浆锆石为主,同时存在少量的变质锆石。碎屑锆石U-Pb测年结果表明,最年轻的锆石年龄为193 Ma,显示枫坪组沉积岩成岩年龄不晚于193 Ma。碎屑锆石年龄可分为4组,分别为2 461～1 743 Ma、887 Ma、435和422 Ma、330～193 Ma。碎屑锆石的主要年龄区间分别与已知的构造-岩浆热事件时间相对应(吕梁期、晋宁期、加里东期和印支-海西期),表明本区的构造岩浆活动与中国大地构造运动相一致,并具有幕式发展的特征。通过对枫坪组沉积岩碎屑锆石U-Pb年龄的系统分析并与可能物源区的年代学对比研究,认为枫坪组沉积岩物质来源主要是周边出露的中条期侵入岩体和浙东南出露的印支期花岗岩体。     

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.     

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).     

HYDROGEOLOGY

正20141756 Chen Ruige(Mathematical College,China University of Geosciences,Beijing100083,China);Zhou Xun Numerical Simulation of Groundwater Level Fluctuation in a Coastal Confined Aquifer with Sloping Initial Groundwater Level Induced by the Tide(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(7),2013,p.1099-1104,6 illus.,16 refs.) Key words:confined water,groundwater level     

METAMORPHIC PETROLOGY

正20141408 Cai Jia(Institute of Geology,Chinese Academy of Geological Sciences,Beijing100037,China);Liu Fulai Petrogenesis and Metamorphic P-T Conditions of Garnet-Spinel-Biotitebearing Paragneiss in Danangou Area,Daqingshan-Wulashan Metamorphic Complex Belt(Acta Petrologica Sinica,ISSN1000-0569,CN11-1922/P,29(7),     

SERIALS

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GEOPHYSICAL EXPLORATION

正20142386An Guoying(China Aero Geophysical Survey and Remote Sensing Center for Land and Resources,Beijing 100083,China)Application of Satellite Remote Sensing in Regional Hydrogeological Investigation:Taking Cenozoic Strata in Wenquan Sheet(1∶250 000)of Karakoram Range as an Example(Geosci-     

QUATERNARY GEOLOGY & GEOMORPHOLOGY

正20141016An Chengbang(Key Laboratory of Western China’s Environmental Systems,Ministry of Education,Lanzhou University,Lanzhou 730000,China);Zhao Yongtao Lake Records during the Last Glacial Maximum from Xinjiang,NW China and Their Climatic Impli-     

PETROLEUM GEOLOGY

正20141538 Cao Qing(School of Earth Sciences and Engineering,Xi’an Petroleum University,Xi’an 710065,China);Zhao Jingzhou Characteristics and Significance of Fluid Inclusions from Majiagou Formation,Yichuan Huangling Area,Ordos Basin(Advances in Earth Science,ISSN1001-8166,CN62-1091/P,28(7),2013,p.819-828,7 illus.,3 tables,43 refs.)     

GEOCHEMISTRY

正20142002 Wei Hualing(Institute of Geophysical and Geochemical Exploration,Chinese Academy of Geological Sciences,Langfang065000,China);Zhou Guohua Element Content and Mineral Compositions in Different Sizes of Soil in Tongling Area,Anhui Province(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(11),2013,p.1861