天山石炭-二叠纪后碰撞花岗岩的Nd、Sr、Pb同位素源区示踪

天山造山带不仅是中亚巨型造山带的组成部分，也是我国西部晚古生代岩浆活动的集中区，蕴含着丰富的古亚洲洋演化的复合地质信息。笔者以探索天山晚古生代花岗岩浆活动的物质来源为目标，采用Sr、Nd、Pb同位素地球化学方法，对该区不同构造单元中具有代表性的花岗岩体进行了全面系统的研究，发现天山不同构造单元中花岗岩Sr、Nd、Pb同位素特征具有明显差异。在与其围岩的同位素特征进行对比研究的基础上，提出了产于不同构造单元石炭-二叠纪花岗岩的可能源区。觉罗塔格石炭-二叠纪裂谷带的晚古生代花岗岩，具有最高的εNd(t)值和最低的(^87Sr／^86Sr)t值，如，以康古尔石英闪长岩为代表的二叠纪花岗岩的源岩可能是早期泥盆纪大南湖岛弧火山岩(新生地壳)；博格达地区的晚石炭-二叠纪花岗岩是早期基性火山岩，亦可能是底侵基性岩部分熔融的产物。中新元古代基底晚石炭-二叠纪裂谷带中花岗岩的源岩亦为同期基性火山岩，但在岩浆演化过程中受到古老基底地壳的混染，导致其εNd(t)值低于石炭-二叠纪裂谷带中花岗岩，而(^87Sr／^86Sr)t高于石炭-二叠纪裂谷带花岗岩。南天山东段和前寒武系微地块及其边缘中的晚古生代(含个别早古生代花岗岩)花岗岩分别是类似于库米什斜长角闪岩的古老地壳和西天山元古代古老地壳部分熔融的产物，因此它们均具有负的εNd(t)值和异常高的(^87Sr／^86Sr)t值。上述认识对于了解天山晚古生代区域岩石圈演化及深部过程具有重要意义。     

集宁地区两类古元古代重熔花岗岩的锆石U-Pb年代学及岩石成因

学术界对集宁-凉城地区的古元古代重熔型花岗岩成因一直持有不同的解释,本文对集宁土贵乌拉-隆盛庄一带两类重熔花岗岩进行了同位素年代学及地球化学研究.锆石LA-MC-ICP-MS U-Pb年代学结果显示,斑状石榴紫苏二长花岗质片麻岩具有1 954 Ma的侵位年龄及1 827 Ma的变质年龄,变质淡色石榴二长花岗岩具有1 956 Ma的侵位年龄.岩石地球化学特征显示斑状石榴紫苏二长花岗质片麻岩低硅、高镁铁,具有Eu负异常及Sr的相对亏损;变质淡色石榴二长花岗岩富硅、贫铁镁,强烈亏损Nb、Ta、Ti等高场强元素,富集K和Rb、Ba等亲石元素.二者形成时代相同,可能源自幔源岩浆底侵造成的重熔,斑状石榴紫苏二长花岗质片麻岩源岩为孔兹岩系沉积岩,混合了一定比例的幔源物质组分并经过分离结晶过程;变质淡色石榴二长花岗岩源岩主要为孔兹岩系沉积岩,较少受到幔源组分的影响.      

天山托洋峰花岗质岩石的同位素地球化学特征

分析了西天山托木尔峰地区花岗质岩石和基底岩石的稀土元素,微量元素以及Ｏ、Ｐｂ、Ｓｒ、Ｎｄ同位素组成。本区北部伊犁地块基底岩石的Ｎｄ同位素模式年龄约为１．９Ｇａ,南部南天山褶皱带的约为０．７０５到０．７３３）表明本区花岗质岩石主要为地壳溶融产物。Ｏ、Ｐｂ、Ｓｒ、Ｎｄ同位素组成批示位于伊犁地块和南天山褶皱带的花岗岩源区岩石的Ｎｄ模式年龄都相当于伊犁地壳,但源区性质不同,前者源区δ＾１８Ｏ低,μ值低,Ｔ     

西秦岭北缘天水地区新元古代花岗质片麻岩地球化学特征及其形成环境

西秦岭北缘新元古代花岗质片麻岩位于天水地区分隔北秦岭造山带和北祁连构造带的新阳-元龙韧性剪切带中。花岗质片麻岩具高Si、高Al的特征,属高钾钙碱性系列,A/CNK在1.104～1.389之间,为硅、铝过饱和类型,属典型的强过铝质S型花岗质岩石。轻、重稀土元素分馏较强,具中等负Eu异常。岩石富集大离子亲石元素（Cs、Rb、Ba、Th、U、K、La等）,强烈亏损高场强元素（Nb、Ta、Ti、Hf等）,明显的Ba、P、Sr负异常,相对富集Zr。该花岗质岩石是一种典型的壳源成因类型,主要为上地壳中以成熟度较低、含泥质成分较高的杂砂岩、岩屑杂砂岩为原岩的古元古界秦岭岩群中含水矿物相脱水部分熔融形成的,可能存在少量的分离结晶作用。该花岗质片麻岩具有同碰撞型花岗岩的特征,可能是北秦岭微地块与相邻地块在新元古代早期发生汇聚的产物,是Rodinia超大陆在西秦岭地区汇聚的响应。     

西秦岭北缘天水地区新元古代花岗质片麻岩 地球化学特征及其形成环境

西秦岭北缘新元古代花岗质片麻岩位于天水地区分隔北秦岭造山带和北祁连构造带的新阳－元龙韧性剪切带中。花岗质片麻岩具高Si、高Al的特征,属高钾钙碱性系列,A/CNK在1.104～1.389之间,为硅、铝过饱和类型,属典型的强过铝质S型花岗质岩石。轻、重稀土元素分馏较强,具中等负Eu异常。岩石富集大离子亲石元素（Cs、Rb、Ba、Th、U、K、La等）,强烈亏损高场强元素（Nb、Ta、Ti、Hf等）,明显的Ba、P、Sr负异常,相对富集Zr。该花岗质岩石是一种典型的壳源成因类型,主要为上地壳中以成熟度较低、含泥质成分较高的杂砂岩、岩屑杂砂岩为原岩的古元古界秦岭岩群中含水矿物相脱水部分熔融形成的,可能存在少量的分离结晶作用。该花岗质片麻岩具有同碰撞型花岗岩的特征,可能是北秦岭微地块与相邻地块在新元古代早期发生汇聚的产物,是Rodinia超大陆在西秦岭地区汇聚的响应。     

西天山新源南部二叠纪辉绿岩墙群地球化学特征、锆石U-Pb年龄及其地质意义

南天山古洋盆闭合、碰撞造山时限等洋-陆格局的演化过程是西天山备受关注的地球动力学问题,紧邻那拉提北缘断裂的新源地区二叠纪放射状辉绿岩墙提供了解决这个问题的良好机会。新源地区辉绿岩具辉绿结构,斑晶为斜长石和普通辉石,基质主要由斜长石、辉石、绿泥石等副矿物组成。岩石为富钠贫钾、过铝质、钙碱性岩浆系列。辉绿岩岩墙富集Rb、Th和La等元素,明显亏损Nb、Ta等元素,显示ε_(Nd)(t)为正值(+3.3～+3.8)和低的初始锶比值((~(87)Sr/~(86)Sr)_i=0.70479～0.70548),幔源物质明显。与该区石炭纪玄武岩地球化学性质相似,岩浆可能为二叠纪软流圈和岩石圈相互作用的产物,其起源与软流圈上涌有关。辉绿岩岩墙LA-ICP-MS锆石U-Pb年龄为280.4±3.6Ma,被解释为岩脉成岩年龄,即岩脉形成于二叠纪。结合区域构造背景,推测辉绿岩岩脉形成于塔里木地块与中天山-伊犁地块碰撞闭合后的板内伸展环境,并与南天山洋洋壳岩石圈板块断离密切相关。     

西天山伊犁地块北缘桦木沟高分异I型花岗岩年代学、地球化学及其构造意义

古生代晚期天山造山带经历了洋壳消减及地块拼合的过程,西天山伊犁地块周缘拼合带的花岗岩岩浆记录可以为俯冲造山作用时限提供有效的约束。岩石地球化学和年代学分析显示,位于伊犁地块北缘的桦木沟花岗岩体高硅,富碱,贫铁,富集HFSE,具强烈铕负异常,亏损Ba、Sr、P、Ti,富集Cs、Rb、U、K,与高分异I型花岗岩地球化学特征一致;Pb同位素指示花岗岩源区为造山带下地壳;LA-ICP-MS锆石U-Pb测年结果表明,该岩体结晶年龄为(330.2±5.7)Ma,说明桦木沟岩体产于汇聚大陆边缘,天山北部洋壳在早石炭世晚期仍在向南俯冲,准噶尔地块与伊犁地块还未碰撞拼合,天山地区可能正处于俯冲消减阶段。     

闽西南地区晚中生代花岗质岩石的同位素年代学、地球化学及其构造演化

本文研究的闽西南地区晚中生代花岗质岩体中莒舟花岗岩体单颗粒锆石u-Pb年龄为136．0Ma，133．9Ma，黑云母Ar-^39Ar年龄为132．3Ma，菜刀岐石英斑岩单颗粒锆石U-Pb年龄为117．4Ma，太华花岗岩体全岩Rb-Sr年龄为114．9Ma，都属早白垩世。莒舟花岗岩富Si、K、Rb．Th，Y含量高，铝弱过饱和，贫Sr、Ba、P、Ti、Eu，过渡元素显著亏损而具壳源型花岗岩特征，菜刀岐石英斑岩是其高程度分异演化的产物，并为锡矿床的形成提供了物质基础。莒舟岩体是在岩石圈伸展的底侵作用下所形成的，岩石中有少量幔源组分加入，岩石的εNd（t）偏低（-7．21），tDM偏高（1．52Ga）。太华花岗岩体的εNd（t）稍高（-3．60--3．68），tDM稍低（1．21Ga），岩石中有较多幔源组分加入，是壳幔混合源花岗岩。过铝质壳源型花岗岩可以在与岩石圈伸展作用相关的张性构造环境中形成，壳幔相互作用对锡矿床的形成具有重要的贡献。     

南天山东段白土滩二叠纪花岗质杂岩体锆石定年、地球化学及构造意义

白土滩花岗质杂岩体主要由黑云二长花岗岩、正长花岗岩和花岗闪长岩构成。通过锆石LA-ICP-MS U-Pb法测得黑云二长花岗岩和正长花岗岩的年龄分别为(291±2)Ma和(277±3)Ma。岩石地球化学研究表明,与黑云二长花岗岩相比,花岗闪长岩中硅、碱较低,而铝较高;高∑REE和∑LREE,低铕负异常;富Cr,Zn,Sr,Zr,Ba和Hf,贫Rb,Ta和Th,Nb/Ta和Zr/Hf均升高,DI,Rb/Sr下降,从花岗闪长岩到黑云二长花岗岩表现出连续分异演化的趋势。结合区域地质特征认为,白土滩花岗质杂岩体为高钾钙碱性I型花岗岩,其源区物质是含水的、碱性和高钾钙碱性的安山岩和玄武质安山岩,形成于南天山东段碰撞造山的碰撞-后碰撞阶段。     

东天山石炭纪企鹅山群火山岩岩石成因

土屋矿区南北大沟企鹅山群火山岩的岩石地球化学研究表明:东天山企鹅山群火山岩主要为拉斑系列,少量为钙碱系列;岩石类型为玄武岩、玄武安山岩、英安岩和流纹岩。稀土、微量元素和Sr、Nd同位素特点揭示:该火山岩系形成于大陆裂谷环境;其源区主要为软流圈地幔,同时有岩石圈地幔源组分卷入,酸性岩浆是玄武质岩浆结晶分异的产物。     

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.     

Late Wuchiapingian (Late Dzhulfian,early Late Permian) limestone olistolites within the Tertiary flysch of Glypia Unit (Mount Parnon,central–eastern Peloponnesus,Greece)

Some olistolites reworked in a Tertiary flysch of Mount Parnon (Peloponnesus, Greece) exhibit a Late Permian assemblage, dominated by Paradunbarula (Shindella) shindensis, Hemigordiopsis cf. luquensis and Colaniella aff. minima. This association corresponds to the Late Wuchiapingian (=Late Dzhulfian), a substage whose algae and foraminifera are generally little known. Contemporaneous limestones crop out in the middle part of the Episkopi Formation in Hydra, but they are rather commonly reworked in Mesozoic and Cainozoic sequences. The palaeobiogeographical affinities shared by the foraminiferal markers of Greece, southeastern Pamir, and southern China, are very strong (up to the specific level), and are congruent with the Pangea B reconstructions. To cite this article: E. Skourtsos et al., C. R. Geoscience 334 (2002) 925–931.     

PALEONTOLOGY

正20141596 Liu Yunhuan(School of Earth Sciences and Resources,Chang’an University,Xi’an 710054,China);Shao Tiequan Early Cambrian Quadrapyrgites Fossils of Xixiang Boita in Southern Shaanxi Province(Journal of Earth Sciences and Environment,ISSN1672-6561,CN61-1423/P,35(3),2013,p.39-43,3 illus.,20 refs.)     

GEOCHEMICAL EXPLORATION

正20141719 Chen Zhijun(State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan 430074,China);Chen Jianguo Automated Batch Mapping Solution for Serial Maps:A Case Study of Exploration Geochemistry Maps(Journal of Geology,ISSN1674-3636,CN32-1796/P,37(3),2013,p.456-464,2 illus.,2 tables,10 refs.)     

MICROPALAEONTOLOGY

正20140962 Chen Fenning(Xi’an Institute of Geology and Mineral Resources,Xi’an710054,China);Chen Ruiming Late Miocene-Early Pleistocene Ostracoda Fauna of Gyirong Basin,Southern Tibet(Acta Geologica Sinica,ISSN0001-5717,CN11-1951/P,87(6),2013,p.872-886,6illus.,56refs.)     

PETROLOGY

正1.IGNEOUS PETROLOGY20142008Cai Jinhui(Wuhan Center,China Geological Survey,Wuhan 430205,China);Liu Wei Zircon U-Pb Geochronology and Mineralization Significance of Granodiorites from Fuzichong Pb-Zn Deposit,Guangxi,South China(Geology and Mineral Resources of South China,ISSN1007-3701,CN42-1417/P,29(4),2013,p.271-281,7illus.,     

ENVIRONMENTAL GEOLOGY

正20141205Cheng Weiming(State Key Laboratory of Resources and Environmental Information System,Institute of Geographic Sciences and Natural Resources Research,CAS,Beijing 100101,China);Xia Yao Regional Hazard Assessment of Disaster Environment for Debris Flows:Taking Jundu Mountain,Beijing as an     

PROSPECTING EXPLORATION

正20141266Fan Chaoyan(Guangdong Provincial Key Laboratory of Mineral Resources and Geological Processes,Guangzhou 510275,China);Wang Zhenghai On Error Analysis and Correction Method of Measured Strata Section with Wire Projection Method(Journal of