东昆仑巴隆地区晚三叠世石英闪长岩成因:U⁃Pb年代学、地球化学及Sr⁃Nd⁃Hf同位素制约

花岗岩的研究对于反演造山带下地壳物质组成、造山作用深部动力学过程具有重要意义.对位于东昆仑造山带东段的巴隆石英闪长岩开展了锆石U?Pb年代学、Hf同位素地球化学、全岩主微量元素地球化学和Sr?Nd同位素地球化学研究,以探讨其岩石成因和构造背景.岩体LA?ICP?MS锆石U?Pb定年结果为229.5±1.4 Ma,为晚三...     

西秦岭党川地区花岗岩的成因及其构造意义

对西秦岭造山带党川地区的党川花岗岩和石门花岗岩进行了LA-ICP-MS锆石U-Pb定年、元素地球化学和Sr-Nd-Pb同位素组成的研究.结果表明, 党川花岗岩和石门花岗岩的岩浆结晶年龄分别为438±3Ma和220±2Ma.在岩石地球化学特征上, 党川花岗岩类似于C-型埃达克质岩石, 岩浆产生于增厚地壳物质的部分熔融, 而石门花岗岩类似于普通的地壳深熔型花岗岩.党川花岗岩的I_Sr=0.70660~0.70929, ε_Nd (t) =-2.24~-4.48;石门花岗岩的I_Sr=0.70581~0.70804, ε_Nd (t) =-3.73~-4.72.Sr-Nd同位素组成进一步指示它们的岩浆派生于地壳物质.然而, 在Pb同位素组成上, 党川花岗岩和石门花岗岩存在着明显的差异.党川花岗岩以相对富放射成因Pb同位素组成为特征, 初始Pb同位素比值为: 206Pb/204Pb=18.288~18.484, 207Pb/204Pb=15.677~15.693, 208Pb/204Pb=38.182~38.283;而石门花岗岩以相对低的放射成因Pb同位素组成为特征, 初始Pb同位素比值为: 206Pb/204Pb=17.989~18.189, 207Pb/204Pb=15.560~15.567, 208Pb/204Pb=37.982~38.000.这表明党川花岗岩和石门花岗岩的岩浆来自于不同地壳物质的部分熔融.区域分析表明, 西秦岭党川地区中古生代和早中生代的岩浆事件、岩石成因机制及岩浆源区均可与东秦岭地区北秦岭构造单元相对比, 由此说明西秦岭党川地区是东秦岭地区北秦岭构造单元的西延, 并且东秦岭地区早中生代南秦岭块体向北秦岭块体的大陆俯冲作用向西一直延至到西秦岭地区.      

阿尔泰花岗岩类型与成岩模型的REE及O、Pb、Sr、Nd同位素组成依据

根据 REE 分布模式和 O、Pb、Sr、Nd 同位素组成特征,采用构造环境、物质来源和形成方式等多级标准,将阿尔泰花岗岩类划分为两个系列、五种类型,即造山花岗岩系列(阿尔泰系列),包括:壳-幔同熔型(青格里型),地壳交代型(额尔齐斯型),地壳重熔型(尚可兰型);非造山花岗岩系列(乌伦古系列),包括:幔源分异型(布尔根型),幔     

新疆北部后碰撞幔源岩浆活动与陆壳纵向生长

新疆北部后碰撞幔源岩浆活动强烈。Nd、Sr和Pb同位素资料表明,在330～250Ma的后碰撞期间,有大量的幔源花岗岩类和少量的镁铁—超镁铁杂岩在上地壳侵位。与加里东、海西和喜马拉雅等造山带起源于再循环陆壳的花岗岩类不同,新疆北部后碰撞岩浆岩一般表现出ε_(Nd)(t)值高、(~(87)Sr/~(86)Sr)值相对较低、Nd和Pb模式年龄年轻等特点。阿尔泰山和天山的一些后碰撞花岗岩类可能具有陆壳源区的特点或表现出地壳物质对幔源岩浆及其分异产物有不同程度的混染,东、西准噶尔花岗岩类很少甚至没有受到陆壳物质混染。新疆北部后碰撞花岗岩类和镁铁—超镁铁杂岩主要是幔源岩浆及其分异产物在上地壳侵位的结果。这些幔源花岗岩类代表了新生的初始地壳,其时代可代表地壳形成时代。在后碰撞阶段,新疆北部的陆壳以纵向生长为特征。     

甘肃北山野马泉岩体同位素地球化学特征

Nd、Sr、Pb同位素研究结果揭示：甘肃北山野马泉岩体第Ⅰ、Ⅱ侵入阶段花岗岩类具有Ⅰ-型花岗岩的特征，(87Sr/86Sr)i=0.708~0.710，εNd=-2.229~-5.866，在207 Pb/204Pb-206Pb/204Pb构造模式图上其投影点落在造山带演化线附近，在εNd-εSr图解中，其投影点落人Ⅰ-型花岗岩类范围内，其成岩物质为壳幔混合来源。第Ⅲ侵人阶段的岩石成因类型为S-型，其(87Sr/86Sr)i=0.7149~0.7358, εNd＝-7.3750~-8.9556。该岩体形成的地球动力学环境是北山陆内碰撞造山带。     

不同来源两个系列Li-F花岗岩的同位素组成区别

根据地质和地球化学特点,特别是同位素组成,将Li-F花岗岩划分为浅源南岭系列(系列Ⅰ)和深源长江系列(系列Ⅱ).系列Ⅰ的δO18＞10‰,ISr＞0.7100,εNd(t)＜-6,在207Pb/204Pb-206Pb204Pb铅同位素构造图上位于上地壳线附近;系列Ⅱ的δ18O＜10‰,ISr＜0.7100,εNd(t)＞-6,在207Pb/204Pb-206Pb/204铅同位素构造图上位于地幔线与造山带线之间.说明浅源南岭系列Li-F花岗岩物质来源比较浅,以上地壳(再循环地壳)物质为主,而深源长江系列Li-F花岗岩物质来源比较深,以地幔、下地壳和造山带(原生地壳)物质为主.     

浙江莫干山花岗岩体锆石U-Pb、全岩Rb-Sr年代学、Sr-Nd-O同位素地球化学及成因研究

莫干山花岗岩体位于东天目山晚中生代火山盆地东端,用LA-ICPMS进行锆石U-Pb定年得到年龄为128.1±2.1Ma,全岩Rb Sr等时线定年结果为135.4±4.3 Ma,表明其属燕山晚期岩浆活动产物.莫干山花岗岩的Sr-Nd-O同位素分析结果为:初始87Sr/86Sr=0.70933;εNd(t)=-3.75～ - 6.4;δ18O=8.86‰～10.78‰,表明其成因类型属Ⅰ型花岗岩,是壳-幔物质混合形成的.按Sr Nd双变量二元混合模型计算得出源区物质中地壳端员和亏损地幔端员的贡献份额分别为47％～49％、51％～53％.莫干山花岗岩与建德群黄尖组火山岩的锆石U-Pb年龄、全岩Rb Sr等时线年龄基本一致,其Nd-Sr同位素组成也很相似,表明它们来自同一岩浆源.     

义敦岛弧带晚白垩世海子山二长花岗岩成因及其地质意义

义敦岛弧是三江特提斯复合造山带的重要组成部分。文章对义敦岛弧海子山花岗岩体进行锆石U-Pb年代学、全岩地 球化学及Sr-Nd-Pb同位素地球化学进行分析,探讨其成因与构造意义。海子山花岗岩锆石U-Pb年龄为93.7±1.1 Ma（MSWD= 2.1, 2σ）,为晚白垩世早期岩浆活动产物,岩石具高硅、富碱的特征,铝饱和指数A/CNK=1.04~1.12,属于弱过铝质岩石。 稀土配分曲线呈燕式分布,Eu/Eu*=0.05~0.32,具有明显的Eu负异常。富集Rb、Th、U、Ta、Pb等元素,明显亏损Ba和 Sr,表现出A型花岗岩的特征。岩石的εNd(t)=–4.8~-3.4,二阶段模式年龄TDM2= 0.91~1.00 Ga,结合岩石的Pb同位素特征及 低的CaO/Na2O比值与高的Al2O3/TiO2比值,说明其应起源于泥质岩石的部分熔融并有少量地幔组分加入。综合地球化学、 同位素特征及义敦岛弧地区构造资料,表明海子山花岗岩是造山后伸展背景下形成的A型花岗岩,为地壳拉张、减薄,软 流圈地幔上涌引起中上地壳泥质岩部分熔融的产物,具有壳幔物质混合的特征。     

安庆早白垩世洪镇花岗岩成因及其对基底构造格局的启示

花岗岩可以有效示踪大陆基底物质,并区分具有不同地壳结构和演化历史的构造块体。洪镇花岗岩位于长江中下游地区江北A型花岗岩带的西延位置,距离郯庐断裂带约30 km。锆石SIMS定年表明,安庆怀宁县洪镇花岗岩形成于126. 2±2. 0 Ma,与长江中下游A型花岗岩以及大别造山带I型花岗岩的形成时代一致。洪镇花岗岩高硅、富钾,属于高钾钙碱性系列I型花岗岩。其富集轻稀土元素和大离子亲石元素,相对亏损中稀土元素和高场强元素,经历了角闪石为主的结晶分异。洪镇花岗岩具有较为富集的Sr—Nd—Hf同位素,和低放射性成因Pb同位素组成,其n(87Sr)/n(86Sr)(t)为0. 7065~0. 7066,εNd(t)值为-10. 9~-12. 0,锆石εHf(t)为-6. 7~-13. 2,n(206Pb)/n(204Pb)(t)、n(207Pb)/n(204Pb)(t)和n(208Pb)/n(204Pb)(t)分别在17. 063~17. 109、15. 568~15. 572和37. 351~37. 373之间。综合研究表明,洪镇花岗岩起源于古—中元古代中低成熟度沉积岩的水致部分熔融,为幔源岩浆底侵导致。从物质来源上,洪镇花岗岩岩浆源区类似于大别造山带经历过俯冲、折返后的中上地壳,而显著不同于长江中下游同时代A型花岗岩源区,表明洪镇地区具有上下地壳分属长江中下游和大别造山带的构造属性。在早白垩世早期郯庐断裂带南段西盘向南的强烈挤压下,大别造山带下地壳发生不规则流动,越过郯庐断裂带进入到洪镇地区下地壳成为洪镇花岗岩的源区。     

豫西南地区北秦岭地体新元古代花岗岩类岩石成因及其地质意义

北秦岭地体中新元古代花岗岩类岩石是秦岭造山带的重要组成部分,记录了造山带基底前寒武纪地壳形成和演化历史。本文报道方庄和德河花岗岩岩体的锆石U-Pb年龄和O同位素组成、全岩元素和Sr-Nd同位素地球化学组成,探讨其岩石成因和地壳演化意义。结果表明,方庄花岗质糜棱岩的锆石结晶年龄为933.4±9.2Ma,δ18O值8.3‰～11.9‰,初始87Sr/86Sr比值0.72455,初始εNd值-6.0,Nd模式年龄2.09Ga(tDM2);德河黑云斜长片麻岩的锆石结晶年龄为948.1±8.9Ma,初始87Sr/86Sr比值变化较大,初始εNd值-5.0,Nd模式年龄2.02Ga。结合已报道的新元古代花岗岩类岩体的年龄和地球化学数据,北秦岭地体新元古代岩浆作用可以划分为980～870Ma挤压碰撞作用和～844Ma伸展裂解作用两大阶段,包括～940Ma强烈变形S型同碰撞花岗岩、～880Ma弱-无变形后碰撞I型花岗岩和～844Ma板内A型碱性岩三类花岗岩体。地球化学组成显示,这些花岗岩类岩石可能源自不同时期形成的秦岭群基底杂岩的部分熔融,但在后碰撞阶段幔源物质或年轻地壳物质的加入明显增加。北秦岭地体中新元古代岩浆活动与Rodinia超大陆演化基本同时代,可能记录超大陆形成过程中的地壳响应。在新元古代之前,北秦岭地体或许具有不同于华北陆块和华南陆块的演化历史。     

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