东天山花岗岩与造山带演化

文章通过建立花岗岩类类型与地球动力学之间的联系,试图利用分类清楚、测年准确的花岗岩解决本区地壳及造山带演化过程。根据K2O等地壳成熟度的指标,得出了该地区地壳性质由不成熟→半成熟岛弧→成熟陆壳演变;构造环境由不成熟岛弧→成熟的"大陆化"岛弧→大陆碰撞带演化。总结了东天山地区经历了三大地壳演化时期,分别为前寒武纪基底演化阶段陆核及超大陆形成期;古生代古亚洲洋形成演化期和中生代特提斯―印欧板块碰撞阶段板内演化期。反演出了东天山造山带经历了俯冲汇聚及不成熟陆壳形成阶段→弧―陆碰撞及半成熟陆壳形成阶段→碰撞造山及成熟陆壳形成阶段→陆内造山及陆壳改造阶段→中生代板内演化阶段。     

三江地区义敦岛弧碰撞造山过程：花岗岩记录

义敦岛弧碰撞造山带是特提斯－喜马拉雅巨型造山带中的一个复合造山带。本文利用义敦岛弧碰撞造山带29个花岗岩体的43件同位素测年数据，结合岩石地球化学特征，建立了造山带花岗岩的时间坐标。初步识别出4套不同成因类型的花岗岩，即印支期弧花岗岩、燕山早期同碰撞花岗岩、燕山晚期A型花岗岩和喜马拉雅期花岗岩。据此，再造了造山带的形成过程与演化历史：印支期的大规模俯冲造山作用（238－210Ma)，形成义敦火山岩浆弧；大约自206Ma始，发生弧－陆碰撞，伴随岛弧地壳挤压收缩和剪切变形，发育同碰撞花岗岩；进入燕山晚期（138－73Ma)，岛弧碰撞造山带发生造山后伸展作用，形成A型花岗岩带；喜马拉雅期发生陆内造山作用（65－15Ma)，岛弧碰撞造山带出现逆冲－推覆和大规模走滑平移，伴随喜马拉雅期花岗岩的侵位和拉分盆地的形成。     

苏东北多期A型花岗岩及其成岩构造环境

江苏东北部地区有宋山、牛山和踢球山3种A型花岗岩（类）。其中宋山岩体属A1亚型花岗岩类，形成于晋宁期苏胶造山带同造山的郯庐走滑断裂带的拉张环境；牛山岩体属A2亚型花岗岩，形成于震旦期苏胶造山带碰撞造山后的拉张环境；踢球山岩体属A1－A2过渡亚型花岗岩，形成于燕山期苏胶造山带陆内造山后和郯庐断裂带的拉张环境。     

湘东北燕山晚期花岗岩构造环境判别

在湘东北中生代多期陆内花岗岩浆活动中，燕山晚期花岗岩占有重要地位，燕山晚期大规模花岗岩侵入代表一种特殊的构造环境。本文通过湘东北主要燕山晚期花岗岩的岩石化学和微量元素来判别成岩构造环境，认为该期花岗岩属于富碱质的钙碱性花岗岩，为陆内拉张环境下的产物，进一步进行构造环境分类，判别其属于后造山PA型花岗岩，形成于造山作用后期的拉张环境，与陆内裂谷长期拉张的构造环境明显不同。在区域构造演化分析的基础上，提出湘东北燕山晚期花岗岩形成于印支－燕山早期陆内挤压－走滑剪切造山作用后期的构造松弛阶段拉张环境，燕山晚期PA型花岗岩的出现标志着陆内活化由挤压向拉张的构造转折，同时也反映湘东北的陆内活化至少经历了陆内挤压和陆内拉张两个演化阶段。     

东准噶尔北缘两类钙碱性花岗岩特征及其构造-成矿意义

依据前人对东准噶尔地区花岗岩类年代学和地球化学研究,将东准噶尔北缘钙碱性花岗岩划分为两类：一类为俯冲钙碱性花岗岩;另一类为后碰撞高钾钙碱性花岗岩。岩石地球化学对比研究发现,两类钙碱性花岗岩存在系统差异,兼具有相似性。岩石地球化学特点差异表现为俯冲钙碱性花岗岩,显示亲岛弧岩浆性,后碰撞高钾钙碱性花岗岩具有陆内后碰撞深成岩浆的特点。两者之间的相似性表明,造山带内花岗岩类由俯冲钙碱性→后碰撞高钾钙碱性系列演化是由于俯冲造山向碰撞造山快速转化、空间上位于同一造山带内,源区岩浆有双重性的特点。钙碱性花岗岩产出的构造环境具有多样性,成岩过程受造山带不同演化阶段相应构造背景制约,洋陆俯冲的岛弧环境和陆内造山的后碰撞环境分别是俯冲钙碱性和后碰撞高钾钙碱性花岗岩形成的构造背景。埃达克质岩浆亲和性显示俯冲钙碱性花岗岩与部分后碰撞高钾钙碱性花岗岩均有形成不同背景（岛弧和后碰撞）斑岩型矿床的潜力。后碰撞高钾钙碱性花岗岩与IOCG型矿床的空间联系,表明造山带伸展背景的后碰撞环境,也可能是IOCG型矿床产出的构造背景。两类钙碱性花岗岩构造背景的差异可能初步印证了具有岛弧斑岩型矿床的哈腊苏-卡拉先格尔和IOCG型矿床的老山口南东一带成矿环境的差异。     

川西雀儿山花岗杂岩体锆石U-Pb年龄、地球化学特征及其成矿专属性

川西义敦岛弧碰撞造山带北段雀儿山复式花岗杂岩体的年代学和全岩地球化学研究表明,雀儿山杂岩体主要由花岗闪长岩、二长花岗岩和正长花岗岩组成。锆石LA--ICP--MS U--Pb测年结果显示,该岩体中的花岗闪长岩形成时代为晚三叠世(224±3 Ma),二长花岗岩则形成于早白垩世(102±1 Ma)。地球化学数据表明,晚三叠世花岗闪长岩为火山弧岩石序列,形成环境为碰撞前俯冲环境;早白垩世二长花岗岩和正长花岗岩为后碰撞岩石序列,形成于造山期后板内或陆内环境。结合区域地质资料,认为雀儿山杂岩体为印支期—燕山期义敦岛弧碰撞造山带经历俯冲--碰撞--隆升过程中的产物。     

满洲里—额尔古纳地区岩浆作用及其大地构造意义

对满洲里－额尔古纳地区不同时代岩浆岩的地质，地球化学特征进行了初步研究，研究表明晚元古代花岗岩具S型花岗岩或地壳改造型花岗岩特征，形成于同碰撞造山环境，加里东早期花岗岩具I型，科迪勒拉I型或ACG特征,代表活动大陆边缘构造属性，加里东晚期花岗岩具S型或地壳改造型特征，代表陆－陆碰撞造山环境，加里东期花岗岩记录了多宝山－牙克石－伊尔施陆间洋壳消减和闭合的过程，海西晚期花岗岩属富碱低钙钙碱性岩石，具S型花岗岩或CPG，KCG花岗岩特征，形成于碰撞后构造环境，中生代早期岩 岩形成于蒙古－－鄂霍茨克残余洋“剪刀式”闭合所造成的张性似裂谷环境，中生代晚期岩浆岩形成于挤压环境。     

内蒙古阿拉善盟巴音诺日公地区中三叠世花岗岩特征及构造意义

分布于巴音诺日公地区的中三叠世花岗岩可分为两个超单元。早超单元属陆—陆碰撞同造山期S型花岗岩,单颗粒锆石U-Pb同位素年龄值234±8Ma;晚超单元属陆—陆碰撞造山后—非造山期A型花岗岩,单颗粒锆石U-Pb同位素年龄值235±4Ma。说明该区中三叠世华北板块与塔里木板块发生陆—陆碰撞造山,随后地壳的构造环境由挤压向拉张转化。     

东秦岭古生代以来花岗质岩浆活动及其构造意义

东秦岭自古生代以来经历了多期花岗质岩浆活动形成了大量的花岗质岩石。依据锆石U-Pb年龄,这些花岗岩可分为三个主要期次:加里东期花岗岩、印支期花岗岩和燕山期花岗岩。详细研究这些花岗岩的岩石地球化学特征发现,早古生代的花岗岩表现为与大洋俯冲作用有关的岛弧钙碱性系列岩石,早中生代花岗岩具有后碰撞阶段花岗岩的地球化学特征,晚中生代花岗岩主要为Ⅰ型花岗岩并伴有A型花岗岩的出现。这说明东秦岭区域上经历了俯冲造山作用到碰撞造山和碰撞后陆内演化等不同阶段。     

天山造山带古生代侵入岩地质特征及构造意义

通过对天山造山带古生代侵入岩岩石类型、岩石地球化学特征及年代学研究,初步厘定不同构造带侵入岩浆序列及形成构造环境。天山地区古生代侵入岩主要包括奥陶—志留纪俯冲期钙碱性花岗岩、泥盆纪后碰撞型正长花岗岩、石炭纪中早期俯冲型钙碱性花岗岩、石炭纪晚期后碰撞型正长花岗岩、石炭纪末后碰撞型镁铁-超镁铁质岩、二叠纪早期后造山型碱性花岗岩及洋壳残片等。俯冲期侵入岩主要为花岗闪长岩-石英二长闪长岩-石英闪长岩组合;同碰撞期为花岗闪长岩-二长花岗岩组合;后碰撞期为组成花岗岩-二长花岗岩组合;后造山期为正长花岗岩-碱性花岗岩组合。认为该地区古生代侵入岩与Terskey洋、北天山洋、南天山洋等洋盆演化密切相关,并建立了天山地区古生代构造演化模式图。     

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).     

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.)