延边开山屯地区二叠纪地质体的构造属性：侵入岩及碎屑锆石证据

本文对延边开山屯地区二叠纪侵入岩和地层中的(碎屑)锆石进行了LA-ICP-MS和SIMS U-Pb年代学及Hf同位素的研究,同时对侵入岩进行了全岩地球化学特征的研究,以便制约开山屯地区的构造属性以及延边地区晚古生代-早中生代演化历史。延边开山屯地区大蒜沟组复成分砾岩和岩屑杂砂岩中锆石最年轻峰值年龄为298Ma和293Ma,此外还存在330Ma、366Ma、438Ma、454Ma、479Ma峰值年龄。这些古生代碎屑锆石的ε_(Hf)(t)值介于-1.14～+15.17之间;开山屯组长石杂砂岩和长石砂岩中的锆石最年轻年龄峰值分别为259Ma和253Ma,此外还存在279Ma、456Ma、476Ma、500Ma、529Ma以及新元古代-古元古代(891～1765Ma)的峰值年龄。其中古生代碎屑锆石的ε_(Hf)(t)值介于-5.22～+10.15之间。开山屯地区中二叠世闪长岩和晚二叠世辉长闪长岩的形成时代分别为261Ma和256Ma,属于低钾拉斑-中钾钙碱性系列,相对富集轻稀土和大离子亲石元素,亏损重稀土和高场强元素,主要来源于受俯冲流体/熔体交代的亏损地幔楔的部分熔融。综合研究认为,开山屯地区与兴凯地块具有亲缘性;大蒜沟组的沉积时限为早-中二叠世,形成于兴凯地块西部活动大陆边缘的弧前盆地或增生楔环境;开山屯组形成于早-中三叠世,具有双向物源的特点(华北板块和兴凯地块)。早-中二叠世延边地区处于活动大陆边缘的构造背景。延边地区的古亚洲洋于早-中三叠世最终闭合。     

藏北羌塘果干加年山花岗闪长岩的锆石U-Pb定年和Hf同位素特征

报道了藏北羌塘中部果干加年山地区花岗闪长岩的锆石U-Pb定年结果和Hf同位素成分。花岗闪长岩的锆石U-Pb定年结果为(225.1±2.4)Ma,与该地区的高压变质带的形成时代一致。样品中锆石的εHf(t)值为-9.8~-17.6,地壳Hf模式年龄为1 874~2 372Ma,表明花岗闪长岩为古元古代地壳物质部分熔融的产物。结合区域地质资料,该花岗岩体可能形成于板块消减的火山弧构造环境,与羌塘地区古特提斯洋的晚三叠世俯冲消减有关。     

内蒙古温都尔庙地区早二叠世岛弧型花岗闪长岩的发现:对古亚洲洋闭合的时限约束

研究区位于西伯利亚板块与华北板块之间的关键部位,可能代表了古亚洲洋最终闭合的位置.在嘎顺地区首次识别出花岗闪长岩,通过对岩石地球化学、锆石U-Pb年代学和Lu-Hf同位素分析,获得LA-MC-ICP-MS锆石U-Pb年龄为294.8±2.7 Ma,形成于早二叠世.SiO₂含量介于64.69%~67.64%;Al₂O₃含量介于15.00%~15.52%;MgO含量介于1.14%~1.77%;Na₂O含量介于1.41%~3.61%;K₂O含量介于3.25%~3.98%.∑REE值介于157.89×10-6~174.43×10-6;LREE值介于147.86×10-6~149.55×10-6;HREE值介于9.34×10-6~11.8×10-6;右倾稀土配分曲线,呈轻度负Eu异常,轻重稀土元素分馏程度大,轻稀土相对于重稀土明显富集.明显富集Rb、K,亏损Ba、Sr大离子亲石元素（LILE）;富集Th,亏损Nb、Ta、Ti等高场强元素（HFSE）.锆石176Hf/177Hf值介于0.282 673~0.282 791;ε_Hf（t）值介于2.7~7.0,其二阶段模式年龄T_DM2介于861~1 129 Ma,176Lu/177Hf值介于0.000 486~0.000 734,结合岩石地球化学特征,认为该套岩石形成于岛弧岩浆作用,证实了早二叠世古亚洲洋仍未闭合.      

早侏罗世新特提斯洋俯冲作用——来自松多高镁闪长岩锆石U-Pb定年及Hf同位素的制约

冈底斯岩浆岩带中东部松多地区新发现的高镁闪长岩对于探讨青藏高原新特提斯俯冲演化历史具有重要意义。通过松多高镁闪长岩的LA-ICP-MS锆石U-Pb年龄、锆石Hf同位素和全岩地球化学组成的研究,表明松多闪长岩的锆石U-Pb年龄加权平均值为186.8±1.3Ma。该类岩石具有高硅、高镁的特点,Si O2含量为54.17%~58.81%,Mg O含量较高,介于6.26%~7.29%之间,Mg~#值介于64~67之间,Cr和Ni含量高。该岩石富集轻稀土元素,具有平滑右倾的稀土元素配分曲线及弱负Eu异常。富集Rb、Ba、Pb、K等大离子亲石元素,亏损Nb、Ta、Ti等高场强元素。锆石负εHf(t)值(-5~-14.3)及远大于其侵入年龄的古老Hf模式年龄(1543~2129Ma),揭示松多早侏罗世闪长岩经历了古老地壳物质的部分熔融。Sr/Y-Y和(La/Yb)N-YbN判别图解显示,其形成可能与赞岐岩的岩浆作用过程相似,形成于消减带之上的地幔楔环境。综合研究表明,松多地区在早侏罗世处于雅鲁藏布新特提斯洋板片向欧亚大陆俯冲的活动陆缘构造背景。     

西乌旗迪彦庙-达青地区石炭纪斜长花岗岩的发现及其对古亚洲洋构造演化的指示意义

本文对西乌珠穆沁旗迪彦庙-达青俯冲增生杂岩带内的斜长花岗岩开展了岩石地球化学、锆石U-Pb年代学和锆石Hf同位素研究。该区斜长花岗岩主要由斜长石、石英和少量黑云母组成,具有较高的SiO_2(68. 24%～79. 34%)、低Al(Al_2O_3为11. 33%～15. 23%)、低Ti(TiO_2为0. 270%～0. 773%)、低MgO(Mg#值为11～47)和富Na贫K(Na_2O/K_2O为4. 90～24. 25)的特征。稀土元素总量为14. 15×10~(-6)～189. 04×10~(-6),稀土元素球粒陨石标准化配分曲线为轻稀土弱富集、重稀土平坦的配分模式。微量元素原始地幔标准化蛛网图中,Nb、Ta和Ti为负异常。LA-ICP-MS锆石U-Pb测年结果显示:样品DYM17-006的锆石U-Pb谐和年龄为330. 1±3. 2 Ma,样品DQ17-007的锆石U-Pb谐和年龄为316. 5±2. 4 Ma,分别代表了迪彦庙和达青地区斜长花岗岩的形成年龄。锆石Hf同位素组成显示具有高的(~(176)Hf/~(177)Hf)_t比值以及正的ε_(Hf)(t)值(9. 387～16. 251),反映其岩浆源自于亏损地幔。综合分析认为,迪彦庙-达青俯冲增生杂岩带内斜长花岗岩应属于结晶分异型花岗岩,由起源于亏损地幔源区的洋脊玄武质岩浆结晶分异形成。迪彦庙-达青一带存在一个长期演化的大洋,在石炭纪处于洋盆扩张阶段,伴随着古亚洲洋的俯冲消减及洋陆转换,最终构成了中亚造山带的一部分。     

闽西南基性岩脉中捕获锆石SIMSU-Pb年龄及Hf、O同位素特征

测定了闽西南地区5件基性岩脉的全岩主微量元素,锆石U-Pb年龄和Hf,O同位素。5件岩脉主要为辉绿岩,其全岩SiO_2含量为45%~53%,稀土元素显示轻稀土富集的右倾配分模式。基性岩脉中大部分锆石具明显振荡环带和扇状环带,为典型岩浆结晶锆石特征。锆石U-Pb年龄(96~2 400 Ma)分布较为分散。除少量锆石年龄(96~142 Ma)可能指示岩脉形成年龄外,其余均为捕获锆石。捕获锆石年龄主要分布在4个范围:早元古代(2 467~1 796 Ma),中晚元古代—震旦纪(1 343~647 Ma),志留纪—晚三叠世(427~225 Ma),晚侏罗世(159~140 Ma)。Hf-O同位素显示早元古代锆石来源于接近球粒陨石均一储库的地幔。中晚元古代以后年龄的锆石其Hf-O同位素均具有亏损地幔岩浆与地壳组分混合的特征;志留纪—晚侏罗世锆石主要来源于S型壳源花岗岩的重熔;早白垩世晚期的锆石ε_(Hf)(t)值与δ~(18)O值清晰地显示出亏损地幔与地壳岩浆混合的趋势。闽西南基性岩脉中锆石的二阶段Hf亏损地幔模式年龄(TDM2)峰值主要分布在1.6~1.9 Ga,说明早元古代晚期幔源岩浆作用形成的基性岩地壳可能是形成后期花岗岩的主要源区。     

南秦岭武当山十堰地区中生代镁铁质岩石成因与构造意义——岩石地球化学、锆石U-Pb年龄和Hf同位素制约

南秦岭的北大巴山-武当山-十堰-随州一带发育大规模的镁铁质岩墙群,其岩石学成因为地质学家所广泛关注。本文对其中的武当山十堰地区黄龙-方滩一带发育的辉长岩体开展了全岩地球化学、SHRIMP锆石U-Pb年龄以及LA-MC-ICP-MS锆石Hf同位素组成研究。结果表明,辉长岩形成于晚三叠世（221.2±2.5 Ma）;岩石地球化学组成显示辉长岩为亚碱性拉斑玄武岩系列,轻稀土富集重稀土亏损,其平滑右倾的稀土配分模式与E-MORB相似;中等Ti、Zr、Hf、Nb含量,亏损Rb、Sr等大离子亲石元素,以及结晶年龄锆石的εHf(t）值在-13.5至-6.18之间,表明岩石具有古老的两阶段Hf模式年龄（2103~1640 Ma）。综合分析表明：该套辉长岩岩浆为尖晶石二辉橄榄岩低压、中等程度部分熔融形成,并且其源区为亏损地幔与富集地幔组分混合成因;结合区域构造演化的相关资料,认为该套E-MORB性质辉长岩形成于类似汇聚边缘的构造环境,可能为受勉略洋壳俯冲影响,为俯冲-碰撞造山阶段产物。     

南秦岭武当山十堰地区中生代镁铁质岩石成因与构造意义——岩石地球化学、锆石U-Pb年龄和Hf同位素制约

南秦岭的北大巴山—武当山—十堰—随州一带发育大规模的镁铁质岩墙群,其岩石学成因为地质学家所广泛关注。本文对其中的武当山十堰地区黄龙—方滩一带发育的辉长岩体开展了全岩地球化学、SHRIMP锆石U-Pb年龄以及LA—MC—ICP—MS锆石Hf同位素组成研究。结果表明,辉长岩形成于晚三叠世(221.2±2.5 Ma);岩石地球化学组成显示辉长岩为亚碱性拉斑玄武岩系列,轻稀土富集重稀土亏损,其平滑右倾的稀土配分模式与E—MORB相似;中等Ti、Zr、Hf、Nb含量,亏损Rb、Sr等大离子亲石元素,以及结晶年龄锆石的ε_(Hf)(t)值在-13.5至-6.18之间,表明岩石具有古老的两阶段Hf模式年龄(2103～1640 Ma)。综合分析表明:该套辉长岩岩浆为尖晶石二辉橄榄岩低压、中等程度部分熔融形成,并且其源区为亏损地幔与富集地幔组分混合成因;结合区域构造演化的相关资料,认为该套E—MORB性质辉长岩形成于类似汇聚边缘的构造环境,可能为受勉略洋壳俯冲影响,为俯冲—碰撞造山阶段产物。     

东昆仑希望沟橄榄辉长岩的岩石成因：地球化学、锆石U-Pb年龄与Hf同位素制约

东昆仑古特提斯域镁铁-超镁铁质岩石的研究极为薄弱,文章报道了青海东昆仑东段希望沟橄榄辉长岩的岩相学、锆石U-Pb年代学、岩石地球化学及锆石Hf同位素资料,以确定该岩体的形成时代、岩石成因及构造环境,为东昆仑晚古生代—早中生代构造岩浆演化提供新的约束。岩石地球化学研究表明,希望沟橄榄辉长岩具有低SiO2(40.91%~42.14%)、低TiO2(0.29%~0.39%)、高MgO(28.18%~30.66%)、贫碱(K2O+Na2O=1.09%~1.36%)的特征,属亚碱性系列岩石,m/f比值介于5.03~5.39,属于铁质超基性岩类。岩石微量元素总体上富集大离子亲石元素(Rb、Th、U、K)和Pb,相对亏损高场强元素(Nb、P、Ti),ΣREE为28.17×10^-6~30.95×10^-6,(La/Yb)N为3.77~4.98,显示轻稀土富集的特征,δEu=0.80~0.95,具有弱的Eu负异常。利用LA-ICP-MS锆石U-Pb定年技术,获得橄榄辉长岩加权平均年龄为(264.9±1.2)Ma(n=26,MSWD=0.71),属中二叠世。锆石176Hf/177Hf比值为0.282709~0.283152,对应的εHf(t)=3.7~19.3,锆石单阶段Hf模式年龄TDM为135~753 Ma,平均为414 Ma,大于锆石U-Pb年龄。研究认为,橄榄辉长岩的岩浆源区主要为亏损地幔,可能有早期流体交代的岩石圈地幔组分的加入,并经历了地壳物质的混染。结合东昆仑区域构造演化,认为希望沟橄榄辉长岩是阿尼玛卿古特提斯洋俯冲阶段的产物,说明古特提斯洋在中二叠世已北向俯冲。     

内蒙古科右中旗地区梅勒图组安山岩年代学特征及其地质意义

对内蒙古科右中旗地区梅勒图组安山岩锆石LA--ICP--MS U--Pb年代学、锆石Hf同位素和岩石地球化学测试分析结果表明,梅勒图组安山岩形成时代约为早白垩世中期(123~125 Ma)。锆石εHf(t)=(+5.84~+9.34),一阶段Hf模式年龄为412~553 Ma。岩石地球化学分析表明,安山岩K2O含量较高,SiO2含量和Mg#值中等,富集大离子亲石元素,高场强元素Nb、Ta、Ti等明显亏损。这些特征反映出梅勒图组安山岩的源区为新形成的富集地幔。结合地球化学特征和区域大地构造背景,研究区梅勒图组安山岩的形成可能与太平洋板块俯冲作用后的陆内伸展环境有关。     

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).     

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.)