汉诺坝幔源单斜辉石巨晶氢同位素组成的离子探针分析:微尺度不均一性

运用离子探针技术测定了河北汉诺坝新生代玄武岩中3个单斜辉石巨晶的氢同位素组成,结果显示同一颗粒内部表现出微尺度的不均一性,2mm范围内δD的变化达到60‰。δD和氢含量之间不存在同步的变化,巨晶内部的化学成分均一,因此我们认为巨晶的氢同位素不均一性继承自母岩浆。母岩浆的氢同位素变化可能是去气过程中气相与熔体之间的分馏引起的。单斜辉石巨晶形成后很短的时间内即被寄主岩浆带至地表并经历了快速淬火。     

安徽女山橄榄岩包体中辉石的氢同位素组成

本文运用离子探针技术分析了来自安徽女山橄榄岩包体中辉石的氢同位素组成。无论是颗粒内部还是同一样品不同颗粒之间,氢同位素比值都是均一的。氢同位素比值和氢含量之间没有相关性,说明氢同位素组成反映的是地幔源区的特征。结合共存的角闪石的氢同位素数据来看,女山上地幔至少经历过两期交代作用：一期交代形成了角闪石中不均一的氢同位素组成;另一期交代形成了包体中单斜辉石、单斜辉石巨晶和云母巨晶中的高δD值(高至-20‰)。高δS值说明女山上地幔曾经经历过俯冲流体的交代作用。     

雷州英峰岭玄武岩中单斜辉石巨晶的地球化学和地幔交代作用

雷州半岛英峰岭火山岩中单斜辉石巨晶以低Mg^#值(0．62—0．47)、贫重稀土(HREE)和富Al2O3、TiO2、Na2O和中稀土(MREE)为特征，并具有明显的成分变化。随着Mg^#降低，单斜辉石的Al：O，(11．58～6．97％，)、TiO，(2．28～1．06％)和HREE逐渐降低。这种变化特征不同于世界上大多数辉石巨晶的变化规律。随着演化辉石巨晶的大多数不相容元素，如Nb、Sr、Zr、Hf和LREE—MREE逐渐增加。低的Mg^#值和Ni、Co、Cr含量指示巨晶母岩浆是一种强烈演化的残余岩浆(Mg^#=0．27～0．35)。分离结晶模拟表明本研究最富镁的巨晶(Lz-54)的母岩浆很可能是由拉斑玄武质岩浆经70～80％，以单斜辉石为主的结晶分异后形成。而本研究的其它辉石巨晶是该母岩浆在不同演化阶段(25～80％)分离结晶的产物。分离矿物中除了单斜辉石还包含了大量的石榴子石、斜长石和钛铁矿。温压计算表明英峰岭巨晶是高温岩浆在56～60km深的上地幔的结晶产物(r=1290℃～1130℃，P=1.73～1．83GPa)，这一深度有利于石榴子石结晶。对比不同地区辉石巨晶的成分特征和形成条件，作者指出不同地区单斜辉石巨晶各种元素的不同变化规律主要受母岩浆成分和结晶条件控制。巨晶母岩浆在地幔结晶时对围岩橄榄岩进行了不同程度的交代作用。早期贫流体的岩浆对橄榄岩的交代作用较弱，只有Sr，La等强活动性元素被明显改变；晚期富流体(F，P，H2O)岩浆对橄榄岩的交代作用强烈，大多数元素被明显改变。因此，可以推断交代熔体中流体的含量是影响地幔橄榄岩交代作用的关键。     

江西安远路迳金伯利质煌斑岩筒辉石巨晶和包体中辉石的氢氧同位素

利用离子探针和质谱技术分别分析测试了江西安远路迳金伯利质煌斑岩筒辉石巨晶和包体中辉石的氢氧同位素组成.结果显示,辉石的氢同位素δ(D)值从-83‰变化到-101‰,平均值为-91.6‰;氧同位素δ(18O)值由5.46‰变化到5.70‰,平均值为5.60‰.路迳辉石巨晶和包体中辉石的氢氧同位素组成均一,表明其来源于地幔,且其形成和演化过程中物理化学环境稳定,继承并保持了原始地幔的氢氧同位素组成.     

华北晚中生代和新生代玄武岩中单斜辉石巨晶来源及其对寄主岩岩浆过程的制约:以莒南和鹤壁为例

本文对华北克拉通晚中生代和新生代碱性玄武质岩石中的单斜辉石巨晶进行了主、微量元素和Sr-Nd同位素的综合研究,发现晚中生代和新生代单斜辉石巨晶存在明显的主、微量元素和同位素组成上的差异。新生代单斜辉石巨晶有Al-普通辉石和次透辉石两类;而中生代单斜辉石巨晶只有Al-普通辉石。新生代单斜辉石SiO_2含量高、REE配分型式为上凸型、LILE和放射性元素含量高,并具有比寄主碱性玄武岩更亏损的Sr和Nd同位素组成;而中生代单斜辉石SiO_2含量低、REE配分型式为LREE富集型、LILE和部分HFSE以及放射性元素含量低,并具有比寄主碱性玄武岩稍富集的Sr和Nd同位素组成;巨晶的结构、矿物成分和地球化学特征,以及Mg-Fe在熔体与单斜辉石间的分配状况皆说明,新生代碱性玄武岩中单斜辉石巨晶是碱性玄武岩浆在高压下结晶的,因此二者是同源的;而中生代单斜辉石巨晶是被寄主岩浆偶然捕获的捕虏晶,是不同源的。华北新生代单斜辉石巨晶存在于碱性玄武岩和拉斑玄武岩中,它们具有比寄主碱性玄武岩更亏损的Sr和Nd同位素组成,说明即使是碱性玄武岩也不能完全代表软流圈来源的原始岩浆,其在上升过程中或多或少存在同位素组成富集的物质的混入。同时,拉斑玄武岩不是碱性玄武质岩浆直接结晶分异的产物,亦不是完全由部分熔融程度的不同造成的。拉斑玄武岩中存在岩石圈地幔物质的贡献或是岩浆房内碱性玄武质岩浆受地壳混染作用的结果。     

山东昌乐新生代碱性玄武岩中的巨晶单斜辉石成因研究

山东昌乐新生代碱性玄武岩中除斑晶单斜辉石和基质单斜辉石外,还发育大量巨晶单斜辉石和同源斜方辉石捕掳晶。巨晶单斜辉石与玄武岩间发育复杂和简单两种类型的反应边。复杂反应边往往发育在颗粒较大的巨晶单斜辉石外围。复杂反应边可分为4个带：内部带、过渡带、外部带和边缘带,其中,内部带、过渡带和外部带均由具不同结构特征的单斜辉石＋熔体＋金属氧化物构成,边缘带为不含熔体和金属氧化物的干净的单斜辉石;内部带的单斜辉石具梳状构造,过渡带的单斜辉石具细密筛孔构造,外部带为具似砂钟构造的筛孔状单斜辉石。反应边中单斜辉石、熔体及金属氧化物的成分显示,只有内部带受到单斜辉石巨晶的影响,其余带均受玄武岩浆的制约。简单反应边往往发育在颗粒较小的巨晶单斜辉石外围。简单反应边仅发育不含熔体和金属氧化物的干净的单斜辉石。巨晶单斜辉石的反应边是巨晶与玄武岩浆间温度差造成的。在与玄武岩浆反应的过程中,大颗粒的单斜辉石巨晶需要较长的时间与玄武岩浆达到温度平衡,从而有足够的时间发育包含4个带的复杂反应边;反之,由于缺乏足够的反应时间,小颗粒单斜辉石巨晶的外围只发育不含熔体和金属氧化物的简单反应边。同源斜方辉石捕掳晶的成分与地幔二辉橄榄岩包体中的斜方辉石类似,其边部发育类似于Bowen反应（1956）形成的单斜辉石环边。在单斜辉石Al^IV-Al^VI图解上,巨晶单斜辉石、二辉橄榄岩包体中的单斜辉石以及部分单斜辉石斑晶的核部,均位于较高压力的“麻粒岩和玄武岩中包体”区域,反应边中单斜辉石、基质单斜辉石以及绝大部分斑晶单斜辉石位于“火成岩”区域,说明部分斑晶单斜辉石核部来源于地幔二辉橄榄岩,属于捕掳晶。结合单斜辉石结晶压力的估算,笔者认为巨晶单斜辉石的成因模式为：来自软流圈的碱质基性熔体上侵到地幔岩石圈下部,结晶形成单斜辉石巨晶,后来该熔体携带巨晶单斜辉石与来自上地幔岩石圈、夹带大量二辉橄榄岩包体以及斜方辉石（和单斜辉石）捕掳晶的玄武岩浆混合,巨晶单斜辉石随混合后的碱性玄武岩浆上升、喷出地表。     

中国东部几个地区新生代玄武岩中单斜辉石—熔体平衡温压—兼论幔源包体的成因

以中国东部宽甸、汉诺坝和明溪含有幔源包体的新生代玄武岩中的单斜辉石斑（巨）晶为研究对象,采用最新的单斜辉石－熔体平衡温压计对单斜辉石斑（巨）晶－熔体进行了平衡温压计算。结果表明,碱性玄武岩中的单斜辉石斑晶结晶温度和压力高于共生的亚碱性玄武岩中的单斜辉石斑晶,单斜辉石巨晶的结晶温度和压力高于单斜辉石斑晶。这说明碱性玄武岩的形成深度大于亚碱性玄武岩,单斜辉石巨晶是更高压力下的结晶产物,单斜辉石斑晶在岩浆上升的不同深度均有晶出。回归分析表明,尽管携带幔源包体的玄武岩浆上升速度较快,但并不是绝热上升。单斜辉石斑（巨）晶的结晶温压条件与同一地点幔源包体平衡温压条件的对比表明,单斜辉石巨晶和碱性玄武岩中的部分单斜辉石斑（巨）晶的结晶温压大于幔源包体的平衡温压,表明了包体寄主岩浆的来源深度大于包体的深度。因此,幔源包体是寄主岩浆上升途中捕虏的上地幔碎块,而非寄主岩浆形成源区的残留体。     

巨晶普通辉石的M1位分裂

巨晶普通辉石的Ｍ１位分裂李一良，支霞臣，李玉芝，李铁，张裕恒（中国科学技术大学，合肥２３００２６）关键词巨晶辉石，Ｍ１位分裂，面积约束法，近邻边效应，Ｔ位铁单斜辉石的穆斯堡尔谱学研究历时已久。但由于其晶体结构和成份的复杂性、化学不均一性及出溶现象等［...     

滇东南马关巨晶单斜辉石原位Sr同位素特征及其含水性

对滇东南马关火山爆砾岩筒以及玄武岩中的单斜辉石巨晶进行了主量元素、微量元素、原位Sr同位素以及含水性研究,结果显示,单斜辉石巨晶均为铝质普通辉石,Mg#与Al、Fe、Ti呈负相关,与Ca呈正相关;稀土元素总量不高,HREE及LREE亏损,而MREE相对富集,大离子亲石元素均出现明显亏损,高场强元素Nb、Zr出现亏损而Hf略富集,Nb、Ta与Zr、Hf分馏明显,Rb、Ba的变化范围较大。原位Sr同位素87Sr/86Sr值为0. 703 92～0. 705 06,巨晶单斜辉石来源于上地幔,形成于同一母岩浆,与寄主玄武岩同源,为源岩浆在高压下的结晶产物。运用显微红外-傅里叶变换红外光谱仪(Micro-FTIR)分析测试了单斜辉石巨晶的水含量,结果显示OH吸收峰位于3 700～2 800cm-1,含水量赋值范围为318×10-6～693×10-6,水含量稍富于女山及汉诺坝地区的单斜辉石巨晶,也高于马关地区幔源橄榄岩包体中的单斜辉石结构水含量,暗示该区上地幔岩石圈具高含水性,这同时证实了俯冲洋壳在研究区的活动。新近纪到达地幔过渡带的西太平洋洋壳俯冲发生转向东撤,此时新特提斯洋洋壳正在NE向俯冲,是马关地区深部地幔富水的主因,到达软流圈(或地幔过渡带)的新特提斯洋俯冲洋壳导致该区地幔熔融,岩浆随之而生。     

南海新生代玄武岩中单斜辉石地球化学特征 及其地质意义

南海新生代玄武岩中发育有大量的单斜辉石斑晶,与橄榄石、角闪石等斑晶共存,多数被熔蚀,呈浑圆状,部分发育有很窄的反应边。研究表明单斜辉石具有巨晶的特征,是在高压下在与寄主岩同源的岩浆中形成,没有经历长时间的沉淀生长而直接向上运移被带到地表,因而具有巨晶的主量及微量元素的特征却不具有巨晶的形态。单斜辉石稀土元素含量不高,HREE及LREE亏损,而MREE富集;大离子亲石元素Rb、Ba、Sr均出现明显的亏损,高场强元素Nb、Zr出现亏损而Hf略富集。Nb、Ta与Zr、Hf分馏明显。Th较为富集,而Pb强烈亏损,U的变化范围较大。研究发现南海新生代玄武岩中的单斜辉石的来源较为简单,为地幔柱的直接产物,并没有受到洋中脊—地幔柱相互作用的影响,由于岩浆上升速度较快压力迅速下降,橄榄石大量晶出,引起了岩浆成分的变化,致使单斜辉石与寄主岩成分和结构上没有达到平衡。     

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