中国夕卡岩矿床中的角闪石

文章综合分析研究了中国21个夕卡岩矿床中的130个角闪石的成分分析数据。根据夕卡岩类型及其伴生金属矿化的不同，把角闪石分为4大类：钙夕卡岩中的角闪石多属钙角闪石，包括绿钙闪石、铁角闪石、镁绿钙闪石、铁浅闪石、阳起石、铁阳起石、铁镁钙闪石和铁韭闪石等；镁夕卡岩中的角闪石以透闪石为主，局部有浅闪石或韭闪石；锰质夕卡岩中的角闪石有锰质阳起石、锰质透闪石、锰直闪石和锰镁闪石；碱质夕卡岩中的角闪石属钠-钙角闪石或钠角闪石类，包括钠透闪石、镁亚铁钠闪石、亚铁钠闪石、镁铝钠闪石和镁钠闪石。碳酸盐围岩和有关侵入岩的成分对角闪石的类型、成分及其伴生金属矿化起重要的作用。     

新疆西天山高压变质带的变质矿物与变质作用演化

新疆西天山高压变质带主要由石榴石，角闪石，绿辉石，多硅白云母，钠云母，绿帘石，绿泥石，钠长石，石英，榍石和金红石等组成，石榴石主要含铁铝榴石组份，角闪石有蓝闪石，亚铁蓝闪石，青铝闪石，冻蓝闪石等类型，变质矿物组合显示高压变质带经历了由硬柱石蓝片岩相，榴辉岩相，绿帘蓝片岩相至绿片岩相的变质作用演化进程。     

藏北羌塘中部绒玛地区蓝片岩岩石学、矿物学和40Ar/39Ar年代学

藏北羌塘中部沿龙木错-双湖-线出露一条低温高压变质带,目前已有多处蓝片岩的报道.然而,除冈玛错地区产有典型的蓝闪石外,多数地区并没有典型蓝闪石的报道.绒玛蓝片岩位于羌塘中部高压变质带的中段,是该带中规模最大、保存最好的蓝片岩,对蓝片岩进行了详细的岩石学和矿物学研究,钠质角闪石主要为蓝闪石、青铝闪石、钠闪石和镁钠闪石.对蓝片岩中蓝闪石和多硅白云母进行了40Ar/39Ar定年,获得了227.3±3.8Ma和215±1.5Ma的坪年龄,分别代表蓝片岩快速俯冲消减和俯冲作用结束开始折返抬升的时代.绒玛蓝片岩岩石学、矿物学和40Ar/39Ar年代学研究为羌塘中部高压变质带的研究提供了新的资料.     

西藏羌塘中部才多茶卡蓝闪石40Ar/39Ar年代学及地质意义

本文报道了藏北羌塘中部才多茶卡地区晚三叠世蓝闪石片岩及蓝闪石矿物的新发现及地质意义。通过对才多茶卡构造混杂岩地质剖面的实测,在剖面第6层灰绿色变基性火山岩(绿片岩)中新发现以产蓝闪石类矿物为特征的中—高压变质岩系——蓝闪石片岩。对蓝闪石片岩的岩石学和矿物学特征进行了详细室内研究。从蓝闪石片岩中挑选出蓝闪石单矿物进行了40Ar/39Ar同位素年龄测定,结果表明,蓝闪石单矿物的坪年龄值为209±4Ma,等时线年龄值为216±4Ma,坪年龄与等时线年龄基本一致,属于晚三叠世诺利期,这与区域上羌塘中部发育的红脊山—双湖蓝闪石片岩的中—高压变质事件相吻合。由于蓝闪石类矿物的产出具有特殊的构造机制和地质意义,因此双湖以东的才多茶卡地区蓝闪石片岩的新发现及蓝闪石矿物的40Ar/39Ar同位素年代学研究进一步补充和丰富了青藏高原腹地羌塘中部龙木错-双湖构造混杂岩带的物质组成和同位素年代学信息,同时也为解决羌塘地区"龙木错-双湖构造混杂岩带是否向东延伸"等重大基础性地质问题,提供了新的重要资料。研究资料表明,羌塘中部自西向东从冈玛错、红脊山、绒马,经嘎尔错到才多茶卡地区,沿构造线方向断续分布的长达600km的含蓝闪石片岩的中—高压变质岩系,都是龙木错-双湖构造混杂岩带印支期构造活动事件的产物。     

北祁连含蓝闪石岩的特征及成因

本文论述了北祁连含蓝闪石岩的岩石类型、原岩类型、特征矿物组合及产态.区内含蓝闪石岩的原岩包括优地槽内发育的各类富钠火山岩、含富钠火山质的沉积岩。在含蓝闪石岩分布区,岩石的变质相有葡萄石-绿纤石相、蓝闪石—绿片岩相、绿帘石-角闪岩相、铁铝榴石—角闪岩相等,未发现高压低温矿物组合.岩石应属区域动力变质作用产物,并对其形成环境进行了探讨.     

西藏新达多地区榴辉岩的变质过程研究及其对古特提斯俯冲带演化的限定意义

位于拉萨地块中部松多榴辉岩带西端的新达多地区出露两种类型榴辉岩:含蓝闪石榴辉岩和双矿物榴辉岩。含蓝闪石榴辉岩主要矿物组合为石榴石、绿辉石、蓝闪石、多硅白云母及少量的绿帘石、角闪石、石英、金红石。石榴石不具有成分环带结构,蓝闪石存在于基质中,边部大多退变为冻蓝闪石并普遍发育有角闪石和石英的后成合晶。双矿物榴辉岩的主要矿物组合为石榴石、绿辉石、石英及少量的绿帘石、角闪石、金红石、钛铁矿、榍石。石榴石具有典型的进变质环带特征,从核部到边部镁铝榴石和钙铝榴石组分先升高后降低,铁铝榴石组分变化与之耦合,石榴石边部发育角闪石和钠长石的冠状体,推断石榴石记录了进变质的生长过程后又受到了退变质改造。结合传统温压计和变质相平衡模拟两种温压计算方法对榴辉岩的峰期变质条件进行限定,得到含蓝闪石榴辉岩的峰期温压条件为:615±5℃,33±0.5kbar;双矿物榴辉岩的峰期变质温度为630±10℃,压力不超过27kbar。变质相平衡模拟计算结果显示:(1)含蓝闪石榴辉岩经历了退变初期近等温减压过程,这一过程以硬柱石和少量滑石的脱水反应生成蓝闪石和绿帘石为主要特征;中晚期退变质阶段以大范围硬柱石消失后局部富余流体的消耗在蓝闪石边部形成冻蓝闪石以及蓝闪石边部发育后成合晶为特征,部分石榴石边部的韭闪石冠状体大致也发生在这一过程;(2)双矿物榴辉岩则记录了从进变质生长阶段到峰期变质阶段,最后再到退变质演化阶段的完整变质过程。结合前人对松多榴辉岩的工作,对新达多地区新近发现的两类榴辉岩的岩石学研究表明:拉萨地块内部的榴辉岩为典型的大洋俯冲带产物,代表了古特提斯洋盆的存在。俯冲折返过程中复杂的构造机制使得不同类型榴辉岩在同一地区出露共生。     

中国蓝闪石片岩带的一般特征及其分布

蓝闪石片岩相可依据其温度划分为蓝闪石-硬柱石和蓝闪石-绿片岩相区,并与一些变质相组成不同相系。中国蓝闪石片岩带根据其平均温度-压力梯度和构造地质环境可分为:(1)元古代克拉通内蓝闪石片岩带;(2)加里东期克拉通内裂谷型蓝闪石片岩带;(3)古生代中国陆台北缘蓝闪石片岩带;(4)中新生代与俯冲作用有关的蓝闪石片岩带。蓝闪石变质作用的形成和演化与构造地质环境有关。中国蓝闪石片岩带大部分形成于硅铝壳环境,从陆壳开始裂开,直至出现洋壳。这一演化与地壳内热流变化格局有关,形成机理不属于均变论的观点。     

滇西双江县勐库地区退变质榴辉岩中闪石类矿物的成因研究

勐库地区新近发现的退变质榴辉岩中晚期退变质作用形成的闪石类矿物十分丰富,其携带了大量晚期退变质过程中的岩石成因信息。本文通过系统的矿物学研究,鉴定出了3期10种闪石类矿物,其中以镁钙闪石、镁角闪石、铁镁钙闪石、铁韭闪石、透闪石、阳起石等钙质闪石类为主,有少量冻蓝闪石、蓝透闪石等钠-钙闪石类。研究发现,随着退变质过程中时间的推移,角闪石的形成环境逐渐由还原环境向弱氧化环境、氧化环境演变。根据角闪石电子探针成分测试结果计算了相应的温度、压力条件。结合岩相学的资料,将退变质过程分为3期:(1)第1期早阶段为近等温降压过程(p=0.56~0.75 GPa,t=642~709℃),主要形成铁韭闪石、铁镁钙闪石、镁钙闪石;晚阶段为等温降压过程(p=0.39~0.56 GPa,t=619~642℃),主要形成镁钙闪石及少量镁绿钙闪石、铁韭闪石;(2)第2期为降温降压过程(p=0.23~0.42 GPa,t=460~610℃),主要形成镁角闪石、冻蓝闪石及铁角闪石;(3)第3期为近等温降压过程(p=0.09~0.31 GPa,t=350~420℃),主要形成透闪石、阳起石、蓝透闪石等。闪石类的成分变化反映了退变质榴辉岩从地壳底部的角闪石榴辉岩-高压麻粒岩相温压环境向中上地壳角闪岩相、绿片岩相温压环境的渐次退变质作用过程。这与昌宁-孟连构造带上印支期的碰撞造山作用、燕山期的区域性地壳伸展、喜马拉雅期的陆内造山运动具有较好的对应关系。     

西藏羌塘中部冈玛错-双湖变质带变质变形作用关系研究

通过对冈玛错-双湖变质带中蓝闪石矿物种属的划分及矿物特征的研究,以及对石榴石和钠长石变斑晶中包裹体痕迹的确定、铁蓝闪石和青铝闪石具明显环带的发现、一系列褶劈理和皱劈理变形及退变质作用特征的描述,并通过对蓝闪石40Ar/39Ar快中子活化分析,获得蓝闪石的年龄谱图.确认了该变质带经历了3期变质变形事件.指出各期变质变形特征的综合分析能指示冈玛错-双湖变质带形成及隆升的演化过程.     

木里县梭罗沟地区蓝闪石片岩的首次发现及地质意义

四川省木里县梭罗沟地区出露的蛇绿混杂岩中首次发现了经高压变质形成的蓝闪石片岩.其原岩分为球粒玄武岩和强蚀变玄武岩两种,具有蓝闪石+绿帘石+绿泥石+次闪石的矿物组合特征.这套蓝片岩形成于晚二叠世-晚三叠世时期,在甘孜-理塘洋盆闭合时存在由东向西的高压俯冲作用.     

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