华北克拉通鲁西地区早前寒武纪表壳岩系重新划分和BIF形成时代

鲁西花岗-绿岩带是华北克拉通早前寒武纪变质基底典型代表.表壳岩系包括泰山岩群、孟家屯岩组和济宁岩群.其中,泰山岩群是鲁西地区规模最大的表壳岩系,曾认为形成于新太古代早期,而济宁岩群曾认为形成于古元古代.根据野外地质和表壳岩系及相关岩石的锆石SHRIMP U-Pb定年,本文对表壳岩系形成时代进行了重新划分.1)新太古代早期(2.70～2.75Ga)表壳岩系,包括原泰山岩群的雁翎关岩组和柳行岩组下段的大部分及孟家屯岩组.2)新太古代晚期(2.525～2.56Ga)表壳岩系,包括原泰山岩群的山草峪岩组、柳行岩组上段和下段的一部分及济宁岩群.它们在岩石组合、变质变形等方面存在明显区别,BIF形成于新太古代晚期.这是华北克拉通迄今唯一分辨出新太古代早期和晚期表壳岩系的地区.     

吉林省夹皮沟花岗岩—绿岩带成因模式探讨

通过对夹皮沟绿岩带层序、岩石成因以及叠加其上的变质变形作用特征的研究,认为绿岩带形成于硅铝壳的扩张环境;英云闪长岩—奥长花岗岩成分的花岗质片麻岩是在大陆或大陆边缘的挤压环境下,由变质镁铁质火山岩经部分熔融侵位的深成花岗质岩石。由此,提出夹皮沟花岗岩—绿岩带的裂谷成因模式。     

鲁西泰山岩群变质玄武岩地球化学特征及地质意义

绿岩带记录了早期地球岩浆活动和表生环境的丰富信息,是揭示地质演化历史和规律的重要研究对象。鲁西地区的泰山岩群具有典型的绿岩带组合,其中雁翎关和柳杭岩组的变质玄武岩是新太古代火山岩系的代表,广泛分布于鲁西中部地区,对还原鲁西新太古代的地质演化过程具有重要意义。在七星台地区雁翎关岩组变质玄武岩中存在变安山岩夹层,对其进行锆石SHRIMP U-Pb定年,11颗岩浆锆石的207Pb/206Pb加权平均年龄为2744±12Ma(MSWD=1.6),表明区域内雁翎关岩组的变质玄武岩系形成于~2.7Ga。地球化学研究显示七星台地区泰山岩群雁翎关岩组的变玄武岩主体属于亚碱性高铁拉斑玄武岩系,它们的Si O2含量为48.2%~51.6%,Mg O介于3.22%~7.66%之间,Ti O2含量为0.63%~1.78%,主量元素Si O2、Ti O2、Al2O3和Fe O与Mg O都没有明显的协变关系。球粒陨石标准化稀土配分模式有两类,多数以轻稀土弱富集为特征,稀土总量为47.5×10-6~143.8×10-6,少数样品的轻稀土弱亏损,配分模式与N-MORB接近。七星台地区雁翎关岩组变玄武岩的主、微量元素组成和演化趋势与区域内柳杭岩组中低Ti和高Ti变质玄武岩都有差别。在Nb/Th与Nb/La、(La/Sm)CN和Ti/Ti*的协变关系图解中,雁翎关岩组一部分样品与现代和一些新太古代岛弧玄武岩的成份类似,另一部分具有接近原始地幔的Nb/Th、(La/Sm)CN和Ti/Ti*比值。这些地球化学特征暗示泰山岩群的雁翎关岩组很可能与北美、西澳和印度等新太古代早期形成的绿岩带火山岩系类似,由科马提岩-拉斑玄武岩和拉斑玄武岩、钙碱性玄武岩及安山岩两类火山岩组合复合而成,鲁西在新太古代早期的演化历史比目前的认识更加复杂。     

鲁西地区太古宙绿岩带硫铁矿床地质特征及成矿机制

鲁西地区新太古代雁翎关组由科马提岩、角闪质岩石、变粒岩和含铁石英岩等组成 ,其原岩为一套超镁铁质镁铁质火山熔岩及火山碎屑沉积的表壳岩建造 ,经历了三期区域变质作用 ,变质程度达低角闪岩相 ,是华北地台上一个典型的绿岩带。鲁西花岗岩绿岩带中分布有大小黄铁矿脉数十条之多 ,呈层状、透镜状或脉状沿片麻理方向展布 ,硫品位 3 .79%～ 3 1.6% ,伴生有用组分Fe、Ni、Ag等。通过对绿岩、矿体和矿石特征、S、Fe分布及变质成矿作用等方面的研究 ,证实绿岩中含有丰富的S、Fe、Ni等造矿元素 ,认为绿岩既是赋矿岩石亦是矿源层 ,矿床属变质热液叠加的变质火山沉积型硫铁矿床。     

山东新泰地区绿岩带金的地球化学特征

本文概述了新泰地区绿岩带的基本特征,构造及其演化规律,提出花岗质岩石是由幔源物质上侵及绿岩带部分重熔形成的。文中用测得κ系数0.37,作为对比太古宙绿岩带中科马提岩的标准,并得出金在科马提岩中初始丰度值,其西带为5.99ppb,东带为2.37ppb,反映了太古宙期间本地区地幔含金的不均一性。运用算术、几何平均法,对绿岩带各岩石类型、地层单元、花岗质岩石及其岩脉的含金性统计结果表明有的岩石变异系数增大,有利于金的分散与集中。文中对金矿化带地质地球化学特征及其成晕机制进行了论述,确定了矿化带的地表与金呈明显正相关元素为Ag、As、Sb、Ph、Zn,负相关元素为Cu、Hg,矿化带的深部与金呈正相关的元素为Sb,而Ag、As、Hg、Cn、Pb、Zn则与金的相关系数趋于零。从而对区内绿岩带金矿成因进行探讨,提出了变质-岩浆-热液充填交代成矿模式,并初步提出找矿地段。     

华北地台绿岩带地质特征类型和演化

中国绿岩带主要分布在华北地台。绿岩带产在古陆核之间或边缘，可能形成在古裂谷或古岛弧的构造环境。按原岩建造、地球化学特征和成矿作用，绿岩带可分夹皮沟型、清原型和小秦岭型。按后期的活化改造作用强度，可分基本稳定型、活化改造型和强烈活化改造型绿岩带。根据变质程度的不同，可分高级变质和中级变质为主的绿岩带。华北地台绿岩带的形成可分四个时期：中太古代、新太古代早期、新太古代晚期和早元古代。华北地台绿岩带同其他国家绿岩带相比较，其岩石类型、不一的变质程度、相似的花岗质岩石、形成在早前寒武纪和赋存丰富矿产资源等基本地质特征相似。但也具有独自的特色：１．分布面积小；２．科马提岩不甚发育；３．同构造晚期的浅成花岗岩侵入体尚未发现；４．变质程度较高；５．赋存的矿产类别有差异；６．受后期的活化改造作用强烈。     

内蒙东红胜花岗岩-绿岩带中韧性变形带的初步研究

该花岗岩—绿岩带位于内蒙武川县境内,是华北陆台北缘花岗岩—绿岩带的一部分。花岗岩—绿岩带主要由花岗岩及花岗质片麻岩系组成,构成绿岩带主体的上壳岩系被花岗质岩石所侵入、分离,呈似层状、大透镜状漂浮于花岗质岩石“海洋”之中。通过实地测量、构造解     

鲁西台上铁矿床地质特征及矿床成因

台上铁矿床位于鲁西蒙阴县境内,为磁铁石英角闪岩型低品位铁矿床,成因上属沉积变质型铁矿床。矿体以条带状、透镜状为主;矿体规模较小,厚度、品位变化较大;主要矿石矿物为磁铁矿,其次为赤铁矿及褐铁矿,并可见少量黄铁矿;矿石主要呈细粒变晶结构,条带状及浸染状构造;矿石自然类型属需选贫铁矿矿石。矿体属泰山岩群雁翎关组的组成部分,与泰山岩群的形成与演化过程一致,在新太古代泰山岩群雁翎关组地层与岩浆岩接触带附近具较好的成矿远景。     

南美洲圭亚那地盾北部绿岩带地质特征、典型金矿床及金成矿作用

圭亚那地盾位于南美洲亚马孙克拉通的北部,其北部广泛发育太古宙典型的花岗岩-绿岩带,主要岩石组成为花岗岩、片麻岩和英云闪长岩,古元古代变质超基性-基性火山岩-侵入岩、其他变质火山岩等。由于独特的地质构造位置和复杂的构造演化历史,形成了良好的绿岩型金成矿地质背景,产生了大量的金矿床。通过总结圭亚那地盾北部绿岩带的岩石特征、成岩时代和构造演化历史,对委内瑞拉埃尔卡劳金矿、圭亚那欧迈金矿和苏里南罗瑟贝尔金矿进行典型矿床剖析,系统研究了该区绿岩带型金矿的成矿地质背景、成矿流体及成矿年代学特征,建立了区域绿岩带型金矿成矿模型,并在分析找矿要素的基础上,提出圭亚那地盾北部的金矿找矿方向。     

额尔古纳地块基底地质构造

额尔古纳地块是额尔古纳-马门-加格达奇拼合地块中的典型代表.研究表明,其基底由前中元古代绿岩及与之伴生的花岗质杂岩组成,它们具有地壳早期演化的地质构造特征.绿岩带为典型的变质基性-酸性火山岩及部分变质沉积岩系构成的火山-沉积建造,火山岩以拉斑玄武岩为主,向上过渡为钙碱性火山岩系列,表现为双峰态型特点.花岗岩类为TTG岩系及石英二长岩-花岗岩组合.花岗岩-绿岩地体内各岩石类型的岩石地球化学特征与国外太古宙及我国华北陆台花岗岩-绿岩带内同类岩石极为相似.双峰态型火山岩及绿岩建造组合,以及类似于TH2、FII型的变质基性火山岩和长英质火山岩特征,结合高铝型英云闪长岩-奥长花岗岩组合,指示了研究区绿岩带的形成环境类似于大陆边缘弧后裂谷型火山-沉积盆地.     

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