辽东古元古代富镁质碳酸盐岩建造菱镁矿滑石矿床成矿流体研究

辽东地区古元古代大石桥组中分布有富镁质碳酸盐岩建造，并产有大型或超大型菱镁矿、滑石矿床。笔者等近期在该地区野外工作中发现了沉积型石膏岩，并对其和菱镁矿滑石围岩进行了相应的稳定同位素和流体包裹体研究。稳定同位素分析结果为δ^13C一般-1．8‰～ 1．2‰、δ^18Ol0‰～20‰，δ^14SVCDT23．9‰～26．5‰；结合菱镁矿和白云岩流体包裹体形态和成分特征，笔者等认为早期镁质非金属矿床的形成与古元古代的海相蒸发岩系有关，古海水演化而来的变质成矿流体对后期滑石矿床的形成起着重要的控制作用。     

与镁质碳酸盐岩建造有关的非金属矿床成矿系列

镁质碳酸盐岩建造因赋存有大型超大型滑石、菱镁矿、块状水镁石、硼镁石和蛇纹石矿床,因近年来的研究并引起矿床学界的日益重视.在此讨论了中国辽东、胶东、东秦岭和桂北等4个主要成矿区的镁质碳酸盐岩建造中产出的非金属矿床成矿系列特征.此成矿系列是在一定的大地构造条件下,由富含镁质碳酸盐岩的矿源层经构造-流体-成矿系统作用下的产物.     

辽东古元古代镁质非金属矿床成矿系统研究

辽东地区古元古代裂谷里尔峪组和大石桥组中分别分布有富镁质的碳酸盐岩建造, 其中产有硼矿、菱镁矿、滑石、岫岩玉等大型-特大型矿床.这些镁质非金属矿床的形成先与古元古代的蒸发岩系有关, 然后经历了吕梁期区域变质和热液交代变质改造, 以及印支、燕山期构造-岩浆作用改造等成矿系统作用过程.其中, 镁质碳酸盐岩建造、成矿构造、成矿流体对镁质非金属矿床的形成起着重要的控制作用.这些矿床也是古元古代矿源场、流体场、热场(能量场)、应力场等在一定的时空条件下耦合和后期构造-岩浆作用叠加改造的综合产物.      

辽东裂谷菱镁矿的成矿环境、分布规律及矿床成因

辽东裂谷为古元古代拉伸环境下产生的EW向陆内裂谷,裂谷的北缘斜坡带赋存有大石桥—塔子岭超大型菱镁矿带,中央裂陷带赋存了瓦峪—青城子大型菱镁矿带。菱镁矿床的产出与成矿物质来源的位置有较大的关系,同时与沉积的环境因素、后期的各种扰动因素有关。在古元古代富含CO₂的环境中,源于太古宙地块剥蚀物中和远源火山喷发物中的镁质进入海水,在持续稳定的陆缘潮间-潟湖蒸发环境中,在藻类生物吸附吸附作用的有力辅助下,沉积了巨厚的富镁碳酸盐岩,经过成岩作用形成原生菱镁矿层。在区域变质-变形过程中,原生菱镁矿层经过褶皱变形和矿物重结晶,完成形态方面的最终定型;因此,辽东裂谷菱镁矿属于沉积-变质型矿床。     

中国镁质碳酸盐岩型温石棉矿床的成矿规律

镁质碳酸盐岩型温石棉矿床是成矿热液交代镁质碳酸盐岩生成的,一般均产于地台环境。按地台稳定性不同,成矿环境分为地台隆起区的基底建造类型和地台拗陷区的盖层建造类型。产于地台隆起区的矿床,以前震旦纪镁质碳酸盐岩为控矿层位。产于太古代及早、中元古代深变质结晶基底中的矿床,由区域变质及混合岩化过程中的变质热液交代碳酸盐岩成矿。产于晚元古代浅变质褶皱基底(扬子准地台)中的矿床,以岩浆期后热液或接触交代(湿矽卡岩)热液为成矿热液来源。产于地台拗陷区的矿床,均以震旦纪镁质碳酸盐岩为控矿层位。其成矿时期较晚,一般与拗陷区内岩浆活动同期,由岩浆期后热液或接触交代(湿矽卡岩)热液对镁质碳酸盐岩进行交代成矿。     

海城滑石矿田成矿地球化学及机理

海域滑石矿矿石质量高，可满足各种工业用途的要求。微量元素含量、包裹体测量、同位素等资料表明矿田成矿物质镁、硅主要来自近矿围岩，成矿热液来自区域变质作用。据稀土元素分馏特征，滑石的成矿时代大约为早元古代末。在区域热动力变质作用过程中，受强应力作用，含有大量二氧化硅的高盐度热液使围岩中的菱镁矿被交代而生成滑石，而白云石很少参与滑石的形成。     

青海省茫崖地区滑石矿地质特征及成因初探

青海省茫崖地区目前有两处滑石矿床，为野马滩滑石矿及茫崖石棉伴生滑石矿，两处滑石矿床的赋存地层及成矿类型不同。野马滩滑石矿赋存于古元古代金水口岩群片麻岩组的大理岩段中，主要含矿岩性为白云石大理岩，由于构造多期叠加、热液活动强烈，滑石矿床具有层控后期热液变质的特征，属区域变质叠加热液交代型；茫崖石棉矿床中的滑石矿体集中产于岩体中下部的蛇纹岩中，受超基性岩体及控岩构造的控制，成因为超基性岩热液蚀变型。通过对成矿地质背景、含矿岩性及矿体特征和矿石质量进行对比，了解区内滑石成矿类型，为寻找高品质滑石矿提供一定的参考。     

辽东-吉南Fe- 菱镁矿 Cu-Au成矿带主要地质成矿特征及潜力分析

辽东-吉南成矿带是2008年确定的首批16个重要成矿带之一,随着新的找矿进展和预测成果不断涌现,需要对其开展新一轮研究总结。本文以新的研究成果和找矿突破为基础,通过综合分析,将其命名为"辽东-吉南Fe-菱镁矿-Cu-Au成矿带"并对其开展成矿作用类型及勘查部署综合研究。该区带范围与III级成矿带辽东(隆起)Fe-Cu-Pb-Zn-Au-U-硼-菱镁矿-滑石-石墨-金刚石成矿带一致,结合区域成矿地质背景、成矿作用类型及典型矿床的综合研究,初步建立了辽东-吉南Fe-菱镁矿-Cu-Au成矿带成矿谱系,并将其主要成矿期归纳为三期:新太古代、古元古代和中生代燕山期;在典型矿床成矿地质特征及潜力评价综合分析的基础上,总结了研究区主要成矿类型为沉积变质型铁-菱镁矿、火山沉积-变质改造型铜锌矿、沉积变质-叠加改造型铅锌矿、岩浆型铜镍硫化物矿、岩浆热液型金矿以及造山带型金矿。结合区域找矿进展和潜力评价最新成果,认为本区Fe、菱镁矿、Cu、Au潜力巨大,为下一步勘查部署的主攻矿种,同时在本区划分了12个远景区,其中10个为重点远景区,2个为远景调查区,对研究区下一步矿产勘查部署工作有一定指导意义。     

辽东南地区菱镁矿矿床成因研究

辽东南地区是我国主要盛产菱镁矿产品基地之一,菱镁矿主要分布在辽宁省海城至大石桥一带。通过地质背景分析,研究菱镁矿的矿区、矿体地质特征和矿石质量特征,认为辽东南地区菱镁矿应属浅海相化学沉积碳酸盐岩建造,菱镁矿层的形成受特定古沉积环境控制,经区域变质重结晶作用或热力变质作用再次重结晶形成菱镁矿层。菱镁矿的形成是原生沉积与变质和变形作用的综合产物,矿床成因类型应属于沉积变质矿床。     

印度南部元古代Cudappah盆地白云岩中的菱镁矿成矿作用及其构造-气候指示意义

Cudappah盆地是位于印度南部的一个元古代盆地,盆地中含有许多矿床,包括菱镁矿和滑石矿。该盆地发育于Chat活动带东部边缘,并发育沙质、粘土质和碳酸盐岩的多期重复沉积旋回。盆地可划分为四个次级盆地,即Papaghni、Nallamalai、Srisailam和Kurnool次级盆地。晶质菱镁矿床赋存于Papashni次级盆地的Vempalli组地层中。每个次级盆地很可能都沿着一系列裂谷中的断块发育,并且这些裂谷形成于中元古代的热事件。每个沉积旋回中发育有相似的沉积岩套表明,在盆地演化过程中具有相同的构造和气候环境。根据盆地中矿床(重晶石矿、菱镁矿和滑石矿)的产出,我们对每个次级盆地均提出了一个多期重复沉积旋回的演化模式,该旋回包括了从角砾岩到白云岩的变化。     

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