甘肃省龙首山地区芨岭铀矿区蚀变特征分析

文章重点对龙首山芨岭铀矿区近矿围岩蚀变特征、分带特征以及蚀变期次进行研究,蚀变大致可分为高温钾钠混合交代阶段、区域性钾交代阶段、中低温热液钠钙交代阶段、矿化期钠交代阶段,其中与成矿关系密切的是矿化期钠交代阶段。通过对新水井铀矿床各中段的系统取样分析表明:与正常花岗岩相比钠交代蚀变岩的Cu、Pb、Ni、Sn、V、Zr、As等微量元素含量显著增加,而W、Rb的含量明显减少;钠交代蚀变岩随着埋深增大其Na2O、SiO2、Al2O3含量减小。Fe2O3、FeO、CaO含量增加;钠交代蚀变岩具有的碱性(A型)花岗岩型稀土分配型式、富集型(La/Sm)N特点、明显的Eu亏损和重稀土显著增加等特征。     

龙首山钠交代岩型铀矿地球化学特征及其控矿因素

龙首山钠交代岩型铀矿化十分发育。钠交代岩几乎全由新生的钠长石及少量新生绿泥石、方解石和粉末状赤铁矿组成。钠交代岩及其中的铀矿化与花岗岩有密切的空间关系.从稳定同位素资料说明,铀主要来自花岗岩,成矿热液以再平衡混合岩浆水为主。钠交代岩及其铀矿化的空间定位受NW向大断裂及其次级近EW向断裂的控制,其多期活动有利于铀矿化形成。大型特大型钠交代岩体保存较完整是形成铀矿床的必要条件之一。铀矿体有明显的扩散晕,在物化探方法配合下,寻找盲矿。     

甘肃龙首山芨岭铀矿区A型似斑状花岗岩地质特征及其地质意义

似斑状花岗岩是芨岭岩体重要的侵入单元,研究其特征可为钠交代型铀矿化的成因机制研究提供依据。本文通过对芨岭铀矿区外围似斑状花岗岩的岩石学、同位素年代学、地球化学研究,认为其具有低硅、富铝、贫铁和镁、低钙和较高TFe O/Mg O值的岩石化学特征,其轻稀土分馏强烈、重稀土分馏较弱,具铕中等负异常,相对富集Rb、Th、U、La、Ce、Hf、Sm、Gd,而相对亏损Ba、Nb、Ta、Sr、Ti等元素,且(Zr+Nb+Ce+Y)含量和Ga/Al值明显高于Ⅰ型和S型花岗岩均值。上述地球化学特征表明它是铝质A型花岗岩,说明早古生代(458.3±2.3Ma)祁连山-龙首山造山作用已进入晚期的后碰撞伸展环境。芨岭铝质A型似斑状花岗岩既是钠交代型铀矿的主要铀源,又为矿体定位提供充足的容矿空间。     

辽东硼矿区层状混合岩的地质地球化学 特征及其成因探讨

辽东硼矿区层状混合岩为含硼岩系的一个重要组成部分,与各种变粒岩和浅粒岩呈整合接触而呈层状展布,在岩性上有过度现象。岩石中交代结构发育;与变质围岩相比,混合岩的SiO2、K2O、Na2O等组分均明显增加,而Fe2O3+FeO、CaO、MgO、MnO等组分明显减少,K2O/Na2O变化较复杂,岩石化学成分的变化与交代作用有关;微量元素具有与围岩相似的特征,稀土元素含量高于围岩,稀土元素配分模式与变粒岩一致,具有典型的重熔特征。这些特征表明层状混合岩是变质围岩经选择重熔交代而形成的。     

甘肃省龙首山成矿带青山堡岩体闪长岩特征及与铀成矿关系北大核心CSCD

青山堡花岗岩体位于龙首山成矿带东段,为探讨该岩体细粒闪长岩与铀成矿的关系,对其进行了岩石地球化学、同位素年代学等研究。分析结果表明,随着U含量的增加,SiO_(2)、Al_(2)O_(3)、Fe_(2)O_(3)、Na_(2)O、K_(2)O、MgO的含量增加,FeO、CaO的含量减少,这与成矿期发育的碱交代蚀变关系有关;同时岩石具Rb、Ta、U、Hf等元素相对富集,Nb、Zr、Ti等元素相对亏损及轻稀土右倾分馏明显的地球化学特征。区内沿断裂分布的细粒闪长岩是铀成矿的有利赋矿岩石之一,而其与花岗(闪长)岩的接触面为铀矿富集提供了物理化学环境突变的成矿结构面;含矿蚀变闪长岩矿石中发现有网脉状、细脉状的沥青铀矿脉。结合区域资料表明,志留纪龙首山地区广泛发育的碱交代铀成矿作用在青山堡岩体中亦有发育。后期龙首山东段抬升剥蚀速度较中段要强烈,潜水氧化作用发育,前期区域性碱交代热液成矿作用所形成的含矿构造蚀变带是后生潜水氧化改造叠加形成浅部淋积型工业富铀矿体的关键。     

赣南银坑山铀矿点地球化学特征及其找矿意义

银坑山铀矿点位于赣南九龙嶂火山盆地南东边缘,矿体呈脉状,水云母化、赤铁矿化明显.与围岩相比,矿石的Al2O3、SiO2含量降低,Fe2O3(FeO)、MnO、CaO、S、Cl呈富集趋势,Mo、Ag、Th为主要伴生组分.从矿化蚀变组合特征看,银坑山矿点属岩浆热液型,且位于岩浆热液成矿系统的上部,深部具成矿前景.     

粤北诸广矿区碱交代岩岩石化学和矿物化学特征及其与铀成矿关系

诸广矿区与铀矿化关系密切的碱交代作用广泛发育,碱交代岩与围岩(正常花岗岩)对比,Na2O、K2O明显增高,Al2O3、Fe2O3也增高;SiO2明显降低,FeO、MgO、CaO也降低,表明K2O和Na2O被带入。矿物化学成分分析得出诸广碱交代岩的长石主要为钠长石与钾长石;绿泥石主要属铁镁绿泥石和蠕绿泥石;黄铁矿有的含铀量较高,据Fe/S值属硫亏损型,据S/Se值属岩浆热液矿床范畴;云母属白云母及少量铁白云母;铀矿物和含铀矿物的UO2含量以沥青铀矿较高,钍石较低,铀矿石的蚀变矿物和造岩矿物有的也含微量铀。碱交代作用既释放矿质又为矿质沉淀创造空间,碱交代岩既提供铀源又是一种有利的成矿围岩。     

甘肃省龙首山成矿带中段钠长岩脉地质特征及其与铀矿化关系研究

钠长岩脉是甘肃省龙首山成矿带中段常见的晚期脉体,与钠交代型铀矿化的关系十分密切。文章在野外调研、钻孔查证、放射性物探测量的基础上,深入研究钠长岩脉的岩石学、地球化学、同位素年代学和稳定同位素特征研究,并探讨其与钠交代型铀矿化之间的关系。钠长岩脉侵位于加里东中期,其LA-ICP-MS锆石U-Pb年龄为442.9±5.7Ma;具有中硅(61.48%~67.14%)、富铝(14.98%~17.59%)、高钠(9.76~%~10.59%)、贫钾(0.08%~0.30%)、低钛(0.11%~0.44%)、低磷(0.02%~0.16%)的特征;N-MORB标准化微量元素蛛网图显示钠长岩脉相对富集大离子亲石元素(LILE)Rb和Ba,不相容元素Th和U显著富集,高场强元素(HFSE)Nb和Ta相对亏损、Sr和Ti显著亏损;球粒陨石标准化稀土元素配分曲线图呈碱性花岗岩类的"海鸥"型。综合研究表明,钠长质岩浆是钠质含铀热液的孪生有效载体,钠长岩脉本身即是钠交代型铀矿有利的赋矿岩石,二者具有同源、等时、共体的特征,作为龙首山成矿带中段钠交代型铀矿的找矿标志,进而指导深部找矿和矿床外围盲矿体预测。     

甘肃省龙首山芨岭铀矿床成矿热液流体特征研究

芨岭铀矿是中国北方最典型的钠交代型铀矿床之一,文章通过对芨岭矿床ZKJ9-4钻孔深部所见含矿蚀变闪长岩、近矿蚀变闪长岩、远矿蚀变闪长岩、闪长岩原岩地球化学特征和组分迁移计算及矿体中心部位的淡粉红色方解石脉流体包裹体特征、均一温度、盐度和激光拉曼光谱研究,认为芨岭钠交代型铀矿床的成矿流体含有大量碳酸铀酰络合物[UO_2(CO_3)_2]~(2–)和[UO_2(CO_3)_2]~(4–)的同时还含有丰富的SiO_2、Na~+、Ca~(2+)、Mg~(2+)、Fe~(2+)、Mn~(2+)、∑REE、U、Th、Ga、Sr、Zr、Ba、Rb、Nb、Mo、Cd、Sn、Hf、Ti、Ta、CO_2、H_2S和CH_4等组分,成矿流体具有较强的还原性,并对MnO、K_2O、Cr和Co具有较强的交代溶蚀作用。成矿流体是起源于岩浆演化晚期的再平衡岩浆水,热液温度为(300±20)℃,盐度为2.99 wt%~4.57 wt%NaCl,密度为0.75~0.77 g/cm~3。流体沸腾是芨岭钠交代型铀矿成矿物质的早期卸载机制,晚期成矿流体中加入了大量的大气降水,流体混合作用进一步促进了成矿物质的卸载。     

甘肃省龙首山成矿带芨岭岩体闪长岩特征及其与铀成矿关系

芨岭岩体是龙首山铀成矿带加里东期岩浆岩,其闪长岩侵位于加里东早期,是芨岭岩体主要岩石类型之一。闪长岩主要有两期侵入,分别为早期灰色、深灰色中粒闪长岩以及晚期深灰色细粒闪长岩,且出露面积较小,集中分布于新水井、芨岭地区。采用LA ICP MS方法对研究区内中粒闪长岩进行锆石U Pb测年,得到年龄值为(4856±14) Ma。研究表明,闪长岩对后期铀成矿起重要作用：破碎蚀变闪长岩作为一种优质赋矿岩石,为含矿热液提供了卸载空间,蚀变后矿物成分主要为钠长石、绿泥石、方解石、赤铁矿等蚀变矿物,同时随着U含量的增加蚀变闪长岩中SiO2含量略有增加,Na2O明显增加,K2O、FeO 和P2O5有下降的趋势,CO2含量先增后减。综合研究分析认为,闪长岩本身是钠交代型铀矿的有利赋矿岩石,而其与花岗岩的接触面为花岗岩内接触带铀矿富集提供了物理化学环境突变的成矿结构面     

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