The upper Bajocian-Lower Bathonian of Pechora River basin and Boreal-Tethyan correlation

Distribution of ammonites in the Bajocian-Bathonian boundary beds of the Izhma River basin is considered. A new scheme of zonal subdivisions suggested for the Pechora basin includes the Arctocephalites arcticus Zone of the upper Bajocian and the Arctocephalites greenlandicus-Arcticoceras ishmae Zone of the lower Bathonian. The Dreshchanka Formation age (late Bajocian-early Bathonian) and the commencement time of the Boreal sea transgression (Late Bajocian) are specified. Correlation of the Bajocian-Bathonian boundary strata of the northern Caucasus, central and northern Russia with stratigraphic scales of Western Europe and East Greenland are discussed. New infrazonal subdivisions, i.e., the faunal horizons, are described. As is shown, the parkinsoni-zigzag zonal boundary accepted to be the Bajocian-Bathonian boundary in standard scale corresponds to boundaries separating the michalskii and besnosovi zones in the Lower Volga region and the arcticus and greenlandicus zones in the Boreal areas.     

Anomalous strontium and lead isotope signatures in the off-rift Öræfajökull central volcano in south-east Iceland: Evidence for enriched endmember(s) of the Iceland mantle plume?

The currently active off-rift central volcano Öræfajökull in south-east Iceland sits unconformably on much older (10–12 Ma) and eroded crust. The composition of recent volcanics ranges from basalt to rhyolite, but the series is more sodic alkaline than the common rift zone tholeiitic suites. In this study we present Sr, Nd, Pb and O isotopic data for a suite of Öræfajökull samples. The complete suite shows typical mantle values for oxygen isotopes. The ⁸⁷Sr/⁸⁶Sr ratios (average of 15 SAMPLES=0.703702) of the modern Öræfajökull rocks (basalts as well as rhyolites) are much higher than observed so far for any other Icelandic rocks. The ¹⁴³Nd/¹⁴⁴Nd ratios (average=0.512947; n=15) are lower than for rift rocks, but similar to rocks of the off-rift Snæfellsnes volcanic zone. Furthermore, the Öræfajökull rocks are enriched in the ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb isotope ratios compared to Icelandic rift basalts. The enriched nature of the suite indicates that Öræfajökull samples a source component that has characteristics common with EM2 type mantle. Furthermore, it is concluded that the silicic rocks of Öræfajökull formed by fractional crystallization from mafic melts rather than by partial melting of older crust.     

黄河三角洲地下水关键水盐因子及其植被效应

为了解黄河三角洲地下水生态环境功能,采用数理统计、地统计和同位素方法及3S技术,对"地下水-陆生植被"系统中关键水盐因子及其植被效应进行了深入研究。结果显示,区域典型植被主要以埋深普遍较浅(1.0～3.0 m)的地下水为水源,说明地下水是生态环境的敏感要素。潜水c(Cl-)与c(TDS)均呈显著的方向性空间变异(沿地下水流向二者浓度递增),且二者具有空间分布一致性(R=0.999),表明Cl-是潜水水质的主控离子。归一化植被指数(I_NDVI)与潜水c(Cl-)间呈较显著的Logistic关系,揭示潜水c(Cl-)是地下水这一生态环境敏感要素中的关键因子,其对上覆植被强烈的胁迫和驱动作用引发了区域典型的生态环境效应。在黄河三角洲高效生态经济区的开发建设过程中,应特别重视植被与潜水c(Cl-)间极为密切的作用与反作用关系,积极采取有效的人为调控措施。     

甘肃省成矿区(带)研究

成矿区（带）是区域成矿学的核心内容,成矿区（带）的划分和研究是成矿规律认识的深化和科学表达,同时是具有矿产资源潜力的成矿单元,是服务于勘查决策的主要载体。文章根据全国成矿区（带）划分意见,对甘肃涉及的4个成矿域、8个成矿省及12个Ⅲ级成矿区带进行分析和研究,依据省内区域矿产空间分布的集中性和区域成矿作用的统一性原则,重点讨论矿床所处的大地构造环境、成矿作用与区域地质演化过程、容矿围岩时空分布一致性或相似性;参考区域地球化学场、地球物理场特征,划分Ⅳ级成矿区（带）26个,Ⅴ级成矿区（带）94个。明确各级成矿区带地质意义及显著特征。文章指出本次对甘肃省成矿区带的划分具有探索性,随着认识不断深化,成矿区带的研究和厘定将更加科学。     

三峡库区丰都-忠县段消落带不同高程土壤镉及其形态的分布特征

镉(Cd)是目前三峡库区消落带主要的污染物之一,其迁移和形态转化直接威胁水环境安全.选择库区丰都-忠县段消落带,按照高程差异分别于不同土地利用类型(农田、林地、果园和村庄)下采集土壤样品,利用化学连续提取法测定Cd的形态组成,探讨影响消落带土壤中Cd及其形态空间分布的关键因素.结果表明,消落带土壤中Cd的平均含量为0.65 mg/kg,可交换态及碳酸盐结合态是土壤中Cd的主要形态,占比达到41.21%,残渣态和铁锰氧化物结合态次之,有机物及硫化物结合态占比最低.不同土地利用类型下消落带土壤Cd的含量整体上不存在显著性差异,表明当地人类活动对土壤Cd的直接贡献较弱.消落带土壤Cd及其形态的含量与高程呈显著负相关,且在160～165 m区域发生明显转变,水位变化导致的泥沙沉积可能是控制消落带Cd空间分布的主要因素.此外,土壤理化性质,尤其是细颗粒泥沙对Cd及其形态分布具有明显影响,将来需重点关注泥沙理化属性对Cd迁移及形态转化的影响.     

利用直达波提取低速带参数进行静校正

介绍了初至拾取方法和提取低速带参数的方法、原理及静校正的应用效果。在煤田地震勘探中,大部分激发井深都在低速带界面以下,用直达波求取低速带参数,既准确又经济。     

阿尔泰塔拉特铅锌矿床的变质叠加改造——地质和流体包裹体证据

塔拉特(阿巴宫)铅锌矿位于阿尔泰克兰火山-沉积盆地南东段,矿床受区域性NW向断裂——克因宫断裂和阿巴宫断裂的控制,Pb-Zn矿体赋存于下泥盆统康布铁堡组下亚组第二岩性段上部(D1k12)的变质岩系中,具明显的层控特征,后期脉状硫化物-石英脉叠加作用明显。根据矿体产出特征可识别出2个明显的成矿期:海相火山沉积喷流成矿期和变质热液叠加成矿期。变质热液期可包括2个阶段,早阶段透镜状石英脉沿含矿层位中绿泥石片岩、浅粒岩等顺层分布,并有浸染状黄铁矿产出;晚阶段含黄铁矿-黄铜矿石英脉穿切绿泥石片岩、浅粒岩或块状铅锌矿石,硫化物稀疏浸染状分布。海相火山沉积喷流成矿期的闪锌矿存在残留的L-V盐水包裹体及后期沿次生裂隙分布的L-V和H2O-CO2包裹体,原生L-V包裹体的均一温度Th,tot=267~334℃,次生H2O-CO2包裹体Tm,CO=-61.2~-60.2℃,T2h,CO=6.5~11.0℃。2变质热液期早阶段石英脉(QI)赋存有大量的H2O-CO2包裹体和较多的碳质流体包裹体(CO2±CH4体系),H2O-CO2包裹体Th,tot=294~368℃,盐度为5.5%~7.4%NaC leqv。碳质流体包裹体的Tm,CO=-60.1~-58.5℃,T.2~20.6℃。2h,CO=-42晚阶段切层含黄铁矿-黄铜矿石英脉中也有大量H2O-CO2包裹体和较多的碳质流体包裹体,H2O-CO2包裹体Th.tot=142~360℃,盐度为2.4%~16.5%NaC leqv。碳质流体包裹体的Tm,CO=-61.5~-57.3℃,T2h,CO0.6℃2有-27.0~-2和27.1~28.7℃两组。次生L-V包裹体的Tm,ice=-9.8~-1.3℃,Th,tot=205~412℃。克兰盆地造山运动过程中形成的区域性富CO2流体,其运移对促进岩(矿)石变形变质以及金属富集产生重要影响。塔拉特铅锌矿床的矿石变形、交代结构及石英脉中富CO2流体的大量出现,说明变质流体参与了叠加改造作用,且具有多阶段的特点。富CO2包裹体形成环境与造山带区域变质晚期或峰期后的P-T演化一致。     

Numerical study of pillar stresses and interaction effects for twin rock caverns

Large underground caverns are increasingly being considered for the construction of industrial facilities and transportation infrastructure in order to optimize the use of surface land in large urban cities. Due to the geological constraints underground, it is sometimes necessary to construct a cavern close to an existing cavern. Pillars serve as an underground support element in twin caverns, without which it is difficult to sustain the weight of the overburden materials. If the strength of a pillar is exceeded, it will fail, and the load that it carried will be transferred and thereby contribute to the collapse of the twin caverns. The lack of confinement in slender pillars also contributes to the complete collapse of pillars at relatively low stress magnitudes. From a design point of view, understanding the pillar failure mechanism and the interaction effect between twin caverns is essential. This paper presents a numerical investigation on the influence of various design parameters on twin cavern interaction. Pillar performances with respect to the changes to the maximum principal stress in the pillar, the peak vertical stress, and the peak principal stress difference in the pillar core are studied in order to examine the failure mechanisms and to identify situations in which there is significant cavern interaction and overlap of the plastic zones. Copyright © 2014 John Wiley & Sons, Ltd.     

滇-黔边境鲁甸沿河铜矿床的发现与峨眉山大火成岩省找矿新思路

滇-黔边境鲁甸沿河铜矿床矿化受二叠纪玄武岩最上部古火山口相角砾凝灰岩-气孔状熔岩和上覆宣威组碳泥质层控制。矿石矿物主要为自然铜、氧化铜与辉铜矿。自然铜呈板片状、网脉状、浸染状产出。矿化与阳起石化、沥青化、硅化和沸石化密切相关。在峨眉山大火成岩省寻找沿河式铜矿应关注以下重要问题：①地球化学急变带所确定的岩石圈不连续界面控制了峨眉山玄武岩裂隙式喷发；②古火山口相从苦橄质到安山质高分异岩浆喷发；③火山口环境联系下的贫硫、贫酸根同生热液活动；④富有机质地层中有机-无机相互作用所产生的强还原性环境；⑤脆韧性断裂带的发育导致矿体的进一步富化。     

Progressive extensional shear structures in a detachment contact in the Western Sierra Nevada (Betic Cordilleras,Spain)

Abstract

The present contact caused by the superposition of the Alpujarride complex over that of the Nevado-Filabride in the western area of Sierra Nevada and Sierra de Filábres corresponds to a detachment. The deformation in the footwall associated with this contact, produced mylonitic fabrics with a significant stretching-lineation, over which brittle structures are superimposed. The deformation in the hanging wall associated with this contact is, on the other hand, essentially brittle. These deformations are subsequent to a series of syn-to post-metamorphic structures related to thrust phases.

The micro- and meso-structures indicate that the hanging wall has moved towards the west-south-west.

Other brittle structures, which began during the same extensional regime, are superimposed on the detachment and have continued to develop up to the present time. These structures were produced in an extensional regime with a non-coaxial deformation component and suggest the possibility of a tectonic evolution similar to that described for core complexes in the USA.