山东省地下水超采漏斗发展演变分析

地下水超采漏斗是山东省平原区最为突出的环境问题.根据多年来地下水动态监测资料,简要分析了山东省平原区浅层地下水超采漏斗的发展过程、发展演变特征及发展原因,旨在为山东省地下水合理开发、有效保护、科学管理及有效控制地下水超采提供依据.     

山东半岛地下水库建设与研究进展

合理建设和管理地下水库是我国北方缺水地区增加水资源可利用量的有效途径.为了有效利用暴雨洪水资源,同时阻止海水沿河道下游入侵地下水含水层,自上世纪80年代以来,山东半岛陆续兴建了多座地下水库.介绍了山东半岛地下水库建设成就、地下水库建设的潜力、采取的技术措施和主要研究进展.指出地下水库环境保护是亟待引起重视的问题.     

滇中红层工程地质特性研究

介绍滇中红层形成的地质历史背景,红层分布范围,主要地层岩性及区内地质构造。重点讨论滇中红层特别是红层软岩的岩体原生结构,及后期受构造改造的岩体结构特性,岩体风化特性,岩体水理作用特性,岩体物理力学性质等四方面的工程地质特性。     

Spatial Analysis Techniques as Successful Mineral-Potential Mapping Tools for Orogenic Gold Deposits in the Northern Fennoscandian Shield,Finland

Geoscientific Information Systems (GIS) provide tools to quantitatively analyze and integrate spatially referenced information from geological, geophysical, and geochemical surveys for decision-making processes. Excellent coverage of well-documented, precise and good quality data enables testing of variable exploration models in an efficient and cost effective way with GIS tools. Digital geoscientific data from the Geological Survey of Finland (GTK) are being used widely as spatial evidence in exploration targeting, that is ranking areas based on their exploration importance. In the last few years, spatial analysis techniques including weights-of-evidence, logistic regression, and fuzzy logic, have been increasingly used in GTK’s mineral exploration and geological mapping projects. Special emphasis has been put into the exploration for gold because of the excellent data coverage within the prospective volcanic belts and because of the increased activity in gold exploration in Finland during recent years. In this paper, we describe some successful case histories of using the weights-of-evidence method for the Au-potential mapping. These projects have shown that, by using spatial modeling techniques, exploration targets can be generated by quantitatively analyzing extensive amounts of data from various sources and to rank these target areas based on their exploration potential.     

Andean evolution at the Guañacos and Chos Malal fold and thrust belts (36°30′–37°s)

The Andes between 36°30′ and 37°S represent a Cretaceous fold and thrust belt strongly reactivated in the late Miocene. Most of the features that absorbed Neogene shortening were already uplifted in the late Cretaceous, as revealed by field mapping and confirmed by previous fission track analysis. This Andean section is formed by two sectors: a western-inner sector generated by the closure of the upper Oligocene-lower Miocene intra-arc Cura Mallín basin between the middle and late Miocene (Guañacos fold and thrust belt), and an eastern-outer sector, where late Triassic-early Jurassic extensional depocenters were exhumed in two discrete phases of contraction, in the latest early Cretaceous and late Miocene to the Present, respectively (Chos Malal fold and thrust belt). Late Miocene deformation has not homogeneously reactivated Cretaceous compressive structures, being minimal south of 37°30′S through the eastern-outer sector (southern continuation of the Chos Malal fold and thrust belt). The reason for such an inhomogeneous deformational evolution seems to be related to the development of a late Miocene shallow subduction regime between 34°30′ and 37°45′S, as it was proposed in previous studies. This shallow subduction zone is evidenced by the eastward expansion of the arc that was accompanied by the eastern displacement of the orogenic front at these latitudes. As a result, the Cretaceous fold and thrust belt were strongly reactivated north of 37°30′S producing the major topographic break along the Southern Central Andes.     

Cooling rate effect as a cause of systematic overestimating of the absolute Thellier paleointensities: A cautionary note

Cooling rate (CR) effects on the intensity of thermoremanent magnetization has been documented for archaeomagnetic materials, where cooling in laboratory conditions is generally much faster compared to natural cooling rates. Since the latter condition also applies to many volcanic rocks, we have investigated in this study the influences of the CR on the determination of absolute paleointensity using recent basaltic rocks. We used magnetically and thermally stable samples mainly containing Ti-poor pseudo-singledomain titanomagnetites (the most widely used material for Thellier paleointensity experiments). These samples previously succeed in retrieving the strength of laboratory field intensities with the Coe’s version of the Thellier method in a simulated paleointensity experiment using similar cooling rates. Our experimental results indicate that the cooling rate effects produce systematic and significant overestimates of the absolute intensity up to 70%. The effect can be much larger than predicted by Neél theory for non-interacting single-domain grains.     

湘中锡矿山式锑矿成矿地质条件分析

湘中锡矿山式锑矿形成于晚白垩-古新世,空间上与岩脉关系密切,各锑矿床、矿化点都伴有或附近发育有煌斑岩及中-酸性岩脉群,在锑矿成矿同期地质事件中,还有周缘一些中-新生代红色盆地的形成及基性火山岩喷发,据之,提出湘中锡矿山式锑矿成矿与燕山晚期拉张构造-岩浆活化作用有关.锑矿床(点)基本上都产出于两组或两组以上断裂的交汇点附近,3组断裂的交汇部位对应于最主要的锑矿床(点).矿体具体受断裂交汇部位附近的次级短轴背斜轴部、倾伏背斜的倾伏端及其翼部被纵向陡倾角断裂构造所切穿的部位控制,是断裂导矿与背斜构造圈闭的体现.岩性组合控矿表现为易于硅化蚀变交代的砂质碳酸盐岩与隔挡层泥质岩所构成的岩性圈闭.根据包裹体均-温度和盐度测定成果,推算成矿压力为(200～300)×10⁵Pa,成矿深度约为1 km.     

山东泰安岩溶水系统地下水化学环境演化

随着地表环境质量的降低以及岩溶地下水的过量开采 ,泰安市岩溶水化学环境在总体上呈现出显著退化的演化规律。自 6 0年代初以来 ,泰安市城区及旧县岩溶水的常规组分、NO-3 浓度、硬度及TDS的浓度呈现不断升高的变化趋势 ,并检出有Cr6+ 、CN-、酚等人为环境物质。水位降落漏斗区与非漏斗区、岩溶塌陷区与非岩溶塌陷区的岩溶水化学组分浓度的对比结果表明 :由于岩溶水的超量开采引起地下水动力场的改变和岩溶塌陷是控制和影响岩溶水化学环境演化的主要因素。人类活动在时间及空间尺度上与岩溶水化学环境的快速退化亦有密切的关系。     

楚雄盆地中—新生界构造变形特征

根据近年笔乾研究，楚雄盆地中生代以后经历三期变形作用：早期（燕山期）主要发育于密者挤压逆冲带，显示横向置换特征，中期（喜马拉雅早期）是主变形期，西带显示由SW向NE逆冲，以叠瓦状闻和冲构造系统为其特征，晚期（喜马拉雅中晚期）发育于陡坡和深切割区，表现为重力滑动构造，这些构造期次的确定为研究该盆的发展，演化提供理论依据，亦为寻找油气资源提供靶区。