娄底地区环境地质灾害问题初探

娄底地区环境地质灾害较严重。主要有地震、地裂、塌陷、滑坡、水土流失和水污染等。这些灾害的形成除受天然状态下的第一地质环境影响外,主要与第二环境即开矿、建厂、修路及兴修水和等人类活动有关。针对各类灾害及其危害性,提出了防治对策与建议。     

基于多媒体技术的昌平区地质灾害演示系统

分析了多媒体技术的应用现状及发展趋势。以昌平区地质灾害多媒体演示系统的制作为例,从制作流程、音视频文件处理等方面,详述了多媒体技术在地质灾害成果演示中的应用。同时,就制作过程中出现的问题,提出了相应的解决办法及建议。     

浅析北京市延庆区西北部地热地质特征

为解析延庆区西北部地区的地热地质特征,本文通过对研究区内的地热流体通道、热储层和盖层条件的总结分析,并综合地温场分布特征和地热流体化学特征,浅析了研究区内的地热资源形成条件。结果表明,研究区内的NEE向与NS向断裂为主干断裂,在其交互处,形成主要的热水通道,发育了以蓟县系雾迷山组为代表的层状热储,地热流体主要来源于1.5～4.6万年前的大气降水补给,与浅层地下水几乎无水力联系。延庆盆地内的地热资源主要受以热传导为主的传热过程控制,热储层和盖层岩石热导率的差异,使得平面上的温度差异显示出受控断裂构造控制的趋势。     

浅谈上杭紫金山矿区的环境地质问题

环境地质问题是紫金山矿区面临的一个重要课题。本文对紫金山矿区的泥石流、水土流失、水资源污染、水资源破坏等环境地质问题进行分析,并提出预防、监测、治理建议。     

临川市文昌桥区工程地质质量的模糊综合评判

城市工程地质质量综合评价是一个复杂的系统问题，影响评价的因素众多，关系十分复杂，各因素的影响程度又不相同，因此，用常规方法难以精确划分质量综合等级分界线，本文选用模糊数学的方法，对临川市文昌桥区工程地质质量作出了综合评判。     

北京昌平南口地区地质新认识

北京南口地区,水文地质钻探揭露地层与设计地层有着较大出入。本文通过CG-T-1、CG-K-1、CG-K-2孔的钻探施工,对比分析区域地质资料,总结了南口—孙河断裂两侧第四系、白垩系和侏罗系的分布埋深情况,重新认识了燕山期侵入岩体的分布范围,认为在南口—孙河断裂的上盘(西南盘)区域分布着较厚的燕山期侵入岩体,蓟县系雾迷山组比以前设计的埋深要深得多,得出在辛店—马池口凹陷平原区内布置基岩供水井适宜性较差的结论。通过对CG-K-2号井热盖层、热储层及导热构造的分析,对比CG-K-2井的测井温度,提出了开发地热资源的建议。     

Geology of the area around Dharmsala,Kangra District,H. P., India

In the present paper an attempt has been made to describe the geology of the area around Dharmsala, Kangra District, Himachal Pradesh. The stratigraphic position of the problematic horizons, i. e., Dharmkot Limestone and Dharmsala Traps is discussed in detail.     

Geology and Genesis of Orogenic Gold Deposits,Xiaoqinling District,Southeastern China

Orogenic gold vein deposits in the Xiaoqinling district are situated in a basement-cored uplift along the southern margin of the North China craton. The deposits are hosted by Late Archean to Paleoproterozoic amphibolite-facies country rocks, varying in lithology from clastic and chemical sedimentary units to felsic and mafic volcanic rocks and plutons. Absolute and relative age relationships indicate a late Mesozoic emplacement of the lodes, which is subsequent to the deformation associated with the Middle to Late Triassic Qinling orogen along the craton margin. All auriferous quartz veins are hosted in faults. The ores are generally composed of quartz veins with various amounts of pyrite, galena, chalcopyrite, sphalerite, and carbonates. Mineralization can be separated into three distinct stages.

Ore fluids are H₂O dominant, with approximately 20 to 30 and 10 to 20 mole% CO₂ for gold-bearing stage I and II veins, respectively. Vein formation pressures and temperatures were 2.2 kbar and 300 to 370°C for stage I and 1.6 kbar and 250 to 320°C for stage II. The narrow range of δ¹⁸O values for ore fluids from the deposits throughout the Xiaoqinling district indicate a common deep fluid source, most likely of magmatic origin. The ³⁴S data suggest sulfur originated from a magmatic fluid of approximately 2 ± 2%, with significant local sulfur contributions leading to large variations in the ore-stage sulfide minerals. The most probable mechanism for the deposition of gold is phase separation caused by the partial loss of volatiles such as CO₂ and CH₄.     

Geology and geochemistry of bauxite deposits in Lushoto District, Usambara Mountains, Tanzania

Bauxite deposits in the Usambara Mountains of north eastern Tanzania occur as remnants of residual deposits on two geomorphologically related plateaus of Mabughai-Mlomboza and Kidundai at Magamba in Lushoto, Usambara Mountains. The parent rocks for the deposits are mainly granulites and feldspathic gneisses of Neoproterozoic Mozambique belt. The plateaus represent a preserved Late Cretaceous–Lower Tertiary old land surface (African surface). Other parts of the Usambara Mountains and the neighbouring Pare Mountains are covered mostly by red–brown lateritic soils and impure reddish-brown kaolinitic clays. The bauxite deposits contain mainly Al₂O₃ (40–69 wt.%), Fe₂O₃ (3–10 wt.%), SiO₂ (0.16–7 wt.%) and other elements occur in quantities not substantial to affect the quality or processing of the bauxite, and are attributed to the presence of relic minerals. Gibbsite makes up to 98 vol.% of the bauxite ore in special cases. Gibbsite is accompanied by goethite in the ore. Boehmite occurs in small amounts and is usually accompanied by hematite. Impurities include goethite, hematite, kaolinite, and minor relic quartz and microcline. Kaolinite is the sole clay mineral encountered in the bauxite ore, suggesting mature soil profiles and a development of the bauxite deposits on a well-drained peneplanation. Ore reserve estimates from the drilling data and surface geological mapping of the deposits yielded bauxite reserves of about 37 million tonnes.     

The Geology of the Western Highlands of New Guinea

Abstract

The oldest rocks in the Western Highlands of New Guinea are granite and metamorphic rocks, and these are unconformably overlain by an incomplete marine succession of Permian, Upper Jurassic, Cretaceous, Eocene, Oligocene and Miocene sediments with a maximum thickness of 34,000 ft. The sedimentary succession in the east of the region is much thicker than in the west. Jurassic seas transgressed from the east. Studies of the faunas and petrology of the sediments show that the western part of the region was out of range of the sources of Cretaceous vulcanism and slow pelagic sedimentation continued into the Lower Miocene. By the Middle Miocene a volcanic island arc had developed in the vicinity of the Lai Syncline and the sediments are of shallow-water type, rich in volcanic debris.

Both sediments and basement were folded into a number of anticlines and synclines at the end of the Pliocene. Vigorous erosion was followed by extensive Pleistocene vulcanism in the west. Pleistocene glaciation occurred in the Bismarck Range down to about 13,000 feet above sea-level.     

Petrology of coronite from the Bergen Arcs Complex,Norway

Petrologic examination of coronites from the Bergen Arcs Complex in Norway revealed that garnet crowns formed due to clinopyroxene interaction with matrix plagioclase and spinel during the Grenville granulite-facies metamorphism (at T ～ 960°C and P = 1.3 GPa). Along with this, the rocks show evidence of reactions related to superimposed Caledonian eclogite-facies metamorphism. These are microscopic coronas consisting of omphacite, kyanite, corundum, amphibole, and biotite. The rims formed under aqueous conditions with potassium introduction ata T ～ 710–730°C and P ～ 1.3–1.5 GPa. Local occurrence of eclogite metamorphism found at a great distance (>100 m) from shear zones of the eclogite metamorphic stage indicates that the whole eclogite succession and not only its local sites (shear zones) were heated to the eclogite-metamorphism temperature.