Trend-surface analysis as an aid in exploration for Mississippi valley-type ore deposits

An examination of the characteristics of Mississippi Valley-type ore deposits shows that these deposits have many similarities which appear to be structurally controlled. To define the relationship between the ore deposits and these structural conditions, trend-surface analysis using the Precambrian surface as the datum plane was performed within the general Missouri area. Examination of the residual maps prepared from this analysis shows that all the ore deposits have the same spatial relationship to areas of strong residual highs. A more detailed study was conducted in the area of the Viburnum Trend using a datum plane just below the ore horizon. The spatial relationship shown on the Precambrian residual map was even better defined in this study. From this study, it appears that the optimum structural conditions necessary for the deposition of Mississippi Valley-type ore deposits exist in regions located next to and slightly downgradient from areas which exceed one positive standard deviation from the trend surface. The methods described in this paper could comprise an extremely useful tool in exploration programs as they can define high probability locations in which to concentrate further exploration efforts.This paper was presented at Symposium 116.3, Quantitative Strategy for Exploration, held as part of the 25th International Geological Congress, Sydney, Australia, August 1976.     

Near-surface lithogeochemical halo as an aid to discovery of deeply buried unconformity-type uranium deposits, Athabasca Basin, Canada

Unconformity-type U deposits are being found to depths of more than 400 m where graphitic rocks underlie the Proterozoic sandstone unconformity. Exploration to date involves drilling weak electromagnetic conductors that reflect the graphitic basement. The deposits are believed to have formed through circulation of heated formation waters which discharged essentially vertically above the deposits. Geochemically detectable zones of alteration are reported for cross-sections through the Deilmann, Midwest, and McClean deposits. Information on the areal dimensions of near-surface haloes was required to justify the drilling of grids of shallow holes along conductors or favourable structures as a cost-effective exploration alternative to deep holes, and to define grid spacings.Orientation surveys were undertaken by sampling the uppermost 10 m of sandstone in a selection of holes from the Cigar Lake, Dawn Lake, and Wolf Lake areas where the deposits are, respectively, 400–430 m, 100–160 m, and 180–210 m below surface. The first two deposits have published reserves of 385 and 30–40 million pounds U₃O₈, respectively, while Wolf Lake is much smaller.Well-developed anomalies lie vertically above the richest portion of the Cigar Lake deposit in an area 150 × 600 m and a weak anomaly in many elements continues over the 1800-m length that was sampled. Total and leachable U are 13 to 8 times background with maximum values of 53 and 26 ppm, respectively. Anomalies of 14 to 8 times background are also present for V, Na₂O and Zn, and 5 to 3 times background for Sr, Y, Pb, Th, As, and P.Of the four Dawn Lake mineralized zones, only the 11B Zone was studied, with partial coverage of the 11A Zone. Anomalies 50–100 m by 250–600 m in size are often displaced up to 100 m northeast of the 11B Zone. B, MgO, Pb and both total and leachable U anomalies are 16 to 8 times background with Y, V and As 7 to 5 times background.By contrast, at the Wolf Lake deposit, only irregular variations occur for most of these elements. The unusual patterns may reflect post-alteration tectonism of the sandstone overlying the deposit as regional thrust faulting occurs nearby.Detection of near-surface lithogeochemical haloes using grids of shallow holes would facilitate discovery of deep deposits and reduce expensive, deep drilling.     

Modeling and assessing land-use and hydrological processes to future land-use and climate change scenarios in watershed land-use planning

Effective information regarding environmental responses to future land-use and climate change scenarios provides useful support for decision making in land use planning, management and policies. This study developed an approach for modeling and examining the impacts of future land-use and climate change scenarios on streamflow, surface runoff and groundwater discharge using an empirical land-use change model, a watershed hydrological model based on various land use policies and climate change scenarios in an urbanizing watershed in Taiwan. The results of the study indicated that various demand and conversion policies had different levels of impact on hydrological components in all land-use scenarios in the study watershed. Climate changes were projected to have a greater impact in increasing surface runoff and reducing groundwater discharge than are land use changes. Additionally, the spatial distributions of land-use changes also influenced hydrological processes in both downstream and upstream areas, particularly in the downstream watershed. The impacts on hydrological components when considering both land use and climate changes exceeded those when only considering land use changes or climate changes, particularly on surface runoff and groundwater discharge. However, the proposed approach provided a useful source of information for assessing the responses of land use and hydrological processes to future land use and climate changes.     

Landslide susceptibility and hazard mapping in Australia for land-use planning — with reference to challenges in metropolitan suburbia

This paper provides an overview of the history and current status of landslide susceptibility and hazard mapping for land-use zoning in Australia. It also describes a case study of landslide hazard mapping in a medium density, coastal, suburban residential area of metropolitan Sydney, New South Wales, Australia, with relatively steep terrain. Issues covered include identification and mapping of existing and potential landslides, and susceptibility and hazard zoning for regulatory management and land-use planning. The method involves application of the principles contained within the AGS (2000) guideline, and as updated by the AGS (2007 a,b,c,d,e) suite of guidelines.     

MAPGIS在地质制图中的应用

MAPGIS是我国自主研究开发的大型基础地理信息系统软件平台,具有机助制图、图形编辑和图形处理等多种功能,是我国地质行业数字化制图的首选工具.本文结合工作实例,介绍了MAPGIS在点参数编辑、线参数编辑等方面的数字制图方法和技巧.     

内蒙古中部地区石墨矿专题地质填图进展与思考

在内蒙古中部地区开展接触变质型石墨矿1：5万专题地质填图试点工作,查明了接触变质石墨矿成矿要素和找矿标志。白云鄂博群尖山组一段炭质地层是石墨矿化的主要层位,经历低程度的区域变质作用,叠加了晚古生代岩浆活动的强烈接触变质改造,发生了大规模的石墨矿化。通过石墨矿专题地质调查,圈定了3处石墨找矿靶区,3处成矿远景区,预测远景资源储量大于2000×104t。不同于传统的矿产地质调查,以成矿作用为核心的专题地质调查工作,是以石墨成矿关键问题为导向,开展石墨成矿作用研究,构建成矿模型和找矿标志,从而指导矿产地质调查填图,可以快速圈定矿化异常,开展异常查证和评价,提高了找矿工作效率。     

Crustal paleo-hydrogeological mapping as a tool in exploration for mineral deposits

Extensive studies in the southern Canadian Cordillera have shown that using geological and geochemical techniques, it is possible to regionally map distinctive paleo-hydrogeological regimes. Since research programs in the Canadian Cordillera and elsewhere have shown that many types of mineralization are created by regional scale flow systems, it is possible to use the regional maps of paleo-hydrogeological regimes to define those areas likely to host particular styles of mineralization.An application of these concepts to exploration is documented using the example of mesothermal Au mineralization in the southern Canadian Cordillera. Approximately 75% of the 300,000 km² study area can be eliminated from consideration for exploration due to the absence of the appropriate geological and geochemical indications of paleo-hydrogeological regimes capable of forming mesothermal Au deposits. Consequently, exploration efforts can be focussed on a much smaller, but more prospective region.     

Engineering-geological mapping of tropical soils for land-use planning and geotechnical purposes: A case study from Jamaica, West Indies

An area of a Tertiary and Cretaceous deposits, 100–310 m above sea level and on predominant 20–45°, highly dissected, concave slopes was investigated to assess its geotechnical characteristics and land use planning implications. Lithologies include turbidites, fluvial conglomerates, breccias, sandstones, mudrocks, carbonates, granodiorite, acid dykes, chloritized and epidotized volcanics, andesite and Holocene fluvial deposits. Bedrock is highly fractured and sheared, hydrothermally altered and highly weathered. Soils are quite variable, with a strong geological control on soil properties. Soils are generally sandy to gravely, with local silts and clays in mudrocks, within Holocene alluvium or in hydrothermally altered and sheared granodiorites. The soils are composed of 0.14–80.00% gravel; 5.36–62.50% sand, 2.33–50.55% silt, 0.17–51.50% clay, and total fine content between 2.50 and 94.50%, with natural moisture between 4 and 44% during the dry season, plastic limit between 6 and 35%, liquid limit between 19 and 83% and plasticity index between 1 and 59%. Sandy soils have residual friction angles between 19 and 39°, PI values less than 35% with cohesion between 1.00 and 5.27 KN/m² for cohesive samples. ASTM classification of soils include soil groups GC, GM, GW, GP, SP, SM, SC, SM, SC, ML, CL and CH.

Based on the characteristics of the terrain, the geotechnical and land use planning problems include high landslide frequency and susceptibility, soil erosion, fluvial and reservoir sedimentation, high debris flow hazard, cut slope failures, potentially expansive clays and silts, seepage erosion and soil piping, differential settlement in interlayered competent and incompetent lithologies, high solution erosion and potential subsidence over limestones, waste water disposal problems and groundwater pollution and seismic induced settlement and ground failures. These phenomena suggest that systematic site investigations should be conducted prior to the utilization of these areas for construction and development in order to minimize the deleterious effects resulting from ground failure.     

苏克塔格能厄肯红柱石矿床地质特征

苏克塔格能厄肯红柱石矿床位于新疆库尔勒市境内,大地构造位置处于南天山冒地槽褶皱带霍拉山复向斜东部,南邻塔里木地台库车凹陷,是苏克塔格能厄肯-玉奇阿恰红柱石成矿带中的红柱石矿床之一.区内褶皱、断裂、岩浆岩发育,矿床产于中上石炭统塔拉克组中.经长期地质研究认为:该矿床成因属较浅部高温低压接触变质型红柱石矿床.     

Societal application of geophysics as an aid to a rescue operation at Jaipur

Geophysical techniques are normally employed to explore the subsurface and determine the anomalies but they are always much larger in dimension. However, a very precise measurement was needed to pin point a misaligned horizontal tunnel made at 47 m depth to intercept an old bore well and rescue a four year child fallen accidently on 9^th November at Jagatpura village in Jaipur, India. Due to the greater depth and presence of iron casing, electric power, etc., no equipment could work to determine the orientation of the tunnel that has lost its direction. The dimension of the site and many other constrains didn’t allow conventional geophysical methods to be used. An innovative method was then designed and successfully applied, which determined 1.92 m deviation of the tunnel end point to the east from the old bore well. The digging was redirected accordingly and the bore well was intercepted. This paper describes the theoretical background, forward simulations and the field experiment of the newly designed geophysical method.     

Fluvial deposits as an archive of early human activity

River terraces are well established as an important source of Lower and Middle Palaeolithic artefacts in Europe, large collections having been assembled there during the years of manual gravel extraction. Now that many terrace sequences can be reliably dated and correlated with the oceanic record, potentially useful patterns can be recognized in the distribution of artefacts. The earliest appearance of artefacts in terrace staircases, marking the arrival of the first tool-making hominins in the region in question, is the first of several archaeological markers within fluvial sequences. The Lower to Middle Palaeolithic transition, with the appearance of Levallois, is another. Others may be more regional in significance: the occurrences of Clactonian (Mode 1) industry, twisted ovate handaxes and bout coupé handaxes, for example. IGCP Project no. 449 instigated the compilation of fluvial records from all over the ‘old world’. Comparison between British and Central European sequences confirms the established view that there is a demarcation between handaxe making in the west and flake/core industries in the east. Other centres of activity reported here have been in the Middle East (Syria), South Africa and India. Data from such areas will be key in deciphering the story of the earlier ‘out-of-Africa’ migration, that by pre-Homo sapiens people. There is clear evidence for diachroneity between the first appearances of different industries, in keeping with the well-established idea of northward migration.     

石膏矿床的地质特征及对硫化矿床的指示意义

从研究划分石膏矿化的成因类型入手,进行热液化学成分来源分析和岩石蚀变分带研究,结合典型矿床实例分析,总结出在碳酸盐岩中出现热液交代型石膏矿化体附近,往往伴生有金属硫化矿体或含硫化矿物丰富的岩石,该规律对寻找硫化物型金属自矿体的意义巨大.     

陇南煤田含煤沉积地质特征研究

通过对陇南煤田已知煤矿点有关资料的分析,研究了该区侏罗纪煤系的沉积特征和古构造展布特征。结果表明,陇南煤田的古构造对含煤沉积的控制作用,主要是通过对古河流展布和古气候的控制而体现的。不同层位的煤层,其下面普遍有河流相沉积,说明煤层是在古河流基础上发展起来的;适于成煤的气候自早侏罗世至晚侏罗世,具有由西向东迁移的特点,因此,陇南煤田的找煤勘探应沿古武都河的西北—东南延伸方向开展。     

Simultaneous determination of sulfide, polysulfides and thiosulfate as an aid to ore exploration

The interaction of water and sulfide minerals yields dissolved species which can be utilized to trace back the presence of sulfide minerals and associated minerals. Computer modeling and laboratory and field results show that the most characteristic dissolved species are hydrogen sulfide (H₂S, HS⁻), polysulfide ions (S_n²⁻) and thiosulfate (S₂O₃²⁻), derived from the hydrolysis of sulfide minerals. Typical concentration ranges are: 10⁻⁵ – 10⁻⁷ mole/l for hydrogen sulfide, 10⁻⁶ – 10⁻⁹ mole/l for polysulfides and 10⁻⁵ – 10⁻⁸ mole/l for thiosulfate. The chemical reactivity of these species at contact with air makes them difficult to assess unless determined immediately after sampling.These sulfur species can be determined rapidly and accurately in field conditions by simultaneous titration with mercuric chloride employing an Ag/Ag₂S electrode for the determination of the end points.The application to ore exploration is exemplified by the results of the research on roll-type uranium deposits in the southwest of France.     

湘南地区钨矿成矿地质特征

湘南地区钨及钨多金属矿矿床(点)分布广泛,类型复杂,它们的形成除与花岗质侵入岩体直接相关外,同时还受到区域地层和地质构造等因素的共同制约?笔者从钨矿的地质背景?分布特征?矿床特征的研究,进而总结了区域钨矿的成矿规律?     

纳米比亚西南部斑岩型铜矿地质特征

纳米比亚西南部奥兰治河海伯地区是纳米比亚重要的铜矿产地之一,区内的海伯铜矿和罗雷铜矿具有明显的斑岩型成矿特征。控制铜矿的斑岩体为古元古代威尔斯锥夫岩基的岩枝、岩株状分支,矿体的围岩为古元古界奥兰治河群海伯亚群。威尔斯锥夫岩基与奥兰治河群均为钙碱性火成岩和火山-沉积岩组合,形成于大陆边缘俯冲带的构造背景环境,结合海伯铜矿和罗雷铜矿地质及同位素特征,文章认为该区斑岩型铜矿可能为板块构造成矿。     

Geological modelling of mineral deposits for prediction in mining

Accurate prediction of the shape, location, size and properties of the solid rock materials to be extracted during mining is essential for reliable technical and financial planning. This is achieved through geological modelling of the three-dimensional (3D) shape and properties of the materials present in mineral deposits, and the presentation of results in a form which is accessible to mine planning engineers. In recent years the application of interactive graphics software, offering 3D database handling, modelling and visualisation, has greatly enhanced the options available for predicting the subsurface limits and characteristics of mineral deposits. A review of conventional 3D geological interpretation methods, and the model struc- tures and modelling methods used in reserve estimation and mine planning software packages, illustrates the importance of such approaches in the modern mining industry. Despite the widespread introduction and acceptance of computer hardware and software in mining applications, in recent years, there has been little fundamental change in the way in which geology is used in orebody modelling for predictive purposes. Selected areas of current research, aimed at tackling issues such as the use of orientation data, quantification of morphological differences, incorporation of geological age relationships, multi-resolution models and the application of virtual reality hardware and software, are discussed.     

散乱离散点数据的三角形网格化快速成图

提出了一种基于三角网格的等值线成图线性插值方法。常规等值线成图都是基于矩形网格进行网格化插值的,三角网格能够更好地逼近地球物理场的形态和散乱离散点数据的边界,得到的等值线图更加光滑。通过搜索边界、三角网格化剖分、线性插值、搜索等值线、Bezier曲线光滑等值线等5个步骤,可以对任意散乱离散点数据进行快速成图。实际数据的成图结果表明:该方法插值效果好,不进行数据外推,得到的等值线图能直接反映散乱离散点数据的空间位置且成图速度快,可大大提高实际工作效率。