Hydrogeochemical prospecting of gold in an alpine bald mountain zone

The investigation was conducted within highly and moderately separated highlands and high plateaus where glaciers, stone streams, solifluction, and glacial and fluvio-glacial deposits are widely developed. A capping of Miocene basalts remains in the divides over the Au ore deposits and their oxidation zones. Young water-filled fractures traverse the ore-bearing structures and control the direction of the glacial and river valleys, as well as the location of the lakes, springs, and icings.Gold occurs in small- to average-sized sulphide-Au-quartz veins and in a sulphidized black shale series of Precambrian and Paleozoic age. Both mechanical and hydromorphic dispersion of Au are exhibited clearly in the highlands. The latter is due to the processes of modern oxidation of the Au-bearing sulphide minerals. The anomalies of Au in streams and small lakes are related to supra- and sub-ice waters. In the water of streams Au is present in three forms; colloidal, dissolved, and sorbed. Gold in colloidal form comprises the most ample and contrasty anomalies. The truly dissolved Au is more local and manifests itself close to the source of the stream. Gold sorbed on suspended matter is evident because of a significant removal from the source into the solution. Migration of Au and formation of long (up to 2.5 km) and contrasty dispersions in waters of low dissolved solids is favoured by the presence of organic matter and argillaceous and ferruginous suspensions as well as other sorbents. The anomalies of Au in water either coincide with anomalies in stream sediments over mineralized zones or indicate new mineralized areas not reflected in stream sediments.     

A preliminary inventory of periglacial landforms in the Andes of La Rioja and San Juan, Argentina, at about 28°S

The Cerro El Potro and nearby mountain chains belong to the Andean Frontal Cordillera (28°S). Cerro El Potro is a glaciated mountain that is surrounded by huge valleys both on its Chilean and Argentinean flanks. Its southern limit is a steep rock wall towards the trough-shaped Río Blanco valley in Argentina, with a wide valley floor. The other sides of the mountain are characterized by well-developed Pleistocene cirques. The predominant landforms in this area have been shaped in a periglacial environment superimposed on an earlier glacial landscape. It is a region with abundant rock glaciers, a noteworthy rock glacier zone, but nevertheless, it is a relatively little known area in South America. In this preliminary inventory, the landforms surveyed were mainly gravitational in origin, including valley rock glaciers, talus rock glaciers, debris cones, landforms originated by solifluction processes and talus detrital sheets on mountain sides. Ancient moraine deposits have been found on the sides of the main rivers that cross the area form west to east, including the Blanco and Bermejo rivers. Present day fluvial activity is limited, and restricted to these main rivers. In this area of glacial valleys and small cirques, there are small lakes and other water bodies, grass covered patches and zones with high mountain vegetation. Present day glacial activity is restricted to the highest part of the area, above 5500 m a.s.l., mainly in the Cerro El Potro (5879 m) where a permanent ice field exists, as well as small mountain glaciers.     

金的地球化学异常与金矿床规模之间关系的统计学特征——以河北省为例

以水系沉积物地球化学调查成果为基础,从统计学角度探讨了河北省金地球化学异常与金矿规模的对应关系。以2.6 ng/g为异常下限,在全省范围内圈定金区域异常28处,局部异常35处。研究发现区域异常与金矿的关系非常密切,100%的大型金矿、81.8%的中型金矿及70.9%的小型金矿都位于区域异常内。局部异常仅与小型金矿的关系密切,小型金矿在局部异常中的产出概率是20%。通过23个金异常面积与金矿储量的相关分析表明,二者相关性非常好,相关系数达0.919,金异常面金属量与金矿储量的相关性也很显著,相关系数达0.924。回归分析表明,金异常面积及异常面金属量与金矿床储量之间符合一元线性相关特征,并分别建立了回归方程。该成果对矿产预测及资源潜力评价具有一定的指导意义。     

滇黔桂卡林型金矿区水系沉积物和岩石金含量与时空分布

为研究滇黔桂卡林型金矿区水系沉积物和岩石中金的地球化学时空分布及其与金矿规模的对应关系,系统收集了该区1:20万区域化探全国扫面计划水系沉积物和全国地球化学基准计划岩石金的地球化学数据,绘制了水系沉积物和岩石金的地球化学分布图。滇黔桂卡林型金矿区以水系沉积物金地球化学异常面积大于1000 km^2为准,共圈定5处金的地球化学省,这些金的地球化学省同时也是矿床大规模产出的部位。区内右江盆地水系沉积物金背景值(1.94×10^–9)高于扬子克拉通(1.68×10^9),其内以泥岩、页岩、砂岩、灰岩为代表的容矿岩石金背景值(0.51×10^–9)也高于扬子克拉通(0.39×10^–9)。研究区不同构造单元及沉积相中水系沉积物金背景值受岩石金背景值的制约。金的地球化学省是地壳演化过程中不均匀分布的高金背景岩石、金矿化作用及金矿床次生风化作用相互叠加的结果。该研究有助于有效判断异常成因、识别成矿作用存在,对研究金的区域成矿规律和聚焦找矿靶区具有重要意义。     

Pleistocene sediment-hosted uranium deposits at Henkries, South Africa: using settling tubes to delineate buried ore bodies

Sediment-hosted uranium ores at Henkries in northwest South Africa occur in fine-grained sands, carbonaceous muds and diatomaceous earth within late Pleistocene lake deposits. The lakes are linked by short fluvial channel reaches and these aqueous beds are encompassed in predominant aeolian dune deposits. The late Pleistocene fluvial-lacustrine-aeolian succession is succeeded by a Holocene dune cover. Textural characterisation of lacustrine, fluvial and aeolian sands was based on volume percentages observed in sediment settling tubes. Vortex action during Holocene dune migration contaminated these aeolian cover sands with small amounts of substrate material, whose presence could be detected in settling tube patterns of surface aeolian sediment samples. It was thus possible to map buried lacustrine ore bodies, which were shown, by a successful drilling programme, to be displaced downwind. Received: 28 August 1996 / Accepted: 3 September 1996     

福建省几种主要金异常的评述

对河流重砂金异常,水系沉积物金异常及土壤化探金异常在寻找金矿中的意义和作用进行简要的评述。     

A revised stratigraphical framework for the Quaternary deposits of the German North Sea sector: a geological‐geotechnical approach

Using extensive data sets from three separate areas in the German North Sea sector, consisting of seismic grids, cores and in‐situ cone penetration tests (CPT), we have established a revised stratigraphical framework for the mid to late Quaternary deposits of the German North Sea sector. This framework consists of four regional unconformities and 15 other local unconformities derived from seismic profiles. Using these unconformities, along with lithological and geotechnical data, it was possible to define and correlate 14 major units and 21 subunits within the framework. The Quaternary cover in the area is characterized by a variety of environmental settings ranging from glacial terrestrial and fluvial to lacustrine as well as brackish and marine environments with associated erosion, reworking and deposition. The complexity of Quaternary deposits within the area is explained by its history of repeated ice advances interrupted by marine transgressions and exposed periglacial landscapes. Within the framework, eight buried tunnel valleys and two shallow buried river valleys are identified from seismic profiles with four phases of tunnel valley generation inferred. These phases of tunnel valley generation are associated with the Elsterian (three) and Saalian (one) glacial stages. Infill of these tunnel valleys consists of glaciofluvial sands, thick sequences of marine and lacustrine fine‐grained sediments and some reworked till remnants. Elsewhere, extensive tabular units have formed consisting of marine and fluvial sediments. We compare this new stratigraphy with previous stratigraphies for the German North Sea sector, attribute informal stratigraphical names and offer preliminary correlations with established stratigraphies from other sectors of the North Sea.     

吉林省海沟金矿床的地球化学异常模式

在总结海沟金矿床区域水系沉积物、矿区水系沉积物及矿体的岩石、土壤地球化学异常特征的基础上,建立了海沟金矿床的地球化学异常模式,并依据该模式对区域47个异常进行了研究对比,预测出一处寻找海沟式金矿床的有望异常。     

Comparison of vegetation and stream sediment geochemical patterns in northeastern New South Wales

This study compares the geochemical response of stream sediments and adjacent vegetation samples, with variations in drainage catchment lithology and the occurrence of mineralisation, within a 14,000-km² block of the northeastern region of New South Wales, Australia. The area contains a range of lithologies within a Devonian–Permian accretionary complex and Mesozoic sedimentary basin, as well as a wide range of mineral deposits. Sampling was designed to confine each sub-catchment to a single lithological group (mafic and ultramafic rocks, acid intrusives, volcanics, metasedimentary and sedimentary rocks or alluvium). Leaves of over 20 genera, dominated by (Allo-)Casuarina, Eucalyptus, Acacia, Callistemon and Melaleuca, and the <250-μm fraction of the stream sediments were analysed by INAA. The uptake of most trace elements varied between genera, with Callistemon displaying the highest median As and La contents and Eucalyptus the highest Co contents. The stream sediment and vegetation geochemistry reflect both hydromorphic and mechanical dispersion within sub-catchments, with regional patterns dominant over local influences. The vegetation appears to be influenced to a greater extent by hydromorphic dispersion, as indicated by differences in the ratio of leaf to sediment Cr concentrations in sub-catchments draining serpentinites and basalts. Although most known mineral deposits in the region produced anomalies in at least one medium, there was little correlation between the trace element concentrations of the vegetation and stream sediments on a site-by-site basis. A number of Au targets were only detected on the basis of the biogeochemistry and others were only reflected in the stream sediment geochemistry. In general, vegetation displayed more extensive dispersion trains away from mineralisation than did the stream sediments. Differences in the response of the two sampling media suggest their joint use in exploration or environmental surveys to maximise the probability of detecting mineralisation.     

Metal transport, partition and fixation in drainage waters and sediments in carbonate terrain in Southeastern Ontario

Lake sediment composition as an indicator of mineralization within the catchment area has found widespread application in recent years, particularly in Canada. Results have indicated, however, the existence of varying relationships between lake sediment composition and mineralization resulting from local features of the limnological environment. Accordingly it was considered appropriate to examine the nature of metal transport in the lake and stream environment, the partitioning of metal between the stream waters and stream sediments and between lake waters and lake sediments to obtain some understanding of the factors that affect the lake sediment-mineralization relationship. This investigation was carried out over an area containing Pb-Zn occurrences of supposed “Mississippi-Valley type” in Grenville and Paleozoic bedrock in southeastern Ontario.The headwater drainage systems comprise active streams, swamps, beaver ponds and small lake-bog systems giving way downstream to open lakes. The beaver swamps and seasonal swamps act as drainage sinks for metals, restricting the extent of geochemical dispersion in drainage systems adjacent to mineralization. Selective extraction analysis of bog, stream and lake sediments indicates that metals are preferentially concentrated with amorphous iron oxides, which readily adsorb and complex lead and zinc and are stable in the alkaline environment common in swamps adjacent to carbonate-hosted lead-zinc mineralization. The accumulation of lead and zinc with amorphous iron oxides combined with the adsorbing and chelating action of organic matter on lead and zinc makes organic-rich sediments from these small swampy areas an excellent sample medium for reflecting local mineralization. Down drainage anomalies of these elements can be accentuated by selective analysis for the amorphous iron oxide-held metal, involving selective extraction techniques.In contrast, within larger lake systems, the analysis of water samples indicates that geochemical dispersion in surface waters in the high pH environment (pH = 8.0) associated with the carbonate-hosted lead-zinc deposits is extremely restricted. In this environment, anomalous metal contents in lake water were not evident in lakes adjacent to mineralization, while anomalous lake sediment compositions exist only in lakes immediately adjacent to Pb-Zn mineralization and do not extend down the drainage system. The restricted dispersion necessitates basing geochemical reconnaissance surveys on collection and analysis of samples from the headwater organic-rich swamps at a higher sample density and resulting higher cost than in areas where a lower sample density is acceptable due to a wider dispersion.     

干旱荒漠覆盖区隐伏金矿上方覆盖层三维地球化学分布模式

深穿透地球化学已被证明是干旱荒漠区寻找隐伏矿的有效方法,但其对元素在覆盖层中的分布模式的探知还较少。为此,在新疆金窝子金矿运用了空气动力反循环钻探技术,以揭示元素三维分布模式,并了解元素迁移轨迹和迁移机理。形成的元素三维分布图表明：(1）元素异常在矿体上方不同深度覆盖层中具有继承性;(2）在覆盖层垂向剖面上,Au趋向于在顶层和底层富集,中间层含量较低;(3）底部异常主要分布在覆盖层和基岩接触部位的低洼位置;(4）底部异常横向延伸,范围较窄,仅数十米宽,而地表异常分布范围广,可扩展至数千米。     

Genesis and continuity of quaternary sand and gravel in glacigenic sediment at a proposed low-level radioactive waste disposal site in east-central Illinois

The Illinois Department of Nuclear Safety has characterized the Martinsville Alternative Site (MAS) for a proposed low-level radioactive waste disposal facility. The MAS is located in east-central Illinois approximately 1.6 km (1 mi) north of the city of Martinsville. Geologic investigation of the 5.5-km² (1380-acre) site revealed a sequence of chiefly Illinoian glacigenic sediments from 6 to 60 m (20–200 ft) thick overlying two major bedrock valleys carved in Pennsylvanian strata. Relatively permeable buried units include basal, preglacial alluvium; a complex of intraglacial and subglacial sediment; englacial deposits; and supraglacial fluvial deposits. Postglacial alluvium underlies stream valleys on and adjacent to the site. In most areas, the buried sand units are confined by low-permeability till, lacustrine sediment, colluvium, and loess. The distribution and thickness of the most extensive and continuous buried sand units have been modified considerably by subglacial erosion, and their distributions have been influenced by the buried bedrock valleys. The most continuous of the various sand units were deposited as preglacial and postglacial alluvium and are the uppermost and lowermost stratigraphic units at the alternative site. Sand units that were deposited in englacial or ice-marginal environments are less continuous. Aquifer pumping tests, potentiometric head data, and groundwater geochemistry analyses indicate minimal interaction of groundwater across localized interconnections of the permeable units.     

A comparative study of stream water and stream sediment as geochemical exploration media in the Rio Tanama porphyry copper district,Puerto Rico

To test the relative effectiveness of stream water and sediment as geochemical exploration media in the Rio Tanama porphyry copper district of Puerto Rico, we collected and subsequently analyzed samples of water and sediment from 29 sites in the rivers and tributaries of the district. Copper, Mo, Pb, Zn, SO₄^2?, and pH were determined in the waters; Cu, Mo, Pb, and Zn were determined in the sediments. In addition, copper in five partial extractions from the sediments was determined. Geochemical contrast (anomaly-to-background quotient) was the principal criterion by which the effectiveness of the two media and the five extractions were judged.Among the distribution patterns of metals in stream water, that of copper most clearly delineates the known porphyry copper deposits and yields the longest discernable dispersion train. The distribution patterns of Mo, Pb, and Zn in water show little relationship to the known mineralization. The distribution of SO₄^2? in water delineates the copper deposits and also the more extensive pyrite alteration in the district; its recognizable downstream dispersion train is substantially longer than those of the metals, either in water or sediment. Low pH values in small tributaries delineate areas of known sulfide mineralization.The distribution patterns of copper in sediments clearly delineate the known deposits, and the dispersion trains are longer than those of copper in water.The partial determinations of copper related to secondary iron and manganese oxides yield the strongest geochemical contrasts and longest recognizable dispersion trains. Significantly high concentrations of molybdenum in sediments were found at only three sites, all within one-half km downstream of the known copper deposits. The distribution patterns of lead and zinc in sediments are clearly related to the known primary lead-zinc haloes around the copper deposits. The recognizable downstream dispersion trains of lead and zinc are shorter than those of copper.     

距今30ka前后我国西北沙漠地区古环境

本文根据实地野外观测和前人的研究,对我国西北干旱地区约30kaB.P.时的环境特征进行了综合分析.选用的古环境指标主要来源于风成沉积、湖泊沉积及河流沉积,年代主要依靠14C测年.依据巴丹吉林沙漠沙丘上的钙质胶结层、植物残体、塔克拉玛干沙漠河流沉积以及巴丹吉林沙漠腹地及其西北缘的高湖面,认为在30kaB.P.前后,我国西北干旱地区雨量较高,气候较湿润.柴达木盆地、腾格里沙漠西部、古尔班通古特沙漠西部及内蒙古地区湖泊同期的高湖面也支持这一观点.     

Evidence for a cold,dry full-glacial climate in the American Southwest

Analysis of the evidence concerning full-glacial (27,000–13,000 yr BP) time in the American Southwest has resulted in a reinterpretation of the past climate. After correction for previous errors, which include the use of (1) the July 0°C isotherm as an indicator of modern snowline and (2) relict cirques at the head of heavily glaciated valleys as indicators of past snowline, orographic snowline is estimated to have been about 1000 m lower. This, combined with similar depression estimates for timberline and for cryogenic deposits, results in an annual cooling estimate of 7–8°C. The cooler temperatures caused deposition of coarse “bouldery” alluvial-fan sediments by streams draining areas at high elevations, as well as hill-slope stability, soil development, and subsurface weathering in the lower desert ranges. Reliability of paleoclimatic inferences from water budgets of the extinct paleolakes is questioned on the basis that they exclude groundwater effects. However, recalculation of two water budgets following traditional methods indicates that lowered evaporation rates accompanying a 7–8°C annual cooling would have sufficed to maintain these lakes. Similarly, increased soil moisture would have allowed coniferous woodland to grow ～700 m lower into the deserts, the maximum recorded by Pleistocene pack rat middens. Therefore, no significant increase in annual precipitation is inferred for full-glacial times.     

The Effects of Applying the Association of Al, K, and Sn in Stream Sediments for Gold Exploration in Different Landscapes

Geochemical data of altered wall rocks are important for the metallogenic prognosis of hydrothermal gold deposits. Indicator elements of altered wall rocks such as K, Al, As, Sb, and Hg have been successfully used to assess gold anomalies in lithogeochemical survey. However, such researches have rarely been done in stream sediment survey for the exploration of gold from various landscapes. On the basis of the geochemical analysis of altered wall rocks of gold deposits in the cold desert areas of Gansu (甘肃) Province in Northwest China, it is found that the combination of Al, K, and Sn could serve as an important indicator of hydrothermal gold deposits and can be used to evaluate the metallogenic prospective of gold anomalies in stream sediments. More studies performed in the cold grassland areas and the moderate-low relief mountainous areas showed that, both weak and strong geochemical anomalies can be extracted, if strictly abiding by the ways of calculation and addition of the binary values of the indicator elements with equal weight, and this provides the sound delineation of metallogenic perspective areas.     

Lake stratigraphy implies an 80 000 yr delayed melting of buried dead ice in northern Russia

Sediment cores from lakes Kormovoye and Oshkoty in the glaciated region of the Pechora Lowland, northern Russia, reveal sediment gravity flow deposits overlain by lacustrine mud and gyttja. The sediments were deposited mainly during melting of buried glacier ice beneath the lakes. In Lake Kormovoye, differential melting of dead ice caused the lake bottom to subside at different places at different times, resulting in sedimentation and erosion occurring only some few metres apart and at shifting locations, as further melting caused inversion of the lake bottom. Basal radiocarbon dates from the two lakes, ranging between 13 and 9 ka, match with basal dates from other lakes in the Pechora Lowland as well as melting of ice‐wedges. This indicates that buried glacier ice has survived for ca. 80 000 years from the last glaciation of this area at 90 ka until about 13 ka when a warmer climate caused melting of permafrost and buried glacier ice, forming numerous lakes and a fresh‐looking glacial landscape. Copyright © 2003 John Wiley & Sons, Ltd.     

Sedimentology and depositional model for glaciolacustrine deposits in an ice-dammed tributary valley, western Tasmania, Australia

Quaternary sedimentary successions are described from the Linda Valley, a small valley in western Tasmania that was dammed by ice during Early and Middle Pleistocene glaciations. Mapping and logging of exposures suggest that an orderly sequence of deposits formed during ice incursion, occupation and withdrawal from tributary valleys. Four principal sediment assemblages record different stages of ice occupation in the valley. As the glacier advanced, a proglacial, lacustrine sediment assemblage dominated by laminated silts and muds deposited from suspension accumulated in front of the glacier. A subglacial sediment assemblage consisting of deformed lacustrine deposits and lodgement till records the overriding of lake-bottom sediments as the glacier advanced up the valley into the proglacial lake. As the glacier withdrew from the valley, a supraglacial sediment assemblage of diamict, gravel, sand and silt facies formed on melting ice in the upper part of the valley. A lacustrine regression in the supraglacial assemblage is inferred on the basis of a change from deposits mainly resulting from suspension in a subaqueous setting to relatively thin and laterally discontinuous laminated sediments, occurrence of clastic dykes, and increasing complexity of the geometry of deposits that indicate deposition in a subaerial setting. A deltaic sediment assemblage deposited during the final stage of ice withdrawal from the valley consists of steeply dipping diamict and normally graded gravel facies formed on delta foresets by subaqueous sediment gravity flows. The sediment source for the delta, which prograded toward the retreating ice margin, was the supraglacial sediment assemblage previously deposited in the upper part of the valley. A depositional model developed from the study of the Linda Valley may be applicable to other alpine glaciated areas where glaciers flowed through or terminated in medium- to high-relief topography.     

二连盆地中东部含铀古河谷构造建造及典型矿床成矿模式研究

二连盆地为中国北方重要的聚煤沉积盆地,同时也发育赛汉组古河谷,古河谷在盆地内呈北东向带状展布,河谷内发育巴彦乌拉、赛汉高毕及哈达图等多个铀矿床。铀矿床具有"同河谷多矿床、同河谷多类型"的特点。作者通过对含铀古河谷构造-建造的研究,将赛汉组古河谷与铀成矿有关的构造演化划分为6个阶段。沉积前断陷期构造形成了古河谷建造沉积的带状谷地;断坳转换期湖相沉积的灰色泥岩,为铀成矿间接提供了还原物质;坳陷期沼泽化沉积,为铀成矿提供了直接还原介质;赛汉组上段热-重力沉降期河流、辫状河三角洲沉积,形成主要的铀储层。挤压隆升剥蚀期,受构造掀斜抬升,影响了成矿作用的类型及规模;成矿后期的热沉降期,导致新一轮的沉积充填,起到保矿的作用。通过对赛汉组沉积体系、砂分散体系等特征的研究,发现下白垩统赛汉组下段沿短轴方向主要发育冲积扇-扇三角洲-湖沼沉积体系,长轴方向发育辫状河三角洲-湖沼沉积体系。赛汉组上段主要发育河流沉积体系,砂体较发育,沿古河谷呈朵状、带状分布,矿床主要产于赛汉组上段古河谷砂体内。建立了赛汉组古河谷内典型矿床的矿床成矿模式,将赛汉组古河谷的矿床成矿模式划分为巴彦乌拉潜水-层间氧化式、赛汉高毕潜水氧化式及哈达图层间氧化式。     

Facies characteristics, morphology and depositional models of clay-slide deposits in terraced fjord valleys, Norway

Many bedrock-confined fjord valleys along the Norwegian coast contain thick accumulations of fine-grained sediments that were deposited during and after the last deglaciation. The deposits gradually emerged above sea level due to glacioisostatic uplift, and fjord marine sedimentation was gradually followed by shallow marine and fluvial processes. During emergence terraces and river-cut slopes were formed in the valleys. Subsequent leaching of salt ions from the pore water in the marine deposits by groundwater has led to the development of quick clay. The deposits are subject to river erosion and destructive landslides involving quick clay. Most slides are of prehistoric age. Others are known from modern observations as well as from historic records.Landforms such as distinct slide scars or the hummocky terrain of slide deposits may be strongly modified by secondary processes. In addition, deposits from the most liquid part of quick clay slides may have planar surfaces. Clay-slide deposits on a fluvial or deltaic terrace, therefore, are not always easily recognized from morphology, and only exposures may reveal their internal structures and allow them to be distinguished from overbank flood sediments. Detailed sedimentological work shows that slide deposits in such setting consist of distinct facies containing reworked marine sediments. We propose three facies successions of clay-slide deposits that form a continuum. The dominant components of these succession types are: slightly deformed blocks of laminated clay and silt (A), highly deformed clay and silt with gravel clasts (B) and massive to stratified clay and silt with scattered clasts (C). We suggest that in many cases a basal muddy diamicton is a characteristic, and possibly diagnostic feature. Processes and depositional models are interpreted from the different succession types. The results may be relevant for identifying clay-slide deposits elsewhere and may be useful during general mapping of fjord marine deposits and characterization of slide-prone areas as well as during identification of prehistoric slides.