江苏镇江韦岗铁矿区深部找矿前景分析   总被引：1，自引：0，他引：1       下载免费PDF全文

黄震  黄建平 《江苏地质》2008,32(3):184-188

镇江韦岗铁矿是一个已经勘查开发数十年的老矿山,目前保有资源储量保证程度已达严重危机。分析矿区成矿地质条件和矿床特征,铁矿体主要分布在碳酸盐岩层与中酸性侵入岩的接触带上,铁矿体普遍磁性强,且在地表形成一定规模的磁异常,梯度北陡南缓,向南有规则地递减呈梯形散开,说明矿体有一定的延伸。深部已施工的见矿钻孔和井中磁测异常对应,反映矿区深部-200m～-800m找矿前景良好。  相似文献   

安徽池州铜山铜矿深部找矿实践与启示   总被引：4，自引：0，他引：4  

SUN Ya-li  张立明  ZHANG Hong-zhou  刘青 《云南地质》2008,27(1):40-45

铜山铜矿资源储量日益枯竭。危机矿山接替资源勘查中,采用地质、物探综合手段圈定异常区,经深部钻探验证,取得突破。  相似文献   

云南勐兴铅锌矿矿体空间特征及预测前景     

赵长江  高建国  王开林  丁秀芳 《云南地质》2008,27(4):496-501

借助ArcGIS软件的空间统计分析功能,对矿体主要参数进行分析,获得矿体空间特征。认为铅和锌品位具有明显的正相关,品位与厚度也属正相关。在此基础上对矿区找矿远景区进行初步圈定,为探矿工程的布置提供依据。  相似文献   

Deep structure of the Central Alps in the light of recent seismic data     

H. Laubscher 《International Journal of Earth Sciences》1994,83(2):237-248

The deep seismic reflection traverses across the Central Alps (NFP 20, ECORS-CROP) contain a new set of data on the lower crust which has been interpreted in different ways. One currently fashionable model depicts the European lower crust (ELC) as gently dipping below the Adriatic crust. However, this model requires that an observed sharp termination of the ELC under the internal border of the External Massifs is due to the non-transmission of organized seismic energy through the complex upper crust. This explanation is questioned as other reflections in this and similarly complex areas are recorded, and as the same sharp termination of the ELC under the internal border of the External Massifs is observed on all seismic lines for a length of 300 km. A tectonic — metamorphic cause appears to more satisfactorily explain the obeservations, and therefore an alternative model combining surface and deep geophysical data is proposed. It consists of three mutually largely decoupled tectonic levels. (1) The shallow obducted part or lid, bounded at its base by the combined Late Miocene Jura and Lombardic basal thrusts. Estimates of shortening based on balanced sections are at least about 100 km. (2) The intermediate level between the brittle-ductile transition and the top of the subducted mantle. It contains a stack of lower crust imbrications (with a minor admixture of upper mantle) accommodated by (inducted into) the ductile middle crust. Estimates of shortening based on area balancing are again of the order of slightly more than 100 km. (3) The subducted upper mantle, for which there are no reflection data.In the Central Alps the Late Miocene phase was dextrally transpressive, producing flower structures at the shallow level (External Massifs); the stacks of lower crust imbrications at the intermediate level may be the equivalent of the External Massifs at that level. Inverted flower structures of the subducted mantle are possible, but no detailed data are available.  相似文献   

A pronounced dry event recorded around 4.2 ka in brine sediments from the northern Red Sea     

Helge W. Arz  Frank Lamy  Jürgen Ptzold 《Quaternary Research》2006,66(3):432-441

Partly laminated sediments were sampled from the brine-filled, anoxic Shaban Deep basin in the northern Red Sea. At about 4200 cal yr BP more than two millennia of anoxic sedimentation is replaced by a sub-oxic facies strongly suggesting the episodic absence of the brine. At the same time stable oxygen isotopes from surface dwelling foraminifera show a sharp increase (within less than 100 yr) pointing to a strong positive salinity anomaly at the sea surface. This major evaporation event significantly enhanced the renewal of deep water and the subsequent ventilation of the small Shaban Deep basin. The timing and strength of the reconstructed environmental changes around 4200 cal yr BP suggest that this event is the regional expression of a major drought event, which is widely observed in the neighboring regions, and which strongly affected Middle East agricultural civilizations.  相似文献   

Non-volcanic deep low-frequency tremors accompanying slow slips in the southwest Japan subduction zone   总被引：5，自引：1，他引：5  

Kazushige Obara  Hitoshi Hirose 《Tectonophysics》2006,417(1-2):33

Non-volcanic deep low-frequency tremors in southwest Japan exhibit a strong temporal and spatial correlation with slow slip detected by the dense seismic network. The tremor signal is characterized by a low-frequency vibration with a predominant frequency of 0.5–5 Hz without distinct P- or S-wave onset. The tremors are located using the coherent pattern of envelopes over many stations, and are estimated to occur near the transition zone on the plate boundary on the forearc side along the strike of the descending Philippine Sea plate. The belt-like distribution of tremors consists of many clusters. In western Shikoku, the major tremor activity has a recurrence interval of approximately six months, with each episode lasting over a week. The tremor source area migrates during each episode along the strike of the subducting plate with a migration velocity of about 10 km/day. Slow slip events occur contemporaneously with this tremor activity, with a coincident estimated source area that also migrates during each episode. The coupling of tremor and slow slip in western Shikoku is very similar to the episodic tremor and slip phenomenon reported for the Cascadia margin in northwest North America. The duration and recurrence interval of these episodes varies between tremor clusters even on the same subduction zone, attributable to regional difference in the frictional properties of the plate interface.  相似文献   

Les failles récentes des Grands-Moulins (Savoie) : un Sackung (tassement gravitaire) majeur dans les Alpes françaises     

Jean-Claude Hippolyte  Marc Tardy  Gérard Nicoud 《Comptes Rendus Geoscience》2006,338(10):734-741

In Savoy, the Grands-Moulins recent fault scarps, previously interpreted as seismic fault ruptures, are in fact part of a major Sackung (deep seated gravitational spreading) of the French Alps (9 km long). We mapped more than 60 sackung scarps, some of them reaching 1330 m long and 30 m high. These antislope scarps stop the active screes and offset relict Dryassic rock glaciers by 16 m. We present geomorphologic observations attesting for their gravitational origin. This Sackung is primarily due to glacial debuttressing, while seismic shaking could be a triggering mechanism. To cite this article: J.-C. Hippolyte et al., C. R. Geoscience 338 (2006).  相似文献   

Weathering characteristics of arctic islands in northern Norway     

yvind Paasche  Jrund Raukleiv Strmse  Svein Olaf Dahl  Henriette Linge 《Geomorphology》2006,82(3-4):430-452

The arctic islands of the Lofoten-Vesterålen archipelago in northern Norway have a wide distribution of weathered land surfaces commonly located above 250 m with several apparent similarities. In order to investigate the characteristics of (deep) weathering in this region, northern Langøya and Hadseløya were chosen for in-depth analyses. Eight weathering profiles were excavated from various surfaces, and the stratigraphies were logged in detail. Material was collected throughout the weathering horizons, and all samples were subsequently analysed for clay mineralogy (< 63 μm fraction) and grain size distribution. The sampling strategy was complemented by samples from additional saprolites and other landforms such as moraines and rock glaciers. The XRD results indicate that the presence of secondary minerals, such as gibbsite (Al(OH)₃) and kaolinite (Al₂Si₂O₅(OH)₄), are very common throughout the profiles. Gibbsite is an extreme end product of silicate weathering and usually associated with a warmer and more humid climate, as found in Scandinavia during the Tertiary. The grain size analyses (< 63 μm) show that the finer silt fractions (< 8 μm) tend to be high in the profiles (20–40%), with significant amounts of clay (5–15%) demonstrating that the regolith itself is susceptible to frost sorting mechanisms.¹⁰Be exposure dates from in situ quartz knobs on tors and boulders of local origin suggest > 40,000 years of subaerial conditions. Considering the steady surface erosion, this figure should be viewed as an absolute minimum age estimate. Mapping of the superficial sediments and geomorphological features of the study areas has revealed several common morphological features, which indicate dominance of glacial and periglacial processes in the areas lying below the lower boundary of blockfields (c. 250 m). The weathering mantles are not a periglacial end product, but rather a relict tertiary landform that were modulated by permafrost processes as well as biological processes at later stages. The regolith cover constrain the vertical extension of warm-based Quaternary ice sheets challenging the notion of a parabolic ice mass consuming every mountain top of Lofoten and Vesterålen.  相似文献   

青藏高原东缘缅萨洼金矿成矿流体地质地球化学特征   总被引：3，自引：0，他引：3  

李晓峰毛景文  刘娅铭徐庆鸿　朱和平 《岩石学报》2005,21(1):189-200

缅萨洼金矿位于中国中轴构造带的中南段,青藏高原的东缘,赋存于金河-箐河断裂带次级断裂羊坪子韧性剪切带中本文根据对该矿床硫化物流体包裹体的氦氩同位素、硫化物的硫同位素以及与硫化物共生的石英的流体包裹体特征、成分以及氢氧同位素组成的测定,讨论了缅萨洼金矿的成矿流体来源及其矿床成因。结果显示,该矿床硫化物流体包裹体中的3He/4He变化较小,为0.69-0.82,显示了地幔流体参与成矿作用的可能性。而4He的含量变化范围较大,一般在2.19-10.62×10-6cm3STP/g(方铅矿除外)与3He/4He相比,40Ar/36Ar的比值则变化较小,一般为251-509。而硫化物的δ34S同位素变化范围在-1.8-2.2‰,平均值为0.5‰,说明硫的地幔来源。与硫化物共生的石英的流体包裹体的类型主要有富液相的盐水溶液包裹体、富气相的盐水溶液包裹体、三相CO2包裹体、纯液相CO2包裹体以及有机流体包裹体。成矿流体的氢氧同位素则显示成矿流体来源于岩浆水(或地幔流体)与大气降水的混合流体,本文认为,缅萨洼金矿的成矿流体为地幔流体与大气降水的混合流体,是渐新世印度大陆与亚洲大陆碰撞之后,该地区大规模走滑与剪切作用过程中,局部伸展作用的产物。  相似文献   

深井水氡主要干扰因素及映震效能分析          下载免费PDF全文

王志高 《地震工程学报》2002,24(3):251-256,261

对甘肃省玉门青6井和平凉泾川泾3井两口深水井的水氡及辅助项目观测资料采用多元逐步回归、相关距平、一阶差分等方法进行处理，分析并排除了主要干扰因素，显示出两井在肃南5.4级、托莱6.0级和礼县5.1级地震前有明显异常，对两井的映震效能和地震预报前景进行了评价。  相似文献