厚层覆盖区综合物化探方法找金试验研究——以广西兴安金石金矿为例     

胡云沪  罗先熔  王桂琴  杜建波  张小路 《矿产与地质》2002,(5)

在兴安金石金矿外围 4号分散流异常区 ,通过地电化学提取金测量法 ,查明测区存在 5个走向规模小于 5 0 m的金异常区 ,W( Au) 最大值为 72 .4× 10 - 9,高出背景值十几倍 ,并藉综合土壤吸附汞测量 ,高精度磁测和激发极化法等多种物化探方法来确定这些异常区的地质、地球化学和地球物理特征 ,提出金矿成矿的有利部位在金的地电提取高异常区、高汞量异常区、高磁性异常区、低视电阻率异常区和中等视极化率异常区的“三高一低一中”的找矿模式。确定测区的北北东角 (右下角 )一带具备有利的金矿成矿条件  相似文献   

中条山同善天窗铜矿类型及找矿新认识     

王昊  郭红党  薛克勤 《华北地质》2002,(Z1)

在总结同善构造—剥蚀窗内成矿地质条件的前提下 ,运用成矿系列理论 ,把区内具有多种表现形式的变基性火山岩型、变砂岩型、大理岩型三大类铜矿分成了八种亚类 ,认为诸类铜矿与区内广泛发育的新太古代基性岩存在着成生联系 ,铜矿的形成经历了一个复杂的过程。早期的海底火山喷发带来的铁、铜、硫等成矿物质 ,经过最初的海水富集、火山活动末期的热液作用富集以及后来区域变质叠加富集进而形成了这一系列矿床。同时提出了新的找矿思路、找矿方法及找矿靶区。  相似文献   

华北陆块北缘西段中元古代与裂谷作用有关的铁、稀土、多金属矿床特征及成因     

曹秀兰 《华北地质》2002,(Z1)

华北陆块北缘西段狼山—白云鄂博裂谷系中元古代形成的大型多金属矿床 ,是我国重要的铁、稀土、铜、铅、锌矿产地。矿床为产于沉积岩中热水沉积型多金属矿床。其形成受地层、构造控制 ,与裂谷作用有着密切的关系。裂谷系内外分支的地质环境及矿床矿种不同 ,导致矿床特征及成因具有一定差异。白云鄂博铁、稀土矿床为钾、钠、磷等含量较高的热水沉积型 ,霍各乞铜、铅、锌多金属矿床为与中基性火山岩有关的过渡热水沉积型 ,东升庙和甲生盘等铅、锌多金属矿床为热水沉积型。文中将对上述矿床分别进行论述。  相似文献   

Geochronology of Gold Deposits and Its Implication for Metallogenesis in the Fengxian-Lixian Area, Qinling Orogenic Belt, China   总被引：2，自引：0，他引：2  

Jianzhong FENG  Dongbo WANG  Xueming WANG  Shicai SHAO  Tifeng LI 《Resource Geology》2002,52(3):263-272

Abstract: A series of super large‐scale and large‐scale Pb and Zn, and Au deposits are distributed in the Qinling orogenic belt, China. Gold deposits were generally ascribed to Carlin‐type originated from circular meteoric water. Visible and coarse‐grained gold (up to over 3mm in grain size) was recently identified in some gold deposits in the Fengxian‐Lixian area, Qinling. Au‐bearing quartz lodes related to magmatism were discovered in the Xiaogouli gold deposit. Two types of Au‐bearing quartz veins, i.e., NW‐trending quartz veins and NE‐trending quartz veins cutting strata are widely present in the Baguamiao gold deposit. Both are spatially associated with each other. The former is generally snake–like, S‐shape or zigzag, which was resulted from plastic deformation by ductile shearing, being generally cut by the latter. The latter is generally linear with widely developed bleaching alteration zones in its adjacent wall rocks, which symbolizes the superimposition of brittle deformation and filling and metasomatism of magmatic hydrothermal solution in ductile shear zones after uplifting of the shear zones near the surface. The NW‐trending quartz veins contain Au of lower than 3ppm. The NE‐trending quartz veins contain Au of more than 3 ppm, so that NE‐trending quartz veins and the adjoining altered rocks are important ores. The NW‐trending Au–bearing quartz vein was dated as 210.61.26 to 232.581.59 Ma by ⁴⁰Ar–³⁹Ar method, i.e., late Indosinian epoch (Triassic). The NE‐trending Au–bearing quartz vein was dated as 131.910.89 to 197.451.13 Ma by ⁴⁰Ar–³⁹Ar method, i.e., Yanshanian epoch (Jurassic). The ⁴⁰Ar–³⁹Ar age of the NW‐trending Au–bearing quartz veins represents the age of the ductile shear formation. The isotope data of the NE‐trending quartz veins indicate that gold mineralization was closely related to Indosinian and Yanshanian granite intrusives not only in time and space, but also in origin.  相似文献   

Caractérisation des paragenèses et des paléocirculations fluides dans l'indice d'or de Bleı̈da (Anti-Atlas,Maroc)Characterization of the paragenesis and the fluid palaeo-circulations in the gold showings of Bleida (Anti-Atlas,Morocco)     

Ahmed Barakat  Christian Marignac  Marie-Christine Boiron  Mohamed Bouabdelli 《Comptes Rendus Geoscience》2002,334(1):35-41

The gold showings at Bleida are hosted in Late Pan-African N50–80 °E quartz–hematite–chlorite 1 tension lenses that are related to the activity of major sinistral sub-east–west thrusts. Ores result from three superimposed stages of fluid migration. Gold occurs in microcracks offsetting the earlier minerals. Fluids evolved from COHN compositions with a saline component to boiling aqueous fluids. Pressure and temperature decreased from 50 MPa and 300 °C to less than 4 MPa and 150 °C. Thus, the gold showings at Bleida were formed in a typical geothermal (epithermal) setting, likely controlled by the Late Pan-African magmatism. To cite this article: A. Barakat et al., C. R. Geoscience 334 (2002) 35–41  相似文献   

Viscous damping formulation and high frequency motion propagation in non-linear site response analysis     

Youssef M. A. Hashash   《Soil Dynamics and Earthquake Engineering》2002,22(7)

Non-linear time domain site response analysis is widely used in evaluating local soil effects on propagated ground motion. This approach has generally provided good estimates of field behavior at longer periods but has shortcomings at relatively shorter periods. Viscous damping is commonly employed in the equation of motion to capture damping at very small strains and employs an approximation of Rayleigh damping using the first natural mode only. This paper introduces a new formulation for the viscous damping using the full Rayleigh damping. The new formulation represents more accurately wave propagation for soil columns greater than 50 m thick and improves non-linear site response analysis at shorter periods. The proposed formulation allows the use of frequency dependent viscous damping. Several examples, including a field case history at Treasure Island, California, demonstrate the significant improvement in computed surface response using the new formulation.  相似文献   

Simultaneous radio and optical observations of the mid-latitude atmospheric response to a major geomagnetic storm of 6–8 April 2000     

E. L. Afraimovich  Ya. F. Ashkaliev  V. M. Aushev  A. B. Beletsky  V. V. Vodyannikov  L. A. Leonovich  O. S. Lesyuta  Yu. V. Lipko  A. V. Mikhalev  A. F. Yakovets 《Journal of Atmospheric and Solar》2002,64(18)

Basic properties of the mid-latitude traveling ionospheric disturbances (TIDs) during the maximum phase of a major magnetic storm of 6–8 April 2000 are shown. Total electron content (TEC) variations were studied by using data from GPS receivers located in Russia and Central Asia. The nightglow response to this storm at mesopause and termospheric altitudes was also measured by optical instruments FENIX located at the observatory of the Institute of Solar-Terrestrial Physics (51.9°N,103.0°E), and MORTI located at the observatory of the Institute of Ionosphere (43.2°N, 77.0°E). Observations of the O (557.7 and 630.0 nm) emissions originating from atmospheric layers centered at altitudes of 90 and 250 km were carried out at Irkutsk and of the O₂(b¹∑_g⁺−X³∑_g⁻) (0-1) emission originating from an atmospheric layer centered at altitude of 94 km was carried out at Almaty. Our radio and optical measurement network observed a storm-induced solitary large-scale wave with duration of 1 h and a wave front width of no less than 5000 km, while it traveled equatorward with a velocity of 200 m/s from 62°N to 38°N geographic latitude. The TEC disturbance, basically displaying an electron content depression in the maximum of the F2 region, reveals a good correlation with growing nightglow emission, the temporal shift between the TEC and emission variation maxima being different for different altitudes. A comparison of the auroral oval parameters with dynamic spectra of TEC variations and optical 630 nm emissions in the frequency range 0.4–4 mHz (250–2500 s periods) showed that as the auroral oval expands into mid-latitudes, also does the region with a developed medium-sale and small-scale TEC structure.  相似文献   

南向行星际磁场事件与磁暴关系的研究   总被引：5，自引：5，他引：5       下载免费PDF全文

刘绍亮  李立文 《地球物理学报》2002,45(3):297-305

利用172-182年IMP-8飞船的太阳风观测资料和相应地磁活动性指数Dst和AE,研究了43个南向行星际磁场事件期间太阳风和磁层的耦合问题. 与这43个事件对应的地磁暴是中等的和强的磁暴(Dst＜-50nT). 结果表明:(1) 在43个事件中有11个(约占25.6髎)紧随激波之后,18个处于激波下游流场中(占42髎),其余14个(占33髎)和激波没有关连. 绝大多数事件都伴有太阳风动压和总磁场强度的增加;(2) 当行星际晨昏向电场强度EI＞-4mV/m时,只引起磁亚暴,对Dst指数没有明显影响. 仅当EI＜-5mV/m时,磁亚暴和磁暴才会同时出现;(3) 太阳风动压的增加会增强能量向环电流的输入,但不是密度和速度单独起作用,而是以PK=ρV2的组合形式影响能量的输入;(4) 虽然行星际磁场(IMF)南向分量BZ对太阳风和磁层的耦合起着关键作用,但IMF的BX和BY分量相对于BZ的大小对太阳风向磁层的能量传输也有一定影响. 当BX、BY相对BZ较大时能量耦合加强.  相似文献   

Study of weathering processes developed on old piedmont surfaces in Western Spain: new contributions to the interpretation of the “Raña” profiles     

E. Molina Ballesteros  M. Cantano Martín   《Geomorphology》2002,42(3-4)

The Hercynian basement of the Iberian Peninsula was uplifted by the Alpine orogeny during the Tertiary. It gave rise to a set of block mountains and tectonic grabens, one of which is the Ciudad Rodrigo Basin. It is located in Western Spain and forms a westward extension of the great Tertiary Duero Basin. The sediments filling this graben are of continental origin, their ages ranging from Palaeogene to Quaternary. Morphologically, the southern part of this basin forms a set of piedmont surfaces (the “Raña” surfaces) appearing above the terrace system of the present rivers. This paper examines the weathering processes developed over these old piedmont surfaces using micromorphological, XR diffraction, scanning electron microscopy (SEM) and microporosity techniques.The Raña sediments are rich in quartzite pebbles and gravel within a clayey matrix. Once deposited, these materials underwent important in situ weathering processes under somewhat hydromorphic conditions, of which hydrolysis, ferrolysis and xerolysis were the most important. All these processes gave rise to: (1) transformation of most of the clasts of shists and slates into a matrix causing the destruction of the original sedimentary structures and a relative concentration of the resistant lithologies (quartzites and quartz); (2) important changes in the clay fraction, leading to a predominance of kaolinite in the upper levels of the profiles, (3) release of elements from primary minerals, Fe being one of the most important, and (4) redistribution of matter, mainly clay and Fe oxyhydroxides, within the profiles.The coexistence of seasonal periods with pF higher than 4.2 repeated over a long time, together with poor internal and external drainage conditions, are the cause of the special features displayed by Raña deposits.  相似文献   

Use of Noise to Augment Training Data: A Neural Network Method of Mineral–Potential Mapping in Regions of Limited Known Deposit Examples     

Warick M. Brown  Tamás D. Gedeon  David I. Groves 《Natural Resources Research》2003,12(2):141-152

One of the main factors that affects the performance of MLP neural networks trained using the backpropagation algorithm in mineral-potential mapping isthe paucity of deposit relative to barren training patterns. To overcome this problem, random noise is added to the original training patterns in order to create additional synthetic deposit training data. Experiments on the effect of the number of deposits available for training in the Kalgoorlie Terrane orogenic gold province show that both the classification performance of a trained network and the quality of the resultant prospectivity map increasesignificantly with increased numbers of deposit patterns. Experiments are conducted to determine the optimum amount of noise using both uniform and normally distributed random noise. Through the addition of noise to the original deposit training data, the number of deposit training patterns is increased from approximately 50 to 1000. The percentage of correct classifications significantly improves for the independent test set as well as for deposit patterns in the test set. For example, using ±40% uniform random noise, the test-set classification performance increases from 67.9% and 68.0% to 72.8% and 77.1% (for test-set overall and test-set deposit patterns, respectively). Indices for the quality of the resultant prospectivity map, (i.e. D/A, D × (D/A), where D is the percentage of deposits and A is the percentage of the total area for the highest prospectivity map-class, and area under an ROC curve) also increase from 8.2, 105, 0.79 to 17.9, 226, 0.87, respectively. Increasing the size of the training-stop data set results in a further increase in classification performance to 73.5%, 77.4%, 14.7, 296, 0.87 for test-set overall and test-set deposit patterns, D/A, D × (D/A), and area under the ROC curve, respectively.  相似文献