Litho-Tectonic Architecture of the Dialafara Area, Kédougou-Kéniéba Inlier, Integration of New Field Data and Geophysics

The Dialafara area is part of the highly endowed Kédougou-Kéniéba Inlier (KKI), West-Malian gold belt, which corresponds to a Paleoproterozoic window through the West African Craton (WAC). This study presents, first of all, an integration of geophysical data interpretation with litho-structural field reconnaissance and then proposes a new litho-structural map of the Dialafara area. The Dialafara area shows a variety of lithology characterized by volcanic and volcano-sedimentary units, metasediments and plutonic intrusion. These lithologies were affected by a complex superposition of structures of unequal importance defining three deformation phases (DD1 to DD3) under ductile to brittle regimes. These features permit to portray a new litho-structural map, which shows that the Dialafara area presents a more complex lithological and structural context than the one presented in regional map of the KKI. This leads to the evidence that this area could be a potential site for exploration as it is situated between two world-class gold districts.

Lithostructural Control of the Gold Mineralization of the Douta Permit of African Star Resources (Kédougou-Kéniéba Inlier, Southeastern Senegal)

The Douta permit of African Star Resources/Thor Explorations, located in the southeast of Senegal, in the Kédougou-Kéniéba Inlier (western part of the West African Craton), is dominated to the East by metasedimentary formations such as greywackes, shales, graphitic shales, quartzites, cherts, claystones and breccias characteristic of the Dialé-Daléma basin. To the West, the mafic formations of the Mako volcanic belt are the most common. Metasedimentary rocks are associated with metavolcanosedimentary terms found at the contact zones between the two (2) Birimian groups. These different geological formations are cut by mafic dolerite and gabbro sills and/or dykes, as well as quartz and microgranite veins. The Douta gold project is crossed from North to South by the MTZ (Main Transcurrent Zone), generally oriented NE-SW and becoming N-S towards the North. The permit is characterized by several shear corridors. The rocks are affected by brittle, brittle-ductile to ductile deformations. The gold mineralization is hosted by a NE-trending shear corridor called the Makosa corridor (Makosa shear zone), therefore sub-parallel to the MTZ. It has a subvertical dip (75˚ to 85˚ to the NW). It is associated with a hydrothermal phase characterized by quartz-sericite-epidote-fine, disseminated pyrite and arsenopyrite ± albite ± chlorite paragenesis. These minerals testify to the existence of a low degree of metamorphism (greenschist facies, epizonal domain) in the area. However, metamorphism reaches amphibolite facies in some places, particularly in the vicinity of intrusive bodies, with the presence of hornblende (amphiboles) and plagioclase. The gold mineralization is mainly hosted by two (2) metasedimentary lithological units: meta-greywackes and shales.

基于Inliers跟踪统计的RGB-D室内定位与地图构建

室内移动机器人同时定位与地图构建(SLAM)的前端位姿估计与后端优化容易受运动模糊的干扰。为此,提出一种基于Inliers跟踪统计的室内定位与地图构建算法。对RGB图像进行特征提取和匹配,运用RANSAC算法得到Inliers后,通过对Inliers数量的跟踪与统计剔除受相机运动影响的模糊图像,然后利用最近邻迭代的非线性优化方法求解相机位姿。在此基础上,通过闭环检测和优化后的全局位姿拼接出运动轨迹和三维稠密点云图。实验结果表明,相对RGB-D SLAM算法,该算法能够有效提高SLAM系统的建图鲁棒性与精度。

Petrological and Structural Approach to Understanding the Mechanism of Formation and Development of Paleoproterozoic Calc-Alkaline Volcanic Rocks of West Africa’s Craton: An Example of the Mako and Foulde Groups (Kedougou Inlier in Western Senegal)

The calc-alkaline volcanic formations in the western part of the Kedougou-Kenieba inlier crop out in three complexes: the Foulde in the North and the areas of Mako and Baniomba in the South. These complexes which either combine with the tholeiites or cut across the sedimentary formations are composed of thin veins and massive lava flows. They have many petrographic similarities and show chemical characteristics that resemble those of island-arc rocks. At the tectonic level, the D1 deformation phase preceding the formation of the basins and the transpressive tectonics including an oblique convergence may account for the structural evolution of the Mako volcanic belt. Its occurrence in different basins may be evidenced by the composition of some lithophilic components like the Sr, Ba, U, Rb and the composition of clinopyroxenes enriched in TiO2, FeO, Na2O in the Foulde calc-alkaline volcanic rocks that developed in a sedimentary environment.

Geological mapping and mining prospecting in the Aouli inlier(Eastern Meseta,Morocco)based on remote sensing and geographic information systems(GIS)

Landsat 8 Oli,ASTER,and Sentinel 2A satellite images processing was used to map geological formations,lineaments and hydrothermal alteration minerals in the Aouli inlier,as a case study to illustrate the application of digital images processing and Geographic Information System(GIS)in geological mapping and mining prospecting.Principal Component Analysis(PCA)applied to the Landsat images allowed good lithological discrimination and contributed to the updating of available geological maps.The Automatic lineament extraction from Sentinel images revealed the main tectonic structures affecting Aouli inlier.The ratio bands(b5+b7)/b6 and the false color composite(b4/b6,b2/b1,b3/b2)allowed the hydrothermal alteration minerals mapping from Aster images.Combined with available geological data and field observations,the satellite derived data were integrated and analyzed in a GIS software to establish mining prospecting guides.The results showed that the anomaly zones are intimately linked to NNE-SSW and NW-SE oriented faults and to highly fractured areas developing argillic and Fe rich alterations.Verified via field survey,this approach was successfully applied to the Aouli inlier to rapidly target potential areas to be explored in the tactical phase.This provides a model for future prospecting efforts for similar mineral deposits in other areas.

Two-Generation of Sphalerite from Pb-Zn Mineralization of Riasi Inlier, Jammu and Kashmir, India: Evidences from Sulphur Isotopes

Precambrian carbonate sequence of Riasi Inlier hosts epigenetic lead-zinc mineralization in the form of pockets, lenses and veins. The mineralization is having variable Pb:Zn ratio and shows lithological preferences. The sphalerite rich pockets are concentrated within the dolostone of older Trikuta Formation while galena rich mineralization occurs in form of veins, lenses and pockets hosted within siliceous varieties of dolostone and quartzite belonging to younger Khairikot Formation. Sulphur isotope geochemistry is reported in the present paper for the sphalerire and galena from the area for first time. Overall?δ34S of sulphides varies from (+9.67‰ to +34.42‰). Sphalerite ores hosted within older Trikuta Formation and younger Khairikot Formation, however, show different?δ34S values. It ranged from +9.67‰ to +10.59‰ for the sphalarite hosted in Trikuta Formation and from +18.38‰ to +34.42‰ for sphalerite hosted within Khairikot Formation. Sulphur isotopic data and ore petrographic data suggest that there is two-generation of sphalerite present in the area.

The Late Neoproterozoïc Continental Tholeiitic Basalts of the Toubkal Inlier (Western High-Atlas, Morocco): A Post-Pan-African Rifting Witness in the Northern Margin of the West African Craton

The late Neoproterozo&#239c Toubkal inlier (Ancient Massif of the High-Atlas, Morocco) contains two igneous basaltic series (Tircht and Sidi Chamharouch). Investigated rocks display characteristics of within-plate continental tholeiitic and are similar to rocks originated in orogenic contexts. The geochemical results allow the assumption that subduction active processes are indirectly responsible for the genesis of theses rocks. The orogenic signature is linked probably to a Pan-African magmatic source previously metasomatized in the northern margin of the West African Craton.

Refining the Stratigraphy of the Taghdout Group by Using the U-Pb Geochronology of the Taghdout Sill(Zenaga inlier,Anti-Atlas,Morocco)

The Anti-Atlas belt of southern Morocco is situated on the northern edge of the West African craton(WAC).It corresponds to a broad anticlinorium some 800 km long and 200 km wide,trending ENE-WSW,parallel to the

基于预检验的快速随机抽样一致性算法

随机抽样一致性算法RANSAC(randomsampleconsensus)是在计算机视觉领域内应用最广泛的Robust估计算法之一,但是RANSAC算法计算效率较低.提出一种基于模型参数预检验的快速RANSAC算法(previewmodelparametersevaluationRANSAC,简称PERANSAC).算法在RANSAC算法模型参数检验前,加入预检验过程,在保证计算结果置信概率不变的前提下,过滤掉大量偏差较大的模型参数,提高了RANSAC算法的整体效率.模拟数据和真实图像数据实验结果表明,此算法和RANSAC算法计算精度保持一致,计算速度高于RANSAC算法.

ODIC-DBSCAN:一种新的簇内孤立点分析算法

长期以来,孤立点的检测一直聚焦于簇边缘的离散点,当聚类后簇的数目低于实际数目,或孤立点被伪装在簇内的情况下,簇内孤立点的判定则会更加困难.为判定簇内孤立点,提出一种基于密度聚类DBSCAN (Density based spatial clustering of application with noise)的簇内孤立点检测方法 ODIC-DBSCAN (Outlier detection of inner-cluster based on DBSCAN).首先在建立距离矩阵的基础上,通过半径获取策略得到针对该点集的k个有效半径Radius集合,并据此构造密度矩阵;然后建立点集覆盖模型,提出了相邻有效半径构造的覆盖多维体能够覆盖点集的思想,并通过拉格朗日乘子法求取最优的覆盖多维体数目之比,输出点比阈值组;最后重建ODIC-DBSCAN的孤立点检测方法,以簇发生融合现象作为算法终止的判定条件.实验通过模拟数据集,公开benchmark与UCI数据集共同验证了ODIC-DBSCAN算法,展示了聚类过程;分析了算法性能;并通过与其他聚类、孤立点判定方法的对比,验证了算法对簇内孤立点的判定效果.

一种全自动稳健的图像拼接融合算法

提出了一种全自动稳健的图像拼接融合算法。此算法采用 Harris角检测算子进行特征点提取 ,使提取的精度达到了亚像素级 ,然后以特征点邻域灰度互相关法进行特征点匹配得到了初步的伪匹配集合 ,并运用稳健的RANSAC算法将伪匹配点集合划分为内点和外点 ,在内点域上运用 L M优化算法精确地估计出了图像间的点变换关系 ,最后采用颜色插值对交接处进行颜色过渡。整个算法自动完成 ,它对有较大误差或错误的特征点数据迭代过滤 ,并用提纯后的数据来做模型估计 ,因而对图像噪声和特征点提取不准确有强健的承受能力。在参数估计时 ,以特征点的坐标位置误差而不是亮度误差来构造优化函数 ,克服了以往算法对光照的敏感性 ,使算法更具有实用性。实验结果表明 ,该算法融合效果比较理想 ,鲁棒性强 。

西昆仑塔木一带山前推覆构造样式浅析

通过大量野外地质调查以及构造剖面测制工作,根据构造样式和变形特征,将西昆仑塔木一带山前推覆构造带,由南西往北东划分为5个带,变形程度依次降低。通过对卡克巴西阿格孜构造窗的调查,显示本区域至少存在2期推覆构造活动:第一期发生在晚古生代末期,具后展式特征;第二期发生于晚新生代开始,显示出前展式特征。

近邻点一致性的随机抽样一致性算法

随机抽样一致性算法是计算机视觉领域中应用广泛的多视几何图像参数估计方法之一。为提高在高噪声条件下原算法计算效率,提出基于匹配点对邻近点集合一致性的过滤方法,可提高原初始匹配点对集合的内点比例,减少使用RANSAC时寻找参数时的抽样次数。宽基线图像极线几何计算的多组实验表明:提出的算法能够保持与原RANSAC一致的结果,并有效地提高计算速度。

松辽盆地东北隆起区砂岩型铀矿成矿条件分析

运用水成矿理论,对松辽盆地东北隆起区砂岩型铀矿成矿的铀源、构造、沉积、水文地质、古气候等条件进行了分析,认为该区具有良好的砂岩型铀矿成矿地质条件.具体表现在区内存在受构造运动影响地层隆起遭受剥蚀的构造天窗,在盆地边缘发育向南西倾斜的斜坡带;有利铀成矿的河流相、三角洲相砂体发育;泥岩-砂岩-泥岩结构层发育良好,有含水透水层和隔水层;补-径-排机制较完善,水动力条件较好,具有渗入型自流水盆地特征.该区具有良好的勘探前景.

一种改进的相邻概率随机抽样一致性算法

为了解决图像配准中因外点引起迭代次数激增而导致的配准效率低下的问题,提出一种改进的相邻概率随机抽样一致性算法。首先通过自适应优化内点被采用概率,淘汰外点从而形成正循环采样,结合模型评价函数估计出临时模型并得到临时内点集,再根据内点相邻原则筛选部分内点进行重采样,最后采用预检验技术得到最佳模型参数。实验结果表明:在数据外点率较高的情况下该算法能有效减少迭代次数,缩短算法时间,从而提高了算法效率。

医疗保险按病种付费的国际借鉴

目前,国际上已有许多国家和地区实施了按病种付费制度,且基本都采用DRGs付费方式。而我国目前还处在单病种付费的试行阶段,各地病种付费的制度设计都较为简单,不利于按病种付费制度的长远推行。本文系统总结美国、德国、中国台湾医疗保险按病种付费的费用测算与支付方法,深入分析这三个地区在正常/异常病例界定,以及正常/异常病例的费用测算和支付标准制定方面的实际做法,为完善我国按病种付费的制度设计,促进按病种付费制度的高效运行提供借鉴。

基于K近邻一致性的特征匹配内点选择算法

宽基线图像特征匹配是计算机视觉应用中一项极具挑战性的工作。由于图像之间存在较大的差异,宽基线图像初始特征匹配的结果中不可避免地包含大量的外点。提出了K近邻一致性算法来实现从宽基线图像初始匹配结果中快速选出高可靠性的点对。该算法采用仿射不变的结构相似度来衡量两组K近邻特征点的结构相似性。K近邻一致性算法采取由粗到精的策略,通过K近邻对应一致性检测和K近邻结构一致性检测两个步骤来选择内点。实验结果表明,提出的算法在查准率、查全率和运行速度等方面接近或优于当前几种最新的内点选择算法,可适用于存在大范围的视点、尺度和旋转变化的宽基线图像。

局部不变特征匹配的快速内点选择算法

为了快速、准确地从局部不变特征初始匹配中选取内点,提出一种联合利用特征点在位置、尺度和方向上的分布一致性进行内点选择的算法.首先,采用均值漂移算法按视差对特征点对聚类实现粗选;然后找出特征点在类内的K近邻特征,再利用特征的尺度和方向估算每个特征点对所在的二局部图像区域之间的变换参数,并计算K近邻匹配相似度;最后,依据K近邻匹配相似度从粗选获得的候选匹配集中选出内点.实验结果表明,该算法在准确率、召回率和速度方面优于当前最新的内点选择算法,对图像间大幅度的视点、尺度和旋转变化具有较高的鲁棒性.

基于误差阈值和最小二乘图像拼接关系矩阵的实现

为了获得图像最佳拼接效果,对相邻图像间变换矩阵的求解问题进行研究,提出了一种全稳健的图像拼接算法。此算法采用SIFT进行特征点提取,初步得到了特征点匹配的伪匹配集合,并运用稳健的误差阈值法将伪匹配点集合划分为内点和外点,在内点域上运用误差的最小二乘优化算法精确地估计出了图像间的点变换关系,最后采用颜色插值对交接处进行颜色过渡。整个算法对有较大误差或错误的特征点数据迭代过滤,并用提纯后的数据来做模型估计,因而对图像噪声和特征点提取不准确有强健的承受能力。在参数估计时,以特征点的坐标位置误差而不是亮度误差来构造优化函数,克服了以往算法对光照的敏感性,使算法更具有实用性。实验结果表明,该算法拼接效果理想,鲁棒性强,具有较高的使用价值。

一种新型遥感图像配准方法

提出了一种新型全自动稳健的遥感图像配准算法。首先,在图像二维平面空间和尺度空间中同时检测局部极值作为特征点,并在特征点邻域提取局部不变特征描述子——尺度不变特征变换(SIFT)。然后,利用距离测度进行SIFT特征匹配得到初步的匹配集合。最后,运用稳健的随机采样一致性(RANSAC)算法将匹配点集划分为内点和外点,在内点域上精确地估计出图像变换模型。实验利用仿真数据测试了SIFT特征的可重复性和可匹配性,利用卫星图像验证了该自动配准算法的有效性和稳健性。