THE APPLICATION OF REMOTE SENSING TECHNIQUE ON GEOLOGICAL INVESTIGATION OF PLACER DEPOSIT

The practice has proved that it is an economic and effective method to investigate placer gold deposit by using multi-level information sources of remote sensing and multi-variate analysis methods, especially for the area with a sparse population and difficult condition like the Da Hinggan Mountains, China.The information sources used in our work includes Landsat TM, aerial infrared photography and their mosaic image maps and enlarged photos with different scales. According to statistic data, in the study area the gold-bearing rocks are mainly granite, alaskite, granodiorite and some old metamorphic rocks. On gold-bearing geological structures, the fault zones in the four directions (NE, NNE, NW and EW) are obvious, in which NNE and EW are the most key fault zones. On fluvial geomorphology the flow courses stored placer are in the tributaries of the 4th and 5th levels, especially in straight or slight curve reaches. On the basis of analysis the interpretative signs were set up, and the interpretative

Exploratory Potential for Gold Placer Deposits in the Coastal Range, BioBío Region, South-Central Chile

Many gold placers located in the Coastal Range of south-central Chile have been exploited commercially during the past decades;nevertheless and until now, there are not any exploration studies of these placers and their basement. In order to provide an overview of exploratory potential, the stream sediments that are part of several gold placers in the northwest area of the BioBío region are analyzed, which have been registered on the basis of empirical evidence from artisanal mining activities. The overview consists of two goals: 1) determine the presence of auriferous occurrences (stream sediments and basement) and 2) identify potentially favorable areas to find gold placer deposits. Through optical microscopy this study characterized the metallic and non-metallic mineralogy of the basement, along with geochemical analyses of stream sediments and surrounding rocks of the placer deposits. The geochemical results show two sectors with high precious metal contents in sediments (up to 24 ppm of Au and 8 ppm of Ag) and two rocky outcrops with Au (757 and 41 ppb). Additionally, there are depressions in the study area that have received large amounts of sediments (reaching up to 170 m-thick), which are favorable places for the accumulation of auriferous sediments from nearby valleys due to the tectonic and structural conditions where they are located. Then, these results show an exploratory potential for gold placers and can be useful to delineate future exploration strategies in the Coastal Range of south-central Chile.

Reconstruction of the Indigenous Sources of Gold of the Glu-Kharinsky Placer (Kolyma River Basin, Magadan Region, Russia)

A comparative analysis of typomorphic features of gold placers and indigenous sources of gold was carried out for the Glukharinsky ore-placer node (the Nadezhda deposit and Glukharinskoye, Tyomnoye, and Tyi-Jurye ore occurrences). A correlation between fineness of placer native gold and composition of relic minerals preserved inside gold particles was obtained for the first time. This made it possible to establish mineral parageneses of native gold from potential indigenous sources. The study of placer gold fineness in combination with com-position of mineral inclusions allowed us to identify seven types of gold paragenesis: petzite-hessite with a fineness of 855‰, pyrite-polybasite-galena (a fineness of 670‰), bismuth telluride (900‰), cosalite-vikingite (790‰), galena (870‰), glaucodot (950‰), and hydrohematite (840‰). It was also shown that the placer contains the material from ore occurrences of different formation: gold-quartz-porphyry occurrences in granitoids (Au-Te-Bi type) and gold-silver occurrences. The method developed by us allows one to estimate the percentage of each ore source in placer formation.

Characterization of Gold Bearing Placers and Associated Minerals in the Elogo Region (North-West Congo Republic)

The Elogo region has been subjected to craft industry and semi-industrial mining for gold-bearing placers, since the colonial times. It is actually undergoing an intensive exploration for a primary gold deposit. The goal of this study is to contribute to the exploration of the primary gold deposit in the Elogo Region (North-West of Congo Republic). The methodology consisted of characterization of placers deposits by their lithology, mineralogy and the gold grains shape, in order to constrain the source of gold with the respect to the local geology. The results obtained show that alluviums are polygenic and yields seventeen mineral species composed of zircon, olivine, magnetite, ilmenite, gold, garnet, rutile, coltan, cassiterite, monazite, apatite, amphibole, tourmaline, pyrite, limonite, chromite, and amphibole. The morphoscopy of gold grain shows single grains and grains with quartz inclusions that suggest their relationship with quartz veins. The gold grains are flattened, sub-flattened, and rounded. The northern region of Elogo characterized by a dominance of coarser quartz-included gold grains indicates a proximal proparte origin (less than 50 m), while the southern region, showing less coarse and more evolved grains with choc marks, appears to be associated with a distal pro-parte origin (more than 300 m). The multivariate statistical analysis shows seven classes of samples corresponding to the mineralogical paragenesis suggesting various sources, consisting of high-grade metamorphic, granitoids, pegmatites, basic and ultrabasic rocks, and BIFs that provided minerals to the placers. Gold mainly comes from hydrothermal quartz veins and probably from the peptization of gold from the weathering of sulfides occurring in the BIF. In the Elogo region, gold exploration for primary deposits should look for and follow the hydrothermal system developed in this region. Chemical analysis for the gold grains and associated minerals is necessary to better guide the proposed geochemical prospecting.

Exploring Placer Gold Deposits through Integrated Geophysical and Geochemical Techniques at the Confluence of the Indus and Kabul Rivers,NW Pakistan

Analysis of the anomalous magnetic mineral intensities and geochemistry for placer gold deposits are presented for those of the Attock area at the confluence of the Indus and Kabul rivers in northwestern Pakistan.Two grids covering an area of 10 x18 m2 and 8 x10 m2 were analyzed using a G-858 Cesium Vapor Magnetometer.The anomalous zones obtained were plotted on contour maps,2 D and 3 D magnetic intensity maps.Based on the magnetic anomalies,grid-1 of the study area was sampled at three different anomalous zones for geochemical analysis.These zones contain gold concentrations,ranging from 2.11 ppm to 6.109 ppm with an average of 4.01 ppm.Increase in gold concentration in the subsurface within the anomalous zones indicates that magnetometer survey followed by a geochemical analysis can potentially narrow down the gold-bearing anomalous zones.

Global placer中框约束问题非线性共轭梯度算法的改进

Global placer其实是一个矩形框约束问题。关于如何改进当前的无约束非线性共轭梯度算法来应用于矩形框约束问题,本文提出了一个实用的改进方法并且通过一些数学方法解决了程序实现执行中数据精度和稳定性问题。改善当前无约束的共轭梯度求解算法是非常有价值的,可以帮助客户缩短产品进入市场的时间周期和减少最后的总成本如最后总的布局布线的导线长度。

Niobium–tantalum oxide minerals in alluvial placer deposits from the Ngoura area,East-Cameroon

This work presents a preliminary mineralogical characterization of Nb-Ta oxide minerals from alluvial placers located in the Ngoura area,eastern Cameroon.The heavy minerals are characteristic of short hydromechanical transport and highlight the stability of Nb-Ta oxides during the weathering and transport.Nb-Ta mineralization in placer deposits from the Ngoura area may derive from local sedimentation.The assemblage of Nb-Ta oxides in the studied placers consists of tapiolite-(Fe)and tantalite-(Mn).Tapiolite-(Fe)exhibits high concentrations in Ta2O5(78.07-80.46 wt%)and FeO(12.18-13.66 wt%)and plots within a narrow range of Ta*(0.900-0.933)and Mn*(0.037-0.119),which correspond to the ranges typically observed in tapiolite-(Fe)worldwide.Tantalite-(Mn)shows Ta2O5 contents ranging from 62.17 to 69.45 wt%,Nb2O5 from 12.09 to 17.37 wt%,MnO from 7.63 to 12.49 wt%and FeO from 1.48 to 6.62 wt%.It is also characterized by a wider range of Mn<sup>*(0.538-0.891)and relatively homogeneous Ta/(Ta+Nb)(0.683-0.779)ratios.Texturally,the studied Nb-Ta minerals exhibit oscillatory zoning characterized by bright Ta-rich zones alternating with dark Nb-rich zones.This oscillatory zoning is progressive in some minerals and the alternating bands may appear regular to wavy with gradual transitions.Oscillatory zoning in Nb-Ta oxides from the Ngoura placers is considered to be a primary magmatic feature and is tentatively explained as a result of magmas mixing,rapid cooling or degassing/decompression of the igneous system.The geomorphology and the tropical humid climate of the eastern region offer suitable conditions for the deposition of alluvial placers.Therefore,niobium-tantalum minerals from the Ngoura placers must have been sourced from the weathering and erosion of alkaline granites and pegmatites widespread in the study area.

Mineralogical Characteristics and its Prospecting Significance of Gold-Mercury Minerals in Davao Gold Placer in Mindanao Islands, Philippines

This paper has systematically researched mineral assemble and the characteristics of gold-mercury minerals in Davao Placer in Mindanao Islands, Philippines. The results show that reflection force of gold-mercury minerals has a strong-weak-strong of changes features as mercury＇s content in minerals increased. Otherwise their hardness of gold-mercury minerals reduced. While the hardness of gold-mercury minerals, which have isometric crystal structure, they are gradually become larger, the goldmalgam and r-Goldmalgamite just be found to exist as natural edge of gold-mercury mineral grains. Overall, mercury content is gradually reduced from the edge to the centre of gold-mercury minerals particles, but mercury-bearing in edge of the grains is lower than in the middle. Combination of the background of geological mineralization, this paper suggests that there are mantle-derived deposits such as Platinum, chromium in Philippines, which accompanied ultramafic-mafic magmation. It＇s most likely to found some large or extra large scale polymetallic deposits of gold and mercury, as well as coastal placers of gold, platinum, etc.

基于Innovus混合放置的布局规划方法优化

随着集成电路后端设计中宏单元数量增多,传统布局规划方法效率低且耗时,而自动布局规划的混合放置(MP)技术存在物理规则违例数量多、电压降大和功耗高等问题。针对传统方式和MP方式的不足,提出了一种优化的MP布局规划方法,通过控制宏单元通道空间和标准单元密度大小、固定边界宏单元位置及脚本修复TSMC芯片集成检查(TCIC)违例的方法解决MP技术存在的问题。研究结果表明,优化的MP方式保留了MP技术的性能、功耗和面积(PPA)优势,且相比于传统方式布线长度优化了28%,时序违例优化了65%,功耗优化了609%。该方案可为多宏单元大规模设计的布局规划提供参考。

金属砂矿勘查中基本分析项目与地质品位的确定--讨论及建议

基本分析项目与地质品位的确定是金属砂矿勘查中基础且重要的环节,对我国金属类砂矿开发与利用产生直接影响。我国现有砂矿地质品位确定方法存在一定差异性,模糊性或矛盾性,对这些重要问题进行讨论是有必要的。本文以多年来滨浅海金属类砂矿调查经验为基础,结合前人研究成果,介绍目前勘查中砂矿品位的主流表示与计算方法,分析其优缺点,继而提出面向新一轮找矿突破要求的改进方法并探讨其可行性。结果表明:金属砂矿勘查品位确定应遵循与时俱进、正确对待误差、综合评价原则,并寻求勘查成本与勘查风险的最佳结合点。建议不采用传统重矿物淘洗+鉴定方法作为基本分析获得矿物品位,推荐视勘查阶段、勘查主要目的、勘查类型灵活选用重矿物含量(THM%)测定、化学分析法换算、自动矿物分析(如MLA)3种方法作为基本分析项目。圈定矿体的边界品位与最低工业品位可直接利用“重矿物含量”或采用“综合圈矿指标”。应选取重点研究区,将其与传统方法进行对比研究与验证,同时对砂矿勘查技术规范体系相关内容进行广泛深入讨论,寻求共识,以求加快补充修订。

南海及邻域砂矿资源分布特征及成矿模式

南海及邻域具有多样的地形地貌和丰富的物源,为海洋固体矿产资源的形成和分布提供了物质来源和堆积环境。为系统查明南海及邻域砂矿资源分布情况,本文通过对南海及邻域2606个站位表层沉积物样品进行粒度测试、碎屑矿物鉴定,以及重矿物的品位计算,分析了南海及邻域有用矿物砂矿资源以及建筑用砂资源分布特征并预测了远景区,总结了砂矿成矿模式。结果表明,南海及邻域具有远景的矿种主要有锆石、钛铁矿、金红石、锐钛矿、独居石和石榴子石等;重矿物高品位矿点主要集中在南海东北陆架、菲律宾海盆、南部陆架,重矿物异常区主要位于周缘陆架浅水区以及越东外陆架浅水海域、菲律宾海盆。锆石品位异常区的范围最大,达到工业品位的面积也最大;其次是磁铁矿、钛铁矿、独居石的异常区;锐钛矿、金红石异常区的面积相当;石榴子石品位异常范围最小。根据砂矿的分布规律、大地构造背景、成矿条件以及成矿元素特征,圈定了24个有用重矿物砂矿成矿远景区和6个成矿带。沉积物中砂(0.063~2 mm)含量大于50%的建筑用砂的远景区9个,主要分布于海南岛西南面到台湾海峡南部一线以北海域,其次为南海南部礼乐滩、万安滩、曾母暗沙附近海域,其余海域极为罕见。基于南海砂矿资源分布特征,初步建立了近岸型、潮流砂脊型、古河道埋藏型、峡口型、陆架坡折带型等五种砂矿成矿模式,为海砂资源进一步勘查提供方向和建议。

威海市东部滨海新城海域海砂资源分布及特征

对威海东部滨海新城海域海底底质样品、浅地层剖面、地质钻探、多波束测量等资料进行了分析,探讨了该区海砂资源的类型、分布特征及沉积环境。结果表明:研究区海砂资源主要分布于鸡鸣岛和苍家岛潮沟附近,均为埋藏砂矿,以粉砂和细砂为主,含泥量较高,可用作回填用砂。研究区埋藏砂矿主要形成于晚更新世末期,成因类型主要有古冲积、残留和海积等类型。

方格网法在资源量估算中的应用探索——以宁夏某建筑用砂矿为例

本文以宁夏某地建筑用砂矿详查项目为研究背景,采用方格网法(fgwtf)建立DEM模型估算资源量,并选取块段采用垂直投影平行断面法进行校验,证实该方法估算结果可靠。通过应用实践,表明方格网法(fgwtf)适宜范围不规则矿区的资源量估算,且具有微地形控制程度高、估算过程简单可视、数据精度高、估算效率更高的优点。

西藏矿山生态环境现状及保护研究——以藏北砂金矿为例

西藏自治区作为建设国家生态安全屏障的重点,对我国生态安全有举足轻重的作用.随着对西藏的矿产资源开发力度的加大,矿山迹地环境问题日益突出.西藏因其独特的高原气候和特殊的自然条件,其矿山迹地的环境治理有别于一般区域的治理经验.在深入西藏阿里、那曲等地区矿山迹地实地考察、测绘勘测的基础上,对研究区高分辨率影像进行遥感解译,以典型矿山为例分析说明了西藏自治区矿山环境现状及矿山环境保护中存在的问题.结果表明:西藏粗放式矿山开发遗留的大量采坑和弃土弃渣等引发了一系列严重的社会及环境问题,增加了生态恢复难度.为保障西藏自治区矿山可持续发展,针对这些问题,根据藏北高原极度脆弱的生态环境特点,以藏北高原生态环境可持续发展为原则,探讨适合西藏砂金矿山迹地治理的理论和技术支撑,在管理和政策上对矿山生态环境保护提出了建设性意见.

大兴安岭漠河砂金富集区岩金找矿思路

大兴安岭漠河地区砂金极为丰富,充分研究区内的地质构造特征、砂金分布和富集规律、区域剥蚀深度等,利用砂金信息寻找岩金是区内岩金找矿工作的有效手段之一.利用砂金矿只能寻找剥蚀残留的那一部分岩金矿.对物源区剥蚀程度和探矿构造分析研究,是在砂金富集区内圈定岩金找矿靶区的关键.溶蚀系数可指示砂金是近或远原生源金矿.Pb同位素可指示成矿母岩,利用矿石、岩浆岩、地层和基底铅同位素全方位对比来判别铅同位素的来源是一种近年来国际上认同的办法,砂矿评价中利用铅同位素寻找母岩已获得成功.本区砂金Pb同位素特征值与源区极为相似,可做为砂金富集区寻找岩金的指示元素.本文旨在论述砂金富集区内砂金与岩金空间位置关系、成因上的联系及岩金成矿特点,为下一步岩金找矿工作提供思路和方法.

中国砂金矿床吨位—品位模型

矿床品位—吨位模型研究属于学科前沿领域 ,它是系统勘查理论的重要组成部分。依据“1997年全国矿产储量数据库”资料 ,对全国 394个砂金矿床建立了地质模型、品位模型、吨位模型、吨位—品位联合模型 ,模型类型包括频率直方图、累积频率分布图 ;分别总结了砂金矿床品位及吨位分布的典型数学地质特征。

几种不同类型金矿的高精度磁测异常特征

许多金矿的赋矿(或伴生)岩石与其周围岩石之间存在着磁性差异,如与中基性脉岩有关的金矿成因模式矿床、破碎蚀变火山岩型金矿等,在其上能观测到磁异常。即使是河床底部缝隙中与砂金相伴沉淀的重砂,由于铁磁性矿物含量较高,与其附近砂石之间存在磁性差异,利用高精度质子磁力仪,也能观测到比较明显的磁异常。在西藏自治区及四川省一些金矿床(点)上的研究取得了良好的进展,对砂金矿、锑金伴生型金矿,中基性脉岩型金矿上的高精度磁测异常特征有了新的认识,为利用高精度磁测方法间接寻找金矿积累了经验。

藏北地区砂金指纹特征及其对原生金的指示意义

砂金指纹(化学成分)特征是利用砂金寻找原生金的重要手段之一。研究表明,藏北地区砂金成色具明显的不均匀性,化学成分在东、西部地区变化较大,反映区内砂金对原生金具有继承性,并受后期地质作用改造明显,表明其原生金来源可能具有近距离搬运的多来源特征;自然金微量元素含量特征则指示:本区原生金的类型主要为浅成低温热液型,矿石富含As、Sb、Cu、Pb、Zn,且剥蚀程度较小,在砂金富集区附近有望找到规模较大的原生金矿床。

我国砂金矿开采造成的环境地质问题与对策

针对我国砂金矿以船采为主,水力及挖掘机开采为辅的开采方式及点多面广的特点,分析了我国砂金矿开采造成的对农田、草地、植被和河道破坏的地质环境问题及产生的原因,提出了砂金矿开采区土地复垦、环境治理的对策建议.

吉林珲春小西南岔地区重砂金矿物的找矿指示意义

吉林小西南岔地区珲春河流域砂金广泛分布,有残坡积、洪积、河谷砂矿和阶地砂矿,以河谷砂矿工业意义最大,砂金资源对寻找区内的岩金矿床具有很好的指示意义。根据收集到的小西南岔地区928件重砂数据,提取金矿物颗粒数、总质量、最大颗粒粒径、平均质量等参数,结合汇水盆地分布提取成矿预测参数。根据重砂金矿物质量、颗粒、粒径大小、平均质量等特征分布变化趋势,追索矿源母体,最终为寻找岩金矿床提供依据,为研究区内金矿资源的进一步勘查评价提供有利信息。