低山丘陵荒漠景观区 1:5万化探方法研究——以东疆夹白山地区化探普查及异常查证为例

水系密度大，上游水系汇水面积小，沉积物成分分布不均，元素迁移距离短是东天山低山丘陵荒漠景观区水系及其沉积物的特点，东疆夹白山地区1：5万化探普查采用水系沉积物测量的方法，采样密度一般5－6点／km^2，重要区域异常和成矿有利地段采样密度为8点／km^2,GPS定位，多点组合采样，在异常查证中，充分利用航空，航天遥感图像资源航空遥感资料，取得较好的找矿效果。     

丘洛金矿的发现是水系沉积物测量找金的成功范例

丘洛金矿是沿川西高原鲜水河断裂带,在长200、宽20公里范围内进行1:20万水系沉积物测量时发现的微细浸染型金矿。化探Au,Hg,As,Sb综合异常是本区微细浸染型金矿的找矿标志。由于水系沉积物测量采样点少,控制面积大,能有效地发现和快速圈定找金有望区,建议在工作程度低的山区大力推广水系沉积物测量找金方法。     

在伊朗的两次区域化探工作

通过在伊朗的2次区域化探工作,按水系沉积物测量基本原理,对采样点密度,组合样和作图方法进行对比和分析。     

安徽北淮阳沙坪沟钼矿区水系沉积物粒级试验研究

通过在安徽省北淮阳沙坪沟超大型钼矿区开展水系沉积物测量粒级试验,基于沙坪沟钼矿区分散流长度试验研究,对不同粒级(截取粒级和细粒级)水系沉积物粒级占比、元素含量变化特征等进行对比分析,探讨研究区主要成矿元素含量衰减特征。通过总结不同粒级水系沉积物的构成特征,认为在北淮阳地区开展水系沉积物测量适宜采用截取粒级的采样方法,为该地区开展1∶50 000化探普查提供参考。     

青海柴达木盆地周缘残山地球化学景观区化探采样方法探讨

青海柴达木盆地周缘残山地球化学景观区风成物分布十分普遍,通过研究该景观区水系沉积物、土壤、风成物和钙积层的分布特征,风成物和钙积层对水系沉积物的干扰特征,总结出一套多点组合采集岩屑代替水系沉积物的化探采样方法,在1∶25万区域化探、1∶5万普查化探以及1∶2.5万地球化学测量应用中,取得了明显的找矿效果。     

化探水系系统计算机模拟

本文阐述了水系的基本概念及其性质，设计了水系网的模拟模型，成功地建立了二维水系网，给出了计算方法和在化探中的初步应用。一个水系是由发源于若干个水源点的流线段组成的，这些流线之间具有地形关系，水流根据地形、构造及宕石类型等特点而进行运动，建立了主概率权随机游动的模拟模型，在决定随机游动最可能朝向的方位时考虑了一些确定性和非确定性控制因素，在产生水流移动轨迹中加入了自回避随机游动的算法，然后对水流线的交会进行处理，最终形成水系网。使用本方法产生了若干二维水系网并用该网计算理想条件下化学元素的迁移数量。由于水系网的构成要素已存于计算机，这种计算易于进行。结果表明：本方法成功地模拟出了二维水系网，而对水系系统的计算机模拟可用于定量地分析元素的迁移和分布等。     

1∶2.5万水系沉积物加密测量法在青海黑山地区找矿中的应用

青海省格尔木市黑山地区地表存在大量风成沙、风成黄土,为避免其影响,选择1∶2.5万水系沉积物加密测量方法开展前期化探扫面工作,确定采样点密度为40个点/km2,采样介质为水系沉积物,采样粒度为-10~+40目筛内样。通过元素含量、分布及组合特征分析,确定工作区滩间山群a段与侵入岩接触部位具有多金属成矿的可能;对圈出的5个综合异常进行查证,在AS4号综合异常内发现、控制了2条含矿矽卡岩带,并在Ⅰ号含矿矽卡岩带内初步圈定了2条铜多金属矿体,证明1∶2.5万水系沉积物加密测量方法在柴达木盆地周缘荒漠化中高山高原景观区具有较好的找矿效果。     

化探方法技术之取样粒度研究——以豫西牛头沟金矿1:5万化探普查为例

水系沉积物测量在我国是一门比较成熟的技术,但在不同的表生环境条件下开展水系沉积物测量的最佳采样粒度也不尽相同。通过对豫西熊儿山金矿田牛头沟矿区不同粒度土壤和水系沉积物样品风化过程中元素行为的研究,发现土壤和水系沉积物样品随粒度变细其风化程度增强,且这一特征在水系沉积物样品中表现更为明显。当样品粒度为4～100目时,元素含量逐渐升高或降低,变化趋势较为稳定;当粒度小于100目时,样品中元素含量发生显著变化,其主导风化机制可能发生了改变。热液成矿元素在土壤样品中相对富集在60～100目的粒度,在水系沉积物样品中相对富集在80～100目的粒度,参考各粒级样品在全粒级样品中的质量分数,建议选择60～100目作为水系沉积物测量的最佳采样粒度。这一粒级样品既可继承原岩在连续风化过程中的元素行为,又不受后期新的风化机制的明显影响,同时可最大限度地风化而分散以达到降低采样密度的需要。选择60～100目粒级样品在牛头沟金矿区开展了1∶5万化探普查,结果发现元素浓集中心与各矿段空间位置吻合较好,为豫西熊儿山地区开展1∶5万化探普查提供了技术参考。     

ICP-AES在新疆哈拉奇地区水系沉积物样品分析中的应用研究

本文采用四酸溶样ICP6300电感耦合等离子体发射光谱法测试了新疆哈拉奇地区水系沉积物样品中的Li P Ti V Cr Mn Co Ni Cu Zn Sr Y Nb Mo Ba La Pb B W Sn Cd 21种微量元素,明确了该方法测试样品中的Li P Ti V Cr Mn Co Ni Cu Zn Sr Y Nb Mo Ba La 16个元素的检出限、准确度、精密度满足规范（DZ/T0130.2006-2006）要求,而Pb B Cd Sn W5个元素测试质量不能满足规范要求,并对新疆哈拉奇地区水系沉积物采样粒度样品进行了分析测试,验证了该区化探扫面选择10-80目粒度是合适的,但在异常查证工作中要选择10-60目采样粒度更合理。     

青海省大柴旦双口山荒漠戈壁景观区1∶5万水系沉积物测量采样方法技术研究

青海省大柴旦双口山地区属于我国干旱荒漠戈壁特殊景观区之一,具典型大陆荒漠气候特征。依托2010年"青海绿梁山—双口山矿产远景调查"项目,开展了干旱荒漠戈壁特殊景观区1∶5万区域化探最佳采样粒度、采样密度等有效性方法实验。通过野外采样、室内分析及数据处理,确定了适合此特殊景观区的1∶5万水系沉积物测量采样方法技术:采样密度为6～8点/km2,采样粒级在-20～+60目,较为经济合理,技术上可行。     

矿产地球化学调查采样密度理论初步研究

矿产地球化学采样密度受到地球化学景观、水系分布和地貌发展阶段的控制,分形面密度、流域面积比和比降系数揭示了三者的形成机制.采样密度因素模型是采样密度理论的基础,可以指导矿产地球化学调查采样密度和采样布局的制定.     

Overbank sediment: a representative sample medium for regional geochemical mapping

In Scandinavia, most fluvial erosion takes place in the Quaternary glacial overburden at a restricted number of small source areas along individual drainage channels. As a consequence, a sample of active stream sediment is representative of only a very limited portion of the drainage area. This restriction makes stream sediment less reliable for regional exploration than generally expected. Overbank (levee or river-plain) sediment produced during large floods is an alternate more representative sampling medium. The sediment suspended during a flood has a much more widespread origin, and when the load is deposited upon the flood plain, nearly horizontal strata are formed and preserved at levels above the ordinary stream channel. A composite sample through a vertical section of such strata represents a great number of sediment sources that have been active at different times and forms an integrated sample of the entire catchment area. Because young sediments overlay older, the uppermost layers will be contaminated by pollutants in industrialized regions, but those at depth may remain pristine and will to a greater extent reflect the natural pre-industrial environment. In regional geochemical mapping, overbank sediment can be sampled at widely spaced sites, keeping costs per unit area low. Examples from Norway (1 sample station per 500 km²) show that overbank sediment produces broad geochemical patterns with high contrasts reflecting the bedrock geochemistry. Some patterns agree with known geological units and metallogenic provinces, but hitherto unknown major structures have also been indicated. A large Mo-deposit missed by a traditional stream survey is readily detected in the overbank sediment. It is concluded that overbank sediment is a promising alternate sample medium that should be tested in other physiographic regions.     

上宫构造蚀变岩型金矿床地质特征及化探找金经验

上宫金矿位于河南省西部熊耳山北麓,在该区1 020 km²范围内进行了1:5万的地球化学水系沉积物测量,按水系划分取样单元,取样本着"小沟多取,支流放稀,大河不管"的原则进行。本次水系沉积物测量的特点是:取样少,控制面积大,速度快,省钱、省人、省物,找矿效果好、经济效益好。本区水系沉积物测量中所发现的金异常,后经异常检查、地质普查评价及钻探验证,确定为一大型构造蚀变岩型金矿床。     

Geochemical dispersion from the Gamsberg Orebody, northwestern Cape, South Africa

The geochemical dispersion, in an arid environment, of Pb and Zn in stream sediments is examined with respect to size fractions and depth of sampling in a stream draining the Gamsberg Zn orebody.Sampling results indicate that there is a well-developed drainage train for approximately 8 km from the orebody for both Pb and Zn. The length of the drainage train is similar for both the minus 80 and minus 200-mesh size fractions but it is less for the minus 10, plus 40-mesh fraction.Higher metal values were obtained from samples taken from the surface of the stream bed. Metal values are generally lower in samples collected below the surface of the stream bed. The sampling position within the stream channel is not important.Sampling of the magnetite fraction from the stream sediments produced a well-defined Zn train for a distance of 14 km from the orebody. This train is more significant than the train found by normal sediment sampling.     

Geochemical mapping using a geomorphologic approach based on catchments

The Extended Sample Catchment Basin (ESCB) mapping technique, discussed in this paper, can be used to display the spatial distribution of geochemical variables measured in stream sediments taking into consideration the geomorphologic settings and the hydrographic patterns of surveyed areas. This approach is based on the association of an area of statistical representativeness with each sample, and on the assumption that the concentrations measured in the stream sediments can be considered as average reference values for this area.ESCBs can be easily identified considering the position of the sampling points within the hydrographic network and using the confluences between the streams of highest rank as break points for representing changes of the geochemical background. This approach, different from the traditional geostatistical and deterministic ones, does not consider the Euclidean distance among the sampling points as a measure of geochemical similarity but only refers to their functional relationship along the streams (following the water and the sediment flow) to measure their proximity.ESCBs can be seen as a specific development of previous techniques based on catchments and proves to be especially useful for supporting land planning in a preliminary survey phase while it is not specifically suitable for the identification of point sources of geochemical anomalies.Due to the fractal nature of the hydrographic network, all the procedures can be driven in a GIS environment by using digital terrain models apart from their spatial resolution.     

Areal versus linear evaluation of relationship between drainage basin lithology and geochemistry of stream and overbank sediments in low-order mountainous drainage basins

The comparison of two multiple regression models is based on the assumption that geochemical composition of the drainage basin alluvial sediments is derived primarily from the underlying bedrock lithology. The parent material is integrated with both stream sediment and overbank sediment geochemistry via the two essentially different approaches as regards the drainage basin geomorphological data: (1) as the relative area of influence representing a portion of the catchment basin occupied by a specific rock type and (2) as the relative “line” of influence representing a narrow zone of the underlying bedrock traversed by the perennial streams which form the active stream network. The model comparison is established on the goodness-of-fit test for both experimental designs and for the same set of data. Both experiments converge on the linear approach as the more appropriate model in evaluating the lithologic influence on the analysed sample media in small mountainous watersheds.     

TIN模型在地球化学勘查的计算机辅助制图中的研究和应用

以济源西北部 1∶ 5 0 0 0 0水系沉积物测量和嵩县小南沟金矿区地球化学勘查两个项目为实例 ,总结了 TIN模型在区域化探扫面和矿区化探剖面的辅助制图中的应用特点及需注意的问题 ,着重介绍了数据布局方法和调整 Delaunay三角剖分网技术 ,对在不规则采样区域边界带圈等值线的形状问题 ,首次采用虚设采样点的方法进行处理 ,取得了很好效果     

Drainage sampling for uranium in the Torrington district, New South Wales, Australia

A brief orientation study has been conducted to evaluate the use of drainage geochemical sampling for U in the granitic and forested terrain of the Torrington district of northeastern New South Wales. Anomalous U levels are present in both stream sediments and waters draining a known W prospect containing accessory U. The U dispersion is affected by interrelated environmental factors such as catchment physiography and the organic content of the stream sediments. The influence of organic content on U level in stream sediments is most significant. Variation in sediment organic content is related to accumulation of vegetal organic debris and charcoal in stream channels by sheetwashing of sparsely covered forest floors particularly in catchments of high topographic relief. The U is apparently absorbed onto the organic material from ephemerally flowing stream waters. Temporal variations in U content of stream sediment are indicated which necessitate careful consideration in planning and interpreting the results of a survey in this environment.     

1:5万地球化学水系沉积物测量两种采样密度效果对比

本文是广东地区一幅1:5万化探水系沉积物测量的结果。常规的取样密度为4－5点/km²,放稀测网是在常规样品中,每km²抽取一个样品。用同样的方法分析十四种元素并编图,对比两种测网的效果。较稀测网可能遗漏个别的单元素异常,但不会漏掉多元素异常。两种密度测网的单元素异常数量特征、空间分布及所提供的找矿信息相似。     

The suitability of floodplain sediment as a global sampling medium: evidence from China

Research undertaken by IGCP 259 (International Geochemical Mapping) indicates that wide-spaced sampling is a fundamental concept of international geochemical mapping as it appears to provide the only practical way to obtain a relative rapid (10–20 years) overview of global geochemistry. The main aim of this study is to test the suitability of floodplain sediment as a global sampling medium.Thirteen floodplain sediment samples and 13 stream sediment samples were taken at the exit of 13 super large drainage basins (SCB). The areal extents of these basins are in the order of 1000–10,000 km². Within each SCB, 3–11 stream sediment samples each representing a component catchment basin (CCB) of 100–1000 km² were also taken. Fourty nine elements were analyzed. The results were compared with the average values derived from calculating thousands of stream sediment data available from China's National Geochemical Mapping (RGNG) program. Strong similiarities were demonstrated in distribution and trends among the three levels of data. The set of floodplain sediment data shows great coincidence with RGNR stream sediment data.