【作者】 张必敏；

【导师】 吕庆田； 王学求；

【作者基本信息】 中国地质科学院 ， 地球探测与信息技术， 2011， 博士

【摘要】 我国的干旱荒漠戈壁区,面积广阔,找隐伏矿的潜力巨大,但由于本区气候干旱、沙漠和戈壁广布,一直被认为是地球化学勘查的技术难点区域。本论文以揭示戈壁覆盖区深穿透地球化学异常形成机理为目标,以地球化学、地质学以及地理景观学理论为基础,在了解荒漠戈壁区景观演化的前提下,对覆盖层的结构特征、理化性质、成因等方面开展分析讨论,同时重点通过对成矿元素在覆盖层中空间三维分布特征的了解,并结合地气、同位素、室内实验迁移柱等方面的证据,系统地研究深穿透地球化学异常形成机理,并对适合此类景观的深穿透地球化学找矿方法进行技术改进。主要取得了如下认识和结论：1、成矿元素在矿体上方不同深度覆盖层中的异常具有明显的继承关系；在矿体上方覆盖层,成矿元素呈现出顶底层高,中间低的特点；覆盖层底部异常主要集中在构造蚀变带矿体附近及其周边低洼处,异常分布面积较小,而对应的地表异常,异常强度大,分布面积广。2、深穿透地球化学异常的形成经历了一系列复杂的过程,从成矿—准平原化过程中元素的侧向分散—元素垂向迁移—元素卸载再到地表元素的侧向分散,并最终形成地表所能观测到的深穿透地球化学异常。准平原化过程使元素侧向迁移至古地形的低洼处；成矿元素通过地气流等方式从矿体向地表垂向迁移,迁移到地表后被地表细粒物质中的粘土等地球化学障所捕获并富集；元素垂向迁移至地表以后又发生二次侧向迁移过程,这个过程使异常得以扩散,形成一个更大面积的异常范围,这是运用低密度深穿透地球化学方法进行区域调查圈定隐伏矿找矿靶区的前提。通过室内地球化学迁移柱的研究,发现绝对浓度高的元素每年可以至少以米的距离迁移,在上百万年的第四纪演化历史中,元素完全有能力迁移几百米的覆盖层到达地表,这为深穿透地球化学技术的使用提供了理论基础。3、通过方法技术的不断总结,建议在不同的勘查阶段使用不同的深穿透方法技术。在区域地球化学调查或区域填图阶段建议使用微细粒测量技术。对于矿区化探可以采用微细粒测量技术、活动态提取技术、地气测量技术和电化学测量技术,这些技术各有优缺点,可以起到互补的作用。对覆盖区异常的查证只有通过穿透覆盖层直接取得原岩样品查证异常源,空气动力反循环粉末取样钻探技术是覆盖区化探异常查证的理想选择。更多还原

【Abstract】 The vast area of China’s Gobi desert has a great potential for prospecting concealed ore deposits. This region is technically difficult for geochemical exploration due to dry climate and overburden covers. The objectives of the paper are to reveal mechanism of deep-penetrating geochemical anomalous formation of a concealed gold deposit in Gobi covering areas based on geochemistry, geology and geomorphology, and analysis of the landscape evoiution of Gobi desert, physical and chemical properties of covering regolith, to understand three-dimensional distribution of Au and associated elements in covering regolith by using overburden drilling, to improves the deep-penetrating geochemical methods. The main conclusions are as follows:1. The element anomalies in covering regolith layer have the obvious inheritance relationship in different depth over ore body and present contents of elements are higher in the top and bottom layers than those in the middle layer. Anomalies in the bottom of the covering layers are mainly concentrated near the altered zones and its surrounding lowlands. In the top layers, there are corresponding surface anomalies, but anomalous distribution area and concentrations are more than those in the bottom layers.2. The study area has experienced a complicated geological and weathering process from the ore formation, to the lateral dispersion under the process of pediplanation, the vertical migration, until to lateral dispersion at regolith surface. The eroded gold mineralization rocks were mechanically transported and deposited in the lowest places. The elements vertically migrate to the soil surface by earthgas extending and are captured by geochemical barrier such as clays in the fine-grained soils. After that the secondary lateral migration at soil surface formed a widely broad range of anomalies, which is the premise of low-density deep-penetrating geochemical methods to delineate regional targets in covered terrains. The laboratory research on geochemical migration finds that some high concentration of elements in the ore can migrate at least several meters every year. This means that at millions-of-years scale of the quaternary evolution history, elements quite have the ability to move hundreds of meters to the earth surface from the depth.3. A deep-penetrating geochemical procedure for different exploration stages from regional to local are proposed based on above-mentioned theoretical studies. In regional survey stage, the micro-particle measurement technique can be cost-effective to delineate regional targets. In local stage, combinations application of the micro-particle measurement, selective leaching of mobile forms, earthgas and electrogeochemical methods can be effective for location of ore body targets. Reverse circulation air drilling technology is an ideal choice for evaluating geochemical anomalies pinpointing ore bodies in covered area.更多还原