相山地区后遥感应用技术示范研究

【作者】 张万良；

【导师】 刘德长； 张静波；

【作者基本信息】 核工业北京地质研究院 ， 矿产普查与勘探， 2006， 博士

【摘要】 后遥感应用技术是指将遥感技术与各领域传统方法和现代信息技术相结合的一种信息深化应用技术。其内容涵盖信息处理、信息解译、信息分析、信息表述和信息应用等。对于铀资源勘查领域,后遥感应用技术理念的应用思路就是要充分挖掘赋存在遥感图像中与铀矿找矿相关的信息,同时,应用现代信息技术,结合其它地学信息进行综合分析,总结认识,发现规律,并对得出的认识和发现的规律进行多维可视化分析和地学过程再现,为铀资源勘查提供有力的技术支持。相山地区是我国目前最大最富的火山岩型铀矿田所在地,也是重要的硬岩型铀资源生产基地,铀矿产于面积300余平方公里的相山火山.侵入杂岩体中,受构造、斑岩体、热液蚀变控制,具有很好的成矿远景和巨大的成矿潜力。作为一种全新的后遥感应用技术,在相山地区开展示范研究,对于后遥感应用技术的自身发展和相山地区的深入找矿均具有重要意义。以地球系统科学理论为指导,在基础地质、遥感、航放、重磁、DEM信息处理分析的基础上,以多源信息在铀资源勘查领域的深入挖掘和深化应用为目标,以相山地区深入找矿方向的厘定为目的,开展了相山火山.侵入杂岩总体研究、新构造运动研究、相山西北与东南部的对比研究,剥蚀程度与保存条件研究,以及华南红盆与铀矿保存研究等内容。通过文献调研、资料收集、建立空间数据库、以及野外地质调查、室内综合分析,取得以下创新成果:（1）通过华南地区构造岩浆演化的综合分析,首次提出相山火山-侵入杂岩受控于华南6条EW向花岗岩带最北的雪峰山—武功山—光泽岩带,其形成的构造背景与前侏罗纪的EW向构造作用有关,经历了前侏罗纪挤压—侏罗纪压扭—白垩-古近纪伸展减薄—中新世以来的挤压抬升这种“开-合”交替演变的构造活动历史,铀矿形成于白垩-古近纪伸展减薄这一特定的构造演化阶段。（2）对相山地区遥感影像进行了深入的判译,发现NE向、NNW向、SN向、NWW向及EW向多组线性构造形迹大多数是新构造运动导致的古构造复活的产物,即它们具有新构造的特点。首次提出新构造运动是矿床空间分布特征的主要影响因素之一。（3）运用中国地质调查局发展研究中心2005年开发的GeoExpl软件,对相山地区重磁数据进行了二次开发,不同高度重磁异常上延图、不同高度重磁异常方向导数计算结果显示,相山地区基底构造主要有EW向、NE向和NW向三组,基底构造的交汇是相山火山-侵入杂岩的定位机制。NE向相山-芙蓉山基底构造（F2）,将杂岩体分划成具不同结构构造特征的西北部和东南部。（4）相山火山-侵入杂岩由酸性火山碎屑岩夹沉积岩、酸性熔岩及中酸性浅成-超浅成侵入岩组成。长期归属溢流相火山岩的流纹英斑岩获得单颗粒锆石U-Pb年龄为129.54±7.93Ma,该年龄小于相山火山-侵入杂岩的主体岩石—碎斑熔岩的年龄,结合其产状形态特征,认为流纹英安斑岩是火山期后的浅成-超浅成侵入体。参照上侏罗统与下白垩统的145.5Ma界线年龄,首次提出相山火山-侵入杂岩的形成时代为早白垩世的新认识（火山岩以前归属晚侏罗世）。（5）相山火山-侵入杂岩从喷发—侵出—侵入,SiO₂含量、Rb/Sr、Rb/Ba比值降低,而TFe（Fe₂O₃+FeO）、CaO、MgO、TiO₂、P₂O₅含量、固结指数SI、δEu则呈增高趋势,岩浆演化与正常岩浆房酸度逐渐增高的岩浆分异趋势相反,作者命名为“反方向岩浆演化系列”。不相容元素的比值如Th/U、Rb/Ba、Th/Nb、Zh/Ta、Nb/Ta、La/Nb变化幅度较大,与SiO₂等主量组分没有明显的正消长或反消长关系,稀土配分曲线也不尽一致,故认为火山喷发相、侵出相和侵入相岩石具有不同的源区性质,突破了前人“形成相山各类火山杂岩的岩浆不仅同源,而且它们是同一岩浆房中岩浆分异演化的产物”的观点。（6）通过对植被发育的相山铀矿田ETM⁺数据主成分变换和比值处理,在一定程度上消除了植被的影响,获得了良好的含水矿物蚀变遥感异常信息,提出分布在相山矿田西北部碎斑熔岩中的或北部西段变质岩中的蚀变遥感异常是热液水云母化引起的,是重要的找矿标志。（7）针对相山矿田铀成矿特征,作者提出铀钍富集系数的概念（FD=U×Th/K）,FD反映的是铀钍组合矿化情况,与（火山）岩浆热液作用有关。认为相山地区铀钍富集系数与矿床空间分布有一定相关性,即铀（含钍）矿床多数分布在FD相对较高区域或其附近。（8）矿床产于相山火山-侵入杂岩体内部及外侧,东南部矿床较少,西北部矿床无论是数量还是品位都明显好于东南部。基于DEM的面积-高程曲线计算表明,相山地区地表总体侵蚀严重,但由于组成地表物质的岩性差异和地质构造活动强度不同,侵蚀程度不均匀。通过地貌形态、花岗斑岩产状、碎斑熔岩物化性质、成矿类型特征的对比分析,提出相山矿田西北部与东南部具有不同的侵蚀程度,矿床不均衡的产出特征,不是成矿作用或地质结构差异引起的,而是侵蚀程度不同所致。从矿田西北部到东南部,矿床侵蚀深度逐渐加大。矿田西北部矿床保存条件较好,多数铀矿完整或较完整地保存下来了,这对相山地区今后找矿具有重要意义。（9）华南红层与铀矿化具有密切的时空关系,二者均形成于白垩—古近纪的拉张构造背景。本文从新的视角,即华南红盆的保矿作用再度审视华南红盆与铀矿的时空关系,首次提出红盆受后生断裂构造（新构造）控制,是残留构造盆地。产于红盆附近的矿床（田）过去曾被红层覆盖过,红盆附近和深部是有利于矿化保存的区域,也是找矿方向之所在。后遥感应用技术在相山地区的应用实践,促进了后遥感应用技术本身的发展,起到了应用研究的示范作用,并在构造-岩浆活动、成矿-保矿条件、找矿方向等方面,获得了一系列创新成果和认识,对相山矿田及其邻区进一步寻找新的富大铀矿提供了新的途径和技术思路。更多还原

【Abstract】 The post-remote sensing application technology refers to a kind of information deepening application technology by combing the remote sensing technology with traditional technologies in various fields and modern information technology and it covers information processing, information interpretation, information analysis, information presentation and information application etc.In the field of uranium resource exploration, the idea of applying the concept of post-remote application technology is to fully dig out the information on prospecting for uranium deposits in the remote sensing images, to comprehensively analyze it by combining with other geologic information, summarize and find out the regularity, to visualize the obtained understanding and regularity and to represent geological processes, providing powerful support for uranium resource exploration and prospective prognosis.Xiangshan area is an important production base of hard rock type uranium resources, where the largest and richest volcanic uranium orefield in China is located. Uranium deposits occur in Xiangshan volcanic - intrusive complex of over 300km in area, they are controlled by structures, porphyry mass and thermal alteration and thus there is a large prospect. As a kind of bran-new technology, the post-remote sensing application technology is applied on trial in Xiangshan area, which is of important significance on the development of post-remote sensing application technology and on the further prospecting for uranium deposits in Xiangshan area.Under the direction of scientific theories of earth system, based on processing and analyses of basic geology, remote sensing, airborne radioactive, gravitational, magnetic and DEM information and by taking the deep digging and application of multi-source information in the field of uranium resource exploration and the determination of further prospecting direction in Xiangshan as objectives, emphases are put on these researches, including the overall research on Xiangshan volcanic - intrusive complex, the research on neotectonic movements, comparative study of northwestern and southeastern parts in Xiangshan area, the research on the degree of erosion and preservation conditions and that on red basins in South China and the preservation of uranium. By searching references related, collecting data and creating a spatial database and though geologic investigation and comprehensive analyses, the following innovative achievements or conclusions are obtained.（1） Through the comprehensive analyses on tectonic and magmatic evolution in South China, it is proposed for the first time that Xiangshan volcanic—intrusive complex is under the control of the belt of Xuefeng Mountain—Wugong Mountain—Guangze, the northernmost belt among six EW-trending granite belts in South China, the tectonic setting for its formation is related to EW-trending tectonic process before Jurassic, undergoing "open-close" alternative tectonic evolution of squeezing before Jurassic - squeezing and twisting in Jurassic—stretching and thinning from Cretaceous to Paleogene and squeezing and uplifting since Miocene, and uranium mineralization was formed in the specific stage of tectonic evolution of stretching and thinning from Cretaceous to Paleogene.（2） The detailed interpretation on remote sensing image of Xiangshan area shows NE, NNW, SN, NWW and EW linear structures and these structural features most are products due to the reactivation of palaeostructures caused by neotectonic movement, that is to say, they have features of neotectonic movement. It is proposed for the first time that the neotectonic movement is one of dominant factors that affect the spatial distribution of uranium deposits.（3） Gravitational and magnetic data of Xiangshan area are developed secondarily using GeoExpl software developed in 2005 by Development Research Center of Geologic Survey Bureau, China. Upward continuations of gravitational and magnetic anomalies at different heights and calculation results of directional derivatives of gravitational and magnetic anomalies at different heights show there are three groups of major basement structures in Xiangshan area: EW, NE and NW trending. NW trending Xiangshan - Furongshan basement structure （F2） divides Xiangshan volcanic—intrusive complex into the northwestern and southern parts with different structural features.（4） Xiangshan volcanic - intrusive complex consists of acid pyroclastic rocks interbedded with sedimentary rocks, acidic lava, intermediate—acidic shallow—super-shallow intrusive rocks. The U-Pb age of single grain zircon of rhyolitic dacitic porphyry that was considered as volcanic rock of effluent facies is 129.54±7.93Ma, which is less than the age of porphyroclastic lava, the main rock in Xiangshan volcanic - intrusive complex. Combined with features in its occurrence and shape, it is believed that the rhyolitic dacitic porphyry is a post-volcanic shallow or super shallow intrusive body. Referring to the fact that the boundary age of Jurassic and Cretaceous is 145.5Ma, it is proposed for the first time that the formation age of Xiangshan volcanic—intrusive complex is early Cretaceous.（5） SiO₂ content, Rb/Sr, Rb/Ba ratios of Xiangshan volcanic - intrusive complex decrease from eruption - effluent - intrusion and however, TFe （Fe₂O₃+FeO） , CaO, MgO, TiO₂, and P₂O₅ contents, solidification index SI and 8Eu increases, and the magmatic evolution is contrary to the magmatic differentiation of normal magmatic chamber whose acidity increases gradually, which is called as reverse magmatic evolution series. Ratios of incompatible elements such as Th/U, Rb/Ba, Th/Nb, Th/Ta, Nb/Ta and La/Nb vary in relatively large amplitude, which is of no evident positive or negative relation with major components such as SiO₂ and so on, REE distribution patterns are not identical totally and therefore, it is believed that rocks of eruptive, effluent and intrusive facies are from different source areas, breaking through the former understanding that "that magma for various complex in Xiangshan area is not only from a same source but also the product of magmatic differentiation from a same magmatic chamber."（6） Through the principal component conversion and ratio processing of ETM⁺ data of Xiangshan uranium orefield where vegetation is well developed, the effect of vegetation is eliminated to some extent and good remote sensing anomaly information on alteration of hydrous minerals is acquired, where the remote sensing anomalies of alteration distributed in the porphyroclastic lava in the northwest or metamorphic rocks in the western section in the north of Xiangshan uranium orefield are caused by hydrothermal hydromicazation and this is an important criteria for ore prospecting.（7） Aimed at the metallogenic characteristics of Xiangshan uranium orefield, the concept of U-Th concentration coefficient （FD=U X Th / K） is presented in this dissertation, FD reveals the combined U and Th mineralization information and thus it is related to （volcanic） magmatic hydrothermalism. The U-Th concentration coefficient has a certain correlation with the distribution of deposits in Xiangshan area; namely, uranium （thorium-bearing） deposits are distributed mostly in or near the areas with relatively high FD.（8） Deposits occur in the interior and outside of Xiangshan volcanic - intrusive complex, fewer deposits are distributed in the southeast and however, whether the number or grade of deposits in the northwest is evidently better than that in the southeast. The calculation results of DEM-based area vs elevation curves show that the earth is eroded seriously in Xiangshan, but the degree of erosion is heterogeneous due to differences in lithology of matter at the earth surface and in intensity of geologic and tectonic activities. Through comparative analyses on geomorphic features, occurrences of granite porphyry, physical and chemical properties of porphyroclastic lava, metallogenic type and characteristics, it is proposed for the first time that the degree of erosion in the northwest is different from that in the southeast of Xiangshan uranium orefield, deposits are characterized by unbalanced occurrence, which is not caused by the differences in mineralization or geologic framework, but by the different degree of erosion. From the northwest to the southeast of Xiangshan uranium orefield, the erosion depth of deposits increases gradually. There are better preservation conditions for deposits in the northwest of orefield and most uranium deposits are well or relatively well kept, which thus is of important significance in the prospecting for uranium deposits in Xiangshan area in the future.（9） Red beds of South China have a close relation of time and space with the uranium mineralization and were formed in the pull-apart tectonic setting from Cretaceous to Paleogene. From a new view, namely, the preservation of red basins in South China to uranium deposits and reconsidering the time and space relation between red basins in South China and uranium deposits, it is proposed for the first time in this dissertation that red basins are under the control of epigenetic faulted structures （neotectonics） and they are residual structural basins; deposits occurring near red basins were covered by red beds and thus area near and in the deep of red beds are favorable for mineralization preservation, which is the prospecting direction as well.The application of post-remote sensing technology promotes its development, plays a role in demonstrating the application and a series of creative achievements or conclusions have obtained in the aspects of tectonic - magmatic activities, metallogenic conditions - preservation conditions for deposits, prospecting direction and so on, providing a new idea to further prospect for new large and high-grade uranium deposits in Xiangshan orefield and its adjacent areas.更多还原