【作者】 张建民；

【导师】 曾昭发；

【作者基本信息】 吉林大学 ， 地球探测与信息技术， 2019， 博士

【摘要】 加强矿产资源储备是国家经济持续稳定增长的重要保障,而勘查深部资源是实现资源保障的重要方向。金川铜镍矿床是我国最大的铜镍生产基地,在此开展深部勘查对增加资源储备具有重要意义。关于深部勘查,地质研究是基础条件,地球物理能够依据地下介质的物性差异进行找矿,方法手段多元、探测深度大、分辨率高,是重要的科学技术支撑条件。本文以地质研究为铺垫,通过对分辨率互补的地球物理位场勘探和电法勘探数据的处理和解释,对金川铜镍矿区深部的成矿有利部位进行了推断。1.通过系统收集和分析前人资料及卫星重力数据处理,野外踏勘,岩矿鉴定及物性测试,获得以下认识:(1)金川铜镍矿床位于区域北西向展布的重、磁异常梯级带上,处于华北板块与祁连地块的交接部位,与已知的龙首山陆缘带相对应,显示了其形成与深大断裂的发育有关。界面反演结果表明,龙首山处于地壳厚度的陡变带,地壳厚度约55 km,北东向的华北板块地壳厚度变化相对较小,反映了其稳定地块的属性;西南部的祁连地块地壳厚度较大,且不均一,说明该区构造运动复杂,曾受到强烈的推覆挤压作用,而导致不均一的变形。(2)铜镍矿床的产出与地层、构造和岩浆岩的关系密切,含矿岩体主要侵位于长城系白家嘴子组地层中,走向北西,倾向南西,倾角较大;与北西向构造关系最为密切,北西向断裂常起控矿作用,褶皱往往起改造富集作用;矿区超镁铁质岩体是成矿母岩,亦是围岩,矿体往往产出于岩体的下部。矿床成因不一,主要以深部熔离-贯入成矿为主。矿石矿物主要由雌黄铁矿、镍黄铁矿、黄铜矿、橄榄石、辉石等组成,完整矿物晶形较少,矿物裂隙发育,且常具有明显的蚀变现象,表明矿体形成具有多期次的特征,且曾受到强烈的后期改造作用。(3)基于密度、磁性和电阻率特征,矿区岩、矿石可大致分为三类,第一类是铜镍矿石,表现出高密度、高磁性、低电阻率的特征;第二类是超基性岩体,呈密度高、磁性强、电阻率中等的特征;第三类是超基性岩体的围岩,具有密度低、磁性弱、电阻率高的特征。这些物性特征的差异性,为研究区地球物理的勘查工作提供了前提条件。2.为获取更丰富的与矿相关的信息,对位场数据处理的方法进行了研究。(1)传统的位场数据分离方法仅强调区域场和局部场或多尺度分离的方法存在模态混叠的现象,为了更多且更有效地提取不同尺度的位场数据信息,一维和二维双树复小波被首次引入到位场数据的处理中,该方法具有近似的平移不变性、更多的方向选择性,以及限制数据冗余的特点,模型试验表明,该方法相比小波分析具有优越性,可以更好地实现多频率混叠信号的不同尺度信息分离。另外,基于数学形态学的基本算子,通过调整不同尺寸的形态学结构元素,提出了对一维和二维信号实现多尺度分解的形态学算子,模型试验表明,形态学算子能够很好地对不同尺度的信号进行分离,而且具有较高的计算效率。(2)针对传统位场数据边界识别方法常存在输出边界模糊、抗噪能力差、不能均衡强弱异常或在正负异常同时存在时具有虚假边界存在的问题,基于数学形态学良好的边缘刻画能力及抗噪性能,本文先构建了一种新的边界识别算子MMA,该算子可以利用其极大值有效地对位场数据的边缘进行识别,为了使其具有均衡强弱异常的能力,提出了MMAZ和MMAT两种均衡的边界识别滤波器,模型试验结果表明,相比倾斜角法、倾斜角的总水平导数、Theta图法等几种传统的边界识别滤波器,这两种滤波器不仅可以均衡不同幅值的异常,而且输出的边界更加收敛,同时在正负异常同时存在的情况下,没有虚假额外边界的产生,以及具有良好的抗噪能力。(3)反演是位场数据处理与解释中定位异常地质体空间位置、物性参数估计及地下构造推断的重要方法,对深部矿产勘查具有重要意义。针对位场数据反演常存在多解性、反演结果精度低以及计算效率低的缺点,本文采用光滑L0范数紧支撑聚焦方法及GPU并行计算,来快速地获取准确度高的位场数据反演结果。并通过不同埋深的两个地质体模型对该方法的效果进行了验证。3.利用这些位场处理方法对矿区的航磁异常数据进行了处理。边界识别结果显示,矿区北西向构造最为发育,北东向次之;已知含矿岩体的及矿区南延区正航磁异常的边界被确定。位场分离及反演结果均表明,矿区深部具有良好的找矿前景。4.为了更好地了解不同地球物理方法的深部探测能力及建立找矿模型,通过多个模型的重、磁模拟以及矿区以往实际的CSAMT数据反演结果,对深部异常体的位场异常特征及CSAMT的找矿指示进行了研究和总结。对于深部找矿,应该重视研究区航磁数据等值线宽缓的低正异常区域,但低正舒缓磁异常未必反映的是深部的超基性岩体,亦有可能是与超基性岩体具有几倍磁性差异的混合岩带或部分变质岩系等其他磁性略大的地质体,这是因为对于同等规模的异常体,由有效磁化强度不同而引起的磁异常差异在浅部表现的比较明显,差异较大,在深部则相反,差异较小。另外,鉴于研究区岩、矿体较大的倾角(50°~80°),该区磁异常变化基本可以忽略岩、矿体倾角的影响。在研究区异常幅值相同的不同区域,正异常水平距离的范围越大,则可能代表目标体埋藏越深,规模越大。相似特征的磁异常可能是分布复杂的磁异常体所引起的,对于深部找矿,要尽可能多地了解和结合丰富的已知地质、钻探等综合信息,从而能更为合理地给出有利的深部找矿位置。面对深部找矿,重力与磁法基本表现出相似的异常特征。电阻率差异反映出的破碎带亦是重要的找矿指示。结合地质、地球化学、遥感及其他找矿标志,建立了以地质-地球物理为主的找矿勘查模型。5.依据找矿勘查模型,结合矿区内实测的重、磁、电剖面数据的处理结果,对矿区及周边深部有利的找矿地段进行了分析,并圈定有利靶区6个。关于主矿区东部大范围的高磁异常区(东湾勘查区),在其深部未找到有利的找矿地段。更多还原

【Abstract】 Strengthening mineral resources reserve is an important guarantee for the sustained and stable growth of national economy,and exploring deep resources is an important direction to achieve resource security.Jinchuan Cu-Ni sulfide deposit is the largest copper-nickel production base in China.Deep exploration in this area is of great significance to increase resource reserve.Geological research is the basic condition for deep exploration.Geophysics can be used to explore minerals according to the difference of physical properties of underground media.It is an important scientific and technological support condition with multiple methods,large exploration depth and high resolution.On the basis of geological research,through processing and interpreting the data of geophysical potential field exploration and electrical prospecting with complementary resolution,this paper infers the potential favorable metallogenic locations in the depth of Jinchuan Cu-Ni sulfide deposit.1.Through the systematic collection and analysis of previous data,field survey,rocks and minerals identifications and physical property parameters tests,the following knowledge is obtained:(1)Jinchuan Cu-Ni sulfide deposit is located in the north-west direction of the region on the gradient belt of gravity and magnetic anomalies,at the junction of North China plate and Qilian block,corresponding to the known Longshoushan continental margin belt,which shows that its formation is related to the development of deep faults.The result of interface inversion shows that Longshou mountain is located in the steep change zone of crustal thickness,with the crustal thickness of about 55 km.The crustal thickness change of North China plate in the NE direction is relatively small,which reflects the attribute of its stable block.The crust thickness of Qilian block in the southwest is relatively large and uneven,which indicates that the tectonic movement in this area is complex and has been strongly pushed and squeezed,resulting in uneven deformation.(2)The occurrence of Cu-Ni deposit is closely related to strata,structures and magmatic rocks.The ore bearing rock body is mainly intruded into the stratum of baijiazuizi formation of the Changcheng system,trending to the northwest,tending to the southwest,with a large dip angle.It is most closely related to the northwest structures.The Northwest faults often control the ore,and the folds often play a role of transformation and enrichment.The ultramafic rock bodies in the mining area are the ore-forming parent rocks,also the surrounding rocks,and the ore bodies often occur in the lower part of the rock masses.The genesises of the deposits are different,and the main ore-forming process is deep fusion and penetration.The ore minerals are mainly composed of orpyrite,pentlandite,chalcopyrite,olivine,pyroxene,etc.The complete mineral crystal shape is less,the mineral fracture is developed,and it often has obvious alteration phenomenon,which indicates that the ore bodies’ formation has the characteristics of multi-stage,and they had been strongly reformed in the later stage.(3)Based on the characteristics of density,magnetism and resistivity,the rocks and ores in the mining area can be roughly divided into three types.The first type is copper-nickel ore,which shows the characteristics of high density,high magnetism and low resistivity;the second type is ultrabasic rock mass,which has the characteristics of high density,strong magnetism and medium resistivity;the third type is the surrounding rock of ultrabasic rock mass,which has the characteristics of low density,weak magnetism and high resistivity.The differences of these physical characteristics provide a precondition for the exploration of geophysics in the study area.2.In order to obtain more abundant information related to ore,the methods of data processing of potential field are studied.(1)The traditional separation methods of potential field data often emphasize the regional field and local field,or the multi-scale separation methods have the phenomenon of mode overlapping.In order to better extract more effective potential field data information of different scales,one-dimensional and two-dimensional dual-tree complex wavelets are introduced into the processing of potential field data for the first time.This method has the characteristics of approximate translation invariance,more direction selectivity,and limitation of data redundancy.Model test shows that this method has advantages over wavelet analysis,and can achieve better separation of information at different scales of multi-frequency aliasing signals.In addition,based on the basic operators of mathematical morphology,by adjusting the morphological structural elements of different sizes,morphological operators for multi-scale decomposition of one-dimensional and two-dimensional signals are proposed.Model tests show that the operators can separate signals of different scales well and have higher computational efficiency.(2)Aiming at the problems of ambiguous output boundary,poor anti-noise ability,unbalanced strong and weak anomalies or false boundaries in the results when both positive and negative anomalies exist of traditional edge detection methods,a new edge detection operator MMA is constructed based on the good performance in edge detecting and noise eliminating of mathematical morphology.The operator can effectively recognize the edges of potential field data by using its maximum.In order to make it have the ability of balancing strong and weak anomalies,two balanced boundary recognition filters,MMAT and MMAZ,are proposed.The model tests results show that compared with the tilt angle method,the total horizontal derivative of tilt angle,Theta map method and other traditional methods,the operator can effectively identify the edges of potential field data.The two filters can not only balance the anomalies of different amplitudes,but also obtain more sharper edges,at the same time,there are no false additional boundaries when the positive and negative anomalies coexist at the same time,in addition they have good anti-noise ability.(3)Inversion is an important method to locate anomalous geological bodies in spatial location,physical parameters estimation and underground structures inference in data processing and interpretation of potential field,which is of great significance to deep mineral exploration.In order to overcome the shortcomings of multi-solution,low precision and low computational efficiency in inversion of potential field data,the smooth L0 norm compact support focusing method and GPU parallel computation are adopted to quickly obtain the inversion accurate and quick results of potential field data with high accuracy.The effectiveness of the method is verified by the model of two geological bodies with different buried depths.3.These potential field processing methods are used to process the aeromagnetic anomaly data of the mining area.The results of boundaries identification show that the NW structures are the most developed in the mining area,followed by the NE structures;the boundaries of known ore bearing rock masses and positive aeromagnetic anomalies in the South extension area of the mining area are determined.The results of potential field separation and inversion show that the deep part of the mining area has a good prospecting prospect.4.In order to better understand the deep exploration abilities of different geophysical methods and establish prospecting model,the potential anomaly characteristics of deep anomalous bodies and prospecting indicators of CSAMT inversion results are studied and summarized through gravity and magnetic simulation of multiple models and inversion results of previous actual CSAMT data in mining areas.It is concretely recognized that for deep prospecting,attention should be paid to the low positive aeromagnetic anomaly area with large horizontal range in the study area,but the low positive anomaly large horizontal range may not necessarily reflect the deep ultrabasic rock mass,but may also be a mixed rock belt or some metamorphic rocks with several times magnetic difference from the ultrabasic rock mass,et al.This is because for the same scale anomalous body,the difference of magnetic anomaly caused by different effective magnetization intensity is more obvious in the shallow part,the difference is larger,but in the deep part,the difference is smaller.In addition,in view of the large dip angle of rocks and ore bodies in the study area(50 ~80°),the influence of dip angle of rocks and ore bodies can be neglected.In different areas with the same anomaly amplitude,if the horizontal distance of positive anomaly is larger,the buried target body may have larger depth and scale.The magnetic anomalies with similar characteristics may be caused by complex magnetic anomalies.For deep prospecting,it is necessary to understand and combine abundant comprehensive information such as known geology,drilling and so on,so as to give a more reasonable prospecting position for deep prospecting.For deep prospecting,gravity and magnetic methods basically show similar anomalous characteristics.Fractured zones reflected by resistivity differences are also important prospecting indicators.Combined with geology,geochemistry,remote sensing and other prospecting indicators,a prospecting model mainly based on geology and geophysics is established.5.According to the prospecting model,combined with the processing and interpretation results of the actual gravity,magnetic and electrical profile data in the mining area,six favorable ore-forming target areas in the deep,edge and periphery of the mining area are delineated.As for the large-scale high magnetic anomaly area(Dongwan exploration area)in the eastern part of the main mining area,no favorable prospecting location has been found in its deep part.更多还原