Integrated geophysical studies to elicit the subsurface structures associated with Uranium mineralization around South Purulia Shear Zone,India: A review

South Purulia Shear Zone in India is an important zone that hosts uranium mineralization. Since detailed geophysical studies have not been carried out in this region, an integrated geophysical study using self-potential, resistivity, very low frequency electromagnetic and radiometric methods was performed to identify the subsurface structures that could host the hydrothermally altered uranium deposits in the area. The study reveals the wide and large magnitude of negative self-potential anomaly across the South Purulia Shear Zone. The peak negative self-potential anomalies are correlated with the low gravity and low resistivity anomalies measured along various profiles. The low self-potential, gravity and low resistivity anomaly zones are also correlated with conducting zones inferred from very low frequency electromagnetic measurements. Interpretation of self-potential data reveals multiple thick sheet-type vertical and/or inclined structures which might be associated with uranium mineralization. Schlumberger resistivity sounding data reveals an increasing trend of apparent resistivity with current electrode separations/depth. Apparent conductance measured simultaneously with resistivity measurement reveals an increase in current flow of current as depth increases. This exhibits the presence of thin conducting layers at these depths, which is not reflected in resistivity sounding data due to suppression problem. Also this conducting layer is consistent in various soundings and is connected from Raghunathpur to the South Purulia Shear Zone. Correlation of very low frequency and self-potential data shows that the structures are comparable and a radiometric profile also advocate that the conducting structure is associated with radioactive minerals. These structures are likely to be mineralized zones as hydro-uranium anomaly has also been reported from various locations in the area. Moreover, drilling results at a specific mine near the study area also confirms the presence of uranium mineralization. The hydrothermal activity associated with uranium mineralization seems to be still active in the area. Such combined geophysical studies are essential to understand this highly complex shear zone for the economic exploitation of its natural resources.     

内蒙古镶黄旗道郎和都格矿区钨多金属成矿地质背景与综合定位预测方法

郎和都格矿区地表沙土和草原覆盖严重,直接寻找钨多金属矿的信息较少。地质地球化学研究结果表明,与钨多金属矿关系密切的是早白垩世钾长花岗岩,赋矿围岩主要是二叠纪辉石闪长岩。根据围岩与矿体之间的物性差异,完成了矿区1∶1万地质填图、磁法和重力测量,对数据进行重磁联合反演,识别出3条走向北东、长度800～3 000 m、宽度50～100 m的重要的构造蚀变带（分别对应于负磁异常带）,均分布在矿区西北侧的辉石闪长岩中,且平行于辉石闪长岩和钾长花岗岩的接触带。预测了6个综合物探异常区,也位于矿区西北侧的辉石闪长岩分布区,单个异常面积为500 800 m²,异常深度不超过1 000 m。经钻探工程验证,在3个异常部位发现了隐伏的构造破碎带型钨多金属找矿靶区,钨多金属矿体埋藏深度为150～650 m,单个矿体厚度为2～4 m。表明成矿地质条件分析与重磁联合反演相结合的定位预测方法,在覆盖区寻找钨矿效果明显,值得进一步推广。     

赣东北塔前-赋春成矿带画子山地区地球物理特征及找矿启示

画子山地区隶属于赣东北塔前-赋春成矿带,其具有地质条件复杂,深部成矿条件优越等特点。在复杂的地质条件情况下,对多种地球物理方法进行有机的结合,可较为客观的反映地下深部信息。而物性差异是地球物理方法的应用研究前提,首先对画子山地区的岩石标本进行物性分析。基于物性分析结果,在画子山地区针对性的布设两条（8 线和11 线）重力、磁法及可控源音频大地电磁法综合地球物理剖面,然后结合地质、物性、钻孔等资料对综合剖面进行解译,解译得到重力高值和低阻异常区是由矿化引起,磁异常带由蚀变所引起。最后通过分析综合剖面反映出地下的高密度体、高磁性体和低阻高极化体的分布规律,圈定出找矿的重点区域为万年群牛头岭组上段地层的西南方向,为画子山地区的下一步工作指明方向。     

福建东洋地区地球物理场特征

为了研究东洋地区深部地质结构,在福建东洋地区开展了综合地球物理勘查,对福建东洋地区地球物理场进行了分析,结合已有的地质资料,分析研究了区域地球物理场特征及区域深部地质结构特征.研究认为:福建东洋地区位于巨型环形构造外环带西南部,研究区处在东部沿海磁场剧烈变化带和西部内陆磁场相对平缓带的过渡区域,区域航磁ΔT异常以北东向条带状异常带为主,区内分布有2处剩余重力异常高;地球物理综合剖面范围被两条北西向深大断裂分割为3部分,结合区域地质特征,推断区域南部的浅层是一套推覆无根的变质岩系高阻体,深部为一套以中生代沉积岩石为主的低阻体,区域北部浅部主要为中生代沉积岩夹薄层火山岩组成的低阻体,深部为下古生代和元古界基底岩系共同反应的高阻体,区域中部是火山岩主要发育区.      

全国铀矿资源潜力评价重力数据处理与研究

通过对全国39个铀成矿带和29个预测区的重力数据处理、重力异常提取、地质构造推断,为全国铀矿资源潜力评价提供了构造单元、断裂构造、岩体范围及深度、盆地范围和地层结构等预测要素。总结了铀成矿环境的重力场特征,与热液成矿作用有关的铀矿（花岗岩型、火山岩型、及部分碳硅泥岩型）主要位于区域重力场从高场向低场过渡的部位或偏向低场区域,主要成矿要素花岗岩岩体、火山盆地均表现为重力低场;大型砂岩型铀矿成矿盆地位于区域重力场的高场区域,而蚀源区则为低场,盆地边缘或内部的隆起区一般位于剩余重力高场区;与上述各类型铀成矿有密切关系的断裂构造在重力场中显示为梯度带、不同性质重力异常的分界线、串珠状异常或条带状异常。     

西藏林周县轮郎铅锌矿区地球物理异常特征评价及找矿意义

林周县轮郎铅锌矿区位于拉萨-林周-墨竹工卡铅锌成矿区中部,属雅鲁藏布江巨型铜多金属成矿带北亚带。根据该区地球物理测量成果,共圈出重力异常区10个、磁力异常区18个。通过对重力异常特征及磁力异常特征综合评价,分析出其中5个磁力异常区和重力异常有明显的对应关系,属矿致异常,具良好的找矿前景;并且得出该区高磁区、局部磁异常与局部重力高的结合部和重、磁双高地带均为找矿潜力区。     

综合物探在新疆1∶50000矿产普查中的应用

为了在新疆1∶50000矿产普查中研究成矿地质条件圈定成矿远景区域,在普查过程中通过重、磁、电等多种物探手段的综合应用,来探测深部和隐伏矿,效果明显。通过采集标本对其工作区的物性特征加以归纳分析,指导物探方法(重、磁、激电)的运用,为后续开展物探工作提供借鉴。首先在工作区利用重力和航磁资料,查明勘探区内地质构造特征及岩体分布规律,得到重、磁高值异常区多与岩体、岩体接触带及断裂带有关,而该区域的成矿与接触带或断裂构造密切相关,在接触带及断裂构造带上有利于硫化物发育,再利用大功率激发极化法的低阻高极化特征圈定含硫化物的有利区域,最后优选重、磁、电综合物探异常特征明显、成矿部位有利地段,并结合地质、化探异常特征对工作区定性的综合评价,指导寻找含硫化物的岩(矿)体,最终圈定找矿靶区一处,为矿产普查工作提供基础资料和找矿依据。     

湖南省东坡铅锌矿区物化探异常特征及找矿作用

东坡矿区内矿产资源丰富,但已探明的铅锌资源经多年开采已出现严重危机。为配合地质找矿,在研究区内采用以地面高精度磁测为主,激电测深为辅的物探工作方法,圈出22个磁测ΔT异常,磁异常主要沿千里山岩体接触带分布。结合地质、物化探资料分析发现野鸡尾—牛角垄、妹子垄、蛇形坪—塘渣水三个有重要意义的异常区。通过钻探验证,在妹子垅预测区的M2磁异常区见到厚度10.86~32 m的矽卡岩型钨锡多金属矿体,矿床规模可达大型;在牛角垅预测区M9磁异常区见到了6.4 m的铅锌矿化破碎带。初步建立起该区物化探找矿模式为"二低三高",即低重力、低视电阻率,高强度的ΔT异常、高视极化率η_s异常,并有地球化学Pb、Zn、Ag、As等异常带。东坡铅锌矿与岩体密切相关,因此在选区上,必须选在反映岩体或隐伏岩体的重力低异常区,视电阻率低异常地段往往是构造破碎带或矽卡岩带发育地段。     

南秦岭池沟地区地物化特征及其找矿意义

池沟斑岩型铜钼矿（化）体产于燕山期中酸性岩体内外接触带中,成岩与成矿年龄一致。区内物化探异常及矿化均围绕斑岩体呈（环）带状分布,构成斑岩型-矽卡岩型铜钼矿成矿系列。近年来,池沟地区采用高磁扫面＋CSAMT（可控源音频大地电磁法）＋钻探等组合方法,显示物化探异常特征与池沟出露岩体相吻合,经钻探,在池沟斑岩体接触带深部发现了厚大低品位铜钼矿体。在总结矿区地质特征的基础上,以区内物化探异常特征为依据,认为地表物化探异常与深部矿体位置形态有对应性关系,找矿潜力巨大,具有寻找斑岩型铜矿床的有利条件。     

安徽省濉溪县杨桥孜铜金矿重磁异常特征

杨桥孜铜金矿是皖北覆盖区以地质理论为指导通过综合物探手段发现的一处中型矽卡岩型矿床。该矿床是皖北地区迄今为止发现的规模最大金矿床,对三铺岩体成矿预测、皖北地区找矿、研究华北陆块找金方向具有重要意义,为覆盖区综合找矿方法提供了成功经验。重磁勘探在该矿床的发现过程中发挥了重要作用,重磁组合异常特征倍受关注。杨桥孜金铜矿位于重力梯级带的次级鼻状重力高异常区,重力二阶导数异常与矿体分布相吻合;地磁场以正异常为背景,局部叠加明显的强磁异常,强磁异常与铁矿体分布一致,铜金矿体对应于磁力梯级带。重高磁高、重高磁梯组合异常在矿床普查过程中发挥了作用。     

Localization of water bearing fractured zones in a hard rock area using integrated geophysical techniques in Andhra Pradesh,India

Knowledge of the existence of fracture zones, their extent, intensity and direction is very useful for assessing groundwater in hardrock regions and in this context geophysical methods are widely accepted as a powerful means of study. In the modern era of exploration, application of the Resistivity Imaging technique gives a new opportunity for groundwater study in hardrock regions. Exploration surveys were conducted at one of the important sites in Maheshwaram watershed, Andhra Pradesh, India with a multielectrode resistivity imaging system. To reduce the ambiguity of geophysical interpretation some complementary geophysical studies like ground Magnetic and VLF were also carried out.A number of 2D resistivity images were prepared in a grid pattern, which clearly show the weathered and fractured zones in different parts of the study area. With the help of all 2D profiles a quasi-3D image has been created, which indicates the orientation and extension of the fracture zone in a horizontal as well as vertical direction in the study area. Strong agreement exists among the anomalies identified using the ground magnetic, VLF and resistivity imaging methods. The litholog data available in the study area also helps to interpret geophysical results to find a potential groundwater bearing zone in that area.     

大兴安岭中段地球物理特征及地质解释

以区域地质资料和物探资料为依据,对大兴安岭中段地区重、磁异常特征及其对应的地质情况进行综合解释,探讨区域矿产分布与重磁场的关系,以及不同属性矿产的磁异常特点,指出该区重磁异常对寻找多金属矿床有指导作用.     

辽宁宽甸红石地区硼矿化物化探综合信息分析

研究区存在古元古界辽河群里尔峪组硼富集层.为确定赋存硼矿化地层层位构造蚀变带分布情况,利用地球化学与地球物理测量方法,在已知见硼矿钻孔构造蚀变带进行测量,总结分析硼矿化地球化学与地球物理特征.结合成矿地质条件,建立本区硼矿化地质物化探找矿模式,认为辽河群里尔峪组复背斜和复向斜与本区硼成矿有关.硼矿化分布区物化探特征为：地面磁力测量磁场值呈偏高磁场值分布;中梯激电测量为低视电阻率与偏高视幅频率;电测深反演电阻率反映为低阻线性构造带与偏高激电异常带,在矿化较强烈部位电阻率相对偏低;地球化学异常以硼为主,硼化探异常有明显的浓集中心,同时伴生铅、锌、银复合地球化学异常.     

内蒙古老国营子金铜矿床地质-地球物理勘查与研究

内蒙古老国营子金铜矿床是近年来利用地质与地球物理相互结合手段新发现的一个矿床。本次研究利用基于电磁原理的地球物理手段进行了找矿测试,结果表明:甚低频(VLF)地球物理扫面发现了近EW向和NW向的高阻带,分别对应了两条相应的矿化蚀变带。音频大地电磁法(EH4)测深影像显示矿化蚀变带表现为高阻异常带,与VLF的测量结果相一致。激电(IP)中梯测量显示矿化蚀变带具有高阻、高充电率和高金属因子异常特征。结合具体的地质特征,在老国营子金铜矿区综合运用这三种地球物理方法,取得了较好的找矿效果。     

黑山铜镍矿重磁电异常解释

通过钻孔与地面物性测定,查明含矿岩体和硅质板岩都具有较高的极化率和相对较低的电阻率,是引起电性异常的主要因素。利用重磁异常推断岩体的空间分布形态为一向下延伸长度大于走向长度的岩柱。由重磁异常圈定的岩体范围内电性异常为矿体引起,其外为岩性异常,这是区分矿与非矿异常排除干扰的最佳标志。     

滇西北香格里拉市红牛—红山铜矿勘查系统模型

滇西北红牛—红山铜矿床是义敦—沙鲁里岛弧上与晚白垩纪中酸性侵入体有关的典型的斑岩-矽卡岩-热液型铜矿床。本文通过对其成矿地质背景、矿床地质特征、矿化富集规律及成矿模式、矿床地球物理和地球化学特征的综合研究，建立了红牛—红山铜矿床的"大比例尺地质填图和综合研究+重力+激电和高精度磁测+土壤化探测+工程验证"组合勘查技术方法、"燕山晚期石英二长斑岩+接触带矽卡岩和层间破碎带矽卡岩+重力低异常+高磁异常+高视极化率和低视电阻率异常+Cu-Mo-Pb-Zn-Ag-Au等元素综合异常"组合勘查模型。地质调查研究确定矿床成矿地质体和找矿地质体、矿化类型及其空间分布规律，建立矿床"四位一体"的成矿模式和区域-矿区地质找矿模型。区域中小比例尺的土壤化探测量确定区域找矿靶区，大比例尺土壤化探测量进一步缩小找矿靶区，逼近矿体赋存部位。矿区处于1∶5万土壤测量圈定的Cu-Pb-Zn-Mo-Au-Ag元素综合高异常区，1∶2.5万土壤测量圈出Cu-Pb-Zn-Ag-W元素综合异常面积较大、强度高、浓集中心明显、元素套合好，与矿区铜（铁）矿体赋存区域异常相对应。区域重力低异常区和正磁异常强度高区域是重要的找矿靶区，矿区大比例尺磁异常和激电异常区确定了矿体的空间位置和产状；矿区铜（铁）矿体赋存区为低视电阻率、高视极化率异常区，高精度磁测表现为正负磁异常相伴。矿区地质-地球化学-地球物理综合勘查模型对矿区深边部找矿起到重要的指导作用。     

青海省玛沁县友后青地区钴铜矿化带成矿地质特征及找矿前景

青海玛沁县友后青地区大地构造位置处于阿尼玛卿缝合带内,在友后清地区发现了与基性-超基性岩体关系密切的钴铜矿化带。本文主要分析了友后青地区钴铜矿化带的成矿地质特征,认为华力西-印支期NW-NWW向的深大断裂控制着钴铜成矿作用。高精度磁测显示,区内有一条近NWW走向的磁异常带,异常强度中等偏高,呈串珠状分布。水系沉积物测量表明,以镍钴铬为主的多金属综合异常规模大,元素组合齐全,镍钴铬元素异常套合好。水系沉积物地球化学异常与高精度磁测异常可以很好的叠合在一起,在空间上与基性-超基性岩关系密切。沿NW-NWW向断裂带,与基性-超基性岩叠合较好的物化探异常区是该地区寻找钴铜矿的有利地段。     

柴达木盆地西缘砂岩型铀矿目标层地球物理响应特征

柴达木盆地西缘地区位于柴西坳陷构造带,断裂构造活动强烈,油气广泛分布,具有较大的铀成矿潜力.为研究砂岩型铀矿找矿目的层地球物理特征与铀成矿关系,先基于地球物理测井响应特征,查明区内砂体发育以及放射性异常范围,分析铀成矿环境;再结合能谱-地质剖面,研究不同地层岩性放射性特征;采用化学分析与伽玛测井,分析铀矿化段岩体中烃类...     

Integrated geophysical mapping of the Ifewara transcurrent fault system, Nigeria

Integrated geophysical methods involving magnetic and dipole–dipole resistivity (DDR) were conducted across a prominent zone of weakness clearly observable in Landsat MSS and SLAR images in the Precambrian basement complex of southwestern Nigeria. Up till now, the location and existence of this megascopic structure have not been confirmed using geophysical methods. With the objective of delineating this weak zone and its structural attributes, three traverses were established at 500 m intervals across it, and geophysical measurements were made at 10 m intervals along these traverses. Qualitative interpretation of the magnetic data obtained shows a diagnostic signature of a near-vertical fault, trending along a NNE–SSW direction. Also, the quantitative interpretation of the data using the non-linear least-squares regression technique indicates that the width of the magnetic anomaly ranges from 90 to 150 m, its dip angle varies between 75° and 85°; the anomaly is concealed by a regolith of approximately 15 m thickness. Furthermore, a 2D resistivity inversion of the field resistivity data reveals a three-layer model, representing thin resistive topsoil underlain by weathered bedrock, resistive bedrock with a distinct low resistivity zone located within the bedrock. The most plausible explanation for this low resistivity zone is that it was formed by shearing activities during Late Precambrian times. Conclusively, the integrated approach employed in this research confirms the existence of the supposed Ifewara shear zone (ISZ).     

秦岭华阳川地区航空伽马能谱异常特征及铀找矿方向

华阳川铀铌铅矿床是北秦岭造山带内一种类型特殊的铀多金属矿床。为了实现在外围快速找矿的目的,在矿床及其周边开展了1∶1万高精度航空磁放测量,获得高精度的航空放射性数据,通过对航放数据的解释,对下一步找矿勘探工作的部署有重要意义。通过对宏观上放射性元素的分布特征的研究,认为铀、钾异常分布特征相似,在测区西部有大面积分布,东部无成规模异常,钍异常在测区中部形成东西向异常带,与韧性剪切带的位置一致。铀异常有明显受北西向和北东向两组断裂控制,且在华阳川断裂北东盘异常面积大,强度高,但南西盘太古宙地层却无明显铀异常。本次研究计算了钍钾比、钍铀比、铀钾比、古铀含量、活性铀含量等参数,掌握了元素在不同地层单元的迁移富集规律。根据航空放射性异常,开展地面验证工作,圈定3条铀矿化带,达到了快速找矿的目的,对铀矿等战略性矿产的成矿规律研究及找矿勘查有积极意义。