The Palaeo- to Meso-Proterozoic (1.0–2.4 Ga) North Singhbhum Mobile Belt (NSMB) is an assembly of multiphase folded, low- to medium-grade meta-sedimentary and meta-igneous rocks, lying within the north Singhbhum crustal province. The mobile belt is situated between the Archean Singhbhum craton in the south and the Meso/Neo-Proterozoic (0.9–1.7 Ga) Chotanagpur Gneissic Complex in the north. Gold mineralisation of moderate concentration is reported from different parts of NSMB along shear /fracture zones within the volcano-sedimentary and meta-sedimentary rocks sequence. The mineralisation is structurally controlled and is associated with higher order shear zones. Gold occurs in association with sulfides like pyrite, arsenopyrite, pyrrhotite, chalcopyrite, sphalerite, etc. This work attempts to map the auriferous shear/fracture zone along the Babaikundi-Birgaon axis (BBA), which lies within the NSMB. In the present study, combined geophysical approach comprising self-potential (SP), electrical resistivity tomography (ERT) and induced polarisation (IP) methods were used for mapping of subsurface gold prospects. SP data were collected along 7 profiles at 10 m station interval with approximate profile separation of 100 m. The anomalies of possible ore bodies were found at depth of about 18–25 m using Euler deconvolution of SP data. The ERT and IP data were collected along four profiles at 10 m electrode spacing with approximate profile separation of 100 m. The inverted resistivity sections indicate very low resistivity value in the depth range of ∼20 m inferring highly conducting, while relatively high chargeability are also observed at the depth range of ∼25 m. The possible existence of Babaikundi-Birgaon lineation and the occurrences of sulfide minerals in quartz reef associated with gold mineralisation were mapped based on the horizontal locations and extensions of negative anomaly in SP data, low resistivity in 2-dimensional (2D)-inverted resistivity section and high chargeability in 2D-inverted IP section. Previous studies based on electron probe micro-analyzer (EPMA) and scanning electron microscope (SEM) analysis over the study area substantiate our combined geophysical interpretations for the presence of gold prospective zones along the BBA. Highlights Integrated geophysical approach comprising SP, ERT and IP methods Delineation of BBA Mapping of subsurface gold prospects/ mineralisation Validation of results using borehole data, EPMA and SEM–SED analysis of rock samples (a) Map showing profiles AA/, BB/, CC/ and DD/across the Babaikundi-Birgaon Axis (BBA). (b) Upward continued (60 m) self-potential (SP) anomaly map showing possible extension of a part of BBA. Schematic resistivity (c) and chargeability (d) distribution models showing possible extension of a part of the BBA. (e) mineralised sample with sulfide hosted quartz reef in BBA. The possible existence of BBA and the occurrences of gold-bearing sulfide minerals in quartz reef are mapped based on the horizontal locations and extensions of negative SP, high conducting / low resistivity in electrical resistivity tomography (ERT) and high chargeability in Induced Polarization (IP). Note that profiles C-C/ and D-D/ are not parallel to each other; their field orientation is shown in Figure 1(c) and Figure 2. GRAPHICAL ABSTRACT

中文翻译：

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结合自电位、电阻率层析成像和诱发极化，用于绘制印度北辛格布姆移动带 Babaikundi-Birgaon 轴部分上的金矿区

古到中元古代 (1.0-2.4 Ga) 北辛格布移动带 (NSMB) 是多相褶皱、中低品位变质沉积和变质火成岩的集合，位于北辛格布姆地壳省内。移动带位于南部的太古代 Singhbhum 克拉通和北部的中/新元古代 (0.9-1.7 Ga) Chotanagpur 片麻岩杂岩之间。据报道，在火山-沉积岩和变质沉积岩序列中，沿剪切/断裂带的 NSMB 不同部分有中等浓度的金矿化。矿化在结构上受到控制，并与高阶剪切带有关。金与硫化物一起出现，如黄铁矿、毒砂、磁黄铁矿、黄铜矿、闪锌矿等。这项工作试图绘制沿位于 NSMB 内的 Babaikundi-Birgaon 轴 (BBA) 的含金剪切/断裂带。在本研究中，包括自电位 (SP)、电阻率层析成像 (ERT) 和激发极化 (IP) 方法的组合地球物理方法用于绘制地下金矿前景。SP 数据沿 7 个剖面以 10 m 站间隔收集，剖面间隔大约为 100 m。使用 SP 数据的 Euler 反卷积在约 18-25 m 的深度发现了可能的矿体异常。ERT 和 IP 数据沿四个剖面收集，电极间距为 10 m，剖面间距大约为 100 m。反演的电阻率剖面表明在约 20 m 的深度范围内电阻率值非常低，推断高导电性，同时在~25 m的深度范围内也观察到相对较高的带电能力。Babaikundi-Birgaon线的可能存在和与金矿化有关的石英礁中硫化物矿物的产状根据SP数据中负异常的水平位置和延伸，二维（2D）反相电阻率剖面中的低电阻率绘制和 2D 倒置 IP 部分的高可充电性。先前基于电子探针显微分析仪 (EPMA) 和扫描电子显微镜 (SEM) 分析的研究区域的研究证实了我们对沿 BBA 存在金矿区的综合地球物理解释。亮点 综合地球物理方法包括 SP，ERT 和 IP 方法 划分 BBA 地下金前景/矿化图 使用钻孔数据、EPMA 和岩石样品的 SEM-SED 分析验证结果 (a) 地图显示横跨 Babaikundi 的剖面 AA/、BB/、CC/ 和 DD/ - 比尔冈轴（BBA）。(b) 向上持续 (60 m) 自我电位 (SP) 异常图，显示 BBA 的一部分可能延伸。示意图电阻率 (c) 和可充电性 (d) 分布模型显示了 BBA 的一部分可能的扩展。(e) BBA 中含有硫化物的石英礁矿化样品。根据负SP的水平位置和延伸、电阻率层析成像（ERT）中的高导电/低电阻率和诱导极化（IP）中的高带电性绘制了BBA的可能存在和石英礁中含金硫化物矿物的出现）。请注意，剖面 CC/ 和 DD/ 彼此不平行；它们的场取向如图 1(c) 和图 2 所示。 图形摘要