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Integrated geophysical investigations in the Mudiyawas–Khera block of the Alwar basin of North Delhi Fold Belt (NDBF): Implications on copper and associated mineralisation

  • G Srinivasa RaoEmail author
  • R C Arasada
  • P R Sahoo
  • Israil Khan
Article

Abstract

Mundiyawas–Khera area of the Alwar basin in the North Delhi Fold Belt is well known for copper and associated gold mineralisation hosted within the felsic volcanic rocks. Gravity and magnetic surveys were conducted over the established mineralised blocks covering an area of \({\sim }\,8\,\hbox {km}^{2}\) in the study regions and these data were interpreted using the Euler deconvolution and 2D potential field modelling to determine the subsurface geometry and depth extent of the ore body. The geophysical signatures in this area reveal three prominent anomalous zones in corroboration with the surface geology and drill hole data. Although basic/mafic rocks have not been found within the area, the observed strong residual gravity high (\({\sim }\,4.0\,\hbox {mGal}\)) and residual magnetic high closures (\({\sim }\,90 \,\hbox {nT}\)) in the Mundiyawas block could be due to the cumulative effect of small-scale structural domes and the occurrence of sulphide mineralisation especially in the form of massive pyrrhotite. Moderate magnetic anomalies without appreciable gravity anomalies over the main copper-bearing zones in the Khera block are possibly due to the disseminated form, vein fillings and stringers of chalcopyrite, arsenopyrite and minor pyrrhotite hosted within the felsic volcanic rocks. The results of Euler depth solutions over these anomalous zones are found to vary from 50 to 250 m. Further, the subsurface geometry obtained across the Mundiyawas block through joint gravity and magnetic modelling constrained with drill hole information clearly depicts the presence of sulphide ore body having a width of 30–80 m within the carbon phyllite and tremolite-bearing dolomite. Combining the geophysical signatures noticed along the lithocontacts with the available geochemical and mineralogical observations of drill hole samples, we further confirm the strata-bound nature of sulphide mineralisation in the Mundiyawas–Khera area and it is controlled by both lithology and structural geometry of the host rocks.

Keywords

Alwar basin sulphide mineralisation gravity and magnetic surveys potential field modelling 

Notes

Acknowledgements

The authors gratefully acknowledge the financial assistance provided by IIT (ISM) under TEQIP-II sponsored projects (Dr S R Gangumalla/MRP-DDF/AGP/TEQIP-II and Dr P R Sahoo/MRP-DDF/AGL/TEQIP-II). We thank two anonymous reviewers for their helpful comments and suggestions that greatly improved this paper.

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Copyright information

© Indian Academy of Sciences 2019

Authors and Affiliations

  • G Srinivasa Rao
    • 1
    Email author
  • R C Arasada
    • 1
  • P R Sahoo
    • 2
  • Israil Khan
    • 3
  1. 1.Department of Applied GeophysicsIndian Institute of Technology (Indian School of Mines) DhanbadDhanbadIndia
  2. 2.Department of Applied GeologyIndian Institute of Technology (Indian School of Mines) DhanbadDhanbadIndia
  3. 3.Geological Survey of IndiaBhubaneswarIndia

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