Investigation of auriferous mineralisation over greenstone schist belt of Dhanjori Basin, Eastern India using 2D electrical resistivity tomography and induced polarisation surveys. Issue 4 (4th July 2019)

• Record Type: Journal Article
• Authors: Gupta, Ashok Kumar; Singh, Roshan K.; Srivastava, Shalivahan
• Is Part Of: Exploration geophysics. Volume 50:Issue 4(2019)
• Page Start: 364
• Page End: 375
• Publication Date: 2019-07-04
• Subjects: Auriferous mineralisation -- greenstone schist belt -- 2D ERT/IP -- inversion; Geophysics -- Periodicals; Prospecting -- Geophysical methods -- Periodicals; 622.15
• DOI: 10.1080/08123985.2019.1606204
• Languages: English
• ISSNs: 0812-3985

Abstract

Abstract : Dipole–dipole resistivity and induced polarisation (IP) surveys were conducted over a conductor identified from an audiomagnetotelluric (AMT) survey run in a greenstone schist belt of the Dhanjori Basin, Eastern Singhbhum, India. The shallow conductors identified in the AMT were not well resolved due to insufficient high-frequency data. The geology of the area suggests that gold mineralisation is associated with quartz pebble conglomerates (QPC) or sulfides. The resistivity and IP surveys were conducted over an area of 1.2 × 0.4 km with an electrode spacing of 10 m and a line spacing of 50 m. This data set was inverted using Gauss–Newton optimisation. Based on the resistivity and IP results, responses were categorised into five distinct geological/geophysical signatures defining local lithology and associated mineralisation. Low resistivity and low to moderate chargeability at depths up to 20 m from the surface indicate the weathered zone (which is not a strong feature in some of the IP models). High resistivity and high chargeability zones are identified as quartz vein/QPC with disseminated sulfide ± auriferous concentrations. Moderate resistivities and chargeabilities are interpreted as being related to the greenstone schists that make up the major part of the geology in the Dhanjori Basin. Zones with high resistivity and low chargeability are interpreted as Proterozoic gabbroic anorthosite ultramafics (PGAU) and/or younger dolerites. PGAU is intrusive to the local greenstone schist/phyllites; we have observed that its resistivity is considerably high and there is no significant gain in its chargeability due to the hindrance in ionic and electronic movement in the formation. Low resistivity and low to moderate chargeability zones below the weathered layer are attributed to mineralisation associated with massive sulfides. The integrated geophysical study indicates the presence of quartz vein/QPC and sulfide hosting auriferous mineralisation over the greenstone schist belt of the Dhanjori Basin, Eastern Singhbhum.