• Fulltext


        Click here to view fulltext PDF

      Permanent link:

    • Keywords


      Meso- to micro-scale structures; Fry method; flattening deformation; bi-directional stretching; uranium mineralization; Singhbhum shear zone.

    • Abstract


      The mineralized (U bearing) rocks, near Bangurdih area, in the western part of the Singhbhum shear zone (SSZ) are strongly deformed and metamorphosed. The host and country rocks are mylonitic in nature with strong linear and planar fabrics. Surface studies indicate that the mineralized bodies are discontinuous in nature and occur sporadically. The thickness of the individual mineralized bodies is also not uniform. Present work is aimed at studying meso- and micro-scale deformational structures, their bearing on regional scale structure and their relation with the occurrences of U-mineralization in and around Bangurdih area. The area comprises predominantly of quartz–chlorite schist/quartz–chlorite–sericite schist with intercalated quartzite, meta-conglomerate and feldspathic schist of varying thickness. Apatite–tourmaline–magnetite-rich quartzite, chlorite schist and conglomerate are commonly radioactive. The uranium mineralized body at Bangurdih shows pinch-and-swell structure. Stretched thin quartz veins, observed within the sheared quartzite layers, have undergone layer parallel flow resulting in bidirectional pinch-and-swell structure lying on YZ and XZ sections of strain ellipsoid with their axes parallel and perpendicular to the shear lineation, respectively. Oriented samples were collected from quartz veins and the country rocks to prepare thin sections parallel to XY, YZ and XZ plane of strain ellipsoid from each sample for microstructural study. Aspect ratios of strain ellipses of XY, YZ and XZ sections are measured using Fry analysis. Flinn diagram shows that the rocks of the Bangurdih were subjected to bi-directional flattening (average k = 0.77), which indicates that in addition to simple shear deformation there is a shortening component perpendicular to the shear plane in this area. To correlate the strain pattern of Bangurdih with nearby areas, deformed pebbles from conglomeratic horizons and oriented samples of other rocks from Bhurkuli–Bundu and Rangamatia–Simulbera area were studied. Flinn diagram, prepared using all data, reveals that while the strain type in Bangurdih area shows intense flattening type of deformation, the Rangamatia–Simulbera area shows constrictional type of deformation (k values range from 0.57 to 0.88 and 1.02 to 2, respectively). Other locations (Bhurkuli–Bundu) in between Bangurdih and Rangamatia–Simulbera show both constriction and flattening type of strain (k values vary from 0.67 to 1.35). Therefore, it is concluded that the intense flattening type of simple shear deformation in Bangurdih area leads the ore rich layers to be stretched and detached in two directions (X and Y), which in turn, causes the mineralized body to occur intermittently with systematic trend on the surface and possibly in subsurface conditions too.

    • Author Affiliations



      1. Department of Geological Sciences, Jadavpur University, Kolkata 700 032, India.
      2. Present address: Hindustan Zinc Limited, B33 Premnagar, Zawar Mines, Udaipur 313 901, Rajasthan, India.
      3. Atomic Minerals Directorate for Exploration and Research, AMD Complex, Begumpet, Hyderabad 500 016, India.
      4. Atomic Minerals Directorate for Exploration and Research, AMD Complex, West Block-VII, R.K. Puram, New Delhi 110 066, India.
    • Dates

  • Journal of Earth System Science | News

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

© 2021-2022 Indian Academy of Sciences, Bengaluru.