• Understanding genesis of iron oxide concretions present in Dhandraul (Vindhyan) Sandstone: Implications in formation of Martian hematite spherules

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      https://www.ias.ac.in/article/fulltext/jess/130/0049

    • Keywords

       

      Iron oxide concretions; geochemistry; Martian hematite spherules; diagenesis; fluids interaction.

    • Abstract

       

      The iron oxide concretions of Shankargarh (Allahabad), India belongs to Dhandraul Sandstone of Vindhyan Supergroup. Petrography of concretions shows abundant quartz grains embedded within the iron oxide cementation. XRD analysis of the concretion shows diagnostic peaks for quartz, hematite, and goethite. The A–CN–K and A–CNK–FM ternary diagrams drawn for concretion and host rock bulk composition clearly indicate the interaction of concretions rock with iron-bearing diagenetic fluids. A negative Ce anomaly, lower Th/U ratio, and enrichment of redox responsive trace element (e.g., vanadium) indicate concretion formation is redox-controlled. The concretions show Fe enrichment and Si depletion as compared to the host sandstone. The mass balance calculations indicate that the total Fe$_{2}$O$_{3}$ in the ferruginous sandstone system is 17.63 wt%. The iron mobilization and recycling in the sandstone pore spaces have formed concretions with Fe$_{2}$O$_{3}$ (25–35% by volume). The sandstone volume required to produce a 6 mm diameter iron oxide concretion is 1807.83 mm$^{3}$. The Fe laminae and random red colouration patterns in Dhandraul sandstone are consistent with the movement of iron-enriched fluid through pores and spaces. These iron oxide concretions have similarities with the hematite spherules discovered in the Burn Formation, Meridiani Planum, Mars.

      $\bf{Highlights}$

      $\bullet$ Random red colouration pattern, iron laminae, the role of advective and diffusive processes during the formation of the iron oxide concretions present in Dhandraul sandstone are discussed in detail.

      $\bullet$ Mineralogical and textural study of the Shankargarh iron oxide concretions using petrography and XRD.

      $\bullet$ Fe bearing paleofluid circulation, redox processes, and elemental mobility (enrichment and depletion of elements) are discussed in detail using whole-rock geochemistry of Shankargarh iron oxide concretions and associated sandstone.

      $\bullet$ The similarities and difference between Shankargarh iron oxide concretions and Martian hematite spherules.

    • Author Affiliations

       

      PRAKASH JHA1 PRANAB DAS1 DWIJESH RAY2

      1. Department of Applied Geology, Indian Institute of Technology (Indian School of Mines) Dhanbad, Dhanbad, Jharkhand 826 004, India.
      2. Physical Research Laboratory, Ahmedabad 380 009, India.
    • Dates

       
  • Journal of Earth System Science | News

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