Discovery of a new kimberlite pipe at Krishnapuram, Wajrakarur Kimberlite Field, Eastern Dharwar Craton: Constraints from Field Geology and Petrochemistry

Systematic exploration by the Geological Survey of India, Hyderabad, involving geological mapping and trenching, led to the discovery of a kimberlite pipe at Krishnapuram (14° 30ʹ 22.50ʺ; 77° 36ʹ 27.20ʺ) within the Wajrakarur Kimberlite Field (WKF) of the Eastern Dharwar Craton (EDC). The identification of this pipe, designated as CC-6 in the Chigicherla (CC) cluster, was confirmed through extensive trenching, heavy mineral sampling and kimberlite indicator mineral (KIM) analysis using electron microprobe (EPMA). Petrographically, the kimberlite exhibits a typical porphyritic texture with macrocrystalline olivine grains (~1000-3000µm) embedded in a groundmass composed of phlogopite, Cr-spinel, perovskite, microcrystalline olivine, and clinopyroxene. Preliminary mineral chemistry analysis indicates that the olivine grains are rich in forsterite (Fo = 86–93), with an average MgO content of 50 wt.%. The groundmass phlogopite exhibits a high Mg# (0.88–0.91), while its Al₂O₃ vs. TiO₂ relationship suggest a kimberlitic affinity. The Cr₂O₃ vs. TiO₂ plot reveals that some spinels fall within the diamond-bearing kimberlite field. Standard major oxide plots (TiO₂ vs. Al₂O₃ and MgO vs. SiO₂) show the kimberlite fields (Group I & II), a classification further supported by trace element geochemistry plots (Y vs. Ce and La/Sm vs. La/Yb). Primitive Mg-numbers, high Ni, Cr contents, and significant enrichment in incompatible trace elements are characteristic features of CC-6. This discovery contributes to the ongoing regional mineral targeting for diamond exploration in the EDC, South India.