Preliminary Resource Potential Assessment of Placer Light Rare Earth Elements (LREEs) from mid-Siwalik Sediments of a late Miocene Himalayan Foreland Basin, Pakistan

Abstract

The present study has assessed the preliminary placer LREEs resource potential of mid-Siwalik Group Dhok
Pathan Formation from Surghar-Shingar Range of NW Himalayan foreland Fold-and-Thrust-Belt and regarded them as
indicative resources only. The analytical results of bulk samples of sandstone did not show any anomalous concentration
of REEs. However, the ICP-MS results of heavy minerals laminations (black sands) revealed high concentrations (ppm)
of LREEs (La: 975, Ce: 2831, Pr: 193, Nd: 746, Sm: 127, Gd: 98.70). We identified monazite-(Ce) [Ce, La, Nd]PO4 as
the primary LREEs-bearing mineral through Electron Probe Micro Analysis (EPMA). The representative quantitative
micro-mineral analysis of monazite confirmed promising concentration of Rare Earth Oxides (REOs) maximum (in
weight %) - La2O3: 16.20, Ce2O3: 37.82, Pr2O3: 4.77, Nd2O3: 21.72, Sm2O3: 5.23, Gd2O3: 4.88. Considering the thickness,
lateral extension and depositional setting of host sediments along-with anomalously high concentrations of LREEs, it has
been concluded that these Siwalik sediments host good indicative placer resource potential for low-cost recovery of
LREEs.