Petrological, Textural, Compositional, and Economic Potential of Carbonatites from the Peshawar Plain Alkaline Igneous Province, Northwestern Himalaya

Carbonatites, which are rare mantle-derived igneous rocks that are mainly enriched in carbonate minerals and host relatively higher amounts of rare earth element (REE)-bearing phases, remain subjects of extensive geological research due to their enigmatic origin and potential economic importance. This study aims to describe the petrographic, mineralogical, and some rare-earth element (REE) abundances of four carbonatite bodies (known as Sillai Patti, Loe Shilman, Warsak, and Jambil) exposed in the Peshawar Plain Alkaline Igneous Province (PPAIP), northwestern Himalaya, Pakistan, to identify their economic potential. The observed petrographic, textural features, and chemical compositions of the constituent minerals of the carbonatites were utilized to elucidate the evolutionary processes through which the rocks evolved. The results indicate distinct mineralogical assemblages dominated by calcite, dolomite, apatite, pyroxene, biotite, and feldspar, with accessory opaque and REE-bearing phases, such as pyrochlore, monazite, and britholite. The apatite grains display compositional zoning reflecting their growth under magmatic conditions. The petrographic features of apatite in some carbonatite samples, exhibiting preferred orientation in a particular direction and spongy or murky textures, indicate that the studied rocks underwent post-magmatic deformation or hydrothermal alteration. Calcite and dolomite, coexisting in some carbonatite samples, exhibit significant Mg-Fe variation, which is possibly related to magmatic differentiation. The pyroxene compositions vary from a low-calcium enstatite–ferrosilite series to high-calcium diopside, suggesting variable crystallization environments among the carbonatite bodies studied. The abundance of REE-bearing phases in the studied carbonatites emphasizes their high economic potential. These findings indicate that the PPAIP carbonatites originated from mantle-derived magmas and subsequently experienced metamorphic/metasomatic overprinting during their tectonic evolution. The abundance of REE-rich phases such as apatite, pyrochlore, monazite, and britholite underscores their high economic potential.