geochemical data of carbonatites

This study reports new occurrence of niobium mineralization from the Loe-Shilmancarbonatite complex, NW Pakistan. The complex is predominantly comprised of calcitecarbonatite, intruded by dolomite carbonatite, and minor late-stage carbonatite veins,intruding the earlier two varieties. Pyrochlore group minerals, which are the majorNb phases in the carbonatites and overlying supergene laterite, manifest numeroustextural and compositional discrepancies. Pyrochlores observed in calcite and dolomitecarbonatites of the complex are typified by oscillatory zoning, and are compositionallyCa-Na-pyrochlore, and therefore, illustrating crystallization under primary magmaticconditions. However, relatively Ta poor (2.42-5.11 wt%) and Nb rich (60.04-62.14 wt%)pyrochlores preserved in dolomite carbonatite are reflecting a more evolved nature ofthe dolomite carbonatite compared to Ta rich (6.89-10.11 wt%) pyrochlore of the calcitecarbonatite. In addition, pyrochlores of the late-stage carbonatite veins record patchyzonation and are characterized by A-site vacancies, likely due to leaching of Na and Ca,and enrichment of Ba-REE-Sr during hydrothermal alteration by a relatively low pH, Naand/or Si poor fluids. Similarly, intensively patchy zoned, porous and Fe3+ bearing A-sitedeficient bariopyrochlore in supergene laterite are produced by complete leaching of Caand Na from A-site, and by partial replacement of strongly-bounded Nb at B-site by Fe3+during supergene conditions.