Genesis and Evolution of Pegmatites in Eastern Colombia: Insights from Mineral Chemistry

Abstract

Pegmatites and granitic intrusives from eastern Colombia, belonging to the Guainía department, were studied to determine the generating magma type, as well as to assess the degree of magmatic fractionation and its relationship with the presence of Nb-Ta-bearing minerals (strategic minerals). To that end, 31 rock samples were studied; EPMA electronic microprobe analyses were conducted on apatite, biotite, garnet, microcline, muscovite, and tourmaline. The results from biotite, garnet, and tourmaline suggest that these rocks originated from a Fe-rich peraluminous melt. Moreover, content variation of Ba in microcline, Na in muscovite, Fe-Mg in biotite, and Mn-Sr in apatite, allowed the proposal of a magmatic evolutionary line for these rocks. Nb-Ta-bearing samples were present in the most fractionated rocks where tourmaline and garnet occurred, and thus, were proposed as possible indicators of strategic minerals.