At east of Colombia outcropping Proterozoic rocks of the Amazonian Craton as The Espina Hills inselberg, located ~10 km to the east of the Chorro Bocón indigenous community closely to the Inírida river in the Colombian Guainía department, hosts colluvial blocks of quartz and muscovite pegmatites enriched in HREE, P, Ta, Nb, U, Th minerals, that are occasionally extracted by local gold miners. Heavy mineral concentrates (~400 g from 10 kg colluvium) consist of up-to 50% xenotime and variable amounts of rutile-(Nb,Ta), monazite, and U-Th-minerals. After pXRF –preselection, crystals were mounted in epoxy resin and polished, and characterized mineralogically and chemically. LA-ICP-MS-dating yield U-Pb-crystallization ages for xenotime of 1382 ± 10 Ma, 1346 ± 14 Ma for monazite and 1342 ± 27 Ma for rutile-(Nb,Ta). These ages indicate an enrichment of Ti, Nb-Ta, REE and U-Th during connected alkaline to pegmatitic mineralizing events probably associated with the 1343-1410 Ma granitic Danta and Matraca intrusions. These critical mineral accumulations may be compared with similar colluvial deposits found near to San Jose at the Guainía River and Barranquilla at the Cuiarí River also in the Guainía department, linked to the presence of Mesoproterozoic granitic intrusions in the Statherian Mitú Complex, which also triggered tantalite and REE mineralization, often together with large gold deposits and wolframite.
- Franco Victoria, José Alejandro1,3*; Cramer, Thomas1,3; Poujol, Marc2,3; Bonilla, Amed3; Amaya, Zeze3