Petrographic and geochemical analyses of dune sands from southeastern Mexico, Oaxaca, Mexico

Abstract

Dune sands in southeastern Mexico are compositionally and geomorphologically controlled by fluvial input, eastward longshore currents, and the intense winds traveling through the Isthmus of Tehuantepec. Tehuano winds are mainly responsible for the remarkable dune sand entrapment circumscribed to the exposure of volcano‐sedimentary outcrops. Compositionally, the dunes are potentially influenced by granite denudation, volcano‐sedimentary rocks, metamorphic units, and Quaternary sediments besides alluvium. Mono‐ to polycrystalline subangular to angular quartz, K‐feldspar, and schists suggest that granitic‐metamorphic rocks control the river and dune sands composition. Subordinate fractions of mica, Fe–Ti oxide minerals, and reduced amphibole (actinolite) indicate metamorphic‐volcano sedimentary‐granite as the potential parent rock of sand sources. The dune sands compositional framework shows slight flat‐type rare earth elements (REE) trends with a low light rare earth elements (LREE)/heavy rare earth elements (HREE) ratio (e.g., 6.13 ± 6.00), suggesting a significant control of granite rocks. Geochemical signals, CIA and CIW chemical indices support moderate weathering. The petrographic and geochemical analyses indicate little dune sand recycling by aeolian transport despite strong wind systems along the SE coast of Mexico. This provenance study evidences the exhumation of granite, metamorphic, and volcano‐sedimentary materials in the Oaxaca dune sands, confined by the regional geomorphology.