Tracking rock sources of 3800-year-old burial goods using X-ray diffraction, electron microprobe analyses and X-ray mapping: a case study from Córdoba, Argentina

Abstract

An axe head and a round bead were found at the burial site of an adult male (dated at 3770 ± 90 14C years BP) at Amboy, Córdoba (central Argentina). These artifacts were studied using electron microprobe, scanning electron microscopy and X-ray diffraction, for a complete characterization of the materials and to infer the source. The axe head is carved from very fine-grained tonalite (composed dominantly of zoned plagioclase, quartz, potassic feldspar, chlorite, magnesiohornblende, titanite and magnetite) with microporphyritic texture. The bead is mainly composed of muscovite, an amorphous Cu–Al hydrated silicate (similar to chrysocolla) and malachite. Based on the coincidence between textures, mineralogy and chemical compositions, the most likely source of the axe is dykes of metaluminous tonalite scattered in the Sierras Chicas Range. The provenance of the bead could not be ascertained, but it is probable that it was carved from material collected from a very localized outcrop. These artifacts associated with a funerary context represent one of the oldest evidences of such materials for hunter–gatherer groups in central Argentina.