The Olmec culture arose and flourished on Mexico's southern Gulf Coast between 1800 and 400 BC, and developed extensive trade relationships for procurement of exotic materials from distant regions. The early capital of Mesoamerica's first civilization, the archaeological site of San Lorenzo, flourished between 1400 and 1000 BC, in the humid tropical coastal plains of southern Veracruz. Previous studies have revealed the regional importation of iron-ore, minerals and stone, such as obsidian, greenstone, and mica, for sculptures, grinding tools and artifacts used in domestic, ceremonial and productive activities. This study focuses on the sourcing of non-local artifacts, made from iron–titanium (ilmenite) oxide mineral and iron-ores, found in large quantities in the archeological excavations, in order to shed light on Early Preclassic trade. We study multi-perforated ilmenite artifacts and iron–titanium oxide ores from potential provenance areas using rock magnetic analyses, macroscopic observations, petrography, scanning electron microscopy and micro-geochemistry. Magnetic analyses include magnetic susceptibility as a function of high temperature, hysteresis, isothermal remanent magnetization (IRM) acquisition and backfield demagnetization of saturation IRM, and first-order reverse curves. Based on the Curie points and coercivity ranges, we suggest that the geographically unidentified source III-a, proposed earlier, corresponds to the Huitzo anorthosites. The mineralogical and textural relations between ilmenite and granulite host-rocks also suggest for the ilmenite in Olmec samples an origin that is similar to the Huitzo anorthosites. The compositional similarity between large apatite grains in the Huitzo and Olmec samples, and the high MgO content (1.3(6) wt%) of Olmec ilmenite are additional evidence that the provenance of the Olmec ilmenite artifacts is in the Huitzo area, within the northern part of the Oaxaquia Precambrian complex.
Mineralogical and magnetic characterization of Olmec ilmenite multi-perforated artifacts and inferences on source provenance
Luis M. Alva-Valdivia, Ann Cyphers, Maria de la Luz Rivas-Sánchez, Amar Agarwal, Judith Zurita-Noguera, Jaime Urrutia-Fucugauchi; Mineralogical and magnetic characterization of Olmec ilmenite multi-perforated artifacts and inferences on source provenance. European Journal of Mineralogy ; 29 (5): 851–860. doi: https://doi.org/10.1127/ejm/2017/0029-2654
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