Luciano López

Geoelectric Exploration of the Purísima-Rumicruz District, Jujuy Province, Argentina

Purisima-Rumicruz district consists of several polymetallic veins, rich in copper and lead. The veins have a breccia texture and are located in shear bands, with locally high concentrations of sulfides in a carbonatic gangue. The host rock of the veins consists of a black shale sequence with thin levels of fine sands, with a low degree of metamorphism, and corresponds to the Acoite formation (Lower Ordovician). The depositional environment was an open clastic platform where storm processes prevailed. An exploratory program using induced polarization and resistivity with the dipole-dipole method was carried out with the objective of establishing geoelectric anomalies in depth, which would permit the identification of exploratory targets. The group of veins was divided into three sectors: Purisima, El Brechon, and La Nueva. Low-resistivity values correspond to faulty zones, some of which are related to surface veins. The presence of diagenetic pyrite in the shales of Acoite formation considerably increases background chargeability (induced polarization) values. However, small chargeability anomalies associated to low-resistivity values represent exploratory targets for the Purisima-Rumicruz district.

Defensibility Analysis with Geographical Information Systems in a Pukara in the Hualfín Valley, Argentina

Cerro Colorado is an archaeological village site located in La Cienaga de Abajo, in the South East of the Hualfin Valley (Belen, Catamarca, Argentina), at the top of a 150 m hill. It can be defined as a pukara—a fortified site—considering not only its location, but also its defensive walls, and the naturally inaccessible character of certain areas. Most of the radiocarbon data dates the site’s occupation to the first half of the fifteenth century, that is, around the beginning of the Inka conquest, although some data points to earlier settlement, and other to later periods. It is one of the most important archaeological sites in the valley in terms of the number of structures distributed in five topographically separated sectors. One of these ‘neighborhoods’ is the Central Sector, where singular archaeological contexts have been excavated in a special architectural complex, different from the typical local pattern. In view of these characteristics, the goals of this chapter are first to analyze the differences in the intrasite space and its relationship with the immediate environment, taking into account accessibility and visibility as elements to define defensibility; and second, to evaluate the results in relation to three fundamental problems for the Late and Inka Periods in Northwestern Argentina: intergroup conflicts, chronology, and social inequality.

Geology of the Manantial Espejo epithermal district, Deseado Massif, Patagonia Argentina

ABSTRACT The silver–gold epithermal mining district, Manantial Espejo, is located southwest of the Deseado Massif, Patagonia. The district is set into Jurassic volcaniclastic rocks of the Bahía Laura Group. A geological map of the district, at a scale of 1:50,000 drawn over a base map prepared from the fusion of satellite imagery and aerial photographs, is included. A suite of andesitic to rhyolitic eruptive units was identified, with prevailing high-grade rhyolitic ignimbrites. Travertine levels show the beginning of a hot-spring system in the region. Quartz veins, with typical crustiform–colloform banded structures, fill WNW, sub-vertical, normal faults, originating from extensional tectonics. The silicification of travertines, tuffs and breccia is the most common hydrothermal alteration.