A Review of the Arroyo Rojo VMS Deposit, Tierra del Fuego

Abstract

The Arroyo Rojo VMS deposit is the most studied polymetallic ore of Tierra del Fuego, Argentina. The first mentions of its existence began in the 80s by Minera Aguilar, which has discovered a small nunatak containing a lens of polymetallic massive sulfides, since then various authors have studied the geology and mineralization of the site. Several anomalies of copper, lead and zinc were also identified in the region during regional prospection in the 70s. The deposit is within the Lemaire formation, a rhyolitic low-Jurassic marine volcano-sedimentary complex formed during the fragmentation of Gondwana. The mineralization consists of a massive sulfide lens that varies from 1.5 to 4 m in thickness in surface and two more massive sulfide lenses at depth with a thickness that varies between 3 and 18.6 m. The ore is composed mostly of pyrite and sphalerite, minor galena, chalcopyrite and pyrrhotite. Some of the original textures like framboidal, colloidal and euhedral type can be still recognized among other deformation and recrystallization textures. The hydrothermal alteration consists of a roughly concentric zonation with an inner silica and clorithic zone and an external sericitic zone. Even though previous works have classified the Arroyo Rojo deposit as Kuroko type, more recent studies have shown evidence that associates this deposit with a brine pool deposition.