Abstract
The oceanic seabed contains a variety of mineral resources related exclusively to submarine environments. Limited information has been documented for the seabed offshore of Chile, which is particularly interesting due to its geodynamic context and large area. Mineralogical and geochemical analyses of 16 sites within the Chiloé–Taitao area, from 83 to 3388 m in depth, were carried out. The most abundant minerals are quartz, feldspars, pyroxenes, amphiboles, epidote, and biotite, with lower quantities of zircon, white mica, olivine, pyrite, magnetite, ilmenite, and hematite. Framboidal pyrites are mainly present at >900 m depth, and could be associated with methane hydrates, which have been reported in the area and its surroundings. Tenorite, sphalerite, tennantite, cordierite, birnessite, and tellurobismuthite were revealed by XRD analysis at low concentrations but at many sites. Birnessite, a Fe–Mn nodule-forming mineral, was widely detected, and Pearson correlations showed elemental associations related to the presence of Mn oxides. Samples did not evidence Fe–Mn nodules, probably due to the redox and depth conditions. Nonetheless, it is probable that to the west, polymetallic nodules are present in deeper zones. In the southern part of the area, reflective grains were identified, with up to 58.3 wt.% Cu; these grains might be derived from the continent or formed by in situ diagenetic precipitation.
Highlights
IntroductionThe exploration of the ocean floor has been increasing due to the presence of mineral resources (e.g., [1,2,3,4])
Other rock-forming minerals such as zircon, white mica, and K-feldspar were observed in low quantities; these were related to continental shelf zone samples
Magnetite, hematite, and ilmenite were present in low proportions but in all samples
Summary
The exploration of the ocean floor has been increasing due to the presence of mineral resources (e.g., [1,2,3,4]). The Pacific Ocean basin has important polymetallic deposits, including Fe–Mn nodules and crusts and volcanogenetic sulphides, as well methane hydrates, but its investigation at high and intermediate latitudes is still incomplete [3,5]. Oceanic ridges and areas near the coast, which record Pleistocene glaciations, are key to the study of these mineral occurrences [6,7]. In Chile, the exclusive economic zone (EEZ) covers an area of approximately five times the continental territory and very limited information about its mineral resources is available (e.g., [8]). Off the shore of southern Chile, between Chiloé
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