Ore Mineralogy, Trace Element Geochemistry and Geochronological Constraints at the Mollehuaca and San Juan de Chorunga Au-Ag Vein Deposits in the Nazca-Ocoña Metallogenic Belt, Arequipa, Peru

Jorge Crespo,Katharina Pfaff,Madeleine Guillen,Roberto Huamani,Elizabeth Holley

doi:10.3390/min10121112

Jorge Crespo, Katharina Pfaff + Show 3 more

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https://doi.org/10.3390/min10121112

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Abstract

The Mollehuaca and San Juan de Chorunga deposits are hosted in the poorly explored gold and copper trends of the Nazca-Ocoña metallogenic belt in Arequipa, Perú, which extends from Trujillo (9 °S) to Nazca-Ocoña (14 °S). The aim of this study is to characterize the age, occurrence, and distribution of quartz vein-hosted Au-Ag mineralization and associated trace elements (e.g., Hg, Pb, Cu, Zn, and Bi) in these deposits. Here, we present geological mapping, geochemical whole rock inductively coupled plasma (ICP)-MS data of the veins, petrographic observations, backscattered electron images, quantitative SEM-based automated mineralogy, and electron microprobe analyses (EMPA). Despite the fact that there are numerous small-scale gold mines in the Nazca-Ocoña metallogenic belt, there have been few studies that document the origin and geological evolution of these deposits or the implications for decision-making in exploration, metallurgical processing, and environmental management. In this research, we document the host rock age of the mineralized veins (129.2 ± 1.0 Ma; U-Pb in zircon), the mineralization age (95.86 ± 0.05 Ma; 40Ar/39Ar in secondary biotite), the occurrence and distribution of Au-Ag in the veins, the mineral zonation present in the vein system, and the zircon geochemistry, in order to provide tools for natural resource management in the metallogenic belt.

Highlights

IntroductionArtisanal and small-scale gold mining is widespread in Peru where more than 200,000 people rely directly or indirectly on this activity [1]
The Nazca-Ocoña metallogenic belt of southwestern Perú hosts numerous gold deposits, many of which are mostly exploited by small-scale methods, but little has been published on the characteristics of the deposits or the host rocks.Artisanal and small-scale gold mining is widespread in Peru where more than 200,000 people rely directly or indirectly on this activity [1]
We suggest that additional case studies should examine whether the observed zircon signatures are consistent across a greater range of deposit types than previously recognized, in which case zircon geochemistry may become a valuable tool to discriminate fertile from infertile plutons in a variety of geological settings

Summary

Introduction

Artisanal and small-scale gold mining is widespread in Peru where more than 200,000 people rely directly or indirectly on this activity [1]. In Arequipa, small-scale mining activities occur in several areas, where miners and communities are exposed to adverse environmental and safety conditions due to the current mining and mineral processing techniques [2,3]. Artisanal miners follow the ore-bearing veins, Minerals 2020, 10, 1112; doi:10.3390/min10121112 www.mdpi.com/journal/minerals. Minerals 2020, 10, 1112 adjusting their mining and processing techniques based on their findings. PEERorigin [4,5,6], small-scale gold mining is the main economic activity there. The ore-bearing veins, adjusting their mining and processing techniques based on their findings. This contribution case studythat datadescribe from two deposits in the Arequipa region, Mollehuaca

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