Sandstone-Hosted Uranium Deposits as a Possible Source for Critical Elements: The Eureka Mine Case, Castell-Estaó, Catalonia

Montgarri Castillo-Oliver,Lisard Torró,Cristina Villanova-De-Benavent,Jingyao Xu,Sandra Amores-Casals,Marc Campeny,Joaquin Proenza,Yael Díaz-Acha,Esperança Tauler,Joan Carles Melgarejo

doi:10.3390/min10010034

Abstract

The Eureka deposit in Castell-estaó in the Catalan Pyrenees is a Cu–U–V deposit, hosted by Triassic red-bed sandstones, and classified here as a low-temperature, sandstone-hosted stratabound metamorphite U deposit. The main mineralisation is stratabound, related to coal-bearing units and produced during the Alpine deformation by migration of hydrothermal fluids. In this stage, the original sedimentary and diagenetic components (quartz and calcite, micas, hematite and locally apatite) were replaced by a complex sequence of roscoelite, fine-grained REE phosphates, sulphides and Ni–Co arsenides and sulpharsenides, Ag–Pb selenides, bismuth phases, sulphosalts and uraninite. The black shales of the Silurian sediments underlying the deposit and the nearby Carboniferous volcanoclastic rocks are interpreted as the source of the redox-sensitive elements concentrated in Eureka. The sulphur source is related to leaching of the evaporitic Keuper facies. The REE transport would be facilitated by SO4-rich solutions. The reduction of these solutions by interaction with organic matter resulted in the widespread precipitation of REE and redox-sensitive elements, including many critical metals (V, Bi, Sb, Co), whereas barite precipitated in the oxidized domains. The occurrence of similar enrichments in critical elements can be expected in other similar large uranium deposits, which could be a source of these elements as by-products.

Highlights

The Eureka deposit has been historically classified as a sandstone-type uranium deposit hosted in a red-bed [1]
In the past these deposits were mainly mined for copper, within the 1940s, the Manhattan Project and the rapid increase of uranium mines in the Colorado Plateau playing out at the beginning of the nuclear power era, they became an important source of uranium [6,7,8] in the major role in the mineralogical characterisation of this type of deposit [9,10,11]
In other uranium sandstone deposits, hydrocarbons or H2 S released from underlying oil or gas fields were interpreted as the reducing agents [16,17], tectonic control plays a major role in these cases [18]

Summary

Introduction

The Eureka deposit has been historically classified as a sandstone-type uranium deposit hosted in a red-bed [1]. It was investigated in the 1960s as part of a development plan to find new resources. In the past these deposits were mainly mined for copper, within the 1940s, the Manhattan Project and the rapid increase of uranium mines in the Colorado Plateau playing out at the beginning of the nuclear power era, they became an important source of uranium [6,7,8] in the major role in the mineralogical characterisation of this type of deposit [9,10,11]. In other uranium sandstone deposits, hydrocarbons or H2 S released from underlying oil or gas fields were interpreted as the reducing agents [16,17], tectonic control plays a major role in these cases [18]

Methods

Findings

Discussion

Conclusion