Copper in Ordinary Chondrites: Proxies for Resource Potential of Asteroids and Constraints for Minimum-Invasive and Economically Efficient Exploitation
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Planetary and Space Science 194 (2020) 105092 Contents lists available at ScienceDirect Planetary and Space Science journal homepage: www.elsevier.com/locate/pss Copper in ordinary chondrites: Proxies for resource potential of asteroids and constraints for minimum-invasive and economically efficient exploitation Katarzyna Łuszczek a, Agata M. Krzesinska b,* a Wrocław University of Science and Technology, Faculty of Geoengineering, Mining and Geology, Wybrzeze_ Wyspianskiego 27, 50-370, Wrocław, Poland b Centre for Earth Evolution and Dynamics, Department of Geosciences, University of Oslo, Oslo, PO1028 Blindern, 0316, Oslo, Norway ARTICLE INFO ABSTRACT Keywords: Ordinary chondrites originate from S-type asteroids. These meteorites can be used for laboratory studies that Native copper further our understanding of the geological conditions on asteroids, including assessment of their resource po- Extraterrestrial resources tential. Asteroids have since long been considered to host significant resources of siderophilic elements such as Fe, ISRU Ni, Co, Cu, that could be exploited in situ. However bulk rock mining would be largely impractical. In this paper, S-type asteroids we report on abundance and mineral occurrences of copper in H chondrites, identify Cu carrier minerals and Ore-forming processes on asteroids Shock-darkening interpret their distribution in the context of processes that must have affected parent bodies. This leads us to suggestion that some parts of S-type asteroids contain Cu in a form and amount that would satisfy requirements of potentially economically and environmentally more efficient exploitation. Parent bodies of chondrites contain 70–100 ppm of Cu in bulk and this is mainly contained in Fe,Ni-alloy. However, parts of asteroids that were affected by shock processes and post-shock thermal annealing may host Cu that exsolved from primary alloy and forms native, pure-Cu grains. Up to 50 ppm of Cu may be present in such phase in these parts of asteroids. Grains of native copper can be extracted from the host rock via mechanical mineral processing methods, releasing need of extensive chemical leaching. This makes potential exploitation more targeted and less destructive for the local environment. A characteristic feature associated with enrichment in native Cu in chondrites is presence of shock-darkened zones. Therefore, we suggest that shock-darkened asteroids are potentially best sites for Cu exploitation. 1. Introduction nickel, copper or cobalt. It is widely assumed that the best prospective sites for extraction of these metals in space would be S-type-like asteroids In the era of space exploration and approaching exploitation, (Kargel, 1994; Sonter, 2006; Badescu, 2013; Martínez-Jimenez et al., increased attention is given to identify environments in space that may 2017; Łuszczek and Przylibski, 2019), both Near Earth Asteroids (NEAs) satisfy demand for resources. As summarized in in-situ resource utiliza- and bodies located in the main asteroid belt. This is because most as- tion (ISRU) initiative (Sacksteder and Sanders, 2007), to fulfill space teroids of S-type contain significant volume of native metal minerals exploration goals, the future missions will need to predominantly base on mixed with silicate minerals. It is known that, compared to the Earth’s resources that are available in-situ in space. This triggers scientific crust, asteroids contain considerably higher amount of Fe, Ni, Co, Cu and searches for resources, but also urges the attempts toward definition of precious metals (Kargel, 1996; Lewis, 1997; Blair, 2000; Tagle and Ber- exploitation actions that would be minimum-destructive to the local lin, 2008; Łuszczek et al., 2012, 2018; Łuszczek and Przylibski, 2019). environment. However, extraction of the above metals from the bulk rock in asteroids Increasing number of studies have been currently conducted to may be impractical as it would require significant chemical reprocessing. identify and to better understand potential of space in providing various On the Earth, mining is typically conducted in places where relative key resources (Kargel, 1996; Lewis, 1997; Blair, 2000; Sercel et al., enrichments of specific metals occurred as a result of so called ore- 2018). Among them are searches for siderophilic metals, such as iron, forming processes. The ore-forming processes are responsible for the * Corresponding author. E-mail address: [email protected] (A.M. Krzesinska). https://doi.org/10.1016/j.pss.2020.105092 Received 21 June 2020; Received in revised form 21 August 2020; Accepted 11 September 2020 Available online 22 September 2020 0032-0633/© 2020 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). K. Łuszczek, A.M. Krzesinska Planetary and Space Science 194 (2020) 105092 transport of certain elements and relative enrichment in specific zones. distribution of elemental Cu in chondrites. As a consequence, this may The chemical and physical environment allows for the formation of imply complex, uneven distribution of elemental Cu in S-type asteroids. specific minerals that are enriched in elements of interest in a way that The aim of our study is to verify whether thermal, shock and post- extraction and reprocessing can be done with methods requiring lower shock annealing may be responsible for formation of native copper in energy or enabling higher yield. By analogy, identification of processes ordinary chondrites. Our goal is to infer in what extent the processes may that may have led to transport of elements within asteroids, can poten- lead to redistribution of the elemental copper and in what scale-distance tially facilitate exploration and increase exploration efficiency. Such the elemental transport may occur. With understanding of the processes studies are, however, lacking so far. Understanding of such processes that control redeposition of elemental copper in ordinary chondrites, we appears especially important considering rather complex collisional estimate the resource potential (and first-constraint distribution) of as- evolution of asteroids (e.g., Beitz et al., 2016; Moyano-Cambero et al., teroids in Cu. Especially, we seek to define most likely host phases of 2017; Gattacceca et al., 2017) that leads to severe reprocessing and copper in asteroids, and to designate where inside these bodies miner- regolith gardening, which altogether puts significant challenges on pro- alogical changes regarding the Cu host phases can occur to the level of spective resource exploitation. being considered ‘ores’ in a practical, exploration sense. This will be In this paper, we discuss processes that may drive transport of copper crucial to define challenges and limitations of copper resource exploita- within asteroids and propose that zones within asteroids can be identi- tion and to support strategies of future in-situ resources utilization. fied, where copper occurrences enable higher gain and efficient extrac- H chondrites were chosen for this study as they show high overall, tion protocols. Copper is an important metal in today’s world. It is the bulk content of copper (McSween and Huss, 2010; Wasson and Kalle- third most commonly utilized metal in the industry, after iron and meyn, 1988) and relatively large range of native copper abundance aluminium. Copper is a main constituent of alloys such as brass or bronze, (Rubin, 1994). which are corrosion resistant, therefore are commonly applied in con- struction industry. Copper is also a perfect electrical conductor and is 2. Samples and methods broadly used in electrical wiring, power transmission, telecommunica- tion etc. Additionally, copper is used in many other industry sectors due Samples of equilibrated H chondrites: Chergach (H5), Tamdakht to the features such as malleability, bendability or easiness of metalwork (H5), Gao-Guenie (H5), Dho 1663 (H5), Thuathe (H4/5), Pułtusk (H4-6) (Friedrich et al., 1986; Craig et al., 2011; British Geological Survey and Zag (H3-6) were selected for the study. These samples record range Report, 2007). Copper will most likely be a similarly essential metal for of shock deformation and post-shock annealing conditions (Rubin et al., human and robotic activities in near-future space exploration. 2002; Reimold et al., 2004; Chennaoui-Aoudjehane, 2009; Swindle, Before direct analysis of environmental conditions on asteroids is 2009; Schmieder et al., 2016; Krzesinska, 2016, 2017). possible, the best approach to address their resource potential is to For these samples, bulk content of Cu was measured. Simultaneously, combine laboratory analyses of chondrites with spectroscopic analyses of all Cu-bearing phases were identified in the samples and the volume asteroids (Dunn et al., 2013; Trigo-Rodriguez et al., 2014; Burbine, 2017; content of these minerals calculated. This allows to identify copper car- Cloutis et al., 2018). In this study we focus on S-type asteroids and or- rier phases and to understand the distribution of elemental copper be- dinary chondrite class, which are genetically connected (Dunn et al., tween these minerals. In next step, textural analysis was performed to 2013). Chondrites are mixtures of silicate minerals, native metals such as understand the relationship between occurrences of Cu-rich host phases kamacite and taenite as well as oxides and sulfides (Bischoff and Stof€ fler, and products testifying on shock heating and annealing of chondritic 1992; Brearley and Jones, 1998; Rubin, 2010). rock.