Naslov
Micro-textural and micro-chemical evidences of mineral origin, alteration and weathering – case studies on REE minerals to understand REE distribution and accumulation in nature

Autori
Tomašić, Nenad

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
4th Croatian Microscopy Congress with International Participation, Book of Abstracts / Macan, Jelena ; Kovačević, Goran - Zagreb : Hrvatsko mikroskopijsko društvo ; Institut Ruđer Bošković, 2022, 16-16

ISBN
978-953-7941-41-3

Skup
4th Croatian Microscopy Congress (CMC 2022)

Mjesto i datum
Poreč, Hrvatska, 18.05.2022. - 20.05.2022

Vrsta sudjelovanja
Pozvano predavanje

Vrsta recenzije
Domaća recenzija

Ključne riječi
rare earth element minerals, granitic pegmatites, bauxite

Sažetak
Rare-earth elements (REE) are a valuable commodity in modern industry and technology, used to optimize the properties of many materials. Also, the distribution patterns and various modes of the occurrence of these metals in nature are of a great significance in interpreting geological processes. All these make REE and REE minerals a frequent topic in geological studies. REE are widespread in various geological environments, though they rarely occur in large amounts at the same place, which makes a search for REE deposits not an easy task. Employment of diverse micro-techniques is essential for the haracterization of REE minerals, particularly in the study of their structural, textural, and chemical properties. Here, two case studies on REE minerals originating from two different environments will be presented, showing features imprinted by their formation and alteration history. Certain types of granitic pegmatites usually accommodate various REE minerals, such as monazite-(Ce), xenotime-(Y), aeschynite-(Y), euxenite-(Y), gadolinite-(Y), and many others. Monazite-(Ce) is a REE mineral frequently used as a REE ore mineral, but also employed in many studies for interpretation of geological settings and a common mineral of choice in geochronology due to U and Th content. Various late- and post-magmatic processes influence the chemistry of the mineral, producing alteration patterns ruled by the dissolution-reprecipitation process and causing redistribution of REE. Similar processes have been observed in gadolinite-(Y), thus helping us understand the nature of REE mobility and constraints in the dating application of these minerals. Micro-chemical studies indicate the alteration paths and evolution of these minerals in granitic pegmatites. Bauxite is a sedimentary rock and aluminium ore, which can also contain elevated abundances of REE relative to its hosting rocks. Thus, it is a potential future source of REE, particularly after its processing in Bayer process for alumina production. Bayer process frequently doubles REE concentrations in the remaining red mud, an industrial by-product, so far considered a harmful waste. REE occurrence in bauxite can be related to various mineral phases and mechanisms, like adsorption to aluminium and iron oxides/oxyhydroxides. Thorough microscopy studies indicate a presence of REE minerals, which can be detrital (inherited from weathered parent rocks) or authigenic (formed in bauxite during episodes of weathering and bauxitization). Micro-textural studies reveal their sedimentation history but also give insight into mobility and accumulation of REE in a bauxite profile.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

POVEZANOST RADA