Analysis was carried out at the Institute of Geosciences, recently recognized by the Meteoritical Society as the official repository of scientific data on these celestial bodies
In October 2020, while looking for gold with a metal detector in the rural area of Conceição do Tocantins (TO), a prospector ended up finding a space rock buried at a depth of almost 30 cm. The finding was recorded as the 85th Brazilian meteorite next to the global database Meteoritical Bulletin Database, maintained by Meteoritical Society.
To carry out the geochemical characterization of that celestial body and enable its recording, a team from the Institute of Geosciences (IG) at Unicamp used a technique in situ unprecedented for this type of material: laser ablation combined with inductively coupled plasma mass spectrometry (LA-ICP-MS). “The analysis has become much simpler and faster. The traditional method used for this type of meteorite is neutron activation analysis (INAA). This is a time-consuming and very specialized technique, which requires the use of a nuclear reactor, something difficult to access in Brazil”, explains Alvaro Crósta, professor at IG and one of the researchers involved in the geochemical analysis and registration in the Meteoritical Bulletin Database.
Regarding the validity of the results, fundamental for the acceptance of the record of a new meteorite, IG researchers carried out previous tests through the analysis of siderites with compositions determined by INAA and compared the results with those of LA-ICP-MS. Among the siderites analyzed are North Chile (standard meteorite for siderites), Campos del Cielo (Argentina), Gibeon (Namibia), Dronino (Russia) and the Brazilian Indianópolis (MG), Santa Catarina (SC), Santo Antônio do Descoberto (GO) and Nossa Senhora do Livramento (MT). “The comparison demonstrated that the results were compatible in terms of the content of chemical elements, crucial for the characterization of siderites, such as nickel, chromium, cobalt, iridium, platinum, iron and gold, among others”, say Jacinta Enzweiler, professor at IG , and Margareth Navarro, technician responsible for the Isotopic Geology Laboratory (LAGIS) and doctoral student at IG, responsible for the geochemical investigation of the meteorite. The analysis was carried out in collaboration with the rock's owner - collector and meteorite specialist André Moutinho - and with researchers from USP, the Federal University of Ouro Preto (UFOP) and the University of Alberta, in Canada.
Recently, the Unicamp Geosciences Institute was recognized as an official repository of scientific data on meteorites from Meteoritical Society, becoming the 5th repository of its kind in the country.
Meteorite record
According to Crósta, the process of recording a meteorite involves analysis by an international panel of experts, which takes into account mainly the quality and precision of geochemical and mineralogical analyses. IIAB siderites are composed mainly of iron and nickel, with small proportions of other metals. With the record of the Conceição de Tocantins meteorite by Meteoritical Society, the LA-ICP-MS technique is now also accepted for the analysis of new siderites. “This opens up wide possibilities, as it is a relatively greater access technique, lower cost and with significantly reduced analysis time when compared to INAA. With this work, the Unicamp Geosciences Institute was able to analyze new finds of meteorites, mainly metallic ones of the siderite type. Furthermore, a small fragment of the new meteorite becomes part of the IG collection, making it available for teaching and research activities in the area of meteoritics”, the Unicamp professor is proud.
Other information and curiosities about meteorites can be found in the two articles recently published in the magazine Super interesting, in partnership between the Brazilian Geology Society (SBG), with the participation of Alvaro Crósta.
