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| Tiros | |||||||||||||||||||||||||||||||||||||||
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| Basic information | Name: Tiros This is an OFFICIAL meteorite name. Abbreviation: There is no official abbreviation for this meteorite. Observed fall: Yes, probable fall Year of probable fall: 2020 Country: Brazil Mass:  400 g | ||||||||||||||||||||||||||||||||||||||
| Classification history: |
This is 1 of 451 approved meteorites classified as Howardite. [show all] Search for other: Achondrites, HED achondrites, and Howardites | ||||||||||||||||||||||||||||||||||||||
| Comments: |
Approved 28 Nov 2020 Revised 23 Jan 2024: reclassified | ||||||||||||||||||||||||||||||||||||||
| Writeup |
Writeup from MB 109:
Tiros 18°54’37.03"S, 45°49’10.14"W Minas Gerais, Brazil Probable fall: 2020 May 8 Classification: HED achondrite (Eucrite, cumulate) History: (M. Zurita, BRAMON, D. Andrade, OV/UFRJ) On May 8, 2020, at 06:25:15 UTC, a bright fireball was seen from some cities of Minas Gerais and São Paulo states, Brazil. A loud explosion sound was heard in at least 18 cities in the Triângulo Mineiro region. Eight weather cameras from "Clima Ao Vivo" recorded the fireball from seven cities in Minas Gerais, São Paulo and Paraná states. The fireball flash was also detected by GLM instrument on GOES-16 satellite. Analyzing the videos the BRAMON (Brazilian Meteor Network) calculated that the meteor traveled on a southwest-to-northeast trajectory, with velocity of 18.5 km/s, in a 15.8 deg inclination (relative to ground) crossing 180.1 km in 9.76 " and extinguished at 29.7 km high, 9.2 km west of Tiros city, MG. A 84 × 7 km2 strewn field was calculated by Jim Goodall covering a vast area between Tiros and Morada Nova de Minas city. Searches were performed by residents and by meteorite hunters, but with Covid 19 and the vast region covered by mountain and vegetation, no fragment was found. In early September when cutting the vegetation, he found a stone that drew his attention, but let it in the same place. On September 18, Mr. Titota found this shiny black stone just 150 m from the farmhouse and brought it to his wife’s rock collection. He made a video and send to a friendship whatsapp group. The priest José Luis de Araujo Paiva, who participated in the group, suspected to be a meteorite and sent the video to Sandro Barcelos, from Tirense Noticias website, that published the video. The video was shared by @mulheresdeestrelas. Through the @mulheresdeestrelas website and Sandro, The Meteoríticas found the owner of the meteorite. The finder and his family assure that they never saw that rock before. Since the find place is only about 30 km from the calculated strewn field and due to the meteorite be so fresh, it is probably associated with the May fireball. Physical characteristics: Single flight-oriented stone with glassy black fusion crust and flow lines. Petrography: (M.E Zucolotto) Three thin sections were analyzed, it is a coarse-grained (~1 mm) eucrite with a cumulate texture. It Consists mainly of anorthitic plagioclase feldspar, ortho and clinopyroxene with minor amounts of ferroan olivine, SiO2, troilite, phosphate and ilmenite. At those small sections no chromite neither Fe-metal were observed. The most abundant pyroxene is pigeonite. Some grains exhibit subsolidus augite exsolution. From the plagioclase An content and the texture, it can be classified as a cumulate eucrite. It shows undulatory extinction and planar fractures in plagioclases and planar and irregular fractures and weak mosaicism in some pyroxene grains are indicatives of a shock stage S4. Geochemistry: (A. Tosi, IGEO/UFRJ) Electron microprobe analysis yields: Low-Ca pyroxene: Fs39.8±11.5Wo6.3±1.8, Fe/Mn=34.1±1.5 (n=36). Rich-Ca pyroxene: Fs49.5±6.1Wo24.8±7.9, Fe/Mn=34.7±7.0 (n=60). Olivine: Fa64.7±0.6 (n=9). Plagioclase: An93.4±2.8Ab6.4±2.7Or0.2±0.1 (n=58). Classification: Cumulate Eucrite. Weathering (W0) and moderately shocked (S4) Specimens: Type specimen at MNRJ. Main mass with Mr. Titota Writeup from MB 113: Tiros, reclassification Petrography: (A. Tosi, UFRJ): After acquisition of 110 g of the meteorite, a whole section could be examined and three thin sections were analyzed under the optical microscope and electron microprobe. Petrographically, the meteorite exhibits a polymict brecciated texture, formed by lithic and mineral clasts. Most clasts consist mainly of cumulate and basaltic eucrites with more than 10 vol.% diogenite component (orthopyroxene) set in a fine recrystallized matrix. These clasts vary from gabbroic, granular to basaltic textures, including symplectic and impact melts. The main population of clasts include: diogenites, cumulate eucrites, basaltic and noncumulate eucrite, cumulate- type achondrite, basaltic-type achondrite, impact melts (eucritic mineralogy with aphanitic textures), and exotic mafic achondrites (anomalous eucritic mineralogy with phaneritic acicular or symplectite texture). The eucrite materials typically contain exsolved augite into pigeonite grains and anorthite plagioclase feldspar. Mineralogically, the major minerals include pigeonite, augite, Ca-plagioclase (An) and silica phase. Accessory minerals: ilmenite, chromite, Ca- phosphate, troilite, metal and olivine. It shows undulatory extinction and planar fractures in plagioclases and planar and irregular fractures and weak mosaicism in some pyroxene grains are indicates of a high shock stage. Geochemistry: Pyroxene: overall Fe/Mn (atomic) 40.7±9,7 (N=419). Diogenite: orthopyroxene Fs25.8±2.3Wo3.1±0.8 (N=78). Cumulate eucrite: Low-Ca pyroxene: Fs39.8±11.5Wo6.3±1.8 (N=36), Ca pyroxene: Fs49.5±6.1Wo24.8±7.9 (N=60), Olivine: Fa64.7±0.6 (N=9). Plagioclase: An93.4±2.8Ab6.4±2.7Or0.2±0.1 (N=58). Granular basaltic eucrite: Low-Ca pyroxene: Fs56.5±1.5Wo9.2±1.6 (N=10), Ca pyroxene: Fs38.4±7.1Wo30.6±8.6 (N=4), Plagioclase: An87.9±20.6Ab12.0±0.6Or0.1±0.1 (N=8). Phaneritic and acicular clast: Low-Ca pyroxene: Fs59.4±2.3Wo7.8±2.3 (N=23), Ca pyroxene: Fs38.6±5.3WO32.4±6.9 (N=6), Plagioclase: An88.8±21.9Ab10.7±1.8Or0.5±0.2 (N=14). Symplectic impact melt: Low-Ca pyroxene: Fs84.4±3.7Wo5.2±3.1 (N=4), Ca pyroxene: Fs44.9±5.6Wo40.7±5.3 (N=17), Olivine: Fa97.0±6.8 (N=9). Dark aphanitic impact melt of cumulate eucrite: Low-Ca pyroxene: Fs40.1±5.6Wo8.8±2.9 (N=26), Ca pyroxene: Fs48.0±14.7Wo23.0±6.6 (N=7), Ferroan olivine: Fa52.1±6.8 (N=9), Olivine: Fa29.9±1.9 (N=4), Plagioclase: An87.7±4.9Ab12.1±4.7Or0.3±0.2 (N=12). Aphanitic impact melt with coarse grainsize: Low-Ca pyroxene: Fs44.6±7.5Wo10.3±3.3 (N=17), Ca pyroxene: Fs47.2±2.9Wo27.7±3.1 (N=3), Plagioclase: An90.1±3.6Ab9.3±3.4Or0.6±0.2 (N=14). Aphanitic impact melt of basaltic eucrite: Ca pyroxene: Fs44.3±2.4Wo27.5±3.3 (N=4), Plagioclase: An88.1±0.9Ab11.8±0.9Or0.1±0.1 (N=7). Dark diabasic impact melt of HED material: Low-Ca pyroxene: Fs42.2±11.3Wo13.6±2.6 (N=9), Ca pyroxene: Fs47.1Wo24.6 (N=1), Orthopyroxene: Fs28.7±0.5Wo4.9±0.3 (N=3). Plagioclase: An84.2±1.7Ab15.7±1.7Or0.1±0.1 (N=12). MATRIX: Low-Ca pyroxene: Fs45.4±10.4Wo7.2±3.3 (N=51), Ca pyroxene: Fs46,1±11.2Wo23.9±7.5 (N=21), Orthopyroxene: Fs25.3±2.6Wo3.1±0.7 (N=31), Ferroan Olivine: Fa71.7±3.4 (N=5), Olivine: Fa27.4±0.3 (N=2), Plagioclase: An90.8±3.6Ab9.0±3.5Or0.1±0.1 (N=41). Classification: HED Achondrite (Howardite). Weathering (W0) and moderately shocked. | ||||||||||||||||||||||||||||||||||||||
| Data from: MB109 Table 0 Line 0: |
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| Institutions and collections |
MNRJ: Museu Nacional, Quinta da Boa Vista, Rio de Janeiro, CEP 20940-040, Brazil (institutional address; updated 26 Dec 2011) |
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| Catalogs: |
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| References: | Published in Meteoritical Bulletin, no. 109, in preparation (2020) Published in Meteoritical Bulletin, no. 113, in preparation (2024)
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Geography:
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Statistics: This is 1 of 22 approved meteorites from Minas Gerais, Brazil (plus 2 unapproved names) This is 1 of 87 approved meteorites from Brazil (plus 6 unapproved names) (plus 7 impact craters) | ||||||||||||||||||||||||||||||||||||||
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| Revision history: |
This lists important revisions made to data for this record.
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