Serra Pelada is the newest Brazilian eucrite and the first recovered fall from Amazonia (State of Pará, Brazil, June 29 th 2017). In this paper, we report on its petrography, chemistry, mineralogy and its magnetic properties. Study of four thin sections reveals that the meteorite is brecciated, containing basaltic and gabbroic clasts, as well of recrystallized impact melt, embedded into a fine-medium grained matrix. Chemical analyses suggest that Serra Pelada is a monomict basaltic eucritic breccia, and that the meteorite is a normal member of the HED suite. Our results provide additional geological and compositional information on the lithological diversity of its parent body. The mineralogy of Serra Pelada consists basically of low-Ca pyroxene and high-Ca plagioclase with accessory minerals such as quartz, sulphide (troilite), chromite -ulvöspinel and ilmenite. These data are consistent with the meteorite being an eucrite, a basaltic achondrite and a member of the howardite-eucrite-diogenite (HED) clan of meteorites which most likely are from the crust asteroid 4 Vesta.Key words: Serra Pelada, meteorite, eucrite, Vesta, Brazilian Meteorite.

The Parauapebas meteorite, third official meteorite discovered in the Brazilian Amazon region, is a "hammer meteorite" which fell on December 9 th , 2013, in the city of Parauapebas, Pará State, Brazil. Mineralogy is dominated by forsterite, enstatite, iron, troilite, and tetrataenite. Albite, chromite, diopside, augite, pigeonite, taenite, and merrillite are minor components. Two main clasts are separated by black shock-induced melt veins. One clast exhibits an abundance of chondrules with well-defined margins set on a recrystallized matrix composed mostly of forsterite and enstatite, consistent with petrologic type 4 chondrites. The other clast displays chondrules with outlines blurring into the groundmass as evidence of increasing recrystallization, consistent with petrologic type 5 chondrites. The clasts of petrologic type 4 have a fine-grained texture compared to those of type 5. It is a genomict breccia (indicated by shock melt veins) with the clasts and matrix of the same compositional group, but different petrologic types, H4 and H5. The melted outer crust of the Parauapebas meteorite is comprised of forsterite with interstitial dendritic iron oxide, and is rich in irregular vesicles, which are evidence of the rapid formation of the crust. The type specimen is deposited in the Museum of Geosciences of the University of São Paulo, Brazil.

Cathodoluminescence (CL) imaging is an outstanding method for sub classification of Unequilibrated Ordinary Chondrites (UOC) -petrological type 3. CL can be obtained by several electron beam apparatuses. The traditional method uses an electron gun coupled to an optical microscope (OM). Although many scanning electron microscopes (SEM) and electron microprobes (EPMA) have been equipped with a cathodoluminescence, this technique was not fully explored. Images obtained by the two methods differ due to a different kind of signal acquisition. While in the CL-OM optical photography true colors are obtained, in the CL-EPMA the results are grayscale monochromatic electronic signals. L-RGB filters were used in the CL-EPMA analysis in order to obtain color data. The aim of this work is to compare cathodoluminescence data obtained from both techniques, optical microscope and electron microprobe, on the Bishunpur meteorite classified as LL 3.1 chondrite. The present study allows concluding that 20 KeV and 7 nA is the best analytical condition at EPMA in order to test the equivalence between CL-EPMA and CL-OM colour results. Moreover, the color index revealed to be a method for aiding the study of the thermal metamorphism, but it is not definitive for the meteorite classification.

Anuário do Instituto de Geociências -UFRJ www.anuario.igeo.ufrj.br 4

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A meteorite fall took place on September 21, 2013 in a tiny village called Vicência (also known as Vila da Borracha), located at Brazil's northeast region, more specifically on the northwest of Pernambuco State. The meteorite almost struck a man (Mr. Adeildo) who noticed that one of the rock sides was still warm. The meteorite is now at the Rio de Janeiro National Museum for petrological classification. In this paper we describe the study of cathodoluminescence (CL) emission after exposing thin specimen of the meteorite slices to an electron beam, as an aid to traditional classification methods.The Vicência meteorite was recognized as a chondrite. Chondrites are the most primitive known rocks of the Solar System. It contains chondrules, roughly spherical aggregates of silicate minerals not found on terrestrial rocks. The study of chondrules brings insights into the processes that occurred in the Solar Nebula, at the most primitive moments in the Solar System history. Since their formation, the meteorites were altered, by thermal metamorphism or aqueous alteration so much that a classification scheme of chondrites was created by Van Schmus and Wood [1]. Obviously the "petrological types" (3 to 6) are based on the amount of metamorphism detected. Sears et al [2] subdivided type 3 into finer divisions ranging from 3.0 to 3.9, covering full variation in their metamorphic properties. Vicência is among the primitive un-equilibrated ordinary chondrites; exhibiting outstanding defined chondrules within a gray matrix (Fig. 1). Notably, it is a very rare type of chondrite and interesting to science because it nearly skipped metamorphism on its parent body. Falls of such primitive chondrite are very rare.In our efforts to confirm early assessments, a thin petrographic slide preparation was examined using an Electron Probe Microanalizer (JEOL EPMA-JXA-8230). The cathodoluminescence signal from a typical representative area of the Vicência meteorite was collected using a red, a blue and a yellow filter. The wavelength of emitted light reflects the chemical composition and crystallographic structure of the analyzed specimen. Subsequently, the generated images (red, blue and yellow) were merged to form a single image. CL maps are known to reveal, for instance, the presence of Fe 2+ known to reduce the luminescence, the presence of calcium intensifies yellows and reds, contrasting with blue feldspars [3]. The presence of activators (increasers) and quenchers (reducers) of CL expose the summation of the chemical character of a meteorite. This capability was quickly envisioned as a rich systematic tool. Cathodoluminescence is currently used in geological classification. In this work we are using a Cathodoluminescence imaging method of meteorite grouping developed by Meier and collaborators [3]. The CL of Vicência exhibits a range of color intensities of yellow CL associated to the chondrule mesostasis slightly higher than the red CL and few grains with blue CL corresponding to the lowest levels of metamorphism (Fig. 2). The CL im...

Disponível on-line no endereço www.igc.usp.br/geologiausp -15 -Resumo Diversos parâmetros têm sido utilizados para a classificação dos meteoritos de ferro, principalmente sua mineralogia e suas propriedades químicas e estruturais. Este artigo resgata e documenta o achado do meteorito férreo Palmas de Monte Alto, apresentando uma sequência de parâmetros classificatórios que amplia e detalha os dados disponíveis sobre o fragmento. Esse meteorito, um siderito, foi achado no topo da serra de Monte Alto antes de 1955 e hoje representa um dos seis espécimes que compõem a coleção de meteoritos do estado da Bahia. Ele é constituído de uma única massa de 97 kg com alto estágio de oxidação externa em locais em que a crosta de fusão foi removida. Sua mineralogia inclui kamacita, taenita e plessita, bem como fases minerais secundárias, tais como o óxido de Fe-Ni akaganeíta. Também estão presentes minerais acessórios de ocorrência comum em ligas metálicas de Fe-Ni de origem espacial, isto é, schreibersita, cromita e troilita, e foi identificada uma rara solução sólida de ortofosfatos de Fe-Mn composta dos minerais heterosita-purpurita ou sarcopsida-graftonita como membros extremos. A largura média de suas lamelas de kamacita (0,95 ± 0,15 mm) permite classificar estruturalmente o meteorito como um octaedrito médio, com padrão Widmanstätten médio e bem definido. Seus teores de Ni (9,40 wt%) e Co (0,46 wt%) comparados aos elementos-traço Ga (22 ppm), Ir (0,70 ppm), As (16,00 ppm) e Au (1,70 ppm) recomendam a inclusão desse meteorito no grupo químico IIIAB.Palavras-chave: Meteorito; Ferro; Níquel; Palmas de Monte Alto. AbstractSeveral parameters have been used to classify iron meteorites, mainly mineralogy and chemical and structural properties. This paper presents these classificatory parameters, allowing a more detailed view to enlarge knowledge about the Palmas de Monte Alto meteorite. This siderite was found on the top of Monte Alto ridge, before 1955, being one of the six specimens that compose the Bahia State meteorite collection. It consists of a single mass of 97 kg which shows a highstage of oxidation in places where the crust has been removed. Its mineralogy includes kamacite, taenite, plessite, as well as secondary mineral phases such the Fe-Ni oxide akaganeite. There are also accessory minerals of common occurrence in Fe-Ni alloys of spatial origin like schreibersite, chromite and troilite, and a rare solid solution of Fe-Mn orthophosphates composed by the minerals heterosite-purpurite or sarcopside-graftonite as extreme members. The average width of its bands of kamacita (0.95 ± 0.15 mm) allows classifying it structurally as a medium octahedrite, with a medium and well-defined Windmasttaten pattern. Its contents of Ni (9.40 wt %) and Co (0.46 wt %) -compared to trace-elements Ga (22 ppm), Ir (0.70 ppm), As (16.00 ppm) and Au (1.70 ppm) -recommend the inclusion of this meteorite in the chemical group IIIAB.

O meteorito Rio do Pires é um condrito tipo L6 achado antes de 1992 na Bahia, Brasil, em data desconhecida, tendo seu registro publicado noMeteoriticalBulletin em 1994, através de análise simplificada requerida para esse procedimento, apresentada por Adrian Brearley da Universidade do Novo México, E.U.A. Esse estudo objetiva ampliar os dados existentes sobre esse meteorito, através do detalhamento de suas características petrográficas, químicas e mineralógicas. Foram realizadas análises em três lâminas polido-delgadas e em uma amostra de mão, utilizando microscópio petrográfico e lupa petrográficaestereomicroscópica, microssonda eletrônica (EPMA) e microscopia eletrônica de varredura (MEV). A análise petrográfica permitiu constatar a existência de veios de choque resultantes de evento colisional do corpo parental que originou esse meteorito. Aproximadamente 93% dos minerais que compõem essa rocha são transparentes, predominando cristais de olivina, piroxênio e plagioclásio, nesta ordem. Os minerais opacos são representados por grãos de Fe-Ni metálicos, troilita, cromita e whitlockita (merrilita).A olivina épredominantemente magnesiana (Fa25). O piroxênio é a enstatita e o plagioclásio oligoclásio. A mineraloquímica observada é similar a do bem estudado meteorito Suizhou, umcondrito do tipo L6. A matriz demonstra sinais de alta recristalização e presença de maskelinita, um importante indicador de choque, sendo significativa para o entendimento da história evolucional do Rio do Pires.Os novos dadosindicam um grau de choque entre S4 e S5 para este meteorito, em vez do grau S6 proposto quando de seu registro no MeteoriticalBulletin.