LAVRAS DO SUL: A NEW EQUILIBRATED ORDINARY CHONDRITE FROM RIO

ZUCOLOTTO M.E.; ANTONELLO, LOIVA; VARELA M.E.; SCORZELLI R; LUDKA, IZABEL; MUNAYCO P.; DOS SANTOS E.

EARTH, MOON, AND PLANETS

SPRINGER

Año: 2012 vol. 108 p. 139 - 150

0167-9295

The new Brazilian chondrite, Lavras do Sul, was found in 1985 at Lavras do Sul, Rio Grande do Sul State. Brazil (33°30’48”S; 53°54’65”W). It consists of a single mass weighing about 1kg, covered by a black fusion crust with grayish a interior. Four polished thin sections were prepared from a slice weighing 67g on deposit at the Museu Nacional/UFRJ. It consists mostly of chondrules and chondrule fragments dispersed in a recrystallized matrix. Most chondrules are poorly defined and range in size from 300μm to 2000 μm, although some of them show distinct outlines, particularly when viewed under cross-polarized transmitted and reflected light. The texture of chondrules varies from non-porphyritic (e.g., barred-olivine, radial-pyroxene) to porphyritic ones (e.g., granular olivine as well as olivine-pyroxene). The meteorite contains mainly olivine (Fa24.9), low-Ca pyroxene (Fs22.6) and metal phases, with minor amounts of plagioclase, chromite and magnetite. Mössbauer Spectroscopy studies indicate that the metal phase is kamacite, tetrataenite and antitaenite. Veins of secondary iddingsite crosscut the thin section and some ferromagnesian silicates. The chemical composition indicates that Lavras do Sul is a member of the low iron L chondrite group. The poorly delineated chondritic texture with few well-defined chondrules, the occurrence of rare clinopyroxene and plagioclase (and maskelinite) with apparent diameters ranging from 5μm to 123μm led us to classify Lavras do Sul as an equilibrated petrologic type 5. The shock features of some minerals suggest a shock stage S3, and the presence of a small amount of secondary minerals such as iddingsite and goethite, a degree of weathering W1. The meteorite name was approved by the Nomenclature Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). stage S3, and the presence of a small amount of secondary minerals such as iddingsite and goethite, a degree of weathering W1. The meteorite name was approved by the Nomenclature Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). plagioclase, chromite and magnetite. Mössbauer Spectroscopy studies indicate that the metal phase is kamacite, tetrataenite and antitaenite. Veins of secondary iddingsite crosscut the thin section and some ferromagnesian silicates. The chemical composition indicates that Lavras do Sul is a member of the low iron L chondrite group. The poorly delineated chondritic texture with few well-defined chondrules, the occurrence of rare clinopyroxene and plagioclase (and maskelinite) with apparent diameters ranging from 5μm to 123μm led us to classify Lavras do Sul as an equilibrated petrologic type 5. The shock features of some minerals suggest a shock stage S3, and the presence of a small amount of secondary minerals such as iddingsite and goethite, a degree of weathering W1. The meteorite name was approved by the Nomenclature Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). stage S3, and the presence of a small amount of secondary minerals such as iddingsite and goethite, a degree of weathering W1. The meteorite name was approved by the Nomenclature Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). covered by a black fusion crust with grayish a interior. Four polished thin sections were prepared from a slice weighing 67g on deposit at the Museu Nacional/UFRJ. It consists mostly of chondrules and chondrule fragments dispersed in a recrystallized matrix. Most chondrules are poorly defined and range in size from 300μm to 2000 μm, although some of them show distinct outlines, particularly when viewed under cross-polarized transmitted and reflected light. The texture of chondrules varies from non-porphyritic (e.g., barred-olivine, radial-pyroxene) to porphyritic ones (e.g., granular olivine as well as olivine-pyroxene). The meteorite contains mainly olivine (Fa24.9), low-Ca pyroxene (Fs22.6) and metal phases, with minor amounts of plagioclase, chromite and magnetite. Mössbauer Spectroscopy studies indicate that the metal phase is kamacite, tetrataenite and antitaenite. Veins of secondary iddingsite crosscut the thin section and some ferromagnesian silicates. The chemical composition indicates that Lavras do Sul is a member of the low iron L chondrite group. The poorly delineated chondritic texture with few well-defined chondrules, the occurrence of rare clinopyroxene and plagioclase (and maskelinite) with apparent diameters ranging from 5μm to 123μm led us to classify Lavras do Sul as an equilibrated petrologic type 5. The shock features of some minerals suggest a shock stage S3, and the presence of a small amount of secondary minerals such as iddingsite and goethite, a degree of weathering W1. The meteorite name was approved by the Nomenclature Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). stage S3, and the presence of a small amount of secondary minerals such as iddingsite and goethite, a degree of weathering W1. The meteorite name was approved by the Nomenclature Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). plagioclase, chromite and magnetite. Mössbauer Spectroscopy studies indicate that the metal phase is kamacite, tetrataenite and antitaenite. Veins of secondary iddingsite crosscut the thin section and some ferromagnesian silicates. The chemical composition indicates that Lavras do Sul is a member of the low iron L chondrite group. The poorly delineated chondritic texture with few well-defined chondrules, the occurrence of rare clinopyroxene and plagioclase (and maskelinite) with apparent diameters ranging from 5μm to 123μm led us to classify Lavras do Sul as an equilibrated petrologic type 5. The shock features of some minerals suggest a shock stage S3, and the presence of a small amount of secondary minerals such as iddingsite and goethite, a degree of weathering W1. The meteorite name was approved by the Nomenclature Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). stage S3, and the presence of a small amount of secondary minerals such as iddingsite and goethite, a degree of weathering W1. The meteorite name was approved by the Nomenclature Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). Brazil (33°30’48”S; 53°54’65”W). It consists of a single mass weighing about 1kg, covered by a black fusion crust with grayish a interior. Four polished thin sections were prepared from a slice weighing 67g on deposit at the Museu Nacional/UFRJ. It consists mostly of chondrules and chondrule fragments dispersed in a recrystallized matrix. Most chondrules are poorly defined and range in size from 300μm to 2000 μm, although some of them show distinct outlines, particularly when viewed under cross-polarized transmitted and reflected light. The texture of chondrules varies from non-porphyritic (e.g., barred-olivine, radial-pyroxene) to porphyritic ones (e.g., granular olivine as well as olivine-pyroxene). The meteorite contains mainly olivine (Fa24.9), low-Ca pyroxene (Fs22.6) and metal phases, with minor amounts of plagioclase, chromite and magnetite. Mössbauer Spectroscopy studies indicate that the metal phase is kamacite, tetrataenite and antitaenite. Veins of secondary iddingsite crosscut the thin section and some ferromagnesian silicates. The chemical composition indicates that Lavras do Sul is a member of the low iron L chondrite group. The poorly delineated chondritic texture with few well-defined chondrules, the occurrence of rare clinopyroxene and plagioclase (and maskelinite) with apparent diameters ranging from 5μm to 123μm led us to classify Lavras do Sul as an equilibrated petrologic type 5. The shock features of some minerals suggest a shock stage S3, and the presence of a small amount of secondary minerals such as iddingsite and goethite, a degree of weathering W1. The meteorite name was approved by the Nomenclature Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). stage S3, and the presence of a small amount of secondary minerals such as iddingsite and goethite, a degree of weathering W1. The meteorite name was approved by the Nomenclature Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). plagioclase, chromite and magnetite. Mössbauer Spectroscopy studies indicate that the metal phase is kamacite, tetrataenite and antitaenite. Veins of secondary iddingsite crosscut the thin section and some ferromagnesian silicates. The chemical composition indicates that Lavras do Sul is a member of the low iron L chondrite group. The poorly delineated chondritic texture with few well-defined chondrules, the occurrence of rare clinopyroxene and plagioclase (and maskelinite) with apparent diameters ranging from 5μm to 123μm led us to classify Lavras do Sul as an equilibrated petrologic type 5. The shock features of some minerals suggest a shock stage S3, and the presence of a small amount of secondary minerals such as iddingsite and goethite, a degree of weathering W1. The meteorite name was approved by the Nomenclature Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). stage S3, and the presence of a small amount of secondary minerals such as iddingsite and goethite, a degree of weathering W1. The meteorite name was approved by the Nomenclature Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). 24.9), low-Ca pyroxene (Fs22.6) and metal phases, with minor amounts of plagioclase, chromite and magnetite. Mössbauer Spectroscopy studies indicate that the metal phase is kamacite, tetrataenite and antitaenite. Veins of secondary iddingsite crosscut the thin section and some ferromagnesian silicates. The chemical composition indicates that Lavras do Sul is a member of the low iron L chondrite group. The poorly delineated chondritic texture with few well-defined chondrules, the occurrence of rare clinopyroxene and plagioclase (and maskelinite) with apparent diameters ranging from 5μm to 123μm led us to classify Lavras do Sul as an equilibrated petrologic type 5. The shock features of some minerals suggest a shock stage S3, and the presence of a small amount of secondary minerals such as iddingsite and goethite, a degree of weathering W1. The meteorite name was approved by the Nomenclature Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). stage S3, and the presence of a small amount of secondary minerals such as iddingsite and goethite, a degree of weathering W1. The meteorite name was approved by the Nomenclature Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). 5. The shock features of some minerals suggest a shock stage S3, and the presence of a small amount of secondary minerals such as iddingsite and goethite, a degree of weathering W1. The meteorite name was approved by the Nomenclature Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99). 1. The meteorite name was approved by the Nomenclature Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99).