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Stratigraphy of amethyst geode-bearing lavas and fault-block structures of the Entre Rios mining district, Paraná volcanic province, southern Brazil
Provedor de dados: 42
Autores: HARTMANN,LÉO A.; ANTUNES,LUCAS M.; ROSENSTENGEL,LEONARDO M.
The Entre Rios mining district produces a large volume of amethyst geodes in underground mines and is part of the world class deposits in the Paraná volcanic province of South America. Two producing basalt flows are numbered 4 and 5 in the lava stratigraphy. A total of seven basalt flows and one rhyodacite flow are present in the district. At the base of the stratigraphy, beginning at the Chapecó river bed, two basalt flows are Esmeralda, low-Ti type. The third flow in the sequence is a rhyodacite, Chapecó type, Guarapuava subtype. Above the rhyodacite flow, four basalt flows are Pitanga, high-Ti type including the two mineralized flows; only the topmost basalt in the stratigraphy is a Paranapanema, intermediate-Ti type. Each individual flow is uniquely...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Amethyst geode; Entre Rios mining district; Paraná volcanic province; Geochemistry; Gamma-spectrometry.
Ano: 2014
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652014000100187

Zircon ages delimit the provenance of a sand extrudite from the Botucatu Formation in the Paraná volcanic province, Iraí, Brazil
Provedor de dados: 42
Autores: PINTO,VITER M.; HARTMANN,LÉO A.; SANTOS,JOÃO O.S.; MCNAUGHTON,NEAL J.
Ion microprobe age determinations of 102 detrital zircon crystals from a sand extrudite, Cretaceous Paraná volcanic province, set limits on the origin of the numerous sand layers present in this major flood basalt province. The zircon U-Pb ages reflect four main orogenic cycles: Mesoproterozoic (1155-962 Ma), latest Proterozoic-early Cambrian (808-500 Ma) and two Palaeozoic (Ordovician- 480 to 450 Ma, and Permian to Lower Triassic- 296 to 250 Ma). Two additional small concentrations are present in the Neoarchean (2.8 to 2.6 Ga) and Paleoproterozoic (2.0 to 1.7 Ga). Zircon age peaks closely match the several pulses of igneous activity in the Precambrian Brazilian Shield and active orogeny in Argentina. A main delimitation of the origin of the sand is the...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Botucatu Formation; Brazil; Neoarchean to Palaeozoic ages; Provenance; Sand extrudite; Zircon U-Pb ages.
Ano: 2015
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652015000401611

Tectonic evolution of the southern margin of the Amazonian craton in the late Mesoproterozoic based on field relationships and zircon U-Pb geochronology
Provedor de dados: 42
Autores: RIZZOTTO,GILMAR J.; HARTMANN,LÉO A.; SANTOS,JOÃO O.S.; MCNAUGHTON,NEAL J.
New U-Pb zircon geochronological data integrated with field relationships and an airborne geophysical survey suggest that the Nova Brasilândia and Aguapeí belts are part of the same monocyclic, metaigneous and metasedimentary belt formed in the late Mesoproterozoic (1150 Ma-1110 Ma). This geological history is very similar to the within-plate origin of the Sunsás belt, in eastern Bolivia. Thus, we propose that the Nova Brasilândia, Aguapeí and Sunsás belts represent a unique geotectonic unit (here termed the Western Amazon belt) that became amalgamated at the end of the Mesoproterozoic and originated through the reactivation of a paleo-suture (Guaporé suture zone) in an intracontinental rift environment. Therefore, its geological history involves a short,...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Amazonian craton; Intracontinental rift; Mesoproterozoic; Western Amazon belt; U-Pb geochronology.
Ano: 2014
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652014000100057

Relation between the sedimentary organic record and the climatic oscilations in the Holocene attested by palynofacies and organic geochemical analyses from a pond of altitude in southern Brazil
Provedor de dados: 42
Autores: GADENS-MARCON,GABRIELLI T.; MENDONÇA-FILHO,JOÃO G.; GUERRA-SOMMER,MARGOT; CARVALHO,MARCELO A.; PIRES,ETIENE F.; HARTMANN,LÉO A.
This paper presents the quantitative and qualitative results obtained from palynofacies and geochemistry analyses carried out on a core covering approximately 8000 years of sedimentation of a pond of altitude located at the mining district of Ametista do Sul, southernmost Brazil. The main objective of this paper is to consider the paleoclimatic and paleoenvironmental significance of these analyses. The hydrological isolation renders this pond climatically sensitive to variations in pluviometric regime and this enabled infer rainfall events during the early Holocene, which was responsible for the beginning of the processes of water accumulation in the gossan and the sedimentation of the pond. Changes in the pattern of moisture over the time become the drier...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Continental environment; Pond; Organic matter; Palynofacies analysis; Total organic carbon; Total sulfur.
Ano: 2014
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652014000301077

Mid amphibolite facies metamorphism of harzburgites in the Neoproterozoic Cerro Mantiqueiras Ophiolite, southernmost Brazil
Provedor de dados: 42
Autores: HARTMANN,LÉO A.; CHEMALE-JÚNIOR,FARID.
Valuable information is retrieved from the integrated investigation of the field relationships, microstructure and mineral compositions of harzburgites from the Neoproterozoic Cerro Mantiqueiras Ophiolite. This important tectonic marker of the geological evolution of southernmost Brazilian Shield was thoroughly serpentinized during progressive metamorphism, because the oldest mineral assemblage is: olivine + orthopyroxene + tremolite + chlorite + chromite. This M1 was stabilized in mid amphibolite facies - 550-600ºC as calculated from mineral equilibria. No microstructural (e.g. ductile deformation of olivine or chromite) or compositional (e.g. mantle spinel) remnant of mantle history was identified. A metamorphic event M2 occurred in the low amphibolite...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Mineral chemistry; Cerro Mantiqueiras Ophiolite; Metamorphism; Neoproterozoic.
Ano: 2003
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652003000100012

Paralavas in the Cretaceous Paraná volcanic province, Brazil - A genetic interpretation of the volcanic rocks containing phenocrysts and glass
Provedor de dados: 42
Autores: BAGGIO,SÉRGIO B.; HARTMANN,LÉO A.; BELLO,ROSA M.S.
ABSTRACT The occurrences of glassy rocks containing long and curved phenocrysts in the Paraná volcanic province, South America, are here interpreted as paralavas. The large number of thin (0.1-0.5 m) dikes and sills of glassy volcanic rocks with hopper, hollow or curved, large crystals of clinopyroxene (up to 10 cm), plagioclase (up to 1 cm), magnetite and apatite are contained in the core of thick (&gt;70 m) pahoehoe flows. They are strongly concentrated in the state of Paraná, coincident with the presence of the large number of dikes in the Ponta Grossa arch. These rocks were previously defined as pegmatites, although other names have also been used. A paralava is here interpreted as the product of melting of basaltic rocks following varied, successive...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Paralava; Paraná volcanic province; Pyrometamorphism; Remelting; Metal remobilization.
Ano: 2016
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652016000602167

Ion microprobe (SHRIMP) dates complex granulite from Santa Catarina, southern Brazil
Provedor de dados: 42
Autores: HARTMANN,LÉO A.; SANTOS,JOÃO O. S.; McNAUGHTON,NEAL J.; VASCONCELLOS,MARCOS A. Z.; DASILVA,LUIZ C.
Complex polymetamorphic granulites have been dated in the Santa Catarina granulite complex of southern Brazil through SHRIMP study of zircon. This complex is dominated by intermediate-acid plutonic rocks and contains small volumes of mafic and ultramafic rocks, and minor quartzite and banded iron formation. Porphyroblasts of orthopyroxene, clinopyroxene and plagioclase in mafic and acid rocks are interpreted as magmatic remnants in a volumetrically dominant granoblastic aggregate (M1) of the same minerals and hornblende. Hornblende formed during a later M2 metamorphic event constitutes rims around pyroxene, but the hornblende is also rimmed by granoblastic simplectites of orthopyroxene, clinopyroxene, hornblende and plagioclase in a second granulite facies...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Granulites; SHRIMP; U/Pb geochronology; Santa Catarina granulite complex; Brazil; Symplectites; Zircon.
Ano: 2000
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652000000400007

Integrated evaluation of the geology, aerogammaspectrometry and aeromagnetometry of the Sul-Riograndense Shield, southernmost Brazil
Provedor de dados: 42
Autores: HARTMANN,LÉO A.; LOPES,WILLIAM R.; SAVIAN,JAIRO F.
ABSTRACT An integrated evaluation of geology, aerogammaspectrometry and aeromagnetometry of the Sul-Riogran­dense Shield is permitted by the advanced stage of understanding of the geology and geochronology of the southern Brazilian Shield and a 2010 airborne geophysical survey. Gamma rays are registered from the rocks near the surface and thus describe the distribution of major units in the shield, such as the Pelotas batholith, the juvenile São Gabriel terrane, the granulite-amphibolite facies Taquarembó terrane and the numerous granite intrusions in the foreland. Major structures are also observed, e.g., the Dorsal de Canguçu shear. Magnetic signals register near surface crustal compositions (analytic signal) and total crust composition (total magnetic...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Aeromagnetometry; Aerogammaspectrometry; Gamma spectrometric provinces; Magnetic provinces; Sul-Riograndense Shield.
Ano: 2016
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652016000100075