Nova contribuiçao ao conhecimento da formação Rio Claro (T) na Folha Rio Claro (SP)

The Rio Claro Formation mainly occurs in the county of Rio Claro (SP) lying unconformably on Paleozoic and Mesozoic rocks. Its thickness is 30-40 m. It shows fine to coarse, regular to poor sorted, Triable sandstones and conglomerates with quartzite and quartz clasts in the base. Thin layers of mudstone occur interbeded. Stratigraphic maps had been elaborated in recent analyses allowing to improve the knowledge about the formation. The biggest thicknesses occur on the east part of the studied area. The coarse/fine clastic ratio map demonstrates that fine sediments are concentrated in the east side, and suggests the existence of barriers which conditioned perennial water body (or bodies) where decantation took place (east, south and southeast sides). The structural contour map of the Rio Claro Formation base indicates a NW/SE trough which was the main depositional axis. The integrated analysis demonstrates that the formation is formed by lacustrine, fluvial and debris flows deposits whose source area was located on NW side, with coalescent alluvial fans from where braided to psamitic meandering fluvial channels came. The location of the source area suggests no link with the Corumbataf River paleo-terraces.

Ritmitos de itu: Petrografia e considerações paleodeposicionais

Rhythmite samples from Varvite Quarry and Park of Itu (SP), and well cores from Rafard (SP), were analyzed by optical microscopy to describe the petrographic characteristics of their light-colored (siltstone) and dark-colored (shale) laminae. The light-colored ones are essentially siltstones, commonly with traces of sands; the mineralogical composition is mainly quartz, with traces of feldspar and scarce mica; quartz or calcite cementation occurs in variable intensity, the first one being more intense in the Itu rhythmites; parallel laminations, internally normal graded or massive are the most common sedimentary structures in these rocks; bioturbations and dropstones are commonly observed in Itu rhythmites; contacts between siltstone laminae, and siltstone beds and shale laminae are commonly non-erosive and sharp. Considering this study and the macroscopic description of these rhythmites it was possible to clarify many questions about their composition, as the grain-size of the light-colored beds composed by silt with subordinate dropped sand, and the inappropriate use of the term varvite to the most of the Itu rhythmites. It was also important to reinforce their proglacial lacustrine origin, with random freezing of lacustrine surface water, and only sporadic ice-contact.

Geoprocessamento aplicado na distribuição espacial da capacidade de uso de uma microbacia

The present study aimed to show the spatial distribution of the Rochas watershed (Avaré-SP, Brazil) soil use capacity using the Idrisi geographical information system in order to contribute to a better territorial organization and the planning of the appropriate soil occupation. The obtained results using this methodology showed that most of the Rocha watershed areas are from the following groups: dystrophic yellow-red latosol (36.64%), eutroferric and distroferric red latosol (30.30%) with sandy texture. There was a predominance of areas with slope classes of 0-12%, plain to wavy relief (61.37% of the watershed area) showing that these areas are appropriate for annual culture plantations with wide use of machinery. Most of these areas were classified as class IV (73.79%) as to use capacity. In the studied area the following subclasses of land use capacity were found: IIe, s; IIIe; IVe; IVs; IVe,s; VIe and VIIe. Capacity subclasses IVe; IVe,s; IVs and Vie were the most significant because they are areas that can be used for agriculture but subject to severe soil impoverishment if there are no special care mainly for annual cultures. The Idrisi geographical information system was efficient to determine soil use capacity of the Rocha's watershed showing that the use of geoprocessing tools makes data analysis easier and faster, allowing digital data storage for future analysis uses mainly for territorial planning and environmental studies.

Diques clásticos na formação corumbataí (p) no nordeste da bacia do paraná, SP: Análise sistemática e significações estratigráficas, sedimentológicas e tectônicas

This paper aims to present the results of systematic survey on clastic dykes in the Corumbataí Formation (Permian), in the northeast region of the State of São Paulo. Besides this, the paper analyses genetic aspects of those features as well as their stratigraphic and sedimentologic implications in terms of geologic evolution of the northeastern Paraná Sedimentary Basin during Permian times. The field works had been developed in 3 main Corumbataí Formation outcrops (2 road cuts and a quarry) supposed to show the most important clastic dikes occurrences in the studied area. Basically, the sedimentary intrusions are formed by fine sand or silt size particles and had penetrated host rocks as near-vertical, centimeter thick, dykes (most common form) or as horizontal sheets, forming clastic sills (subsidiary form), both with variable geometric forms and dimensions. A lot of dyke walls show undulations suggesting pre-diagenetic clastic intrusions, probably near the ancient depositional surface. Almost all intrusions occur in the superior third portion of the Corumbataí Formation and some similar features seem to appear in the adjoining superposed Pirambóia Formation base. In this article the authors defend a seismic origin hypothesis for the clastic intrusions. It is important to mention that clastic intrusions tend to occur linked to expressive seismic events, with magnitude upper to 5. The analysis of isopach maps of the Permian and Mesozoic units of the Paraná Sedimentary Basin in the study area suggests a depositional system changing, from epicontinental sea conditions to shallow platform and, finally, to coastal deserts. Probably, this environmental change was driven by regional uplift accompanied by seismic events. It is possible that ancient seismicity triggered liquefaction processes and the resulting clastic intrusions. In this sense, those clastic features might be properly namedseismites.

Litogeoquímica E aspectos Petrogenéticos dos basaltos da Província Magmática do Paraná na porção centro-norte do Estado de São Paulo

The petrographic and geochemical characterization of flood basalts of Serra Geral Formation are here presented. The investigated areas are situated in four different regions of São Paulo state: Jaú, Ribeirão Preto, Franca and Fernandópolis. They represent almost the total area of outcrops of basalts in the São Paulo State. The petrographical data reveals that these rocks are constituted mainly by plagioclase (30-40%), pyroxenes, augite and pigeonita (20-30%) and magnetite (5-15%), and show a intergranular texture and its varieties intersertal, hialophitic and pilotaxitic. The geochemical data show a basic and tholeiitic affinity of the studied basalts, with high-Ti content (TiO2 > 1.8%), typical of the northern region of Paraná Basin. Three different magma-types were recognized: Paranapanema, Urubici and Pitanga. The first magma-type is concentrated in the Fernandópolis region, the second in the Franca region, and the Pitanga occurs in the Ribeirão Preto and Jaú regions. The distribution patterns of these magma-types and the detailed study of geochemical data showed that they are, probably, generated by a melting of a continental lithospheric mantle.

Geocronologia do maciço Granítico Sararé no SW do Cráton Amazônico

Sararé Massif occurs in the southwest Mato Grosso state intruded into Mesoproterozoic units of the Jauru Block inside the Amazonian Craton. It presents an extension of approximately 80 km2 and NW-SE tectonic structures control the elongated shape. It is constituted by three major monzogranitic petrographic facies, represented by leucocratic, reddish, isotropic, equi-inequigranular to locally porphyritic rocks. The composition indicates S-type, peraluminous, with indicatives of late- to post-kinematic magmatism. Geochronological studies with 40Ar/39Ar in biotites and muscovites resulted in ages of 903 to 906 Ma was interpreted as massif rocks cooling period and U-PB 917 ± 18 Ma. ages points to the crystallization of the intrusive body. The massif is formed by melting of material of the upper crust, in an environment of continental collision and/or of post-collisional decompression at the ending of the Aguapeí-Sunsás event, in more stable environments of consolidation and tectonic stabilization of the Amazonian Craton.

Paisagem natural paleógena da bacia sedimentar de São Paulo no município de guarulhos, estado de São Paulo

Paleogene sediments of this region represent a significant source of water for urban, industrial and agricultural activities. This basin is part of the Southeastern Brazilian Continental Rift, which occupies a large portion of this geographical area. This study aims to present the evolution of the natural Paleogene landscape, through an analysis of its stratigraphic intcrops and underground portions based on the concept of facies and facies associations. A total of nine clastic and separate lithofacies were recognized and grouped into two main facies associations. These data suggest the existence of two depositional interdigitated systems: fluvial braided fans, which were predominant in parts of the northern and central area, and another composed of lacustrine sediments found in its central-south region. The paleogeography herein outlined will help considerably in the detection of new areas for mineral and water resources prospection, as well as in urban planning projects of this region.

Contexto geológico e estrutural do Maciço Rio Apa, sul do Cráton amazônico - MS

Rio Apa Massif crops out in the Mato Grosso do Sul state and corresponds to the southeastern portion of the Amazonian Craton dominantly Paleoproterozoic in age. Rio Apa Complex is oldest and it is composed mainly by migmatitic orthogneisses, beyond amphybolites, tonalities and granodiorite. Alto Tererê Group is composed by schists, biotitemuscovite gneisses and micaceous quartzites generally rich in garnets, beyond metabasic rocks of low amphibolite facies. The Amoguijá Group is constituted by Alumiador Intrusive Suite, which is represented by a sieno to monzogranitic batholith and Serra da Bocaina Volcanic Suite composed of volcanoclastic rocks of alkali riolites to monzoriolites compositions and pyroclastic products. Overlaying towards East and South occurs Neoproterozoic metasedimentary rocks from the Paraguai Folded Belt (Cuiabá, Corumbá and Jacadigo Groups - Urucum Formation). Structural-metamorphic framewok is identified by five deformational phases but the actual tectonic and metamorphic structure shows the superposed tectonic array of the Paraguai Folded Belt. Rocks from Rio Apa Complex, Alto Tererê Group and Amoguijá Group record an older structural evolution defined by (Dn-1 and Dn). The deformational phases (Dn+1 and Dn+2) are visible mainly in rocks of Paraguai Folded Belt beyond the last deformation (Dn+3) that imprints all sequences.

Geologia e litogeoquímica da formação serra geral nos estados de mato grosso e mato grosso do sul

The basalts of the Formação Serra Geral in Parana Basin in the Mato Grosso do Sul and Mato Grosso states cover an area of 180,000 km2. They rest on the Botucatu sandstones and they are recovered by the sedimentary rocks of Bauru and Caiuá Groups. The mineralogical composition of these rocks are plagioclase (40%-55%), clinopyroxenes (19%-40%; augite and pigeonite), opaque minerals (2%-10%; magnetite and ilmenite) and olivine (1.5%). Geochemical data show two different types of basalts, named ATi-Pitanga (2.6% < TiO2 < 4.2%; 396 ppm < Sr < 438 ppm) and BTi-Ribeira (1.7% TiO2 <2.4%, 246 ppm < Sr < 286 ppm). In general, ATi-Pitanga have gently higher La/Yb(n) (6,1 ± 1,5ppm) than those BTi-Ribeira (5.6 ± 1,7ppm). The geochemical differences between ATi-Pitanga and BTi-Ribeira probably are related to different degrees of partial melt of a same mantle source, or to different mantle sources. The field relations show that BTi-Ribeira is displaced towards the north-western margin of the Paraná Basin and the thickness of lava flows increases towards the Paraná Graben, suggesting that ATi-Pitaga overlies BTi-Ribeira.

Viabilidade de aplicação das coberturas argilosas da região de Alfenas na indústra cerâmica

The region of Alfenas, in the state of Minas Gerais, Brazil, is predominantly constituted of Pre-Cambrian rocks with well developed alteration profiles in association with colluvial and alluvial sediments. No study to date has examined in detail its potential use in the ceramic industry. The scarce knowledge of its mineralogical and technological properties limits its value and consequently its industrial use. Until now, these clay materials have been used in a rudimental manner, in small scale in the fabrication of red tiles. The present study aimed at analyzing these clays mineralogically (X-ray diffraction), chemically (major and minor elements by X-ray fluorescence and organic carbon analysis) and technologically (pressing granulometric distribution; mechanical resistence; water absorption, apparent porosity; linear firing shrinkage; color of firing and others) in order to better understand the raw material and develop adequate technological applications. The best results of ceramic properties were the samples with higher organic content (more plastic clays) and higher values of Al2O3 (kaolinite and gibbsite) and Fe2O3 as well lower SiO2 content and finer grain size which contribute to a better sinterization.

Parâmetros físicos pré-eruptivos do magmatismo ácido da província magmática do Paraná: Resultados preliminares

A set of 12 samples of acid rock types Palmas (ATP) and Chapecó (ATC) was used to determine the chemical composition of plagioclase and pyroxene by electron microprobe, with the purpose to get information about the pressure and temperature of crystallization of these rocks. The results show that the pyroxene of ATP rocks (3,2 ± 1,2 kbar, max = 5,1 kbar and 1028 ± 38°C) were formed under pressure conditions higher than those ATC (1,8 ± 0,9 kbar, max = 3,4 kbar and 995 ± 26oC). However, the pressures obtained from plagioclase showed higher pressures for ATC (3.2 ± 1 kbar, max = 6,4 kbar and 1033 ± 12°C) than ATP (1,9 ± 1 kbar, max = 4,8 kbar and 1043 ± 5°C), suggesting that the crystallization of rocktype ATP began with the formation of pyroxene and plagioclase almost simultaneously at a depth of around 17 km while the ATC, began with the crystallization of plagioclase at a depth of about 21 km (assuming a gradient of 3,3 kbar/km). The geothermometry of plagioclase allow us to calculate the concentration of water from about 1 ± 0,3% H2O for both acid rock types. Additional calculations allow us to get the depth of water exsolution of magmatic liquid at 30m below the surface. Although the data are still preliminary and insufficient to model the extrusion of these rocks, they point out to an effusion mechanism of a partially fluidized magma by volatile, which would spread to large areas with small friction with the surface that would increased with the increase of viscosity caused by the loss of volatile and decreasing of temperature, developing coherent structures as lava flows.

Magmatismo do batólito rapakivi Rio Branco, sw do Cráton Amazônico (MT)

Rio Branco Rapakivi Batholith is located on the southwestern portion of the Amazonian Craton in Mato Grosso and belongs to the Cachoeirinha Tectonic Domain, part of the Rio Negro-Juruena Geochronological Province, Central Brasil. The batholith is constituted by microgabbros to quartz microgabbros and microdiorites to quartz microdiorites, middle to fine-grained equigranular to porphyritic varieties form the Rio Branco Intrusive Basic Suite, showing a discontinuous distribution and located near the margins of the intrusion.Majorly constituted by porphyritic, granophyric and isotropic facies of Rio Branco Intrusive Acid Suit which is composed by older dark red rapakivi monzogranites to quartz monzonites and quartz sienites (1403±0.6 Ma) and the younger red rapakivi leuco-monzogranites (1382±49 Ma) and late equigranular to pegmatitic monzogranites. The magmatism is constituted by two distinct magmas related to the end of the collisional event of Cachoeirinha Orogeny, one with alkaline basalts generated in an intraplate environment and the other postorogenic to anorogenic with peraluminous to metaluminous compositions and define a high-K calc-alkaline to shoshonitic magmatism in transition among the I- and A-types. The contacts are marked by extensive mafic sills and dikes of alkaline basalts derived from intraplate environment of the Salto do Céu Intrusive Basic Suite (±808 Ma) associate to the Sunsás-Aguapei Orogenic Belt and metasedimentary rocks of the Aguapeí Grup.

Investigação tecnológica de arenitos silicificados da Formação Botucatu (ne do Paraná) para uso como rocha de revestimento

For many years the silicified sandstone associated of the Botucatu Formation has been the target of interest to researchers and miners, either for understanding the genesis of silicification or for your use as dimension stone and covering on the building industry. If in the first there are several articles available in the geological literature the second there are only technical data marketing available. In the northeast portion of the Paraná State and southwest of the São Paulo State these rocks are mined and traded as covering stones. Not much is known about their intrinsic characteristics and technological properties. To improve the knowledge of the technological behavior of these materials, samples from a quarry from Ribeirao Claro region were petrographically and physically characterized according to the standards established by the Brazilian Association of Technical Standards to dimension stones. Therefore, two bulk samples of silicified sandstone of the Ribeirão Claro/PR region were studied and characterized following the norms established by Brazilian Association of Technical Standards for dimension stones. The results obtained in the petrographical and technological studies are presented and indicated that, in general, the technological performance presented by sandstone studied induces limitations of use as covering materials, mainly horizontally as pavements, door stone and step ladder.

Geotermobarometria de Granulitos Associados à Supracrustais na Porção Norte do Complexo Guaxupé - Região de Arceburgo - Santa Cruz do Prata, MG

This paper is a contribution for the understanding of the geological evolution of Guaxupé Complex. New data on petrography and mineral chemistry as well as estimates of metamorphic (P-T) conditions in the region of Arceburgo - Santa Cruz do Prata (MG) Brazil, at the southern portion of the Brasília Belt, more specifically at the Guaxupé Complex (Domain) are now presented. The lithotypes are high-grade metamorphic rocks subdivided into two groups: metasediments and granulites (orthoderivates). Chemical analysis of minerals was performed in three steps including core and rim of amphibole, pyroxene, feldspar, biotite, and garnet from samples of the following rock types: enderbites, mafic granulites, charnockites, and alkali feldspar charnockites. Results obtained with geothermobarometric calculations show metamorphic peak around 900°C of T and 10 kbar of P. Enderbites and tonalite granulites (mafic) show the highest values of temperature and pressure, while alkali feldspar charnockites show the lowest probably due to their late generation in relation to mafic rock types (enderbites and mafic tonalite granulite). Chemical mineral analysis in metamorphic parageneses and geothermobarometric calculations indicate that the possible metamorphic peak may be higher than 900°C of temperature and around 10 kbar of pressure, within a isothermal decompression (ITD) regime.

Polarização induzida aplicada no estudo de ocorrencia de cobre localizada a nordeste de Caçapava do Sul (RS)

Mineral research works are fundamentals for recognition and incorporation of new reserves. This paper present an integrated analysis of geologic and metallogenetics data, with results gotten from the application of the Induced Polarization geophysical method, in an copper ore occurrence, inserted in Camaquã sedimentary basin, situated in northeast of Caçapava do Sul city (RS). In area ocurr arkosean arenites average coarse, the intensely silicified and recrystallized, pertaining to Passo da Promessa Formation. The presence of azurita and malachite in breakings and high porosity zones of the host rock characterizes the mineral occurrence in surface, located in the crossing two fault families. The inversion models indicate the predominance of high chargeability in vulcanics tuff, rock of high porosity in relation to the andesites and metaconglomerates gifts in the area. The strong structural control of the mineral occurrence associated the high chargeability in volcanic tuff is indications of the hydrothermal fluid access by means of faults, until rocks with great porosity, where it occurred disseminations of copper sulfides in depth and carbonates in surface.