Investigação Geofísica do Alto Estrutural de Anhembi - SP

The Limeira Intrusion is an occurrence related to the Mesozoic continental flood basalts of Paraná Magmatic Province, cropping out at the eastern São Paulo state. It is made up of basic-intermediate rocks with a great diversity of structures, textures and modal compositions, related to specific evolutionary process in a magma chamber. Previous geological and stratigraphic evidence suggests it has a lopolithic-like geometry rather than a conventional sill-like, assumed for most regional similar occurrences. 2D forward modeling of magnetometric data, based on available aerial and newly obtained ground data integrated with in situ rock magnetic susceptibility measurements, were used to test such hypothesis. The results, even considering intrinsic drawbacks of magnetometric theoretical models, are compatible with the geologic-based presumed intrusion geometry. The determination of intrusive bodies geometry is quite significant to explain their different emplacement mechanisms. In the case of Limeira Intrusion, the results suggest that the emplacement mechanism may occur, apparently, by inner-accretion of fresh magmatic pulses in its central region. Importantly, the magmatic evolution of lopolith-like basic-intermediate intrusions may open the way for extensive differentiation processes, with strong implications to petrology and metallogenesis.

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“…Data processing and treatment procedures are summarized in Figure 3 (see also Cavallaro 2013, Milsom 2003.…”

Section: Data Acquisition and Treatmentmentioning

confidence: 99%

2D magnetometric modeling of a basic-intermediate intrusion geometry: geophysical and geological approaches applied to the Limeira intrusion, Paraná Magmatic Province (SP, Brazil)

et al. 2018

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“…A estrela branca indica a localização do poço l-AB-l-SP da Petrobrás, enquanto que a estrela vermelha indica onde ocorrem arenitos asfálticos. Modificado de Araújo (2006) e Cavallaro (2013).…”

Section: éPocaunclassified

Investigação paleontológica do evento hidrotermal de Anhembí (SP) na Formação Teresina (Grupo Passa Dois, Permiano, Bacia do Paraná)

Roberto¹

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In the Anhembi County, siliceous cones occur in the Teresina Formation (Permian) which are now interpreted as accumulations generated fìom a hydrothermal event that took place in shallow waters. The occurrence of such hydrothermal deposits is very rare in the geological record, making this deposit unique, especially when considering that more than 4,500 of these siliceous cones outcrop in less than 1,5 km2. The remarkable characteristics of this locality have made it an important object of scientific investigation, aside from suggest the comparison with the supposedly most ancient life forms ever found, fiom 3.5 Ga, deposited in similar context. This work consists of an analysis of the fossils found in intervals below, laterally continuous and above the place where such cones outcrop, an evaluation whether possible changes in the biota in this area are due to this hydrothermal event, and also to perform an analysis of the state ofthe controversy around Earth's most ancient microfbssils. Three diffcrent intervals (4, B and C) in which samples from three distinct levels (1,2 and 3) were collected were analyzed both macroscopically and pehographically. In the Interval A (Level l) we have observed bivalve shells, ostracod valves, oncoids and {ïagments of fish teeth including a big fragmented tooth of a dipnoi fish. In Interval B (Level 2) were observed only ostracod valves and oncoids. In Interval C (Level 3) were found ostracod valves, oncoids and bivalve shells. The silicification that took place in these 2 initial intervals difler from the third one, which suggests a diflbrent event for the silicification of the lower strata. The apparent dill'erence found in the biota fiom the three intervals strongly suggests a connection of the biota with the hydrothermal event that took place in that locality. The presence of 3.5 Ga microfossils is not entirely discarded by this work, though one must be cautíon about the reservations about the biogenicity of such microlbssils.

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“…Data processing and treatment procedures are summarized in Figure 2 (see also Cavallaro, 2013 andMilsom, 2003 The final processing steps included data interpolation by the minimum curvature (MC) method (Briggs, 1974), analytical signal amplitude (ASA) filtering and the reduction to pole (RTP) systematics. The RTP systematics followed suggestions set out by Phillips (2007) The ASA filter may be used to detect the main edges and geometric features of geological occurrences with significant magnetic contrast (e.g., Nabighian, 1972).…”

Section: Ii11 Geophysical Data Acquisition and Treatmentsmentioning

confidence: 99%

Geometry and stratigraphy of the Limeira tholeiitic intrusion, Paraná¡ magmatic province (SP-Brazil)

Santos¹

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Dr. Silvio RF Vlach (Silvião), for guiding me in the last five years over the universe of igneous rocks and their processes. Thank you very much for your uncommon patience, the enormous encouragement, scientific discussions, conversations, and especially our friendship. Certainly, this research would not be the same without his comments and suggestions. I would like to thank Dr. Francisco A Negri (Chico), who accompanied me on the first reconnaissance work of the main outcrops in the Limeira Intrusion, at the beginning of my undergraduate scientific work. Thanks to the NAP GeoAnalítica staff (José Paulo, José Vinícius, Marcos and Leandro) for their support during sample preparation and analysis steps.

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Investigação Geofísica do Alto Estrutural de Anhembi - SP

Cited by 3 publications

References 27 publications

2D magnetometric modeling of a basic-intermediate intrusion geometry: geophysical and geological approaches applied to the Limeira intrusion, Paraná Magmatic Province (SP, Brazil)

2D magnetometric modeling of a basic-intermediate intrusion geometry: geophysical and geological approaches applied to the Limeira intrusion, Paraná Magmatic Province (SP, Brazil)

Investigação paleontológica do evento hidrotermal de Anhembí (SP) na Formação Teresina (Grupo Passa Dois, Permiano, Bacia do Paraná)

Geometry and stratigraphy of the Limeira tholeiitic intrusion, Paraná¡ magmatic province (SP-Brazil)

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