Low-temperature thermochronology of the South Atlantic margin along Uruguay and its relation to tectonic events in West Gondwana

The authors gratefully acknowledge the support from Shell Brasil through the “Shell - BG05: UoA-UFRGS-SWB Sedimentary Systems” project at UFRGS and the strategic importance of the support given by ANP through the R&D levy regulation. We thank Peter Reiners and his team at the Arizona Radiogenic Helium Dating Laboratory (US) for the (UTh)/He analyses and support during the data evaluation. The first author thanks the CNPq scholarship (SWE 204254/2017-5) during the exchange period at the University of Aberdeen. A.R. Jelinek also thanks the support from CNPq (Project 303184/2017-5). This manuscript was improved after helpful reviews by Mathias Hueck and an anonymous reviewer.Peer reviewedPostprin

Simulating Araponga - The High-Resolution Diffractometer of Brazilian Multipurpose Reactor

The Brazilian Multipurpose Reactor (RMB) is a fundamental project that aims to turn Brazil into a self-sufficient country in the production of radioisotopes and radiopharmaceuticals to supply the Unified Health System (SUS) as much as the private institutions. In addition, the RMB project describes other applications as irradiation and testing of nuclear fuels and structural material analysis, for instance. There are many techniques in the project to study structural aspects of materials, where neutron diffraction represents one of the priorities for implementation. This technique will take place mainly on two diffractometers on Thermal Neutron Guide 1 (TG1), namely Araponga, a high-resolution diffractometer, and Flautim, a high-intensity diffractometer. In this work, we study the performance of the Araponga diffractometer through McStas simulations with input produced by the MCNP code of the RMB core. We investigate the neutron flux values considering a state-of-art high-resolution diffractometer, and the results are promising since some simulated scenarios present values compatible with high-intensity devices

Decay of 155 Sm

The beta decay of 155 Sm (T 1/2 ∼ 22min) has been investigated by gamma spectroscopy measurements. The single and coincidence spectra were taken using HPGe detectors with high energy resolution. The energy and relative intensities of 42 γ-rays have been determined, most of them with a better precision than previously. The γ-transitions at 205.7keV and 224.8keV were observed for the first time and 40 of them were confirmed and 39 of them placed in the decay scheme. The present results, together with the results of earlier studies, allows to confirm the energy levels, in the energy range 0.05-1.6MeV, as well as the assignments of spin for most of them

Phanerozoic cooling history of Archean/Paleoproterozoic basement in the southern Espinhaço Range, southeastern Brazil, through apatite fission-track analysis

Apatite fission track thermochronology of basement rocks from the southern Espinhaço Range and QuadriláteroFerrífero in southeastern Brazil unravels the tectonic history of this portion of the Brazilian Shield. The studyarea encompasses an Archean and Paleoproterozoic granitoid-gneiss basement, in the southern border of the SãoFrancisco Craton, and an Archean to Paleo-Mesoproterozoic sedimentary cover. Apatitefission track ages (AFT)vary from 187 ± 18 to 91.8 ± 7.3 Ma and horizontal confined track lengths vary from 9.62 ± 1.81μmto12.85 ± 1.35μm. Thermal history modeling shows an accelerated cooling episode starting in the UpperDevonian to Early Permian. After this event, quiescence lasted from 115 to 170 Ma. Apatite samples lack evi-dence of far-field effects from rifting and opening of the South Atlantic Ocean, and also evidence from alkalineand basaltic magmatism emplacement during Mesozoic-Cenozoic. The AFT thermochronometer remained un-disturbed during Transminas mafic dyke swarm intrusion. Finally, the last cooling event in the Espinhaço Range-Quadrilátero Ferrífero basement records ascension to surface temperatures due to epeirogeny after new con-figurations of the Nazca, South American and African plates. A climatic origin for the ascension is supported byaccentuated erosion rates, even though a weathering-prone phase is registered in weathering profiles

Gamma transition intensity determination using multidetector coincidence data

This work describes two similar methods for calculating gamma transition intensities from multidetector coincidence measurements. In the first one, applicable to experiments where the angular correlation function is explicitly fitted, the normalization parameter from this fit is used to determine the gamma transition intensities. In the second, that can be used both in angular correlation or DCO measurements, the spectra obtained for all the detector pairs are summed up, in order to get the best detection statistics possible, and the analysis of the resulting bidimensional spectrum is used to calculate the transition intensities; in this method, the summation of data corresponding to different angles minimizes the influence of the angular correlation coefficient. Both methods are then tested in the calculation of intensities for well-known transitions from a (152)Eu standard source, as well as in the calculation of intensities obtained in beta-decay experiments with (193)Os and (155)Sm sources, yielding excellent results in all these cases. (C) 2009 Elsevier B.V. All rights reserved