Programa de Pós-Graduação em Geologia e Geoquímica - PPGG/IG
URI Permanente desta comunidadehttps://repositorio.ufpa.br/handle/2011/2603
O Programa de Pós-Graduação em Geologia e Geoquímica (PPGG) do Instituto de Geociências (IG) da Universidade Federal do Pará (UFPA) surgiu em 1976 como uma necessidade de desmembramento do então já em pleno desenvolvimento Curso de Pós-Graduação em Ciências Geofísicas e Geológicas (CPGG), instalado ainda em 1973 nesta mesma Universidade. Foi o primeiro programa stricto sensu de Pós-Graduação (mestrado e doutorado) em Geociências em toda Amazônia Legal. Ao longo de sua existência, o PPGG tem pautado sua atuação na formação na qualificação de profissionais nos níveis de Mestrado e Doutorado, a base para formação de pesquisadores e profissionais de alto nível. Neste seu curto período de existência promoveu a formação de 499 mestres e 124 doutores, no total de 623 dissertações e teses.
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Item Acesso aberto (Open Access) Desenvolvimento de uma metodologia para análise química de inclusões silicáticas em cristais de quartzo: estudo de caso em granitos estaníferos da Mina Pitinga (AM)(Universidade Federal do Pará, 2021-05-02) SANTOS, Gabrielle Cristine Silva dos; BORGES, Régis Munhoz Krás; http://lattes.cnpq.br/4220176741850416; https://orcid.org/0000-0002-0403-0974Silicate inclusions (melt inclusions) are small globules of silicate melt, containing some combinations of crystals, glass and vapor, entrapped in different minerals during their growth, and can be found in volcanic and plutonic rocks. They are easily identified in volcanic rocks. On the other hand, one of the major difficulties in the study of melt inclusions in plutonic rocks is their identification, because, after being trapped, their evolution results in total or partial crystallization. Based on international literature, they provide important information about the origin, nature of magmas and their petrological evolution. In addition¸ the detection of metals in melt inclusions is a unequivocal geological evidence of the genetic association of these elements with magmatic liquids (source) and is crucial in the study of orthomagmatic or hydrothermal deposits. The techniques for studying silicate inclusions for petrological and metallogenic purposes have evolved very rapidly in the last four decades, but it is a methodology that has not yet been implemented in Brazil, both due to the absence of laboratories with adequate equipment and the inexistence of research groups engaged in this field. Recently, pioneering studies were developed at the CDTN (Centro de Desenvolvimento da Tecnologia Nuclear), in Belo Horizonte (MG), with the tin granites of the Pitinga mine (AM), through high temperature microthermometric experiments and analysis of trace elements by LA-ICP-MS, in silicate inclusions hosted in quartz crystals of these granites. However, the tests were carried out on doubly-polished sections, which made it difficult to perform chemical analyzes of major elements by electron microprobe, since the inclusions were very deep in the quartz crystals, and any attempt at polishing to expose the inclusions would damage the samples. Based on this preliminary experience, this specific work is a technique for preparing quartz crystal concentrates containing silicate inclusions, using as such tin granites from the Pitinga mine (AM), representatives of the later facies of the Madeira pluton, porphyritic hypersolvus alkali feldspar granite and albite-rich granite. Thus, the developed work at the Laboratório de Inclusões Fluidas, with the crucial support of the Oficina de Laminação, the Laboratório de Análises Químicas and the Laboratório de Microanálises of the Instituto de Geociências of the Universidade Federal do Pará (UFPA), allowed the research to establish a routine involving the following steps: detailed petrography; crushing and grinding of the samples; granulometric separation; preparation of quartz crystal concentrates; muffle furnace heating and cooling experiments; selection of crystals with appropriate inclusions; assembly of the crystals in mounts with epoxy resin and subsequent polishing; monitoring and imaging of inclusions through the SEM; particle analyzes by EDS and, finally, analysis of major element (WDS) by electron microprobe. The microanalytical data (major elements) chosen especially in those silicate inclusions containing two or more solid phases (glass, spherical globules), demonstrated that the preparation technique provided a good exposure of the inclusions. In this way, the methodology developed in this work is relevant to the study of silicate inclusions and can be applied for the preparation of concentrates of any transparent magmatic mineral (quartz, olivine, pyroxene, plagioclase, etc.), host of silicate inclusions, and that can be analyzed by any of the traditional microanalytical techniques (electron microprobe, LA-ICP-MS, Raman spectroscopy, SEM, etc.).Item Acesso aberto (Open Access) Estudo de inclusões fluidas e química mineral do depósito aurífero do alvo Jerimum de Baixo, campo mineralizado do Cuiú-Cuiú, província aurífera do Tapajós, Pará(Universidade Federal do Pará, 2018-03-06) OLIVEIRA, Helder Thadeu de; BORGES, Régis Munhoz Krás; http://lattes.cnpq.br/4220176741850416The Jerimum de Baixo gold target is located in the Cuiú-Cuiú golfield, central region of the Tapajós Gold Province, Amazonian Craton. The target comprises monzogranitic rocks, essentially isotropic, that were weak to strongly hydrothermal and carriers of Fe-rich biotite. Chloritization, sericitization, sulfidation, silicification and carbonatization are the most important types of alteration. The produced chlorite is enriched in Fe of the chamosite type and was formed mainly between 280 and 315°C, whereas the white mica assumes muscovitic compositions. The mineralization is represented by quartz veinlets with low sulfide content (pyrite + pyrrhotite ± chalcopyrite ± galena ± sphalerite) in which gold occurs as free-milling particles and in more fragil and altered zones, usually associated with pyrrhotite. The petrographic and microtermometric study of fluid inclusions hosted in quartz veinlets defined aqueou-carbonic, carbonic and aqueous inclusions. The fluids with CO2 represent the probable mineralizing fluid and were generated by phase separation processes between 280 and 380°C, mainly. Further infiltration and mixing processes are indicated for the later aqueous fluids. Temperatures <400°C and the reduced character of the environment (pyrrhotite compounding the ore) point to H2S as the major ligand in the mineralizing fluid and Au (HS)-2 as the primary gold transporting complex. Phase separation, changes in pH conditions, and fluid/rock interaction were the important mechanisms for Au precipitation, which occurred at the brittle to locally brittle-ductile level of the crust (between 2 and 6 km). In general terms, Jerimum de Baixo presents similarities among the other deposits/targets previously studied in terms of hydrothermal alteration, fluid types and mineralization. The features observed in Jerimum de Baixo do not allow a classificatory framework absolutely adequate to any of the classical metalogenetic typological models. Characteristics such as type and style of hydrothermal alteration, type and low content of sulfides, types of fluids involved, estimated depth for mineralization, metallic association (e.g., S, Bi, Te), together with the good correspondence between the data collected in other deposits/targets in the Cuiú-Cuiú goldfield indicate for the Jerimum de Baixo target a gold deposit with magmatic-hydrothermal affiliation, presenting greater similarity to those deposits classified as belonging to Reduced Intrusion-Related Gold Systems (RIRGS).