Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-08-16T20:54:14Z No. of bitstreams: 1 SamirDoNascimentoValcacio_DISSERT.pdf: 5025545 bytes, checksum: 86238af38914f484b62ba415688d27cb (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-08-19T21:40:00Z (GMT) No. of bitstreams: 1 SamirDoNascimentoValcacio_DISSERT.pdf: 5025545 bytes, checksum: 86238af38914f484b62ba415688d27cb (MD5) / Made available in DSpace on 2016-08-19T21:40:00Z (GMT). No. of bitstreams: 1 SamirDoNascimentoValcacio_DISSERT.pdf: 5025545 bytes, checksum: 86238af38914f484b62ba415688d27cb (MD5) Previous issue date: 2016-02-15 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / A Bacia Potiguar, localizada na margem equatorial Brasileira, possui diversas rochas sedimentares que s?o afetadas por intrus?es ?gneas b?sicas cenozoicas, conhecidas como Magmatismo Macau. Dentre os efeitos mais proeminentes, relacionados a estas intrus?es, temos a forma??o de buchitos, rochas pirometam?rficas que ocorrem em altas temperaturas e baixas press?es, na f?cies sanidinito. Por meio de revis?o bibliogr?fica, observa??es de campo, petrografia, petrof?sica, acesso a bancos de informa??es de trabalhos pr?vios na ?rea e resultados da presente pesquisa, foi poss?vel caracterizar e estimar os efeitos termais produzidos na aur?ola de alguns corpos hipabissais nesta bacia. As fei??es mais relevantes associadas ?s intrus?es s?o: compacta??o, faturamento hidr?ulico, fus?o parcial e recristaliza??o das rochas encaixantes. De acordo com as ocorr?ncias minerais registradas, interpretam-se de 800 a 1200oC e press?es inferiores a 0,5 kbar nas proximidades dos corpos ?gneos. O modelamento t?rmico do plug S?o Jo?o registrou o efeito metam?rfico at? 150 m do contato com dissipa??o de calor total em aproximadamente 265 mil anos. Ap?s o pico de temperatura, seguiu-se a fase de arrefecimento registrada com remobiliza??o e precipita??o de minerais de baixa temperatura em falhas, fraturas e geodos, derivados de rea??es com de por??es sedimentares e fluidos metassom?ticos / hidrotermais, com abundante silicifica??o e carbonatiza??o. / The Potiguar Basin is located in the Brazilian Equatorial Margin and presents sedimentary rocks affected by Cenozoic basic igneous intrusions, known as Macau Magmatism. The most prominent effect related to these intrusions is the formation of buchites, pyrometamorphic rocks that occur at very high temperatures and very low pressures in the sanidinite metamorphic facies. Through literature review, field observations, petrographic and petrophysical data, accessing the database of previous studies and results from this research, it was possible to characterize and estimate the effects produced in the thermal aureole of some hypabyssal bodies in the basin. The most relevant features associated with the intrusions are: compactation, hydraulic fracturing, partial melting and recrystallization of country rocks. According to the observed mineral occurrences, temperature of 800 to 1200 ?C and pressure below 0,5 kbar were estimated at the contacts of the igneous bodies. The thermal modeling of the S?o Jo?o plug indicates thermal effects extending up to 150 m away from the contact and cooling time of approximately 265,000 years. After the peak of temperature, followed a cooling phase registered by remobilization and precipitation of minerals at low-temperature in faults, fractures and geodes, interpreted as derived from reactions with sedimentary rocks and metasomatic / hydrothermal fluids with abundant carbonatization and silicification.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-07-25T19:35:26Z No. of bitstreams: 1 SilviaAmorimTerra_DISSERT.pdf: 8312476 bytes, checksum: 1f02e20db0fedd2c8dc5413db2f0b262 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-08-01T20:19:56Z (GMT) No. of bitstreams: 1 SilviaAmorimTerra_DISSERT.pdf: 8312476 bytes, checksum: 1f02e20db0fedd2c8dc5413db2f0b262 (MD5) / Made available in DSpace on 2016-08-01T20:19:56Z (GMT). No. of bitstreams: 1 SilviaAmorimTerra_DISSERT.pdf: 8312476 bytes, checksum: 1f02e20db0fedd2c8dc5413db2f0b262 (MD5) Previous issue date: 2015-03-27 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico - CNPq / O presente trabalho objetiva a caracteriza??o de rochas carbon?ticas da Forma??o Janda?ra, termalmente afetadas no contato com intrus?es b?sicas do Pale?geno e Ne?geno, na regi?o dos munic?pios de Pedro Avelino e Janda?ra (RN), nordeste do Brasil. Para o estudo em tela, foram utilizados dados de campo, microsc?picos, difra??o de raios-X, microssonda eletr?nica e litogeoqu?mica de rocha total. Os calc?rios n?o afetados termalmente s?o wackstones, grainstones e packstones. Podem constituir fragmentos de foramin?fero bent?nico, espinhos de equinoderma, ostracode, algas, bivalve, gastr?pode, pel?ides e intraclastos. A porosidade encontrada se enquadra nos tipos vugular, intrapart?cula, interpart?cula, intercristalina e m?ldica. Como minerais essenciais, tem-se calcita, anquerita e dolomita; como fases detr?ticas, citam-se montmorilonita, pirita, limonita, quartzo e microclina. Os calc?rios termalmente afetados apresentam granula??o muito grossa a muito fina e colora??o cinza clara a escura. Os componentes fossil?feros desaparecem totalmente, e a porosidade tende a desaparecer. Com os dados obtidos, infere-se que os prot?litos carbon?ticos seriam calc?rios calc?feros a dolom?ticos, ambos com pequena quantidade de minerais do grupo das argilas. Os calc?rios cristalinos de prot?lito dolom?tico cont?m calcita rombo?drica e bastante sulfeto e ?xido / hidr?xido de ferro, tornando as rochas bem mais escuras. Os carbonatos de prot?lito calc?tico mostram grande varia??o de granula??o em fun??o do grau de recristaliza??o, que aumenta na dire??o do contato com os corpos b?sicos. Neste grupo, foram identificados os minerais pirometam?rficos lizardita e espin?lio nas amostras pouco e moderadamente afetadas, e espin?lio e espurrita nas fortemente afetadas, al?m da calcita que ocorre em todos os casos. O contexto geol?gico (intrus?es rasas de diab?sios), a presen?a dos minerais pirometam?rficos espurrita e olivina (pseudomorfisada para lizardita, serpentina, brucita), e compara??o com diagramas da literatura permitem estimar temperaturas e press?es em torno de 1050-1200?C e 0,5-1,0 kbar, respectivamente, para PTOTAL=PCO2. O resfriamento p?s-intrus?o teria propiciado a remobiliza??o de por??es de mat?ria org?nica do sedimento original e libera??o de fluidos metassom?ticos / hidrotermais, ensejando a abertura do sistema metam?rfico, com eventual contribui??o de elementos qu?micos das unidades hospedeiras (arenitos, folhelhos) e das pr?prias intrus?es b?sicas. Isto favoreceria a hidrata??o de fases pr?vias, resultando em forma??o de serpentina, clorita e brucita. Os resultados mostram a forte influ?ncia do calor aportado por intrus?es b?sicas no pacote sedimentar. Considerando que na por??o offshore da bacia ocorrem soleiras com espessura de at? 1000 m, o entendimento do pirometamorfismo poder? ser de grande utilidade na compreens?o e dimensionamento desses dep?sitos. / The present study aims the characterization of thermally affected carbonate rocks from Janda?ra Formation in contact with Paleogene and Neogene basic intrusions in the region of the Pedro Avelino and Janda?ra municipalities (RN), northeastern Brazil. For this study, field, petrographic, x-ray diffraction, electron microprobe, and whole rock litogeochemistry data of carbonates were undertaken. The thermally unaffected limestones are classified like wackstones, grainstones and packstones. They may constitute carbonates grains of benthic foraminifera, echinoderm spines, ostracods, algae, corals, bivalves, gastropods, peloids and intraclasts. The porosities are classified like vug, intraparticle, interparticle, intercrystal and moldic types. The major minerals are calcite, ankerite and dolomite; the detrital are montmorillonite, pyrite, limonite, quartz and microcline. The thermally affected limestones are very coarse to very fine-grained and light to dark gray color. The fossiliferous components totally disappear, and the porosity tends to disappear. With the data obtained, it can be inferred that the carbonate protoliths would be calciferous to dolomitic limestones, both with small amount of clay minerals. Crystalline carbonates from dolomitic protolith have rhombohedral calcite and iron oxides / hydroxides, making the rocks much darker. The carbonates from calciferous protolith have a wide variation of grain size according to the recrystallization degree, increasing toward contact with the basic bodies. In this group, it was identified the minerals lizardite and spinel in weakly to moderately affected samples, and spinel and spurrite in strongly affected rocks, as well as calcite, that occur everywhere. The geological context (shallow level diabase intrusions), the crystallization of the pyrometamorphic minerals spurrite and olivine, and comparison with diagrams from the literature allow estimating temperatures and pressures around 1050-1200 ?C and 0.5-1.0 kbar, respectively, for PTOTAL=PCO2. The post-intrusion cooling would have afforded the releasing of metasomatic / hydrothermal fluids, allowing the opening of the metamorphic system, with possible contribution of chemical elements from host units (sandstones, shales) and from basic intrusions. This would induce hydration of previous phases, allowing the formation of serpentine, chlorite and brucite. The results discussed here reveal the strong influence of the heat from basic intrusions within the sedimentary pile. Whereas in the offshore portion of the basin occur sills with up to 1000 m thickness, the understanding of pyrometamorphism might be useful for understanding and measuring the thermally affected rocks.

Made available in DSpace on 2015-03-13T17:08:39Z (GMT). No. of bitstreams: 1 LarissaS_DISSERT.pdf: 4305557 bytes, checksum: 7f5031ea79015e9573b6354a457ad4a9 (MD5) Previous issue date: 2013-12-19 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Pyrometamorphism results from conditions of high temperatures and very low pressures provoked by the intrusion of hypabyssal basic bodies into sedimentary or metassedimentary hosting rocks. The onshore portion of the Potiguar Basin in NE Brazil offers examples of this type of metamorphism nearby the contacts of Paleogene to Neogene plugs, sills and dikes of diabases and basalts crosscutting sandstones, siltstones and shales of the A?u Formation (Albian-Cenomanian). The thermal effects over these rocks are reflected on textures and minerals assemblages that characterize the sanidinite facies of metamorphism, often with partial melting of the feldspathic and mica-rich matrix. The liquid formed is potassic and peraluminous, with variably colored rhyolitic glass (colorless, yellow, brown) comprising microcrystals of tridymite, sanidine and clinoenstatite, besides residual detrital clasts of quartz and rarely zircon, staurolite and garnet. Lenses of shale intercalated within the sandstones display crystallites of Fe-cordierite (sekaninaite), mullite, sanidine, armalcolite (Fe-Ti oxide) and brown spinel. The rocks formed due to the thermal effect of the intrusions are called buchites for which two types are herein described: a light one derived from feldspathic sandstone and siltstone protoliths; and a dark one derived from black shale protoliths. Textures indicating partial melting and minerals such as sanidine, mullite, tridymite and armalcolite strongly demonstrate that during the intrusion of the basic bodies the temperature reached 1,000-1,150?C, and was followed by quenching. Cooling of the interstitial melts has as consequences the closure of pores and decrease of the permeability of the protolith, which varies from about 17-11% in the unaffected rocks to zero in the thermally modified types. Although observed only at contacts and over small distances, the number of basic intrusions hosted within the Potiguar Basin in both onshore and offshore portions leaves opened the possibility of important implications of the thermal effects over the hydrocarbon exploration in this area as well in other Cretaceous and Paleozoic basins in Brazil / Pirometamorfismo ?gneo resulta de condi??es de altas temperaturas e baix?ssimas press?es provocadas pela coloca??o de corpos b?sicos hipabissais em encaixantes sedimentares ou metassedimentares. A Bacia Potiguar (NE do Brasil), em sua parte continental, oferece exemplos deste tipo de metamorfismo nas proximidades e contatos de plugs, soleiras e diques de diab?sios do Pale?geno e N?ogeno, intrusivos em arenitos e folhelhos da Forma??o A?u (Albiano-Cenomaniano). O efeito termal nestas rochas se reflete em texturas e associa??es minerais que caracterizam a f?cies sanidinito, com frequente fus?o parcial da matriz feldsp?tica a mic?cea. O l?quido formado pela fus?o ? pot?ssico e peraluminoso, formando um vidro riol?tico de cores variadas (incolor, amarelo, marrom) englobando microcristais de tridimita, clinoenstatita e sanidina, al?m de clastos de quartzo e raramente zirc?o, estaurolita e granada. Lentes de folhelho, intercaladas nos arenitos, cont?m cristalitos de Fe-cordierita (secanina?ta), mullita, sanidina, armalcolita (?xido de Fe e Ti) e espin?lio marrom. As rochas formadas devido ao efeito termal das intrus?es se chamam buchitos, sendo aqui descritos os tipos claros (prot?lito arenito e siltito feldsp?tico) e escuros (prot?lito folhelho escuro). Texturas indicativas de que houve fus?o parcial e minerais tais como sanidina, mullita, tridimita e armalcolita demonstram que foram atingidas temperaturas da ordem de 1000-1150?C, seguido por arrefecimento ultrarr?pido. O resfriamento do l?quido intersticial tem como consequ?ncia o fechamento de poros e a diminui??o da permeabilidade dos prot?litos, passando de 17-11% nas rochas n?o afetadas a zero naquelas mais transformadas. Apesar de essas rochas serem observadas apenas nos contatos ou a pouca dist?ncia dos mesmos, o grande n?mero de corpos b?sicos intrusivos na Bacia Potiguar, tanto na parte emersa como na por??o oce?nica, deixa em aberto a possibilidade de fortes implica??es do efeito termal na explora??o de hidrocarbonetos nesta ?rea como tamb?m em outras bacias cret?ceas e paleozoicas no Brasil