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New radiometric ages and field relations within the Coastal Maine Magmatic Province suggest a bimodal distribution of igneous rocks in both space and time. The earlier magmatic event is represented by the development of large igneous complexes which occur along a magmatic axis extending from Calais to Penobscot Bay, Maine. These complexes are dominated by mafic magmatism ranging in composition from olivine norite through quartz diorite and granodiorite. Partially crystallized mafic magmas are often intruded by slightly peraluminous biotite ± hornblende granites as demonstrated by the occurrence of a wide range of enclave-host relationships. The igneous complexes are commonly cut by younger voluminous biotite ± hornblende granites and represent the development of a new tectonothermal perturbation of the crust. New radiometric data on igneous rocks from the Moosehorn Igneous Complex (MIC) near Calais, Maine indicate that the earlier magmatic event occurred during the interval of 440-420 m.y. This magmatic event in the MIC is marked by the emplacement of a large, complex assemblage of olivine norite, hypersthene gabbro, gabbro, biotite ± hornblende diorite, quartz diorite, and granodiorite. Compositional layering is present in many mafic bodies, and most commonly strikes northwest and dips gently to the southwest. The Moosehorn complex was intruded by the Baring granite before complete crystallization, resulting in the development of texturally diverse enclave swarms within the granite. / Master of Science

O Sienito Pedra Branca, com cerca de 90 km2, é um plúton tardi-orogênico com idade de 610 Ma intrusivo na Nappe Socorro-Guaxupé, e é truncado a oeste por rochas alcalinas (fonolitos e nefelina sienitos) do Maciço de Poços de Caldas, de idade cretácea. O plúton é formado por quatro unidades sieníticas, que intrudiram em três pulsos principais. O primeiro pulso é representado pela unidade Sienito Laminado Saturado a Insaturado (SLSI) de tendência alcalina que aflora na parte N e S-SE do plúton. O segundo pulso consiste na intrusão do Sienito Laminado Supersaturado (SLS), que trunca o interior do SLSI. O último pulso trunca internamente SLS, e constitui o centro do plúton, denominado Sienito Supersaturado Interno (SSI). Externamente ao plúton, separado por um septo de granitos, está o Sienito Supersaturado Externo (SSE), que pode estar associado ao segundo ou terceiro pulso. O Sienito Pedra Branca é denominado por sienitos hipersolvus com índice de cor entre 20-25, nos quais as variações mineralógicas mostram diferentes condições de cristalização. O SLSI atingiu condições mais oxidantes que os sienitos supersaturados, como demonstrado por suas paragêneses máficas (egirina-augita + flogopita + hematita + magnetita versus diopsídio + flogopita ± hornblenda + ilmeno-hematita ± magnetita). Embora em todos os sienitos a cristalização tenha ocorrido sob condições oxidantes, o Mg# maior dos minerais máficos e as maiores proporções do componente hematita nos óxidos romboédricos indicam que a fugacidade de oxigênio foi mais elevada nos SLSI. Dois tipos principais de enclaves são encontrados. Enclaves máfico-ultramáficos são encontrados em todas as unidades, enquanto os microgranulares são exclusivos dos sienitos supersaturados, e têm composições vairáveis nos campos dos sienitos, monzonitos e dioritos. Os enclaves monzoníticos e dioríticos são interpretados com produtos de magmas básicos que interagiram com o sienito hospedeiro em câmaras magmáticas mais profundas, e foram trazidos durante a ascensão. Característica particular dos sienitos supersaturados é a presença de cristais de plagioclásio corroídos, englobados por feldspato alcalino, que possuem composições semelhantes à do plagioclásio presente nos enclaves dioríticos (\'An IND.25-35\'). Estimativas de temperatura liquidus utilizando a saturação em apatita mostraram altas temperaturas dos magmas sieníticos, entre 1040 e 1160º C. Já estimativas de pressão e fO2 foram frustradas devido à ausência de plagioclásio magmático nestas rochas (limita o uso do barômetro de Al na hornblenda) e à ausência de equilíbrio para os óxidos de Fe-Ti (pares ilmeno-hematita + magnetita). As unidades do Sienito Pedra Branca mostram uma pequena variação composicional e diferem principalmente conteúdo de \'Al\' IND.2\'\'O IND.3\', compartilhando assinaturas geoquímicas com elevados teores em LILE como Ba (4000-10000 ppm) e Sr (2000-4500 ppm), além de outros elementos como \'P IND.2\'\'O ind.5\' (1-2%) elementos terras raras leves (La= 100-380 ppm). As semelhanças geoquímicas entre as unidades indicam que, apesar de suas diferenças, elas têm origem comum. Os modelos de gênese de magmas potássicos da literatura sugerem como área fonte mais provável dessas rochas o manto enriquecido. As altas razões LILE/HFSE, demonstradas pelas pronunciadas anomalias negativas em Nb-Ta, Ti e Hf-Zr, indicam vinculo com áreas ativas onde a injeção de fluidos ricos em REE e LILE durante a subducção gera meassomatismo no manto superior. As assinaturas isotópicas com Nd(t) pouco negativo (-7.6 a -8.1) e razões \'ANTPOT.87 Sr\'/\'ANTPOT.86 \'Sr IND.(t)\'+ 0.7077- 0.7078 associadas ao elevado conteúdo de Ba, Sr e ETH, reforçam que estes magmas estão associados à fusão parcial de horizontes enriquecidos do manto litosférico. A associção de sienitos insaturados e supersaturados em sílica, em paralelo com a presença de enclaves dioríticos exclusivamente nos sienitos supersaturados sugerem que a violação da barreira térmica ocorreu devido à interação de magmas saturados de tendência alcalina com magmas básicos. A falta de evidências de interação in situ (e.g. diques sin-plutônicos) e a ocorrência de rochas microgranulares mais máficas apenas como enclaves retrabalhados indicam que a interação entre os magmas e consequentes mudanças composicionais deve ter ocorrido em níveis mais profundos da crosta. / The Pedra Branca Syenite, with about 90 Km2 in area, is a 610 Ma late-orogenic pluton intrusive in the Socorro-Guaxupé Nappe and truncated to the west by alkaline rocks (phonolite and nepheline syenite) from the cretacic Poços de Caldas Massif. The pluton is made up of four syenite units that intruded as three main magmatic pulses. The first pulse is represented by the laminated silica-saturated to undersaturated syenite (SLSI) with alkaline tendency that occurs at N and S-SE of the plúton. The second pulse corresponds to the laminated oversaturated syenite (SLS), which truncates SLSI. The last pulse, named internal oversaturated syenite (SSI), cuts SLS internally and makes up the plutons core. Externally, separated from the main pluton by a granite septum, occurs the external oversaturated syenite (SSE) that may be associated to the second or third pulse. The Pedra Branca Syenite is dominated by hypersolvus syenites with color indices 20-25, whose mineralogical variations show contrasts in crystallization conditions. The SLSI reached more oxidizing conditions than the oversaturated syenites, as recorded by their mafic assemblages (egirine-augite + phlogopite + hematite + magnetite versus diopside + phlogopite ± hornblende + ilmeno-hematite ± magnetite). Although in all syenites the crystallization occurred under oxidizing conditions, the SLSI have higher Mg# in the mafic minerals and grater proportions of the hematite component in the rhombohedral oxides, indicating higher oxygen fugacity, close to the HM buffer. Two main types of enclaves are present in the Pedra Branca Syenite. The mafic-ultramafic enclaves occur in all units, while microgranular enclaves are exclusive of silica-oversaturated syenites, and have compositions varying in the compositional fields of syenites, monzonites and diorites. Monzonitic and dioritic enclaves are interpreted as products of basic magmas that interacted with the syenitic host in deeper magma chambers and were carried during ascension. Another particular feature of the silica-oversaturated syenites is the presence of corroded plagioclase included in alkali-feldspars, which have compositions similar to the plagioclase crystals from the diorite enclaves (\'An IND.25-35\'). Estimatives of liquidus temperatures using apatite saturation showed high temperatures for the syenitic liquids, between 1040 and 1160° C. Pressure and fO2 estimates were frustrated by the lack of magmatic plagioclase (restricting the use of the Al in hornblende barometers) and the lack of equilibrium between the Fe-Ti oxides (ilmeno-hematite + magnetite). The Pedra Branca Syenite units show small compositional variations, and differ mostly in \'Al IND.2\'\'O IND.3\' content (higher in silica-oversaturated syenites), sharing geochemical signatures with high contents of LILE such as Ba (4000-10000 ppm) and Sr (2000-4500 ppm), plus other elements as \'P IND.2\'\'O IND.5\' (1,0-2%) and light rare earth elements (La= 100-300 ppm). Geochemical similarities between the units indicate that despite their differences, they have common origin. Models of potassic magmas genesis in the literature suggest as most likely source areas the enriched mantle. The high LILE/HFSE ratios, highlighted by strong negative anomalies of Nb-Ta, Ti and Zr-Hf in spiderdiagrams are suggestive of links with active areas where rich-REE and LILE fluid injection during subduction caused metassomatism in upper mantle. Isotopic signatures with moderately negative Nd(t) (-7.6 to -8.1) and \'ANTPOT.87 Sr\'/\'ANTPOT.86 \'Sr IND.(t)\'=0.70767 to 0.70779 associated with the high trace elements contents (Ba, Sr and REE), reinforces that these rocks are associated with partial melting of enriched horizons of the lithospheric mantle. The association of silica undersaturated and oversaturated syenites, and the presence of dioritic enclaves only in the oversaturated units suggests that the violation of the thermal barrier may be connected to the coexistence with basic magmas. The lack of evidence of in situ interaction (e.g., synplutonic dykes) and occurrence of more mafic microgranular rocks only as reworked enclaves indicates that the magma interaction and consequent compositional changes must have occurred at deeper crustal.

O Sienito Pedra Branca, com cerca de 90 km2, é um plúton tardi-orogênico com idade de 610 Ma intrusivo na Nappe Socorro-Guaxupé, e é truncado a oeste por rochas alcalinas (fonolitos e nefelina sienitos) do Maciço de Poços de Caldas, de idade cretácea. O plúton é formado por quatro unidades sieníticas, que intrudiram em três pulsos principais. O primeiro pulso é representado pela unidade Sienito Laminado Saturado a Insaturado (SLSI) de tendência alcalina que aflora na parte N e S-SE do plúton. O segundo pulso consiste na intrusão do Sienito Laminado Supersaturado (SLS), que trunca o interior do SLSI. O último pulso trunca internamente SLS, e constitui o centro do plúton, denominado Sienito Supersaturado Interno (SSI). Externamente ao plúton, separado por um septo de granitos, está o Sienito Supersaturado Externo (SSE), que pode estar associado ao segundo ou terceiro pulso. O Sienito Pedra Branca é denominado por sienitos hipersolvus com índice de cor entre 20-25, nos quais as variações mineralógicas mostram diferentes condições de cristalização. O SLSI atingiu condições mais oxidantes que os sienitos supersaturados, como demonstrado por suas paragêneses máficas (egirina-augita + flogopita + hematita + magnetita versus diopsídio + flogopita ± hornblenda + ilmeno-hematita ± magnetita). Embora em todos os sienitos a cristalização tenha ocorrido sob condições oxidantes, o Mg# maior dos minerais máficos e as maiores proporções do componente hematita nos óxidos romboédricos indicam que a fugacidade de oxigênio foi mais elevada nos SLSI. Dois tipos principais de enclaves são encontrados. Enclaves máfico-ultramáficos são encontrados em todas as unidades, enquanto os microgranulares são exclusivos dos sienitos supersaturados, e têm composições vairáveis nos campos dos sienitos, monzonitos e dioritos. Os enclaves monzoníticos e dioríticos são interpretados com produtos de magmas básicos que interagiram com o sienito hospedeiro em câmaras magmáticas mais profundas, e foram trazidos durante a ascensão. Característica particular dos sienitos supersaturados é a presença de cristais de plagioclásio corroídos, englobados por feldspato alcalino, que possuem composições semelhantes à do plagioclásio presente nos enclaves dioríticos (\'An IND.25-35\'). Estimativas de temperatura liquidus utilizando a saturação em apatita mostraram altas temperaturas dos magmas sieníticos, entre 1040 e 1160º C. Já estimativas de pressão e fO2 foram frustradas devido à ausência de plagioclásio magmático nestas rochas (limita o uso do barômetro de Al na hornblenda) e à ausência de equilíbrio para os óxidos de Fe-Ti (pares ilmeno-hematita + magnetita). As unidades do Sienito Pedra Branca mostram uma pequena variação composicional e diferem principalmente conteúdo de \'Al\' IND.2\'\'O IND.3\', compartilhando assinaturas geoquímicas com elevados teores em LILE como Ba (4000-10000 ppm) e Sr (2000-4500 ppm), além de outros elementos como \'P IND.2\'\'O ind.5\' (1-2%) elementos terras raras leves (La= 100-380 ppm). As semelhanças geoquímicas entre as unidades indicam que, apesar de suas diferenças, elas têm origem comum. Os modelos de gênese de magmas potássicos da literatura sugerem como área fonte mais provável dessas rochas o manto enriquecido. As altas razões LILE/HFSE, demonstradas pelas pronunciadas anomalias negativas em Nb-Ta, Ti e Hf-Zr, indicam vinculo com áreas ativas onde a injeção de fluidos ricos em REE e LILE durante a subducção gera meassomatismo no manto superior. As assinaturas isotópicas com Nd(t) pouco negativo (-7.6 a -8.1) e razões \'ANTPOT.87 Sr\'/\'ANTPOT.86 \'Sr IND.(t)\'+ 0.7077- 0.7078 associadas ao elevado conteúdo de Ba, Sr e ETH, reforçam que estes magmas estão associados à fusão parcial de horizontes enriquecidos do manto litosférico. A associção de sienitos insaturados e supersaturados em sílica, em paralelo com a presença de enclaves dioríticos exclusivamente nos sienitos supersaturados sugerem que a violação da barreira térmica ocorreu devido à interação de magmas saturados de tendência alcalina com magmas básicos. A falta de evidências de interação in situ (e.g. diques sin-plutônicos) e a ocorrência de rochas microgranulares mais máficas apenas como enclaves retrabalhados indicam que a interação entre os magmas e consequentes mudanças composicionais deve ter ocorrido em níveis mais profundos da crosta. / The Pedra Branca Syenite, with about 90 Km2 in area, is a 610 Ma late-orogenic pluton intrusive in the Socorro-Guaxupé Nappe and truncated to the west by alkaline rocks (phonolite and nepheline syenite) from the cretacic Poços de Caldas Massif. The pluton is made up of four syenite units that intruded as three main magmatic pulses. The first pulse is represented by the laminated silica-saturated to undersaturated syenite (SLSI) with alkaline tendency that occurs at N and S-SE of the plúton. The second pulse corresponds to the laminated oversaturated syenite (SLS), which truncates SLSI. The last pulse, named internal oversaturated syenite (SSI), cuts SLS internally and makes up the plutons core. Externally, separated from the main pluton by a granite septum, occurs the external oversaturated syenite (SSE) that may be associated to the second or third pulse. The Pedra Branca Syenite is dominated by hypersolvus syenites with color indices 20-25, whose mineralogical variations show contrasts in crystallization conditions. The SLSI reached more oxidizing conditions than the oversaturated syenites, as recorded by their mafic assemblages (egirine-augite + phlogopite + hematite + magnetite versus diopside + phlogopite ± hornblende + ilmeno-hematite ± magnetite). Although in all syenites the crystallization occurred under oxidizing conditions, the SLSI have higher Mg# in the mafic minerals and grater proportions of the hematite component in the rhombohedral oxides, indicating higher oxygen fugacity, close to the HM buffer. Two main types of enclaves are present in the Pedra Branca Syenite. The mafic-ultramafic enclaves occur in all units, while microgranular enclaves are exclusive of silica-oversaturated syenites, and have compositions varying in the compositional fields of syenites, monzonites and diorites. Monzonitic and dioritic enclaves are interpreted as products of basic magmas that interacted with the syenitic host in deeper magma chambers and were carried during ascension. Another particular feature of the silica-oversaturated syenites is the presence of corroded plagioclase included in alkali-feldspars, which have compositions similar to the plagioclase crystals from the diorite enclaves (\'An IND.25-35\'). Estimatives of liquidus temperatures using apatite saturation showed high temperatures for the syenitic liquids, between 1040 and 1160° C. Pressure and fO2 estimates were frustrated by the lack of magmatic plagioclase (restricting the use of the Al in hornblende barometers) and the lack of equilibrium between the Fe-Ti oxides (ilmeno-hematite + magnetite). The Pedra Branca Syenite units show small compositional variations, and differ mostly in \'Al IND.2\'\'O IND.3\' content (higher in silica-oversaturated syenites), sharing geochemical signatures with high contents of LILE such as Ba (4000-10000 ppm) and Sr (2000-4500 ppm), plus other elements as \'P IND.2\'\'O IND.5\' (1,0-2%) and light rare earth elements (La= 100-300 ppm). Geochemical similarities between the units indicate that despite their differences, they have common origin. Models of potassic magmas genesis in the literature suggest as most likely source areas the enriched mantle. The high LILE/HFSE ratios, highlighted by strong negative anomalies of Nb-Ta, Ti and Zr-Hf in spiderdiagrams are suggestive of links with active areas where rich-REE and LILE fluid injection during subduction caused metassomatism in upper mantle. Isotopic signatures with moderately negative Nd(t) (-7.6 to -8.1) and \'ANTPOT.87 Sr\'/\'ANTPOT.86 \'Sr IND.(t)\'=0.70767 to 0.70779 associated with the high trace elements contents (Ba, Sr and REE), reinforces that these rocks are associated with partial melting of enriched horizons of the lithospheric mantle. The association of silica undersaturated and oversaturated syenites, and the presence of dioritic enclaves only in the oversaturated units suggests that the violation of the thermal barrier may be connected to the coexistence with basic magmas. The lack of evidence of in situ interaction (e.g., synplutonic dykes) and occurrence of more mafic microgranular rocks only as reworked enclaves indicates that the magma interaction and consequent compositional changes must have occurred at deeper crustal.

>Magister Scientiae - MSc / The late− to post−collisional Cape Granite Suite (CGS) located in the southwest of South Africa is comprised of S−, I−, and A−type granites, mafic intrusives, and volcanic flows. The CGS is interpreted to have formed during the closing of the Adamastor Ocean during the Late−Proterozoic to Early−Cambrian. Recently, the S−type granites have received much attention concerning their petrogenesis and sources. However, the I− and A−type granites remain poorly understood and little studied. Therefore, with new geochemical and isotopic data the petrogenesis, sources, and tectonic settings of I− (Vredenburg Batholith) and A−type (Cape Columbine) granites of the CGS form the focus for this study. The major and trace element data presented in this thesis show that the granites from the Vredenburg Batholith are weakly peraluminous to metaluminous, ferroan, and alkali−calcic. Associated with the granites are metaluminous, magnesian, and calc−alkalic igneous enclaves. Formerly, the granites have been interpreted to have formed by fractionation. However, with new geochemical analyses and reassessment of such models, it can be shown that such processes are incompatible with accounting for the chemical variation displayed by the granites and their enclaves. Moreover, the I−type granites and enclaves exhibit positive linear trends between whole−rock major and trace elements vs. maficity (Fe + Mg), which can be explained by co−entrainment of peritectic and accessory phases. The lithogeochemical characteristics of the enclaves and host granite reflect melting of a heterogeneous source. Moreover, the granite and enclave's εNd(t) values reflect melting of Paleoproterozoic-aged crustal sources. Finally, with tectonomagmatic discrimination diagrams, it can be shown that the tectonic setting of the granites indicates a transition from a collisional to extensional regime which corroborates the inferences of previous studies. The Cape Columbine Granites lithogeochemical characteristics are ferroan, calc−alkalic and weakly peraluminous. They show typical A−type granite characteristics in having high silica content, high Na + K values, REE enrichment as compared to S− and I−type granites and strong negative Eu anomalies. For this thesis, it can be shown that anatexis of quartzofeldspathic protolith in an extensional regime produced the chemical variation of the Cape Columbine Granite. Moreover, their isotope ratios are typically radiogenic, indicative of a crustal origin. With this new geochemical data evidence is provided against and in support of previous inferences made about the petrogenesis of the I− and A−type granites of the CGS. This also betters our understanding of the magmatic processes involved in the construction of the CGS over time.

The Early Proterozoic Agnew Intrusion is a well-preserved leucogabbronoritic to gabbronoritic layered intrusion that is a member of the East Bull Lake suite of layered intrusions (ca. 2490-2470 Ma) occurring in central Ontario. These intrusions are related to the development of the Huronian Rift Zone, which may be part of a much more widespread rifting event that involved the Fennoscandian Shield. Structural data suggest that these intrusions have been subjected to ductile deformation and are erosional remnants of one or more sill-like bodies originally emplaced along the contact between Archaean granitic rocks of the Superior Province and an Early Proterozoic Huronian continental flood basalt sequence in the Southern Province.

The Early Proterozoic Agnew Intrusion is a well-preserved leucogabbronoritic to gabbronoritic layered intrusion that is a member of the East Bull Lake suite of layered intrusions (ca. 2490-2470 Ma) occurring in central Ontario. These intrusions are related to the development of the Huronian Rift Zone, which may be part of a much more widespread rifting event that involved the Fennoscandian Shield. Structural data suggest that these intrusions have been subjected to ductile deformation and are erosional remnants of one or more sill-like bodies originally emplaced along the contact between Archaean granitic rocks of the Superior Province and an Early Proterozoic Huronian continental flood basalt sequence in the Southern Province.

The Alto Chicama district, Central Andean Cordillera Occidental, La Libertad, northern Perú, hosts the 14 M oz, Miocene Lagunas Norte high-sulphidation epithermal Au-(Ag) deposit (Latitude 7° 56ʹ30ʺ S; Longitude 78°14ʹ50ʺ W), in addition to several important, epithermal and mesothermal precious ± base-metal vein systems and porphyry Cu-Au-(Mo) deposits and prospects. The district is underlain by lower Oligocene-to-Middle Miocene, subaerial, Calipuy Supergroup volcanic rocks, unconformably overlying Upper Jurassic – Lower Cretaceous marine sedimentary strata affected by late Eocene-early Oligocene thin-skinned fold and thrust deformation. Mineralization at Lagunas Norte is largely hosted by intensely-folded Valanginian Chimú Formation quartz arenite, but extends into overlying, weakly-deformed, Lower Miocene dacitic volcaniclastic deposits. Fold- and thrust-related deformation at the deposit, and subsequent magmatic and hydrothermal activity, were localized along a long-lived, crustal-scale cross-strike discontinuity. Hydrothermal activity at Lagunas Norte was associated with local extension within an overall regional compressive regime. Ore formation occurred during the terminal stages of andesitic-to-dacitic magmatism in the deposit area, immediately following the sector collapse of an adjacent volcanic centre, and during eruption of late-stage peripheral dacitic domes. Intense advanced-argillic alteration occurred in at least two major pulses over a ~ 0.9 m.y. period, implying repeated magma influx in a shallow subjacent chamber. The ensuing Au-(Ag)-pyrite-enargite deposition resulted from mixing of magmatic vapour with oxidized groundwaters, a process stimulated by the contiguous incision of a steep-walled valley-pediment. The local volcanic rocks record a transition from “normal arc” to higher-pressure “adakitic” magmatism, initiated during ore deposition at Lagunas Norte, but exhibited by the entire Calipuy arc in northern Perú, and interpreted to reflect the destabilization of plagioclase and stabilization of garnet in inferred lower-crustal magmas. The progressive depletion of 18O and D in meteoric water recorded in late Oligocene-to-Late Miocene hypogene and supergene minerals is in permissive agreement with major uplift from ~ 1000 m to over 3000 m a.s.l. during hydrothermal activity. Hydrothermal activity and related ore deposition at Lagunas Norte unambiguously predated, by at least 2 m.y., the impingement of the aseismic Nazca Ridge at the Perú Trench and the ensuing flattening of the subducting slab / Thesis (Ph.D, Geological Sciences & Geological Engineering) -- Queen's University, 2012-04-05 11:09:14.751

No description available.