Petrogenetic analysis of arc-related Devonian magmatic rocks in relation to the formation of magmatic hydrothermal Cu±Mo±Au deposits in the New Brunswick segment of the Northern Appalachians
| dc.contributor.advisor | Lentz, David R. | |
| dc.contributor.advisor | McFarlane, Christopher R. M. | |
| dc.contributor.author | Yousefi, Fazilat | |
| dc.date.accessioned | 2024-11-20T19:43:01Z | |
| dc.date.available | 2024-11-20T19:43:01Z | |
| dc.date.issued | 2024-10 | |
| dc.description.abstract | Devonian adakitic porphyritic intrusive rocks in New Brunswick (NB) are associated with porphyry Cu-Mo-Au mineralization and are similar to Cu-Mo-Au porphyries in Québec and Maine, implying a shared genesis. These granitoids are similar petrologically and feature oxidized I-type arc-like compositions with SiO2 ≥66.5 wt.% and Al2O3 >15.5 wt.%, among other distinctive geochemical characteristics. Trace element compositions characterize the link between adakite formation, slab failure, and porphyry Cu-Mo-Au system potential. These rocks are enriched in Cs, Rb, and Ba, but depleted in Nb, Ta, P, and Ti, reflecting subduction-related magmatism. The slab breakoff process involves the breaking of part of the subducted oceanic plate, leading to asthenosphere upwelling and selective partial melting of the slab, the suprasubduction zone lithospheric mantle, the upwelling mantle, and the basal continental crust; transpressional to transtensional tectonics can facilitate magma ascent and emplacement in the post-subduction setting. Zircon, because of its refractory nature and prevalence in igneous rocks, is useful for assessment of magmatic evolution, specifically its oxygen and U-Th-Pb isotopic compositions. This information can be used to predict magmatic fertility in terms of Cu ± Mo ± Au porphyry mineralization. LA-ICP-MS analyses of zircons from the adakitic intrusions investigated reveal diverse compositions, reflecting varied magmatic conditions. The Zr/Hf and Ce/Ce* values provide insights into porphyry fertility, aiding mineralization potential assessment. This study also employs petrography, µXRF-EDS mapping, and LA-ICP-MS to analyze titanite compositions in these oxidized I-type granitoids. Titanite is enriched in high field strength elements (Ta, Zr, Hf, Th, U), rare earth elements, and Sr and can serve as a petrogenetic and metallogenic indicator. Zr-in-titanite thermometry reveals varied crystallization temperatures (784° to 1098°C) among the intrusions investigated. Magnetite phenocrysts in these intrusions have euhedral to subhedral morphology and lack oscillatory zoning (according to SEM-BSE imaging). The diverse trace element compositions offer insight into the magmatic to magmatic-hydrothermal systems. EPMA analysis reveals variable concentrations of SiO2, Al2O3, MgO, Mn, Fe, Ti, Cr, and V in magnetite, with distinguishing features for various deposit systems. When comparing Ti+V with Al+Mn concentrations in magnetite crystals, all samples exhibit similar crystallization temperatures (>500ºC). | |
| dc.description.copyright | © Fazilat Yousefi, 2024 | |
| dc.format.extent | xx, 325 | |
| dc.format.medium | electronic | |
| dc.identifier.uri | https://unbscholar.lib.unb.ca/handle/1882/38193 | |
| dc.language.iso | en | |
| dc.publisher | University of New Brunswick | |
| dc.relation | NB Geological Survey (NB Department of Natural Resources and Energy Development) | |
| dc.relation | University of New Brunswick | |
| dc.rights | http://purl.org/coar/access_right/c_abf2 | |
| dc.subject.discipline | Earth Sciences | |
| dc.title | Petrogenetic analysis of arc-related Devonian magmatic rocks in relation to the formation of magmatic hydrothermal Cu±Mo±Au deposits in the New Brunswick segment of the Northern Appalachians | |
| dc.type | doctoral thesis | |
| oaire.license.condition | other | |
| thesis.degree.discipline | Earth Sciences | |
| thesis.degree.grantor | University of New Brunswick | |
| thesis.degree.level | doctorate | |
| thesis.degree.name | Ph.D. |