Origin to emplacement of Pabineau Falls aplitic granite dykes, northeastern New Brunswick, Canada: evidence of extreme fractionation.
In: Atlantic Geoscience, Jg. 59 (2023), S. 51-52
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Zugriff:
The post-tectonic Middle Devonian Pabineau Falls Granite (PFG) is a porphyritic coarse-grained biotite granite located in northeastern New Brunswick (Canada) that has been previously dated by U-Pb zircon (397.2 ± 1.9 Ma). The western part of the PFG has been intruded by an unrelated coarse-grained to pegmatitic Be-bearing molybdenite-mineralized (endogranitic) leucogranite that is named the Pabineau Lake Granite (PLG). The PLG has been dated at 390 ± 1 Ma (U-Pb zircon), and therefore cannot be related to the cooling of the PFG. Narrow felsic dykes (<1 m width) are also known in the PFG that have textures ranging from quenched aplitic to microcrystalline, so four were sampled at Pabineau Falls to examine their composition and ascertain their ages. The microcrystalline dyke is the youngest and cross-cuts the other dykes orthogonally. All four of these leucocratic dykes are more fractionated than the PFG (Zr/ Ti, Zr/Hf, Nb/Ta, Rb/Sr), but similar to the PLG, although none are mineralized; these dykes and the PLG are high silica (>75 wt.%), calc-alkalic, mostly ferroan with ASI of 1.05 to 1.08 like the PLG, and hence typical of post-orogenic suites. Chemical characteristics such as low CaO (<0.5 wt.%), P2O5 (<0.04 wt.%), and Al/Ga (3659) are consistent with within-plate (A-type) granites, although these characteristics are exaggerated by very low T fractionation. The youngest microcrystalline dyke has low Zr (38 ppm) consistent with extreme fractionation. The ratios Zr/Hf, Nb/Ta, and Y/Ho covary and decrease to 13.6, 2.2, and 30.4, respectively, whereas Rb/Sr increases to 9.1. The Th and Y decrease as Nb, Ta, and U increase with fractionation. These dykes have bird-wing chondrite-normalized REE profiles, with pronounced Eu/Eu* (0.206 to 0.132) consistent with considerable feldspar fractionation. Pqz for the most pressure-quenched dyke is 220 MPa, similar to the result from the PLG. [ABSTRACT FROM AUTHOR]
Titel: |
Origin to emplacement of Pabineau Falls aplitic granite dykes, northeastern New Brunswick, Canada: evidence of extreme fractionation.
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Autor/in / Beteiligte Person: | LENTZ, DAVID ; YOUSEFI, FAZILAT ; MOHAMMADI, NADIEH |
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Zeitschrift: | Atlantic Geoscience, Jg. 59 (2023), S. 51-52 |
Veröffentlichung: | 2023 |
Medientyp: | academicJournal |
ISSN: | 2564-2987 (print) |
DOI: | 10.4138/atlgeo.2023.002 |
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