Produção Nacional
Elemental and Isotopic (Sr-Nd- O) Geochemistry and U-Pb Zircon Geochronology of Late-Stage Post-Collisional Magmatism in the Northern Segment of the Dom Feliciano Belt
2022; RELX Group (Netherlands); Linguagem: Inglês
10.2139/ssrn.4178126
ISSN1556-5068
AutoresLucas Vargas Moraes, Luana Moreira Florisbal, Valdecir de Assis Janasi, Maria de Fátima Bitencourt, Lucilene Martins, Larry M. Heaman, Barry Shaulis, Richard A. Stern,
Tópico(s)earthquake and tectonic studies
ResumoThe Ediacaran post-collisional magmatism of the Dom Feliciano Belt is widespread in southern Brazil and Uruguay and is represented by the Florianópolis Batholith in its northern sector. The Zimbros Suite (Area 1) comprises the Zimbros Granite, emplaced within the Major Gercino Shear Zone (MGSZ) at the final stages of its activity, and the Morro dos Macacos Granite, emplaced nearby but outside the high-strain zones. Conversely, the Cambirela Plutono-volcanic Suite (Area 2) occurs far from the deformation sites of the MGSZ and encompasses the Ilha, Vila da Penha, and Serra do Tabuleiro granites and the Cambirela Silicic Volcanic Sequence (rhyolites + ignimbrites). The plutonic units from both areas are coeval (ca. 590 Ma) and characterised by high-SiO 2 (74-79 wt.%, except for the Zimbros Granite < 74 wt.%) , metaluminous to slightly peraluminous, mildly alkaline, high-K, reduced (Fe# > 0.84) A 2 -type granites that compose two distinct shallow-level plutono-volcanic systems installed in a post-collisional setting at the late stages of the Dom Feliciano orogenic cycle. The units emplaced far from the MGSZ (Area 2) are derived mostly from crustal sources with minor mantle contribution, as indicated by the weakly negative ƐNd t (-4.39 to -6.77), high Fe#, Ce/Nb and Y/Nb ratios and intermediate δ 18 O values (~7 ‰), and show a highly fractionated character with "seagull-shaped" REE pattern and high Eu (Eu/Eu* 0.02-0.7), Ba and Sr negative anomalies. In contrast, the Zimbros Suite (Area 1) is derived from mantle sources activated and channelised by the MGSZ, with progressive crustal assimilation enhanced by this large-scale structure. The volcanic units from the Cambirela Plutono-volcanic Suite share all characteristics presented for the granitic rocks and are composed of earlier poor-crystal rhyolites (586.3 ±2.5 Ma) and later ignimbrites with abrupt faciological variation (579.7 ±2.4 Ma) indicating different maturity stages of long-lived magma chambers. The variable U-Th contents and the bimodal δ 18 O signatures associated with wide intra-sample variations (+3.4 ± 0.4‰ and +6.9 ± 0.2‰) further indicate open-system magmatic processes and the co-eruption of distinct melts and points to the interaction of the volcanic units with distinct magma chambers of the Cambirela plutono-volcanic system.
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