Petrogenesis of metamorphosed Paleoproterozoic, arc-related tonalites, granodiorites and coeval basic to intermediate rocks from southernmost Brazil, based on elemental and isotope geochemistry

摘要: Abstract In southern Brazil, three associations of metamorphosed tonalites and granodiorites that are compositionally similar to tonalite–trondhjemite–granodiorite (TTG) or adakitic have been identified in the Arroio dos Ratos Complex (ARC) Paleoproterozoic magmatism. The metatonalites Association 1 (A1; 2148 ± 33 Ma) a well-developed fabric, compatible with strong solid-state deformation. metagranodiorites 2 (A2; 2150 ± 28 Ma) intrusive A1 composition, but less deformed, their primary structures partly preserved. Both display contemporaneity relations basic intermediate magmas. 3 (A3; 2077 ± 13 Ma) is represented by tonalitic granodioritic gneisses, without any associated magmatism, its main characteristic banding resulted from Partial melting features locally present A3. geochemical compositions indicate sources related continental magmatic arc environment. 87 Sr/ 86 Sr (i) ratios (between 0.701 0.703), positive Ɛ Nd (t) values (+ 1.45 + 5.19), T DM ages close crystallization juvenile for A2 associations. A3 rocks ratio 0.715, an value + 0.47 age age, indicating source composition different those other Pb isotope evolution mantle orogen ( 208 Pb/ 204 Pb = 37.3–37.6; 207 Pb = 15.62–15.65; 206 Pb = 18.0–18.2). differ A2, more Th-poor Pb = 37.1; Pb = 15.64; Pb = 18.5). geochemistry suggests contamination crustal material. However, Sr–Nd–Pb signature this contaminant material originated these This may be crust generated arc, which geochronological results. dataset points occurrence self-cannibalism processes generation ARC rocks. chemical relative one A2. slightly lower Pb, higher association has also addition distinct source. high parameter Rb U, low Th contents. Such features, moreover depletion HREE combined near igneous suggest sediments. greater degree contribution, lack rocks, younger possibly mark mature late stages arc. major trace elements, as well data obtained study metasomatized wedge can process (A1 A2). characteristics i.e. , heavy rare earth elements A1, A3) arisen garnet-rich fractional magmas, time increased assimilation under high-pressure conditions. could newly placed at base crust, derived partial mantle. remobilization liquids depleted REE due presence garnet residue. microstructures two episodes recrystallization, temperature temperature. high-temperature structure remains discussion attributed metamorphic event. low-temperature event conditions observed adjacent areas, host Neoproterozoic post-collisional granitoids emplaced along Southern Brazilian Shear Belt (SBSB). Zircon crystals cores exhibit overgrowth 635 ± 6 Ma, SBSB granitoids.