The Conlara Metamorphic Complex: Lithology, provenance, metamorphic constraints on the metabasic rocks, and chime monazite dating

The Conlara Metamorphic Complex, the easternmost complex of Sierra de San Luis, is a key unit to understand relationship between late Proterozoic-Early Cambrian Pampean and Upper Cambrian-Middle Ordovician Famatinian orogenies Eastern Sierras Pampeanas. Complex extends east foothills Comechingones west up Río Guzmán shear zone. main rock types CMC are metaclastic metaigneous rocks that intruded by Devonian granitoids. units comprise fine medium-grained metagreywackes scarce metapelites with lesser amounts tourmaline schists tourmalinites whereas encompass basic granitoids rocks. former occur as rare amphibolite interlayered within metasedimentary granitic component corresponds series orthogneisses migmatites (stromatite diatexite). divided in four groups based on dominant lithological associations: Martin La Cocha correspond mainly some gneisses Santa Rosa Felipe paragneisses, orthogneisses. Metamoprphic underwent polyphase metamorphic evolution. penetrative D 2 -S foliation was affected upright, generally isoclinal, N-NE trending 3 folds control NNE outcrop patterns different groups. An earlier, relic S 1 preserved microlithons. Discontinuous high-T zones related 4 fine-grained discontinuous bands attest for 5 deformation phase. Geochemistry both non-migmatitic amphibolites suggest represents an arc basin. Maximun depositional ages indicate pre- 570 Ma deposition sediments. ample interval sedimentation granite emplacement already indicated 497 ± 8 age El Peñon granite. -D history took place at 564 21 one PbSL calculated M garnet Group. constrained pervasively solid-state deformed Early which exhibits folded xenoliths Pressure-temperature pseudosections were using geologically realistic system MnNCKFMASHTO (MnO–Na O–CaO–K O–FeO–MgO–Al O –SiO –H O–TiO –Fe ). Peak metamophic conditions (M ) 6 kbar 620 °C. Late chlorite rims cracks garnet, along titanite ilmenite matrix plagioclase breaking down albite suggests P-T path moved back down. Monazite analyses yield isochron Th–U–Pb ranging from 446 418 Ma. oldest migmatite Monazites samples group crystallized decreasing temperatures, followed 10 low-Y2O3 monazites sample la Group also obtained migmatite, would likely mark later stage retrograde metamorphism New CHIME monazite presented here represent post-peak fluid assisted recrystallization similar amphibole muscovite cooling ages. Therefore may re-equilibration basement complex. • evolves during orogenies. made (schists- gneisses) (gneisses, migmatites, orthogneisses) evolution Neoproterozoic early Ordovician. 6kbar-620°C. Textures 418Ma recrystallisation.