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The western Argentinian sector of Gondwana has been the focus of several recent studies related to the Famatinian orogeny; however, the geologic history of arc activity in hinterland areas remains poorly understood. We present new data from the Monte Guazú Complex that reveal arc-related magmatism in the Sierras de Córdoba, which we consider part of the Famatinian hinterland. Igneous rocks comprise a diorite unit which includes an amphibole quartz-gabbro/diorite and a tonalite unit comprising amphibole- and biotite-bearing tonalites to minor granodiorites. Both units constitute a medium-K calc-alkaline series ranging in composition from metaluminous to moderately peraluminous. Trace-element signatures show Ti and Nb depletion and strong incompatible element enrichments (large-ion lithophile elements, Pb, Th, U, and light-rare earth elements) relative to normal mid-ocean ridge basalts, suggesting that they formed in an arc setting. U–Pb zircon geochronology constrains magmatism to 455–498 Ma, while weighted mean ages of 474–489 Ma are mostly synchronous with the Famatinian arc beginning. We demonstrate that fractional crystallization of mantle wedge-derived melts controlled the early magmatic evolution, while country rock assimilation and anatectic melt mixing were prevalent in evolved rock members. These results spatially extend the Late Cambrian–Late Ordovician Famatinian retro-arc to the southern Sierras de Córdoba. Our findings show that magmatism involved coeval anatexis of host rocks, conversely to previous geodynamic models. Our data have fundamental implications for Paleozoic tectonic and magmatic processes operating along the western Argentinian sector of Gondwana, demonstrating the importance of crustal reworking and the addition of mantle material in the Famatinian arc inboard sector. [ABSTRACT FROM AUTHOR]

Situated in the western Sierras Pampeanas of San Luis, the Nogolí Metamorphic Complex has become a key geological locality for unraveling the construction of the western Gondwana margin on the South American tectonic plate. This study presents a comprehensive analysis, encompassing new petrological and geochronological data, along with a meticulous structural examination of two distinct regions within the Nogolí Metamorphic Complex. Our primary aim is to assess the age and provenance of the protoliths, thereby shedding light on their geodynamic evolution. Detrital zircon U–Pb ages, obtained from a quartz–feldspathic-schist paleosome within a metatexite exposure in the La Barranquita area, disclosed a polymodal distribution. The predominant age population, centered around 616 ± 11 Ma, suggests a late Neoproterozoic source (Brasiliano–Pan African orogen). A secondary, yet significant, age peak at 542 ± 12 Ma points to a late Ediacaran to Early Cambrian origin (Pampean orogen). Additionally, a peak ranging from 930 to 1144 Ma indicates contributions from an early Neoproterozoic source (Grenvillian–Sunsas orogen). The maximum depositional age was determined to be 533 ± 14 Ma, based on the calculation of the youngest grain cluster at 2σ uncertainty. This polymodal zircon-age spectrum indicates that the sedimentary protolith of the Nogolí Metamorphic Complex derived from a Cambrian-age crystalline basement situated along the western margin of Gondwana. Contrary to models invoking continent–continent collision in western Gondwana during the early Cambrian, our findings better support a ridge–trench collision as the most plausible hypothesis for the origin of the Pampean orogeny. [ABSTRACT FROM AUTHOR]

The Laguna Amarga Metamorphic Complex is a major stratigraphic component of the southern Central Andes. The occurrence of crystalline basement pieces extensively exposed in the western Andes of Catamarca (Argentina), has been known for decades, nevertheless, a lack of detailed field-based and geochronological survey has precluded an accurate correlation of the Laguna Amarga Complex with other basement exposures in the Central Andes. The Laguna Amarga Metamorphic Complex outcrops in several fault-bounded blocks spread over about 360 km2, always underlying Neopaleozoic strata and Neogene volcanic strata from the Central Volcanic Zone. The northern part of the complex consists of amphibolite-facies metamorphic rocks derived from sedimentary and igneous precursors grouped in an association named Cazadero Grande. The original stratigraphic succession was interbedded siliciclastic sediments, carbonaceous, and mafic rocks. The southern segment of the complex is dominated by granulite-facies migmatites and ortho-amphibolites grouped in an association called Los Aparejos. In the Cazadero Grande Association, four deformational events are recognized. The first three phases gave rise to an imbricate S-verging over-thrusting system and prevailing tectonic transport to the south in response to progressive non-coaxial strains. The mineral assemblages linked to the metamorphic climax equilibrated coeval with the early stages of fabric-forming deformation. The posthumous fourth phase of deformation produces gentle folds with kilometer-scale wavelengths whose axial planes (non-penetrative) have an NNE strike, and are as related to Andean deformation. Three incremental deformation events coeval with the metamorphic climax are registered in the Los Aparejos Association that indicate a kinematics transport to the east. First U–Pb zircon ages are reported for the Laguna Amarga Metamorphic Complex. Age distributions are polymodal, but the dominant populations make well-defined clusters. The most prominent concord age peak is at 389 Ma, revealing the age of the metamorphic climax. Another noteworthy aspect is the presence of dominant Mesoproterozoic concord age peaks (1119-1082 Ma), interpreted as inheritance ages of their protolith. A point to highlight is the absence of ages reflecting the source with Brasiliano-Pan-African orogenic ages that dominates detrital provenance from the West Gondwana. The Mesoproterozoic protolith ages allow the correlation of this metamorphic complex with nearby basement detached from Laurentian realms. The analysis of the ages shows that the metamorphic peak and the generalized deformation that affected the entire basement of the complex developed in the Middle Devonian (Eifelian), this being a very little known event for the Paleozoic evolution of western Gondwana. The work discusses how a better understanding of the crystalline basement of the high Andes impacts the geodynamic history of the proto-Andean Gondwana margin. It also provides new information on the geodynamic configuration of the Lower to Middle Paleozoic and its link with the processes of accretion-collision of terranes. • Tectonic cover slices from the Cuyania/Precordillera terrane are exposed in the high Andes of Catamarca, Argentina. • Zircon U–Pb dating yields Mesoproterozoic ages in inherited grains while Devonian ages in metamorphic rims. • Structural analyses imply top-S nappe stacking closely following a Devonian metamorphic peak. • A narrow suture zone separating Laurentia-derived crust from the Early Ordovician Famatinian arc. [ABSTRACT FROM AUTHOR]

The Suri Formation is a sedimentary-volcanic succession in the Famatina belt formed during Lower - Middle Ordovician arc magmatism along the western margin of Gondwana. This study reports new lithostratigrafic data relating to the Suri Formation in the Chaschuil valley (Catamarca). The survey defines the main characteristics of volcanism and sedimentation through facies analysis. Epiclastic, volcaniclastic, pyroclastic and peperitic facies were recognized and interpreted in five facies association. The features and relationships of the facies associations indicate environments such as apron volcaniclastic, inner to an outer shelf, and fan distal delta, interbedded with effusive and explosive volcanism. Volcanic activity and relative sea-level changes were controls on sedimentation style in basins adjacent to the volcanic edifice. The study reports U–Pb geochronological analysis of zircon from a sandstone sample of the Suri Formation to infer detrital provenance. The detrital zircon pattern with peaks at 486 Ma points to active Famatinian magmatism as recorded on the nearby Narváez batholith. Eruptive masses experienced rapid reworking, short sedimentary transport and intra-arc deposition. The maximum deposition age of detrital zircon corresponds to a subordinate age cluster at 464.4 ± 4.4 Ma and reflects synchronism between volcano-sedimentary deposition in the Suri Formation and plutonic-volcanic construction of the Las Planchadas Formation. • This study reports a stratigraphic analysis of the Suri Formation in the northern Famatina System. • The Suri Formation reflects apron volcaniclastic, internal to external shelf and fan distal delta. • Variable intensity of volcanism controlled the sedimentary environment of Suri Formation. • Volcanic facies contain abundant proximal deposits suggestive of explosive eruptive activity. • Sedimentation of the Suri Formation reveals a topographic surface with high slope gradient. [ABSTRACT FROM AUTHOR]

The Famatinian arc, over central-western Argentina, is one of the few examples of exposed crustal arc cross-section in the world. This Paleozoic magmatic arc and orogenic system on the Earth's surface offers unique insights into the nature of whole-arc processes, continental crust generation, and preservation. A detailed account of birth, growth, and closure is integrated throughout the region, and the entire geodynamic history of the Famatinian arc is presented. The Famatinian magmatic arc grew during a single-cycle episode that spanned a few tens of million years. Upon waning of the Cambrian Pampean orogen, an Upper Cambrian – Lower Ordovician marginal and open sea basin developed mostly on the recently stabilized Cambrian crystalline crust and was flooded by a turbidite wedge. Typical subduction zone magmatism resumed outboard of the Pampean orogen in the Lower Ordovician. After about 20 My of magmatism driven by subduction zone dynamics at plate scale, magmatism waned and stopped with the entry of a Laurentia-rifted continental microplate in the subduction zone. A full phase of a mountain-building process accompanied the continent-arc collision. The orogenic collapse occurred during the Devonian, ending the Famatinian system after nearly 150 My of magmatic arc, plate convergence, and continent-arc collision development on the proto-Andean Gondwana margin. • Geology shows a well-preserved Paleozoic magmatic arc and orogenic system on the Earth's surface. • A full plutonic crustal section formed in about 20 My of subduction-related magmatism. • A segment of Famatinian arc ended sandwiched between a Laurentian microplate and Gondwanan margin. • The subducting continental crust merged the overriding plutonic arc crust to make stable Continental Crust. [ABSTRACT FROM AUTHOR]

The Valle Fértil-La Huerta batholith is a differentially tilted, compositionally stacked, calc-alkaline plutonic sequence in the central Famatinian arc of Argentina. It consists of two major lithologic units: these are (1) an intermediate unit largely dominated by amphibole- and biotite-bearing tonalites but encompassing from gabbro to leucogranite; and (2) an overlying silicic unit that shows the same petrological diversity as the intermediate unit, but granodiorite and monzogranite are its prevailing lithologies. The silicic unit is separated into four subunits using lithological changes at regional mapping scale. All the boundaries are gradational among lithologic units and subunits. The internal fabric along the entire batholith is either magmatic or submagmatic and it was developed during the arc formation. The original magmatic foliation is north–south striking and steeply-dipping. The magmatic foliation crosses over and transposes the gradational contacts among lithologic units. Petrological architecture, structural geology, geobarometric estimates and geochronology show that the entire batholith is a comagmatic system exposing more than 13 km of a middle arc crust. Crystallization-fractionation models computed using whole rock and mineral chemistry account for the mineralogy of plutonic rocks and coincide with the results of experimental petrology. Mass-balanced modeling predicts that the unexposed cumulate roots of the Famatinian arc should have been about 1.3 times larger than the intermediate and silicic plutonic batholith. However, the mass of calculated cumulate would diminish significantly if a portion of the host metasedimentary material were consumed in constructing the batholith. The batholith grew progressing upward from the lowest levels and acquired a stratified compositional organization. The driving mechanism was continuous influxes of mantle-derived mafic magmas that made up the lower crust, caused crustal-level melting and magma mixing, and formed intermediate – silicic rocks at increasingly shallower depths. • The plutonic middle crust of the Famatinian arc was at least 13 km thick. • The plutonic crust grew progressing upward and acquiring a stratified organization. • Pre-arc metasedimentary sequences play a role in fertilizing the magmatic system. • Modeling yields a 1.3:1 ratio of cumulates over derivatives to make the magmatic column. • A few tens of kilometers of cogenetic cumulates are lost in the Famatinian arc. [ABSTRACT FROM AUTHOR]