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The Chuschín formation is a sedimentary-volcanic succession of the Famatina System subduction-related arc magmatism. This formation developed along the western margin of Gondwana during the early and middle Ordovician. The interpretation of the Chuschín formation is significant for the understanding of the Famatinian arc. This study provides a detailed facies analysis, which allows characterizing the deposits as well as defining some of the characteristics of the volcanism and sedimentation. Coherent, autoclastic, peperitic, pyroclastic and volcaniclastic facies were recognized between the different volcanic facies. The characteristics and relationships between these facies indicate events of effusive subaqueous volcanism as well as explosive volcanism showing predominantly high temperature features. Both types of volcanism are interbedded with volcanogenic deposits and epiclastic sediment that are associated mainly with turbidity currents. The magmatic and volcanic rocks are dominantly subalkaline, weakly peraluminous and silicic. Two new U-Pb zircon crystallization ages on volcanic rocks from the Chuschín Formation show that this section of the Famatinian arc formed between 463 and 469 Ma (Middle Ordovician). [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 Famatinian arc formed around the South Iapetus rim during the Ordovician, when oceanic lithosphere subducted beneath the West Gondwana margin. We present combined in situ U–Th–Pb and Lu–Hf isotope analyses for zircon to gain insights into the origin and evolution of Famatinian magmatism. Zircon crystals sampled from four intermediate and silicic plutonic rocks confirm previous observations showing that voluminous magmatism took place during a relatively short pulse between the Early and Middle Ordovician (472–465 Ma). The entire zircon population for the four plutonic rocks yields coherent εHf negative values and spreads over several ranges of initial εHf (t) units (−0.3 to −8.0). The range of εHf units in detrital zircons of Famatinian metasedimentary rocks reflects a prolonged history of the cratonic sources during the Proterozoic to the earliest Phanerozoic. Typical tonalites and granodiorites that contain zircons with evolved Hf isotopic compositions formed upon incorporating (meta)sedimentary materials into calc–alkaline metaluminous magmas. The evolved Hf isotope ratios of zircons in the subduction related plutonic rocks strongly reflect the Hf isotopic character of the metasedimentary contaminant, even though the linked differentiation and growth of the Famatinian arc crust was driven by ascending and evolving mantle magmas. Geochronology and Hf isotope systematics in plutonic zircons allow us understanding the petrogenesis of igneous series and the provenance of magma sources. However, these data could be inadequate for computing model ages and supporting models of crustal evolution. [ABSTRACT FROM AUTHOR]

Subduction zone magmatism plays a crucial role in driving the exchange of chemical elements between Earth's interior and surface. This survey focuses on the compositional analysis of primitive mafic rocks within an ancient Early Palaeozoic subduction-related magmatic belt. The primary objective is to assess the petrological processes involved in the cycling of chemical elements from the Earth's surface, through the slab and mantle reservoirs, to the crustal arc magmatic systems. By examining the composition of primitive mafic rocks and utilizing inverse modelling techniques, we estimate the composition of the ambient mantle source, which appears to have undergone depletion due to melt extraction before being metasomatized by slab agents. The inverse approach reveals that fluid-mobile elements (Th, U, La, Ce, and Sr) were primarily derived from the slab contribution and suggests that subduction had influenced the abundances of Nb and Ta in the modified mantle source. Conversely, Zr, Hf, and Ti were sourced from the ambient mantle. However, the available mineral/melt partition coefficients used in inverse modelling may overestimate the contribution of Sr and Nb from the slab. Instead, forward modelling is limited by the incomplete preservation of ancient volcanic arc geology. The forward mixing models that consider the interaction between slab-released sedimentary-derived melts and the ambient depleted mantle can explain the observed variations in Nd and Sr isotopic ratios in primitive mafic rocks. Two-component mixing shows that a small mass fraction (≤1.5 wt%) of average Cambrian continental sediments subducted beneath the Early Ordovician arc into a MORB-depleted mantle source account for the abundance of sedimentary-supplied elements such as Th, La, and Ba, as well as radiogenic isotope ratios of 143Nd/144N and 87Sr/86Sr in the primitive mafic magmas. The chemical and isotopic composition of deep-seated primitive mafic rocks reveals a decoupling between incompatible trace elements, which display minimal variation, and radiogenic isotopic ratios, which exhibit a wide range and reflect contributions from continental crustal reservoirs. To explain the observed variations in trace elements and isotopes, we propose a simple model involving simultaneous bulk assimilation (A) and imperfect fractional crystallization (IFC) in an open igneous system, where crystal accumulation and assimilation occur concurrently. Especially, deep crustal physicochemical interaction of primitive arc magmas with supracrustal host rocks may mask the expected clear signature of subarc mantle petrological processes. Our assessment of the Famatinian-Puna arc, an ancient subduction zone, concurs with estimates from active volcanic arcs, underscoring the general applicability of this study case to subduction zone magmatism. [Display omitted] • The study stresses underlying phenomena complicating the geochemical interpretation. • The pre-arc continental crust is an essential part of the subduction factory. • Crustal contamination could mask the signature of the subducting sedimentary layer. • Lithophile trace elements influx into the mantle wedge comes from subducted sediments. [ABSTRACT FROM AUTHOR]

Las Cañas Plutonic Complex (LCPC) is a small representative of the Famatinian Ordovician plutonism (470.4 ± 8.1 Ma) located in the northeastern sector of Sierra Grande de San Luis, Argentina. The LCPC was emplaced into a metasedimentary sequence, which reached their metamorphic climax under high-temperature/low-pressure conditions (∼680 ± 37 °C and 550 ± 120 MPa). The bodies of the LCPC are zoned by rocks of different compositions that represent ultrabasic, basic, intermediate and acidic trends (hornblendites, gabbros, tonalites, and granodiorites). Their petrological, mineralogical and geochemical characteristics indicate that multiple processes formed them, mainly crystal fractionation of magnesian, calc-alkaline and metaluminous magmas (typical of arc), but also different assimilation degrees of crustal melts from the fusion of metawackes involving AFC processes. Fieldwork (structural and petrological data), the geochemical characteristics of rocks [eg. Low Sr/Y and (Gd/Yb) C- N ], and thermobarometric results, indicate a relatively shallow fractionalization for the LCPC, which is in line with a pre-collisional arc stage linked to an extensive retro-arc setting for the Famatinian orogeny in Sierra de San Luis. • A new Ordovician absolute age was determined for Las Cañas Plutonic Complex. • The geology and petrology show that the plutons are composed of several facies. • Geochemical modeling indicates multiple processes for the plutonic rocks origin. • The geotectonic setting during the emplacement of the plutons is discussed. [ABSTRACT FROM AUTHOR]

The reactivation of existing faults has long been recognized to control the location and style of deformation in orogenic systems including the Sierras Pampeanas in the southern Central Andes; however, it can remain difficult to resolve the timing and fault kinematics across multiple orogenic phases. In the Sierras Pampeanas, basement-cored range-bounding faults mark a Paleozoic terrane boundary and are seismically active; however, the protracted history of deformation along this lithospheric-scale regional fault system - located ~400 km from the plate boundary - has been poorly constrained. In this study, we present new apatite (U–Th-Sm)/He and fission track thermochronology data and thermal history models from ten samples from the Sierra de Valle Fértil-La Huerta in the Western Sierras Pampeanas of Argentina. The spatio-temporal patterns of rock heating and cooling identified by our thermal history models throughout this fault system are consistent with four discrete phases of deformation. Thermal patterns indicative of Mesozoic extensional deformation and latest Miocene - Pliocene compressional deformation corroborate previous interpretations of regional deformation episodes in the Sierras Pampeanas. Our study also identifies a period of middle-Miocene cooling that revises the location of the Andean thrust front. This episode of deformation was previously unrecognized in the Sierras Pampeanas and is contemporaneous with thin-skinned deformation in the adjacent Precordillera thrust belt. A Paleogene phase of cooling may also support a phase of compressional deformation in the Sierras Pampeanas during a period in which neutral tectonic conditions have been proposed along the Andean margin. Our findings outline a history of fault reactivation suggesting that the long-lived fault systems in the Sierras Pampeanas are sensitive to plate-margin processes. • Thermal modeling of AHe-AFT data records fault reactivation across orogenic cycles. • Faults in the Sierras Pampeanas are highly sensitive to distal plate-boundary stress. • Thermal record of Mesozoic extension preserved along Cenozoic reverse fault. • Near-fault cooling shows multi-phase Cenozoic compression events. • High Mio-Pliocene exhumation is identified in nearly all samples in the Sierra Valle Fértil-La Huerta. [ABSTRACT FROM AUTHOR]

The granulite-complexes of the Sierras de Córdoba, inside context of Sierras Pampeanas, expose the deeply-uplifted internal metamorphic zone of an early Cambrian orogen. One of the largest granulite-complexes in the north-central of Sierra de Comechingones consists mainly of a set of stromatic and diatexitic migmatites all derived from metasedimentary progenitors. Migmatites vary over a spectrum of morphologies ranging from patch, net, and stromatic metatexites to schollen-schlieren and nebulite diatexites with widespread interspersed anatectic granites. The granulite-complex subordinately includes amphibolites, marbles, serpentinized ultramafic rocks, and mafic plutonic rocks. Petrographic analysis, textural and structural interpretation, thermobarometric estimates, and inherited and metamorphic zircon dating reveal the metamorphic history of migmatites in the north-central part of the Sierra de Comechingones. Metastable preservation of kyanite reflects that migmatites were buried (0.69–0.78 GPa) and heated (~650 °C) along a prograde trajectory before the onset of extensive anatexis. Then migmatites were further heated to granulite-facies peak temperatures (≥800 °C) at similar pressures (0.77 ± 0.06 GPa) through the sillimanite stability field. Widespread partial melting of the metasedimentary sequence occurred during peak metamorphism. The entire granulite-complex cooled to temperatures below 550 °C and ascended to middle crustal depths (0.3–0.5 GPa). The prograde heating trajectory and decompression during uplift overcoming cooling and tectonic exhumation are compatible with a predominantly compressive deformation. Coeval widespread partial melting with contractional non-coaxial deformation triggered self-reorganization of anatectic melts giving rise syn-deformational migmatites. In all the analyzed migmatites, U–Pb zircon geochronology yields inherited ages corresponding to those of orogenic systems that characterize the West Gondwana supercontinent. Inherited ages show a polymodal distribution pattern with contributions from Neoproterozoic (551–734 Ma; i.e., Brasiliano - Pan-African) and Mesoproterozoic detrital zircons (850–1182 Ma; i.e., Grenvillian), and minor proportions of Paleoproterozoic zircon grains (1751–1839 Ma). Ages interpreted as metamorphism and anatexis suggest the development of a single metamorphic event and restricted anatexis to a relatively short period of about 15 Ma (ca. 540-525 Ma). Metamorphic ages associated with the metamorphic peak trajectory are related to the Cambrian Pampean Orogeny. • P-T- t path shows a clockwise evolution along a single metamorphic event. • U–Pb zircon geochronology constraints granulite-facies metamorphism to ~540-525 Ma. • Metamorphic evolution was coeval with a compressive non-coaxial deformation. • Metatexites and diatexites are Early Cambrian syn-deformational lithological products. [ABSTRACT FROM AUTHOR]

Four major igneous suites with different geochemical characteristics are identified in the accretionary complex of the Pampean orogeny from the southern Sierras de Córdoba, Argentina. Crystallization ages of gabbroic and trondhjemitic plutonic rocks are Early to Middle Cambrian. The plutonic suites include mafic to intermediate alkaline OIB-like rocks, mafic tholeiitic N-MORB rocks, transitional mafic rocks, and minor trondhjemitic rocks with adakitic geochemical signature. The multiple igneous suites are spatially and temporally related to what reveals simultaneous tapping of distinct source reservoirs with their respective melts remaining distinctive from extraction to emplacement at middle crustal depths. The alkaline mafic-intermediate rocks with OIB-like geochemistry were generated by the partial melting of an enriched or metasomatized mantle source. By contrast, tholeiitic mafic rocks with N-MORB geochemical signature came out from a depleted mantle source. Trace element abundances of the transitional mafic magmas reflect variable mixtures between OIB-like and MORB-type magmas. Trondhjemitic rocks exhibit geochemical features highlighting their parent melts formed by low degree melting of a metasomatized subducting oceanic crust. The most reliable setting to generate all these diverse magmatic suites at the same time is a convergent margin where the opening of a slab window followed ridge-trench interaction. A corollary is that widespread mafic magmatism enhanced heat advection and gave rise to extensive intra-crustal anatexis in an accretionary complex of crustal extension. • Coexistence of multiple magmatic sources in the Early to Middle Cambrian Pampean orogen. • Alkaline, transitional and N-MORB mafic magmas intruded into metamorphic sequences. • Trondhjemite silicic adakite magmas spatially associated with alkaline mafic magmas. • Atypical subduction environment driven by slab-window following active ridge subduction. [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]