The late Ediacaran to early Cambrian Pampean magmatic arc in Argentina represents an excellent example of subduction-related magmatism and continental crust formation. This study presents new geochemical, isotopic, and geochronological data from the Guasayan intrusive complex, which is a significant body within this magmatic arc. The data are integrated with a comprehensive compilation of published data from the arc elsewhere. The Pampean arc exhibits a wide range of rocks, from metaluminous I-type diorites to strongly peraluminous S-type granites, with the majority displaying hybrid compositions (mostly magnesian, calc-alkalic and slightly peraluminous compositions). Zircon U-Pb geochronology indicates that the Guasayan granitoids were emplaced mainly during a flare-up of arc magmatism between ca. 530 and 535 Ma. However, the presence of zircon antecrysts with ages of ca. 545 Ma in most of the Pampean arc granitoids, suggests that the magmatic system was long-lived, and the early crystallized zircon crystals were recycled into younger magmatic pulses. Geochemical and isotope data (Sr-Nd-Hf) highlight the interaction between mantle-derived magmas and crustal components, with magma mixing identified as the dominant process in the generation of the hybrid granitoids. Local-scale processes such as crustal assimilation, fractional crystallization, and peritectic entrainment also contributed to the geochemical and isotopic diversity. The involvement of the Puncoviscana Series as the crustal component of the mixed magmas is evidenced by zircon inheritance patterns and isotopic signatures. This study underscores the importance of magma mixing in the evolution of the Pampean arc and provides insights into the geodynamic processes driving continental crust formation in subduction-related settings.

The El Fierro pluton represents one of the late-stage plutons of the Choiyoi Magmatic Province in the Colang & uuml;il batholith (Frontal Cordillera, Argentina). New U-Pb zircon dating yields a crystallisation age of 262 +/- 2 Ma, with zircon antecrysts (similar to 273 Ma) indicating prolonged magmatic activity that overlaps with the early-stage Choiyoi I-type magmatism (ca. 270-290 Ma). This pluton is ferroan, alkali-calcic to calc-alkalic, and essentially weakly peraluminous (av. 1.05 +/- 0.06), exhibiting high Ga/Al ratios, elevated HFSE concentrations (Ce + Zr + Nb + Y; av. 310 +/- 147 ppm; range: 150-584 ppm), extreme F enrichment (6101-31,442 ppm) and relatively high zircon-saturation (775 +/- 45 degrees C) and apatite-saturation temperatures (887 +/- 78 degrees C), consistent with an A-type affinity. Isotope data (epsilon Hf-t = -7.0 to +1.25; epsilon Nd-i approximate to -3), together with geochemical compositions, reflect a hybrid crustal source involving metasedimentary components likely metasomatized by mantle fluids. Accordingly, we interpret the El Fierro pluton as the product of crustal melting during lithospheric thinning and slab retreat, marking the onset of incipient rifting in southwestern Gondwana. This study highlights that A-type granites can be generated in extensional regimes within arc settings.

The Santa Rosa kinzigite is a Cambrian Pampean orogeny granulite containing cordierite, garnet, and anthophyllite. It forms a lensoid body with tectonic foliation and sharp concordant contacts (parallel foliations) amidst migmatites (stromatites and diatexites) containing cordierite and garnet but lacking anthophyllite. It has long been interpreted as a metasedimentary restite. In this revision, using new isotopic (Sr), mineralogical, and geochronological (U-Pb zircon) data and new metamorphic modelling, we propose that this unique rock originated from a metapelite that underwent migmatization and complete extraction of the K-rich anatectic melt at approximately 6-7 kbar. Subsequently, the resulting restite (sillimanite + garnet ± cordierite) was invaded by intermediate to mafic magmas (gabbroic and tonalitic) from the Pampean syn-orogenic magmatic arc (ca. 900 °C). The present-day rock resulted from mingling of the restite and magma whose crystallization produced the kinzigite matrix (quartz, plagioclase, and orthopyroxene). The mingled restite and magma underwent further cooling to subsolidus temperature (ca. 750 °C) under isobaric conditions, followed by burial to 10 kbar, which gave rise to kyanite. These processes took place between ca. 540 and 520 Ma of the collisional Pampean orogeny. The kinzigite underwent a stage of exhumation and water infiltration at ca. 510 Ma when anthophyllite and abundant cordierite formed from garnet after a long period (ca. 10 My) of hot residence at depth. The Santa Rosa kinzigite is a good example of the complexity of processes at the roots of magmatic arcs during subduction and eventual collision.

Felsic microgranitoid enclaves (FMEs) are underexplored components of granitic plutons that preserve key evidence of magma chamber processes. This study examines FMEs and the coexisting fine-grained units in relation to the porphyritic regional granites that host them within the Characato suite of the Achala Intrusive Complex, Argentina, integrating field observations, petrography, whole-rock geochemistry, mineral chemistry, and Nd isotope analyses. Our main conclusions indicate that the FMEs and associated fine-grained units represent autolithic fragments derived from solidification fronts within granitic magma chambers. Their finer grain size and relatively higher crystallization temperatures (e.g., Delta TZr approximate to 60 degrees C and Delta TBt approximate to 40 degrees C) suggest early crystallization under enhanced undercooling conditions near chamber margins. Field evidence-such as spatial association of FMEs with marginal fine-grained units, gradational contacts, ductile felsic dykes, and magmatic layering and deformation-indicates multiple episodes of solidification front collapse into the host magma. The observed diversity in enclave size, texture, and degree of interaction reflects a continuum of rheological states, ranging from crystal-rich suspensions to partially solidified mushes. Furthermore, the neodymium isotopic compositions and geochemical trends of the FMEs and marginal fine-grained units are consistent with those of the regional host granites. This supports a cogenetic and crustal origin, with the enclaves and associated lithologies representing more primitive crystallization products. This study emphasizes the dynamic role of solidification fronts as zones of instability, and magmatic recycling, contributing to the construction and internal evolution of felsic plutonic systems.

The Carboniferous-Permian Tarija basin of southern Bolivia evolved under major tectonic and climatic influence. The timing of transition from glacially influenced to arid conditions, after the Gondwanide tectonic event, has been based mainly on palynological correlations. This study presents data from three U-Pb detrital zircon samples (similar to 500 grains each), providing two robust maximum deposition ages (327 +/- 4 and 259 +/- 3 Ma). These results are integrated with stratigraphic cycles defining the Macharet & iacute;, Mandiyut & iacute; and Cuevo Groups. Our interpretation, supported by our data and previous studies, constrains a Mississippian to earliest Pennsylvanian age for the Macharet & iacute; Group and a Pennsylvanian age for the later Mandiyut & iacute; Group, both bounded by the regional Intra-Carboniferous unconformity (similar to 318 Ma). A major depositional hiatus followed the end of glaciation, with arid sedimentation recorded only after the late Permian (Cuevo Group).

A robust U-Pb zircon dataset previously published in this journal revealed a magmatic system with protracted activity, characterized by three major crystallization events at 391 +/- 1, 384 +/- 1, and 379 +/- 2 Ma. Based on these data, we proposed a conceptual model that suggests the existence of a deep mush reservoir, which enabled prolonged zircon antecrysts crystallization (ca. 395-384 Ma), followed by the crystallization of younger zircon (i.e. authocryst, 379 Ma) during emplacement. New Lu-Hf zircon data from the same U-Pb dated domains reveal that the parental magma was derived from a single heterogeneous source involving both subcontinental lithospheric mantle and Early Palaeozoic lower continental crust. Notably, Lu-Hf data from zircon indicate significant compositional variability in the magma, with a wide epsilon Hft ranges during the zircon crystallization events. This marked compositional diversity in epsilon Hft values are attributed to the crystallization of zircon antecrysts from isotopically distinct microdomains that formed melt pockets within the mush reservoir, accounting for the complex Hf isotopic signatures observed in magmatic zircon populations. These conditions persisted during magma ascent and shallow emplacement, where zircon autocrysts grew. Zircons that previously crystallized from compositionally distinct microdomains were juxtaposed within a single rock volume at the hand specimen scale, resulting in the presence of zircon crystals with different U - Pb ages but similar epsilon Hft values, or crystals with the same U - Pb ages but contrasting epsilon Hft values, all within the same rock sample. epsilon Hft zircon data, combined with geochronological and whole-rock chemistry evidence, support a model in which differentiation occurred mainly within the mush reservoir, with subsequent ascent and emplacement involving magmas with diverse geochemical compositions. Our findings indicate that whole-rock isotopic systems (e.g. Sm-Nd, Rb-Sr) reflect only the final integrated signal of the magmatic system, masking internal heterogeneity.

The San Clemente satellite pluton (SCP), located on the eastern flank of the Achala Intrusive Complex (AIC) or Achala Batholith in southwestern Gondwana, represents a crucial record of Devonian foreland magmatism. This study integrates petrological and geochemical data, including whole-rock Sr-Nd and zircon Hf isotopes, as well as geochronological data (U-Pb in zircon and titanite), to constrain the petrogenesis of the SCP. The pluton consists of two main units: the San Clemente granodioritic unit (SCU) and the La Herradura monzogranitic unit (LHU), along with quartz-dioritic and tonalitic enclaves. Petrographic and field evidence suggest an incremental, east-to-west magmatic construction history, involving sequential and nearly synchronous emplacement of quartz-dioritic and tonalitic magmas, followed by the SCU and subsequently the LHU. U-Pb geochronological data indicate a protracted magmatic history for the satellite pluton and its enclaves, spanning from the Early to Middle Devonian. This activity is recorded in both antecrysts (similar to 404 Ma) and autocrysts (390-384 Ma), marking the onset of construction of the Achala Intrusive Complex. The presence of antecrysts points to early magmatic processes occurring in a deep crustal mush reservoir, whereas the autocryst ages reflect the development of a magma chamber at or near the final emplacement level. Petrological, geochemical, and isotopic data classify the SCU as High-SiO2 Adakites (HSA) (SiO2 = 68.7-70.7 %, K2O/Na2O = 0.4-0.6, A/CNK (molar percent Al2O3/[CaO + Na2O + K2O]) = 1.04-1.05, with high Sr/Y and La-N/Yb-N ratios, suggesting a source derived from the partial melting of a thickened mafic lower crust with limited input from the mantle (epsilon Nd-t = -2.3 to -1.8; Sr-87/Sr-86(t) = 0.7047-0.7043; epsilon Hf-t = -9.0 to +2.2). The LHU exhibits hybrid compositions, combining peraluminous two-mica granites with adakitic affinities (SiO2 = 71.9 %, K2O/Na2O = 1.12, ASI = 1.07, with high Sr/Y and La-N/Yb-N ratios), indicative of a dominant felsic crustal source with minor mafic contributions (epsilon Nd-t = -4.6; Sr-87/Sr-86(t) = 0.7057; epsilon Hf-t = -12.0 to +2.2). The enclaves show geochemical affinities to primitive andesites and sanukitoids (SiO2 = 56.1-57.4 %, MgO = 5.2-7.0 %, Mg# (molar percent 100 x MgO/(MgO+FeOt)) = 59-65, Cr = 124-151 ppm, Ni = 121-124 ppm, Ba = 235-1323 ppm, Sr = 501-753 ppm, Ce = 47-275 ppm), reflecting a metasomatized lithospheric mantle source with crustal contamination (epsilon Nd-t = -2.8 to -3.0; Sr-87/Sr-86(t) = 0.7066-0.7091; epsilon Hf-t = -3.5 to +3.8). These findings indicate that the San Clemente pluton preserves key evidence that the formation of the AIC began with partial melting near the base of a thickened crust, followed by more extensive melting of the lower to middle crust, resulting in the formation of the voluminous, peraluminous A-type magmatism characteristic of the AIC.

As is well known, the advent of plate tectonics in the early 1960s brought about a worldwide revolution in the Earth Sciences. In Argentina, a pioneer in applying plate tectonic thinking in the early 1980s was Dr. Victor Ramos, who introduced provocative ideas about the presence of various terranes that formed Argentina and South America. Many of the proposed terranes were quickly adopted by the national and international geological community, although some crucial data were still lacking to be conclusive. One of these terranes, called Chilenia, corresponds to an alleged extensive continental block of near 1100 km long and 200 km wide, with a Grenville-age basement outcropping in the Cordon del Portillo, Frontal Cordillera of Mendoza province. This terrane is thought to have been accreted to the southwestern margin of Gondwana during the Late Devonian. Forty years after the birth of this idea, we revisit the existence (or not) of a Grenville-age basement within this terrane, integrating previous and new U-Pb zircon ages. New findings reveal no evidence of a Grenville-age basement, but instead indicate a Neoproterozoic or middle to upper Cambrian sedimentary succession overprinted by late Devonian metamorphism occur, i.e., the Guarguaraz Metamorphic Complex.

The Sierra de Famatina of northwestern Argentina contains one of the best Cambro-Ordovician stratigraphic records of the SW Gondwana margin. Two lithotectonic belts (Calalaste–Narváez and Famatina–Valle Fértil), separated by master faults, preserve evidence of two former volcano-sedimentary basins (Eastern and Western, respectively). The Calalaste–Narváez Lithotectonic Belt consists of an Ediacaran to early Cambrian basement unconformably overlain by a 490–480 Ma cover of very low-grade volcano-sedimentary and volcanic succession that presumably formed in an extensional tectonic regime. In contrast, the Famatina–Valle Fértil Lithotectonic Belt comprises a basement consisting of the late-lower-to-middle Cambrian metasedimentary Achavil and Negro Peinado formations unconformably overlain by meta/sedimentary and metavolcanic rocks ranging in age from the late Cambrian to the Middle Ordovician (ca. 490–460 Ma). This belt includes the Famatinian Cordilleran-type magmatic arc active mainly at ca. 473–468 Ma, coeval with andesite to rhyolitic volcanism (Suri and Las Planchadas formations). Rhyolitic tuffs of ca. 473 Ma (εNdi = − 4.1) were found in the La Aguadita Formation, allowing this unit to be re-assigned to the late Floian. The oldest magmatism of the Sierra de Famatina is characterized by isotopically evolved (εNdi = − 5.1) rhyolitic tuffs of ca. 490 Ma in the Bordo Atravesado Formation, which was coeval with deposition of Mn-enriched hydrothermal cherts. This early Famatinan volcanism contrast with that of similar age and isotopically less evolved occurred in the Calalaste–Narváez Lithotectonic Belt suggesting variations of the source of magmas across the space and time within the Famatinan Orogenic Cycle. We propose that both described lithotectonic belts likely diverge northwards into Chile and Peru, wrapping around the Arequipa–Antofalla Proterozoic block.

We propose a conceptual model for the magmatic system that gave rise to the Devonian and Carboniferous subduction-related magmatism in the Frontal Cordillera of Argentina, (representing the pre-Andean margin of SW Gondwana), integrating previous geochronological studies with new geochronological data from granitoids and subvolcanic dikes, which include reported petrological, geochemical, and isotopic data. This conceptual magmatic system postulates an extended magmatic activity, similar to that reported in a previous study for the Devonian foreland magmatism located in the present-day Sierras Pampeanas of Argentina. The geochronological data play a central role in the model, and lead us to postulate the presence of a deep mush reservoir, where a prolonged magmatic activity, permitted the extended crystallization of Devonian (ca. 400 +/- 3 and 414 +/- 3 Ma) and Carboniferous antecrysts (334 +/- 2 Ma, 341 +/- 2, and 348 +/- 2, where the age of 348 Ma maybe considered as derived from the source, i.e. xenocrysts). Migration of the parental magma from the mush reservoir zone occurred near the time of emplacement and culminated in the formation of an ephemeral magma chamber located in shallow levels, where Devonian and Carboniferous zircon autocrysts crystallized (382 +/- 5 Ma and 325 +/- 2 Ma, respectively). Age spectra reported within individual sample, favors the idea of a massive migration of magma when conditions were favorable (e.g., thermally matured crust). Notably, the Carboniferous geochronological data is strongly consistent with previous geochronological data recently reported for the granitic rocks of the Tabaquito batholith. Although this model supports a protracted magmatic system for the Devonian and Carboniferous subduction-related magmatism, previous and new isotopic data reveal a significant difference in the petrogenetic processes. While the Carboniferous arc magmatism shows significant juvenile material contribution, this is not the case for the Devonian magmatic arc, where isotopic data suggest an older continental lithosphere as the dominant source. These different sources are attributed to two contrasting geodynamic settings, with advancing and retreating oceanic slabs, respectively.

It is widely acknowledged that thermal models clearly demonstrate that crustal magma bodies should solidify rapidly upon emplacement. Small plutons can cool below the solidus in thousands of years, while even large plutons require hundreds of thousands of years, but not more than a million years. However, recent U-Pb zircon geochronological data contradict these results, strongly suggesting that magmatic systems are often characterized by protracted events. Therefore, a conceptual framework that reconciles thermal models and the geochronology data is necessary. The Devonian foreland magmatism of the Sierra de San Luis is made up of two distinctive suites, the Monzonite suite (<65 wt.% SiO2) and the Granite suite (>65 wt.% SiO2), both emplaced at ca. 3.7 kbar. Classification of the studied Devonian granitoids is debatable because they have a hybrid I- to A-type granite signature. Based on a robust geochronological U-Pb zircon dataset we corroborate the development of a protracted magmatic activity with three major crystallization events for this Devonian magmatism: 391 +/- 1, 384 +/- 1, and 379 +/- 2 Ma. Considering these geochronological data, we postulate the presence of a deep mush reservoir, where a prolonged magmatic activity, permitted the prolonged crystallization of antecrysts (ca. 395-384 Ma). Migration of the parental magma from the mush reservoir zone occurred near the time of emplacement and culminated in the formation of an ephemeral magma chamber located at shallow levels, where zircon autocrysts crystallized (ca. 379 Ma). Age spectra reported within individual samples support the idea of a massive migration of magma when conditions were favourable (e.g. thermally matured crust). Individual crystallization ages recorded by monazites hosted in two-mica granites are comparable to those obtained from zircons, supporting the presence of a long-lasting hot source. Additional geochronological data indicate that a later thermal event (ca. 353 Ma) could have partially affected some areas of the Devonian magmatic zircons promoting Pb loss, with subsequent partial resetting of the isotopic clock.

Based on a relevant geochronological U-Pb zircon dataset (n = 47) from a sample (PBL-109) of the Cerro Punta Blanca pluton (CPB), which is part of a calc-alkaline suite, we corroborate the development of protracted magmatic activity with three major crystallization events for this Permian magmatism: 278 f 1, 283 f 2, and 289 f 2 Ma, which outcrop in the Cordon del Portillo, Cordillera Frontal (CF) of Argentina. These ages can be assigned to the lower section of the magmatic record of the Choiyoi magmatism (ca., 290-265 Ma), while the age of 289 Ma represents the oldest known age for the Choiyoi, indicating the start of this magmatism during the Artinskiense. Considering these geochronological data, we postulate the presence of a deep mush reservoir where protracted magmatic activity permitted the prolonged crystallization of antecrysts (ca. 283-289 Ma). Migration of the parental magma from the mush reservoir zone occurred near the time of emplacement and culminated in the formation of an ephemeral magma chamber at shallow levels, where zircon autocrysts crystallized (ca. 278 Ma). Age spectra reported within individual samples support the idea of massive magma migration when conditions were favorable (e.g., thermally matured crust). In this view, the studied "older" Choiyoi magmatism represents a continuous magmatic event lasting 11 Ma and corresponds to a single magmatic episode rather than different periods of magmatic activity and subsequent emplacements. A later alkali-calcic magmatic event is recorded at 265 f 4 Ma from a sample of the Cerro Bayo pluton (MH-0113), which could represent the end of the lower section of the Choiyoi magmatism. Whole-rock Sm-Nd, Rb-Sr, and Lu-Hf data in zircon, along with ages reported for the studied igneous and inherited zircon from the CPB; together with isotopic data and ages from the detrital zircon found in the Carboniferous accretionary complex of Chile, indicate that the source of the Permian parental magma in this region was a heterogeneous continental crust mainly formed by Devonian and Carboniferous rocks, related probably to a magmatic arc. However, some contribution from the Carboniferous accretionary complex of Chile to the parental magma should be consider.

Cordilleran Granitic batholiths or Andean/Cordilleran batholiths serve as plutonic expressions of continental arcs, offering valuable insights into the processes that operate in large silicic magmatic systems at subduction environments. This work presents a comprehensive geochronological study of the Carboniferous Tabaquito batholith in the Frontal Cordillera of western Argentina, which is the best exponent of the Carboniferous arcrelated magmatism in this region. Using new data obtained through LA-MC-ICP-MS and comparing it with previously published data (LA-MC-ICP-MS and SHRIMP techniques), we identify five distinct magmatic events in the Tabaquito batholith: 325 +/- 2 Ma; 332 +/- 2 Ma; 337 +/- 2 Ma; 346 +/- 1 Ma, and 362 +/- 2 Ma. The 325 Ma event is considered as the best estimate of the crystallization age during the emplacement. The 332 Ma, 337 Ma, 346 Ma and 362 Ma events suggest the presence of zircon antecrysts, implying a complex magmatic system that worked for a protracted time lapse of ca. 40 Myr, or ca. 15 Myr if we consider the ages of 346 and 362 Ma as xenocrysts from a source like the Potrerillos pluton (346 +/- 3 Ma to 356 +/- 3 Ma), which was interpreted in previous studies as possible source of the parental magmas of the Tabaquito batholith. Furthermore, it has been also identified inherited zircons with ages older than ca. 370 Ma that are consistent with the detrital zircon pattern obtained for the country rock. Inherited zircon ages from the referred country rock yield a maximum deposition age estimated at 387 Ma that is consistent with the fossil ammonoids record, indicating that the granitic rocks were emplaced in Devonian rocks.

The southwestern paleo-margin of Gondwana is interpreted as an accretionary margin that was active from the late Neoproterozoic to the late Paleozoic. The basement of this paleo-margin is widely exposed in the centralwestern part of Argentina (Sierras Pampeanas area), where a protracted evolution from the Mesoproterozoic to the late Paleozoic is recorded. Part of this evolution is preserved in the El Gigante Metamorphic Complex (Sierra de El Gigante; Western Sierras Pampeanas), a small rotated block within the Valle Fertil Lineament fault zone that separates the Western and Eastern Sierras Pampeanas. The complex is composed of medium-grade meta-siliciclastic and meta-carbonate rocks and medium- to high-grade meta-igneous rocks, affected by tight to isoclinal folds and a pervasive east-west foliation resulting from the Famatinian orogeny (broadly late Cambrian to early Devonian). Later events include localized ductile shear zones. The isotopic and geochronological data from El Gigante Metamorphic Complex reveal at least three distinct lithological assemblages: (1) metamorphosed felsic igneous rocks of ca. 1.11 Ga, i.e., late Mesoproterozoic, (2) a Neoproterozoic metasedimentary succession composed of quartzites and mica-schists, (3) possibly mid- to late-Cambrian marble and graphite-schist. The Grenvillian assemblage (1) was part of a large reworked Paleoproterozoic continental block called MARA (acronym of Maz-Arequipa-R & iacute;o Apa) and was the basement over which the Neoproterozoic and Cambrian sedimentary successions were deposited. Based on U-Pb zircon ages, lithological similarities and Srisotope data, the three lithological assemblages of the El Gigante Metamorphic Complex can be correlated with similar ones in the nearby geologically better-known Sierra de Pie de Palo. The Neoproterozoic and the Cambrian metasedimentary successions are respectively equivalent to the Difunta Correa Metasedimentary Sequence and the Nikizanga-Caucete Groups, which are recognized throughout the Sierras Pampeanas, east and west of the Valle Fertil Lineament.

Carboniferous plutonic activity in the Sierra Pampeanas region of NW Argentina resulted in the emplacement of several magma bodies at shallow levels, while contemporaneous volcanism was primarily recorded in the neighboring Puna region. One of these plutons, known as Los & Aacute;rboles in the Sierra de Fiambal & aacute;, formed through two periods of significant felsic magma additions (326-322 Ma) and the subsequent development of tuffisites associated with subvolcanic dikes of predominantly mafic composition (315 +/- 3 Ma). The presence of 2-5 -m wide tuffisite dikes, indicating subvolcanic depths (similar to 1 km), provides an excellent opportunity to understand the connections between plutonic and volcanic processes. Our study reveals that for felsic magma batches to reach these subvolcanic depths, the input of synchronous mafic magmatism is a critical step. The Los Arboles pluton grew through alternating stages of accommodation by sheet intrusions, which subsequently merged during incubation into larger magma bodies with dominant lateral growth, forming a ductile halo. Both mildly alkaline mafic dike swarms and tuffisites intrude the pluton. The tuff-filled clastic dikes exhibit a variety of textural features and bulk rock compositions that indicate processes of late-stage heating and low-temperature remelting (similar to 700 degrees C) of the host granite. Our findings document that magmatic plumbing systems, driven by mantle processes, can reach subvolcanic levels, induce brittle-ductile transitions in the host rock, and persist in a cold storage stage for millions of years, with temperatures below the granite solidus, and be potentially eruptive through defrosting.

We provide a thorough review of the literature on peraluminous magmatism of Late Neoproterozoic and Early Palaeozoic (mostly Late Cambrian-Middle Ordovician) age cropping out in many places around the world (SW South Africa, NE Patagonia, NW Argentina, Colombia, SE Mexico and Guatemala, the European Variscan Massifs and from Turkey to northern Burma through Tibet). Petrographically, these volcanic and plutonic rocks contain K-feldspar phenocrysts and sometimes smaller bluish-quartz phenocrysts in a glassy/fine-grained (volcanic/subvolcanic) or medium- to coarse-grained (plutonic) matrix of quartz, plagioclase, K-feldspar and biotite, with other Al-bearing phases such as muscovite and garnet as minor phases. Notably, amphibole is conspicuously absent. Geochemically, these dacitic (tonalitic) to rhyolitic (granitic) rocks are silica-rich, peraluminous and with a strongly crustal SrNd isotopic signature, pointing to S-type magmatism, but they also show characteristics of I-type subduction (a trace element signature typical of continental-arc magmatism) and A-type (enrichment in Ga) magmatism. A prominent geochemical feature is a marked depletion in Sr, resulting in low to very low Sr/Y ratios (usually <5). This, together with flat HREE slopes, suggests melting at low pressures. The arc signature is inherited from their crustal sources, which may comprise an old crustal basement and sediments derived from Pan-African and from Andean-type orogenic belts. Coeval, volumetrically minor mafic rocks are also common in many outcrops and are part of a bimodal sequence. Researchers have mostly attributed this magmatism to extensional tectonics in a back-arc setting, where the upwelling of the asthenospheric mantle triggered the high-temperature-low-pressure partial melting of a largely metasedimentary (upper continental) crust with little or no contribution from the mantle. In a reconstruction of Early Palaeozoic Gondwana, all outcrops are situated in peri-Gondwanan terranes, implying that they are related to (and the consequence of) rifting processes that led to the opening or aborted opening of several oceans (Rheic, proto-Tethys), reflecting a common evolution of the margin of Gondwana during the Cambrian and Ordovician. Given the similarities in petrography and geochemistry (major and trace elements and SrNd isotopes) and the very large volume, several silicic Large Igneous Provinces have been proposed for some sectors, and the possibility that the entire magmatism comprises a single LIP is evaluated. Although correlations of this magmatism in different regions have been established previously, to our knowledge, this is the first study to integrate detailed petrographic, geochemical and geochronologic data from all outcrops and to conclude that the peraluminous porphyritic magmatism reviewed here is the main magmatic expression of extension in the peri-Gondwanan area during the Early Palaeozoic.

The Permian-Triassic magmatism of western Argentina and Chile represents one of the most outstanding silicic magmatic events of the southwestern Gondwana margin, notably marked by the development of the Choiyoi Magmatic Province (CMP). We provide a comprehensive review of its volcanic and plutonic record in the Argentine Frontal Cordillera. The volcanic rocks form three distinct sequences. The oldest is depicted by the Las Lozas volcanic sequence of the northern Frontal Cordillera for which new U–Pb zircon data (288 ± 2 Ma and εHft values ranging from −3.97 to +0.73) reassigns these outcrops to the early Cisuralian, aligning with volcanic records of northern Chile (ca. 297-288 Ma). The middle sequence, deposited during the late Cisuralian-late Guadalupian interval, is ascribed to the Choiyoi Group, which is characterised by a transition from andesitic (ca. 280-270 Ma) to rhyolitic compositions (ca. 270-262 Ma), including a remarkable mid-Guadalupian ignimbrite flare-up event (ca. 265 Ma). The upper sequence, composed of andesite-dacite-rhyolite, is associated with the Guanaco Sonso basin situated in the westernmost region, deposited from the late Lopingian to the middle Triassic period (ca. 254-240 Ma). The volcanic successions were developed in an extensional/transtensional setting, with facies and thickness variations controlled by normal faults, some of them active during the eruption of caldera-forming ignimbrites. Regarding the plutonic component, it comprises over sixty granitoid bodies forming the Colangüil and El Portillo batholiths and scattered stocks throughout the Frontal Cordillera. The early-stage plutons (ca. 285-272 Ma) exhibit calc-alkaline tonalite-diorite to granodiorite-monzogranite compositions and overlap in age with the lower andesitic section of the Choiyoi Group, while the late-stage plutons (ca. 265-252 Ma) display syenodiorite and alkali granite compositions and are in most cases younger than the Choiyoi Group succession. Compiled U–Pb zircon geochronological data reveal a distinctive Permian-age phase characterized by a rapid expansion of magmatism from the Gondwana margin towards its interior, followed by a slower westward shift of the main magmatic belt, predominantly recorded in the Frontal Cordillera of Argentina.