Journal of South American Earth Sciences最新文献

{"title":"Evolution of magnetic declination in South America since the 17th century","authors":"Germán Guillén-Arandía ,&nbsp;Rafael García-Ruiz ,&nbsp;Avto Goguitchaichvili ,&nbsp;Miguel Ángel Cervantes Solano","doi":"10.1016/j.jsames.2025.105434","DOIUrl":"10.1016/j.jsames.2025.105434","url":null,"abstract":"<div><div>Magnetic declination, the first measurable angular component of the magnetic field was longtime considered as an essential element to facilitate the navigation. Direct, historical measurements of the Earth Magnetic Field's components were commonly carried out during maritime exploration campaigns. Therefore, this invaluable source of information provides an almost unique tool to reveal the ‘geomagnetic past’ of our planet. Thanks to the development (and continuous updating) of historical and global geomagnetic databases, it is now possible to access a numerous geomagnetic field measurement. In particular, 400 years of continuous declination data are available for South America. The primary objective of this study is to estimate the temporal and spatial variation of historical declination values and try to define some fine characteristics of the geomagnetic field. A database of 12,462 well-distributed declination measurements across South America including the margins of Atlantic and Pacific Oceans, was compiled. The whole area was divided into six sub-regions in Brazil (2), Peru (1), Chile (1), Argentina (1) and Uruguay (1) in order to obtain local paleosecular variation curves and meet the mandatory requirement of relocation error procedure. These curves were generated using the Bootstrap algorithm and the penalized cubic spline method. The paleosecular variation curves were compared with currently available global geomagnetic models. Three local curves showed significant differences from the models due to the relatively uneven distribution of the geomagnetic data. First and second temporal derivative of paleosecular variation curves revealed the most significant fluctuations while the global data analysis confirms the existence of the so-called westward drift.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"156 ","pages":"Article 105434"},"PeriodicalIF":1.7,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143474407","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hydro-morphological reconstruction of the Blanco River in the eruptive event 2008: Variables that influenced the change of the channel course in Chaitén, Chile","authors":"Ivan Javier Rojas-Castillo ,&nbsp;Bruno Mazzorana ,&nbsp;Pablo Iribarren-Anacona ,&nbsp;Duilio Fonseca-Gallardo ,&nbsp;Jorge Berkhoff ,&nbsp;Gonzalo Durán ,&nbsp;Andrés Iroume","doi":"10.1016/j.jsames.2025.105412","DOIUrl":"10.1016/j.jsames.2025.105412","url":null,"abstract":"<div><div>Chaitén, a city in Chilean Patagonia, was hit by lahar flows from the Blanco River in May 2008 following a massive volcanic eruption. This cascade process resulted in the avulsion of the active channel of the Blanco River, dividing the city into two sectors, destroying built environments, and causing displacement of the local population. Hydrodynamic studies in the area have generally been based on post-event environmental conditions. However, an exhaustive reconstruction of the hydrodynamic behavior and associated river dynamics has not been performed. More fundamentally, no clear methodological approach has been proposed to accomplish this task. The present study addresses these challenges by applying non-conventional methods to reconstruct the initial and boundary conditions of the event and to trace the intervening factors that decisively influenced the hydrogeomorphic adjustments in the distal river segments. The reconstruction of the initial and boundary conditions of the event was performed by collecting primary and secondary information (using mixed methods and applying information triangulation). A conceptual model of the hydro-geomorphic evolution of the Blanco River in May 2008 was generated, elucidating the role of rainfall and morphodynamical responses and effects in the Blanco River and emphasizing the hydraulic behavior of the Blanco River bridge. Through the detailed reconstruction of the hydro-geomorphic processes, it could be corroborated that the channel responses were not exclusively due to the volcanic eruption but instead to a combination of massive sediment injections into the fluvial system, the intensity and spatiality of the precipitation pulses (associated with the presence of a frontal system and an atmospheric river), the mobilization of inorganic and organic sediments and the interaction of the flow with the Blanco River bridge.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"156 ","pages":"Article 105412"},"PeriodicalIF":1.7,"publicationDate":"2025-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143465019","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Monitoring land subsidence using Sentinel-1A, persistent scatterer InSAR, and machine learning techniques","authors":"Usha S ,&nbsp;Eatedal Alabdulkreem ,&nbsp;Nuha Alruwais ,&nbsp;Wafa Sulaiman Almukadi","doi":"10.1016/j.jsames.2025.105433","DOIUrl":"10.1016/j.jsames.2025.105433","url":null,"abstract":"<div><div>Land subsidence is a significant environmental issue in coastal regions, leading to infrastructure damage and increased vulnerability to flooding. This study focuses on monitoring land subsidence in the coastal region of Maceió using Sentinel-1A Synthetic Aperture Radar (SAR) data in conjunction with Persistent Scatterer Interferometry (PSI) and machine learning (ML) techniques. Sentinel-1A data, including both ascending and descending track datasets, were utilized to capture ground displacement over time. The analysis incorporated a range of environmental variables, including slope, elevation, aspect, curvature, land use/land cover (LULC), geology, Hillshade, and flow direction, which were used as training sets for the ML models. The Persistent Scatterer in SAR (PSI) technique was employed to extract precise displacement data from the SAR imagery, revealing land subsidence trends over the study period. ML models were applied to analyse the correlation between the subsidence patterns and environmental factors, enhancing the accuracy and reliability of the results. The ML techniques utilized included regression models and classification algorithms to predict and interpret subsidence rates and spatial distribution. The results show that land subsidence in Maceió ranged from 52 mm/year to −60 mm/year, with significant spatial variability. The findings highlight areas of rapid subsidence that may be linked to geological and anthropogenic factors, such as urbanization and groundwater extraction. Incorporating machine learning methods into this analysis improved the spatial resolution of the subsidence estimates, offering a more comprehensive understanding of the underlying causes and trends. This study demonstrates the potential of integrating remote sensing, InSAR, and ML techniques for monitoring and understanding land subsidence in coastal regions. The results can inform mitigation strategies and urban planning in areas susceptible to subsidence and related hazards.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"155 ","pages":"Article 105433"},"PeriodicalIF":1.7,"publicationDate":"2025-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143437295","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Episodic magmatism and segmentation of the Gondwanan arc in Chile (21–38°S): Insights into Carboniferous to early Permian subduction processes and deformation","authors":"Christian Creixell ,&nbsp;Juan Díaz-Alvarado ,&nbsp;Javier Álvarez ,&nbsp;Carmen Rodríguez ,&nbsp;Ricardo Velásquez ,&nbsp;Verónica Oliveros","doi":"10.1016/j.jsames.2025.105421","DOIUrl":"10.1016/j.jsames.2025.105421","url":null,"abstract":"<div><div>The Gondwanan cycle unfolds along the southwestern margin of Gondwana during the late Paleozoic, driven by the subduction of the proto-Pacific plate beneath the continental margin. Its geological record in Chile comprises accretionary complexes that emerge discontinuously along the coast, together with belts of igneous rocks, predominantly intermediate in composition, which constitute the coeval Gondwanan magmatic arc.</div><div>Based on extensive geochemical data, geochronology and field observations, the magmatic belt can be divided into three segments: Northern (21°–27° S), North-Central (27°–31° S), and Southern-Central (33°–38° S), according to varying percentages of exposed plutonic and volcanic rocks, the ages of magmatic pulses, and proximity to coeval accretionary complexes. The northern and north-central segments exhibit continuous activity for over 50 million years, from 330 to 280 Ma, with arc-trench distances of about 100–150 km. In contrast, the Southern-Central segment is located close to the accretionary complex (0–30 km) and concentrates its magmatic activity during the Pennsylvanian (322-300 Ma).</div><div>The marked episodic behavior of the Gondwanan arc in the northern and north-central segments is characterized by a High Magma Addition Rates (HMAR) event at 300-279 Ma that coincides with a peak in basal accretion within the coastal prism and localized orogeny in the foreland (San Rafael orogenic stage). Despite these events, various petrogenetic indicators suggest that both crustal and mantle magma sources remained stable throughout most of the Gondwanan cycle, with no evident arc thickening during the HMAR event. These deformation processes correlated in time with the diachronous arrival of oceanic reliefs to the margin, previous to onset of the Choiyoi Province.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"156 ","pages":"Article 105421"},"PeriodicalIF":1.7,"publicationDate":"2025-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143474409","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"GLOF modelling of Torre Lake and its potential impact in El Chaltén, Santa Cruz, Argentina: Preliminary results","authors":"Daniela I. Schmidt ,&nbsp;Diego A. Winocur ,&nbsp;Pierre Pitte ,&nbsp;Anahí Benitez","doi":"10.1016/j.jsames.2025.105417","DOIUrl":"10.1016/j.jsames.2025.105417","url":null,"abstract":"<div><div>The northern slope of the Cerro Solo, located in Southern Patagonian Andes, has a significant instability which could trigger a sudden release of large amounts of water contained in the Torre proglacial lake (Glacial Lake Outburst Flood, GLOF). Such events are highly complex phenomena, with diverse origins and often catastrophic consequences. This paper examines the potential for a rapid increase in the water level caused by a sudden landslide into the Torre Lake, which could lead to an overflow. The subsequent release of water could flood the Fitz Roy River, with the potential to produce damage downstream in El Chaltén locality and its surroundings, affecting inhabitants and tourists visiting the area.</div><div>In this study, various empirical methods for predicting landslide-generated impulse waves are compared. These methods are then applied to model the potential GLOF. The advantages and disadvantages of this procedure are analyzed and discussed. Based on the estimation of peak discharges of lake outflow using empirical formulas, a two-dimensional (2D) hydrodynamic model was implemented to simulate two potential outburst scenarios, with estimated peak discharges of 1166 m³/s and 1769 m³/s. The possible inundation extent and its impact were assessed based on the depth of water and the flow velocity. This study is a preliminary step toward understanding the magnitude of a potential future GLOF event and what elements that could be affected in order to develop an effective response to minimize impact.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"156 ","pages":"Article 105417"},"PeriodicalIF":1.7,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143527354","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Streamflow prediction based on the soil and water assessment tool in the Pajeú river basin, Brazilian semiarid","authors":"Thieres George Freire da Silva ,&nbsp;Ana Karlla Penna Rocha ,&nbsp;Alanderson Firmino de Lucas ,&nbsp;Gabriel Thales Barboza Marinho ,&nbsp;Alexandre Maniçoba da Rosa Ferraz Jardim ,&nbsp;Luciana Sandra Bastos de Souza ,&nbsp;Abelardo Antônio de Assunção Montenegro ,&nbsp;Werônica Meira de Souza","doi":"10.1016/j.jsames.2025.105420","DOIUrl":"10.1016/j.jsames.2025.105420","url":null,"abstract":"<div><div>It is considered highly important for developing strategies to conserve water resources and minimize environmental impacts, especially in places with low rainfall and high potential evapotranspiration, such as semiarid regions. In this context, the main objective of this study was to evaluate the ranking of the most sensitive parameters and the calibration and validation of the streamflow between 1976 and 2018 in the Pajeú river Basin using the SWAT hydrological model. The SUFI-2 algorithm, integrated into the SWAT-CUP software, was used for sensitivity analysis (SA), calibration (from 1976 to 1995), validation (from 1999 to 2018), and uncertainty analysis. Results showed that only seven parameters related to land use and land cover (initial SCS runoff curve number for moisture condition II – CN2), groundwater (baseflow alpha factor – ALPHA_BF, groundwater delay time – GW_DELAY, threshold depth of water in the shallow aquifer required for return flow to occur – GWQMN, and groundwater “revap” coefficient – GW_REVAP), and runoff (slope length for lateral subsurface flow – SLSOIL and lateral flow travel time – LAT_TTIME) were considered the most sensitive and were subsequently calibrated. Thus, CN2 was reduced by 28%, consequently decreasing surface runoff. ALPHA_BF showed a slow response to recharge, while GW_DELAY affected groundwater discharge by 47 days. GWQMN increased by approximately 2586.9 mm, improving streamflow simulation. GW_REVAP, with a value close to zero, exhibited a reduction trend in the groundwater table during the dry season and in the upward movement of water to the root zone. The basin slope class ≤8% increased SLSOIL to 29.41 m, which in turn increased LAT_TTIME by 99.47 days. SWAT also simulated maximum streamflows associated with extreme precipitation events in an acceptable manner. The Floresta gauging station achieved more satisfactory performance, as observed in the percentage of observations covered by the 95% prediction uncertainty – 95PPU (P-factor), the average thickness of the 95PPU band divided by the standard deviation of the measured data (R-factor), the coefficient of determination (R²), Nash-Sutcliffe efficiency (NSE), and percent bias (PBIAS), with respective values of 0.68, 1.05, 0.64, 0.63, and 6.5% for calibration. Therefore, investigating hydrological processes in this region allows for the development of water planning strategies, given the significant impacts on water resources and agricultural production, especially during drought events.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"156 ","pages":"Article 105420"},"PeriodicalIF":1.7,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143453617","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterization of a shallow aquifer in Acoculco geothermal area (Mexico) by applying Transient Electromagnetics","authors":"D. Ruiz-Aguilar ,&nbsp;C. Arango-Galván ,&nbsp;J.M. Romo-Jones ,&nbsp;E. García-Suárez ,&nbsp;L.E. Ochoa-Tinajero","doi":"10.1016/j.jsames.2025.105424","DOIUrl":"10.1016/j.jsames.2025.105424","url":null,"abstract":"<div><div>We present a characterization of the aquifer located in the Acoculco geothermal area in Mexico using Transient Electromagnetic (TEM) data. A total of 65 TEM soundings were collected, spatially distributed across the survey area, using a 100 × 100 m² single-loop configuration. The acquired TEM data were interpreted using one-dimensional Occam and Marquardt inversion techniques. At all stations, a three-layer model was sufficient to explain the data.</div><div>Prior to interpretation, we analyzed model uncertainties by evaluating parameter importance and equivalent models. The second and third layers are well resolved. The relatively more resistive second layer was correlated with the shallow aquifer of the area, whereas the deeper, more conductive layer was associated with the clay cap resulting from hydrothermal alteration, which acts as an impermeable unit.</div><div>To visualize the subsurface structures, we generated nine profiles by interpolating the information derived by the inversion, creating thus quasi-2D models across the survey area. This allowed us to better delineate the aquifer's configuration, identify its lateral boundaries, and detect zones of heterogeneity due to high clay content. The aquifer's thickness ranges from 150 to 200 m.</div><div>We conclude that our results are consistent with observations from the exploratory well EAC-1 and that TEM is a highly effective technique for hydrogeophysical exploration in a cost-efficient manner.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"156 ","pages":"Article 105424"},"PeriodicalIF":1.7,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143474408","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A shallow landslide induced by soil strength deterioration: Serra da Aliança mountain range (SE Brazil)","authors":"Marcos Eduardo Hartwig ,&nbsp;Cleber Gonzales de Oliveira ,&nbsp;Prêntice Filho ,&nbsp;Rogério Pinto Ribeiro ,&nbsp;Lázaro Valentin Zuquette","doi":"10.1016/j.jsames.2025.105419","DOIUrl":"10.1016/j.jsames.2025.105419","url":null,"abstract":"<div><div>In southeastern Brazil, landslides are often associated with prolonged and/or intense rainfall events. The km 14 sign of the ES-177 road located in the Espírito Santo State (SE Brazil) was blocked by a large translational landslide (∼31,000 m³) that occurred in the driest month of 2018. This study aimed to estimate the magnitude and the spatial distribution of surface displacements and to investigate the underlying reasons that led to slope failure. The study included the compilation of existing data, remote sensing techniques such as visual satellite image interpretation and Digital Image Correlation (DIC), site reconnaissance, geotechnical data, and 2D numerical modeling. The slope encompasses highly weathered banded gneiss covered by residual soil. The landslide appears to have evolved in different stages. Surface displacements reached up to 10 m. The slip surface is made of a thin clay band consisting of expansive clay (montmorillonite). It is believed that time-dependent mechanisms reduced shear strength triggering the landslide.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"156 ","pages":"Article 105419"},"PeriodicalIF":1.7,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143465020","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multiple provenance of inter-eruptive fluvial sandstones of the Albian Cerro Castaño Member, Patagonia","authors":"A. Martín Umazano ,&nbsp;Pablo M. Villegas ,&nbsp;Mauro I. Bernardi ,&nbsp;Leandro J. Amodeo ,&nbsp;Bruno C. Rosso","doi":"10.1016/j.jsames.2025.105423","DOIUrl":"10.1016/j.jsames.2025.105423","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The Albian Cerro Castaño Member is a volcanogenic fluvial-alluvial succession deposited in the Somuncurá-Cañadón Asfalto Basin, extra-Andean Patagonia, Argentina. During the deposition of the unit, the basin was affected by recurrent volcaniclastic inputs from sources including either directly active volcanoes or secondary volcanogenic material from upstream positions. In this study, we analyzed the provenance of fluvial sandstones of the Albian Cerro Castaño Member, for which detailed palaeoenvironmental interpretations have been previously established suggesting accumulation during inter-eruptive phases. The methodologies included the petrographic analysis of thirty-seven thin sections with the definition of petrofacies, as well as U-Pb zircon dating of a tuff layer from the underlying stratigraphic unit, located approximately 2 m below the contact with the Cerro Castaño succession. The new U-Pb depositional-crystallization age of 114.86 ± 0.44/0.56 Ma is consistent with the previous geochronological framework and constrains the Cerro Castaño Member to the Albian. The fluvial sandstones are predominantly composed of volcanic lithic framework grains both effusive and volcaniclastic, spanning the acidic to basic geochemical spectrum, with subordinate quartz, feldspars, intraclasts, micas, olivines, pyroxenes, amphiboles, and opaques. They were classified as feldspatho-lithic to quartzo-lithic, indicating provenance from tectonic settings associated with arc (both undissected and transitional) and recycled orogen sources. Four lithic petrofacies, designated A to D, were identified to distinguish sediment sources. The data indicate that the majority of samples from the western sector of the study zone are derived from volcanic rocks with effusive and explosive origin, with a minor contribution from mafic to intermediate volcanic rocks (petrofacies A). In contrast, samples from the eastern sector indicate a source-rock lithology dominated by siliceous rocks, similarly formed by effusive and pyroclastic eruptions but with minimal input from mafic to intermediate volcanic sources (petrofacies B). Additionally, specific samples from the western basin sector display a significant contribution of volcanic lithic grains, likely indicating substantial contributions of siliceous volcaniclastic sediments (petrofacies C and D). The combination of the information obtained with the literature data set, primarily comprising paleocurrents and paleogeological reconstructions, led to the conclusion that the principal source rocks are Jurassic intraplate volcanites, which are extensively distributed in extra-Andean Patagonia. In particular, the rocks of the Lonco Trapial and Marifil Formations constitute the main sources for sandstones in the western and eastern sectors of study zone, respectively. Furthermore, in the western localities, the subordinate participation of the Paleozoic-Triassic crystalline basement as source rocks was identified, as well as ","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"155 ","pages":"Article 105423"},"PeriodicalIF":1.7,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143421349","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Records of 2.9 G.a crustal anatexis on South American crust - Source and melt segregation in the Porteirinha Complex, Araçuaí Orogen (SE, Brazil)","authors":"Diogo Gabriel Sperandio ,&nbsp;Matheus Kuchenbecker ,&nbsp;Danilo Barbuena ,&nbsp;Amós Martini","doi":"10.1016/j.jsames.2025.105418","DOIUrl":"10.1016/j.jsames.2025.105418","url":null,"abstract":"<div><div>Crustal anatexis is a key process in the evolution and differentiation of the crust. Many Archean terranes record a transition from typical sodic TTG magmatism to extensive calc-alkaline potassic magmatism, similar to modern ones. At SE Brazil, within the Araçuaí orogen, the Paleoarchean TTG orthogneisses (3.4 Ga) of the Porteirinha Complex (PC) are exposed as a basement inlier. These rocks document a evolution to a variety of migmatites during the Meso-Neoarchean (2.9 Ga). This study presents field data, microstructures, and geochemistry to investigate the petrogenetic processes related to the crustal anatexis of Paleoarchean TTG orthogneisses. The PC is the basement unit of the Porteirinha Block, an Archean crustal segment associated with the São Francisco-Congo paleocontinent. Field and petrographic structures reveal a gradual evolution from TTG orthogneiss to partially melted domains, characterized by distinct morphological changes. This progression includes the development of metatexite and diatexite, which reflects increasing degrees of partial melting and syn-anatectic deformation. As deformation progresses, it induces textural, mineralogical, and geochemical changes, with notable shifts in the composition of the rocks, culminating in a network of metatexite-diatexite transitions. Four main rock types are recognized in the PC: (i) orthogneisses; (ii) metatexites; (iii) diatexites; and (iv) amphibolite lenses. The REE content suggests isochemical processes during crustal anatexis, suggesting that PC migmatites may result from incomplete segregation with varying degrees of melt-residue separation. Typical water-fluxed melting reactions are recognized by Hbl + Plg + melt (Kfs-rich) phases and linked to P-T scenarios of amphibolite-granulite transition facies, marked by key-melting microstructures. Processes of crustal thickening, lithospheric delamination, and gravitational collapse are proposed as tectonic triggers for the melting of the orthogneiss protolith, generation of migmatites, and emplacement of Neoarchean BP granitoids.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"155 ","pages":"Article 105418"},"PeriodicalIF":1.7,"publicationDate":"2025-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143429742","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}