Pub Date : 2026-04-01Epub Date: 2026-01-20DOI: 10.1016/j.jsames.2026.105956
Gladis N. Palacio Balderramo , Brígida Castro de Machuca , Ana C. Mugas Lobos , Gustavo F. Ortíz , Gimena M. Bazán , Cristian E. Robledo
In this contribution, the first occurrence of pseudotachylyte veins in the crystalline basement of the Sierras Pampeanas of San Juan province, Argentina, is presented.
The Pan de Azúcar and El Retamo pseudotachylyte veins were found closely related to the NNW-SSE trending Valle Fértil and Portezuelos fault zones, two major ductile-brittle shear zones that were tectonically active since the early Paleozoic.
Macro- and microstructures observed in both pseudotachylytes suggest that they are the product of rapid cooling of silicate melts along paleoseismic zones during faulting. This inference is supported by the presence of distinctive features like intrusive margins, flow banding and melt-corroded rims in clasts. Acicular and globular microlites, as much as lesser quantities of spherulites, were identified in the matrix of these rocks are considered as a product of direct crystallization from the melt. The presence of vesicles and amygdules indicates a possible formation depth of less than 7 km.
The chemical composition of pseudotachylyte veins closely resembles that of their host rocks, greenschist facies mylonitic rocks and mylonitized granitoid rocks, indicating that they were formed by frictional melting.
The pseudotachylytes described from the Pan de Azúcar and El Retamo fault zones were found occurring in veins, which is interpreted as an “in situ” origin. These pseudotachylytes were formed long after host rocks mylonitization. Well preserved microstructures and absence of subsequent overprinting suggest that they were formed in the late stages of faulting.
在这一贡献中，首次在阿根廷圣胡安省塞拉斯帕米亚纳斯的结晶基底中发现了伪achylyte静脉。Pan de Azúcar和El Retamo伪岩脉与NNW-SSE走向的Valle f - rtil断裂带和Portezuelos断裂带密切相关，这是早古生代以来构造活跃的两个主要韧性-脆性剪切带。从宏观和微观结构上看，这两种伪水杨酸盐是断裂过程中沿古地震带硅酸盐熔体快速冷却的产物。这一推断得到了碎屑中侵入边缘、流带和熔融腐蚀边缘等独特特征的支持。在这些岩石的基质中发现了针状和球状微晶，以及少量的球晶，这些岩石被认为是熔融直接结晶的产物。囊泡和杏仁核的存在表明其形成深度可能小于7公里。绿片岩相糜棱岩和糜棱岩化花岗岩的化学成分与其寄主岩、绿片岩相糜棱岩和糜棱岩化花岗岩的化学成分非常相似，表明它们是由摩擦熔融形成的。在Pan de Azúcar和El Retamo断裂带中发现了伪羟基酸盐，这被解释为“原位”起源。这些伪长柄岩是在寄主岩石糜棱化作用后形成的。微结构保存完好，未见后续叠印，表明其形成于断裂后期。
{"title":"New findings of pseudotachylytes and their paleoseismic significance, Sierras Pampeanas of San Juan, Argentina","authors":"Gladis N. Palacio Balderramo , Brígida Castro de Machuca , Ana C. Mugas Lobos , Gustavo F. Ortíz , Gimena M. Bazán , Cristian E. Robledo","doi":"10.1016/j.jsames.2026.105956","DOIUrl":"10.1016/j.jsames.2026.105956","url":null,"abstract":"<div><div>In this contribution, the first occurrence of pseudotachylyte veins in the crystalline basement of the Sierras Pampeanas of San Juan province, Argentina, is presented.</div><div>The Pan de Azúcar and El Retamo pseudotachylyte veins were found closely related to the NNW-SSE trending Valle Fértil and Portezuelos fault zones, two major ductile-brittle shear zones that were tectonically active since the early Paleozoic.</div><div>Macro- and microstructures observed in both pseudotachylytes suggest that they are the product of rapid cooling of silicate melts along paleoseismic zones during faulting. This inference is supported by the presence of distinctive features like intrusive margins, flow banding and melt-corroded rims in clasts. Acicular and globular microlites, as much as lesser quantities of spherulites, were identified in the matrix of these rocks are considered as a product of direct crystallization from the melt. The presence of vesicles and amygdules indicates a possible formation depth of less than 7 km.</div><div>The chemical composition of pseudotachylyte veins closely resembles that of their host rocks, greenschist facies mylonitic rocks and mylonitized granitoid rocks, indicating that they were formed by frictional melting.</div><div>The pseudotachylytes described from the Pan de Azúcar and El Retamo fault zones were found occurring in veins, which is interpreted as an “in situ” origin. These pseudotachylytes were formed long after host rocks mylonitization. Well preserved microstructures and absence of subsequent overprinting suggest that they were formed in the late stages of faulting.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"173 ","pages":"Article 105956"},"PeriodicalIF":1.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146039671","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}
Pub Date : 2026-03-01Epub Date: 2025-12-31DOI: 10.1016/j.jsames.2025.105936
Mariano S. Arnaiz-Rodríguez , Noel Crasto , Ana Jaramillo , Ivan Koulakov , Ana K. Sánchez-Gamboa , Franck A. Audemard , Carlos E. Reinoza , Michael Schmitz
We present results from local earthquake tomography in northeastern Venezuela, where the Caribbean and South American plates meet. The region, dominated by strike-slip faulting, subduction and inhabited by the Paria Seismic Cluster, offers a unique setting for studying the mechanisms of lithospheric tearing, Subduction-Transform Edge Propagator structures and seismic cluster formation. To perform the tomography, we use a compilation of data, including: the ISC catalog, the database of the University of the West Indies, and the data collected by the temporary array of the BOLIVAR (Broadband Ocean-Land Investigation of Venezuela and the Antilles Arc Region) Project. The combined and revised dataset was composed of 286 stations, 4384 events, 70891 P-wave arrivals and 42532 S-wave arrivals. In our results, the Paria Seismic Cluster appears as a weak region (P-wave low velocity zone) where the lithosphere beneath the active strike-slip system and the subduction slab meet. Hence, the lithosphere tears in response to the dominant shear stress aided by the slab. Furthermore, the cluster appears to be a superposition of the seismicity derived from this process and that of the subducted slab. Crustal-scale high velocities in the Paria Peninsula, associated with the intrusive bodies documented in the area are indicative of subduction-related volcanism active beneath the continent from the Late Miocene to Early Pliocene. Furthermore, we image a high-velocity and seismically active zone beneath Trinidad, which is interpreted as a piece of the Atlantic slab that was torn before subducting underneath the South American lithosphere. Finally, we identify several magmatic chambers beneath the southern Lesser Antilles Arc, as well as an LVZ that we interpret as an upwelling that feeds the volcanism.
{"title":"Insights on northeastern South America tectonics from local event tomography","authors":"Mariano S. Arnaiz-Rodríguez , Noel Crasto , Ana Jaramillo , Ivan Koulakov , Ana K. Sánchez-Gamboa , Franck A. Audemard , Carlos E. Reinoza , Michael Schmitz","doi":"10.1016/j.jsames.2025.105936","DOIUrl":"10.1016/j.jsames.2025.105936","url":null,"abstract":"<div><div>We present results from local earthquake tomography in northeastern Venezuela, where the Caribbean and South American plates meet. The region, dominated by strike-slip faulting, subduction and inhabited by the Paria Seismic Cluster, offers a unique setting for studying the mechanisms of lithospheric tearing, Subduction-Transform Edge Propagator structures and seismic cluster formation. To perform the tomography, we use a compilation of data, including: the ISC catalog, the database of the University of the West Indies, and the data collected by the temporary array of the BOLIVAR (Broadband Ocean-Land Investigation of Venezuela and the Antilles Arc Region) Project. The combined and revised dataset was composed of 286 stations, 4384 events, 70891 P-wave arrivals and 42532 S-wave arrivals. In our results, the Paria Seismic Cluster appears as a weak region (P-wave low velocity zone) where the lithosphere beneath the active strike-slip system and the subduction slab meet. Hence, the lithosphere tears in response to the dominant shear stress aided by the slab. Furthermore, the cluster appears to be a superposition of the seismicity derived from this process and that of the subducted slab. Crustal-scale high velocities in the Paria Peninsula, associated with the intrusive bodies documented in the area are indicative of subduction-related volcanism active beneath the continent from the Late Miocene to Early Pliocene. Furthermore, we image a high-velocity and seismically active zone beneath Trinidad, which is interpreted as a piece of the Atlantic slab that was torn before subducting underneath the South American lithosphere. Finally, we identify several magmatic chambers beneath the southern Lesser Antilles Arc, as well as an LVZ that we interpret as an upwelling that feeds the volcanism.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"172 ","pages":"Article 105936"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145927671","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}
Pub Date : 2026-03-01Epub Date: 2026-01-03DOI: 10.1016/j.jsames.2025.105939
Amanda Vilar , Pierre Belart , Joalice de Oliveira Mendonça , Thiago Carelli , Lazaro Laut
This study aims to utilize a multiproxy approach, incorporating physical-chemical parameters, sedimentological, and climate data, to evaluate the trophic status and environmental sediment characteristics of Brejo do Espinho Lagoon during the winter (July 2022) and summer (January 2023). The results revealed significant seasonal and spatial variations, with summer showing lower salinity and higher values for water temperature, total dissolved solids (TDS), and total organic carbon (TOC), indicating a higher inflow of rainfall periods and an increase in primary productivity. In contrast, the BE winter conditions were characterized by higher salinity due to lower precipitation and intensified evaporation. The predominance of fine sediments and high TOC contents in both analysed periods were related to the presence of microbial mats and suggest redox conditions at the bottom. Statistical analyses confirmed that seasonality is a key factor in modulating hydrological and sedimentological dynamics, directly influencing the stability of the different four lagoonal sectors. Sector 4 stood out as the most ecologically stable, while Sectors 2 and 3 exhibited higher seasonal variability. The study emphasizes the lagoon system's sensibility to changes in the hydrological regime, providing essential baseline data to support long-term monitoring and conservation strategies, particularly in the context of ongoing climate change.
{"title":"Interannual variations in the araruama hypersaline system: Implications for the sedimentological and hydrological characteristics of brejo do espinho lagoon (Rio de Janeiro, Brazil)","authors":"Amanda Vilar , Pierre Belart , Joalice de Oliveira Mendonça , Thiago Carelli , Lazaro Laut","doi":"10.1016/j.jsames.2025.105939","DOIUrl":"10.1016/j.jsames.2025.105939","url":null,"abstract":"<div><div>This study aims to utilize a multiproxy approach, incorporating physical-chemical parameters, sedimentological, and climate data, to evaluate the trophic status and environmental sediment characteristics of Brejo do Espinho Lagoon during the winter (July 2022) and summer (January 2023). The results revealed significant seasonal and spatial variations, with summer showing lower salinity and higher values for water temperature, total dissolved solids (TDS), and total organic carbon (TOC), indicating a higher inflow of rainfall periods and an increase in primary productivity. In contrast, the BE winter conditions were characterized by higher salinity due to lower precipitation and intensified evaporation. The predominance of fine sediments and high TOC contents in both analysed periods were related to the presence of microbial mats and suggest redox conditions at the bottom. Statistical analyses confirmed that seasonality is a key factor in modulating hydrological and sedimentological dynamics, directly influencing the stability of the different four lagoonal sectors. Sector 4 stood out as the most ecologically stable, while Sectors 2 and 3 exhibited higher seasonal variability. The study emphasizes the lagoon system's sensibility to changes in the hydrological regime, providing essential baseline data to support long-term monitoring and conservation strategies, particularly in the context of ongoing climate change.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"172 ","pages":"Article 105939"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145927672","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}
Pub Date : 2026-03-01Epub Date: 2025-12-13DOI: 10.1016/j.jsames.2025.105919
Ramón Yosvanis Batista Cruz , Yuri Almaguer Carmenates , José Alberto Batista Rodríguez , Felipe de Jesús López Saucedo , Yalina Montecelos Zamora , Brenda Margarita Salas Ramos , Aylin Karel Ibarra Torres , Frida García Robles , Luis Eutiquio Canales Gutiérrez
The hydrogeological potential of Coahuila, Northeast Mexico, is evaluated through an integrated approach that combines cartographic datasets, bibliometric analysis, and a GIS-based assessment of 1912 groundwater points distributed across 28 aquifers. Beyond synthesizing existing regional knowledge, this study introduces a comprehensive methodological framework that links geological, hydrological, and socio-economic dimensions through 18 thematic GIS layers, offering a spatially explicit understanding of the key factors controlling groundwater availability and quality. The bibliometric evaluation also provides the first systematic diagnosis of water-related scientific production in Coahuila, revealing a significant disconnect between local research output and the state's critical water-management challenges. The results indicate that extensive carbonate formations, enhanced by karst processes (e.g., the Cupido, Aurora, Glen Rose, and Edwards formations), constitute the most productive aquifer units, while stratigraphic heterogeneity and local tectonics exert strong controls on permeability, compartmentalization, and groundwater flow. Geomorphological and hydrological conditions further shape the distribution of wells: nearly three-quarters are concentrated in plains and piedmont slopes; whereas, mountain ranges function as primary recharge zones in an arid to semi-arid climate. Hydrological indices, including the Topographic Wetness Index and catchment coefficients, refine the interpretation of recharge-discharge dynamics and explain the high well densities found in lowland basins, which are more vulnerable to salinity and sulfate enrichment. Socio-economic drivers, such as accessibility and population density, also influence drilling patterns. However, groundwater quality remains a major constraint, with widespread salinity and excessive sulfate and heavy-metal contamination being particularly associated with the evaporitic La Virgen Formation (and other hydrogeologically unfavorable lithologies), frequently compromising water suitability. Overall, this study provides a novel, integrated framework that strengthens the scientific basis for groundwater evaluation and offers actionable insights to support more-informed and sustainable water-resource management in Coahuila.
{"title":"Hydrogeological suitability of Coahuila, Northeast Mexico: An integrated bibliometric, GIS, and water quality assessment","authors":"Ramón Yosvanis Batista Cruz , Yuri Almaguer Carmenates , José Alberto Batista Rodríguez , Felipe de Jesús López Saucedo , Yalina Montecelos Zamora , Brenda Margarita Salas Ramos , Aylin Karel Ibarra Torres , Frida García Robles , Luis Eutiquio Canales Gutiérrez","doi":"10.1016/j.jsames.2025.105919","DOIUrl":"10.1016/j.jsames.2025.105919","url":null,"abstract":"<div><div>The hydrogeological potential of Coahuila, Northeast Mexico, is evaluated through an integrated approach that combines cartographic datasets, bibliometric analysis, and a GIS-based assessment of 1912 groundwater points distributed across 28 aquifers. Beyond synthesizing existing regional knowledge, this study introduces a comprehensive methodological framework that links geological, hydrological, and socio-economic dimensions through 18 thematic GIS layers, offering a spatially explicit understanding of the key factors controlling groundwater availability and quality. The bibliometric evaluation also provides the first systematic diagnosis of water-related scientific production in Coahuila, revealing a significant disconnect between local research output and the state's critical water-management challenges. The results indicate that extensive carbonate formations, enhanced by karst processes (e.g., the Cupido, Aurora, Glen Rose, and Edwards formations), constitute the most productive aquifer units, while stratigraphic heterogeneity and local tectonics exert strong controls on permeability, compartmentalization, and groundwater flow. Geomorphological and hydrological conditions further shape the distribution of wells: nearly three-quarters are concentrated in plains and piedmont slopes; whereas, mountain ranges function as primary recharge zones in an arid to semi-arid climate. Hydrological indices, including the Topographic Wetness Index and catchment coefficients, refine the interpretation of recharge-discharge dynamics and explain the high well densities found in lowland basins, which are more vulnerable to salinity and sulfate enrichment. Socio-economic drivers, such as accessibility and population density, also influence drilling patterns. However, groundwater quality remains a major constraint, with widespread salinity and excessive sulfate and heavy-metal contamination being particularly associated with the evaporitic La Virgen Formation (and other hydrogeologically unfavorable lithologies), frequently compromising water suitability. Overall, this study provides a novel, integrated framework that strengthens the scientific basis for groundwater evaluation and offers actionable insights to support more-informed and sustainable water-resource management in Coahuila.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"172 ","pages":"Article 105919"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145847573","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}
Pub Date : 2026-03-01Epub Date: 2026-01-07DOI: 10.1016/j.jsames.2026.105949
Roberta Maciel Pacheco Valente , Heloisa Helena Gomes Coe , Karina Ferreira Chueng , Aline Gonçalves de Freitas , David Oldack Barcelos Ferreira Machado , Kita Chaves Damasio Macario , Marcelo Alves Ribeiro , José Sebastián Carrión García
The area of this study is the Lagoa Grande das Queimadas archaeological site, located in the southwest of the state of Piauí, in the semi-arid region of Northeast Brazil, a region that is globally recognized for its archaeological and paleontological heritage. The use of biogenic silica (especially phytoliths) as proxies for paleoenvironmental reconstruction aimed to evaluate the paleoenvironment of ancient human occupations. The phytolith assemblages recovered from the sediment record of the Lagoa Grande das Queimadas archaeological site are predominantly composed of Poaceae morphotypes, mainlyBlocky, Bulliform flabellate, Acute bulbosus, and Elongate, with a reduced presence of woody dicotyledons (Spheroid ornate). Arecaceae phytoliths (Spheroid echinate) are also observed throughout the profile, increasing from the oldest to the most recent sample, along with fragments of sponge megascleres and microcharcoals. The results revealed that this region experienced climatic variations during the Greenlandian to Meghalayan, as demonstrated by the phytolith and aquatic bioindicator (sponge spicules and diatom frustules) records. The analyses indicate that between 12,908–12,478 and 4420–4233 cal yrs BP, the temperature and humidity increased progressively, followed by a transition from a more humid climate than at present to drier conditions starting from 4420–4233 cal yrs BP. The qualitative and quantitative results of the phytolith analyses, associated with other proxies studied at this site, contributed to constructing information about the archaeological site and its insertion into the landscape, in addition to understanding the mobility and subsistence models of past human groups during the Holocene in the interior regions of Northeast Brazil.
这项研究的区域是Lagoa Grande das Queimadas考古遗址，位于巴西东北部的半干旱地区Piauí州西南部，该地区因其考古和古生物遗产而享誉全球。利用生物硅（特别是植物岩）作为古环境重建的代用物，旨在评价古人类活动的古环境。从Lagoa Grande das Queimadas考古遗址的沉积物记录中恢复的植物岩组合主要由Poaceae形态类型组成，主要是块状，鳞状，急性球型和细长型，木质双子叶（球形华丽）的存在较少。在整个剖面中也观察到槟榔科植物岩（球状刺状），从最古老的样本到最近的样本，以及海绵大颗粒和微炭的碎片。结果表明，该地区在格陵兰-梅加拉亚时期经历了气候变化，这是植物岩和水生生物指示物（海绵针状体和硅藻体）记录的结果。分析结果表明，在12908 ~ 12478 ~ 4420 ~ 4233 cal年BP之间，温度和湿度逐渐增加，随后从4420 ~ 4233 cal年BP开始由较湿润的气候过渡到较干燥的气候。植物岩分析的定性和定量结果，以及在该遗址研究的其他代用物，有助于构建有关考古遗址及其融入景观的信息，以及了解巴西东北部内陆地区全新世时期过去人类群体的流动性和生存模式。
{"title":"Paleoenvironmental and paleoclimatic reconstruction of the Lagoa Grande das queimadas archaeological site, Piauí, Brazil","authors":"Roberta Maciel Pacheco Valente , Heloisa Helena Gomes Coe , Karina Ferreira Chueng , Aline Gonçalves de Freitas , David Oldack Barcelos Ferreira Machado , Kita Chaves Damasio Macario , Marcelo Alves Ribeiro , José Sebastián Carrión García","doi":"10.1016/j.jsames.2026.105949","DOIUrl":"10.1016/j.jsames.2026.105949","url":null,"abstract":"<div><div>The area of this study is the Lagoa Grande das Queimadas archaeological site, located in the southwest of the state of Piauí, in the semi-arid region of Northeast Brazil, a region that is globally recognized for its archaeological and paleontological heritage. The use of biogenic silica (especially phytoliths) as proxies for paleoenvironmental reconstruction aimed to evaluate the paleoenvironment of ancient human occupations. The phytolith assemblages recovered from the sediment record of the Lagoa Grande das Queimadas archaeological site are predominantly composed of Poaceae morphotypes, mainly<span>Blocky, Bulliform flabellate, Acute bulbosus</span>, and <span>Elongate</span>, with a reduced presence of woody dicotyledons (<span>Spheroid ornate</span>). Arecaceae phytoliths (<span>Spheroid echinate</span>) are also observed throughout the profile, increasing from the oldest to the most recent sample, along with fragments of sponge megascleres and microcharcoals. The results revealed that this region experienced climatic variations during the Greenlandian to Meghalayan, as demonstrated by the phytolith and aquatic bioindicator (sponge spicules and diatom frustules) records. The analyses indicate that between 12,908–12,478 and 4420–4233 cal yrs BP, the temperature and humidity increased progressively, followed by a transition from a more humid climate than at present to drier conditions starting from 4420–4233 cal yrs BP. The qualitative and quantitative results of the phytolith analyses, associated with other proxies studied at this site, contributed to constructing information about the archaeological site and its insertion into the landscape, in addition to understanding the mobility and subsistence models of past human groups during the Holocene in the interior regions of Northeast Brazil.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"172 ","pages":"Article 105949"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145979089","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}
Pub Date : 2026-03-01Epub Date: 2026-01-12DOI: 10.1016/j.jsames.2026.105955
Geysianne Morais , Matheus Kuchenbecker , Danilo Barbuena , Lucas Almeida de Souza , Hugo Marques Ascendino Teixeira , Lucília Aparecida Ramos de Oliveira
The Orosirian São Francisco-Congo paleocontinent (SFCP) was one of the crustal segments involved in the Neoproterozoic-Early Paleozoic assembly of the Gondwana supercontinent. During this collisional event, its margins were reworked and fragmented, becoming preserved as basement inliers within the Brasiliano-Pan-African orogenic system. Despite its key role in understanding the processes responsible for the formation of Earth's earliest continental masses, the tectonic evolution and true extent of the SFCP remain poorly constrained. Within the Neoproterozoic Araçuaí Orogen there are several basement inliers, whose Archean and Paleoproterozoic rocks have been valuable to reconstructing SFCP. Here we report the discovery of a small basement inlier in the Southern Espinhaço Range, western domain of the Araçuaí Orogen. Based on integrated field observations, petrography, whole-rock geochemistry and U-Pb zircon geochronology, we characterize the rocks exposed in this inlier and discuss their regional significance. This inlier corresponds to a tectonic slice in which a Mesoarchean (ca. 2.87 Ga) metagranite - herein referred to as the Algodoeiro Metagranite - thrust over the metasedimentary rocks of the Espinhaço Supergroup. The Algodoeiro Metagranite consists of leucocratic, peraluminous, magnesian calc-alkaline metagranites that display moderately to strongly fractionated REE patterns with marked negative Eu anomalies. Petrographic and geochemical similarities, particularly REE slopes and multi-element patterns, combined with geochronological constraints, link these rocks to the gneisses of the Guanhães Complex, exposed in the Guanhães basement inlier, further east. Deformation and metamorphism recorded in the Algodoeiro Metagranite are interpreted as syn-to post-collisional in the context of the Brasiliano-Pan-African orogeny. Taken together, the data indicate that the Algodoeiro Metagranite represents a fragment of the SFCP tectonically reworked within the Araçuaí Orogen during the assembly of West Gondwana. This newly identified inlier therefore adds an important piece to the ongoing efforts to refining the tectonic evolution of eastern South America.
{"title":"The Mesoarchean Algodoeiro Metagranite: a new piece in the Araçuaí Orogen basement inliers puzzle","authors":"Geysianne Morais , Matheus Kuchenbecker , Danilo Barbuena , Lucas Almeida de Souza , Hugo Marques Ascendino Teixeira , Lucília Aparecida Ramos de Oliveira","doi":"10.1016/j.jsames.2026.105955","DOIUrl":"10.1016/j.jsames.2026.105955","url":null,"abstract":"<div><div>The Orosirian São Francisco-Congo paleocontinent (SFCP) was one of the crustal segments involved in the Neoproterozoic-Early Paleozoic assembly of the Gondwana supercontinent. During this collisional event, its margins were reworked and fragmented, becoming preserved as basement inliers within the Brasiliano-Pan-African orogenic system. Despite its key role in understanding the processes responsible for the formation of Earth's earliest continental masses, the tectonic evolution and true extent of the SFCP remain poorly constrained. Within the Neoproterozoic Araçuaí Orogen there are several basement inliers, whose Archean and Paleoproterozoic rocks have been valuable to reconstructing SFCP. Here we report the discovery of a small basement inlier in the Southern Espinhaço Range, western domain of the Araçuaí Orogen. Based on integrated field observations, petrography, whole-rock geochemistry and U-Pb zircon geochronology, we characterize the rocks exposed in this inlier and discuss their regional significance. This inlier corresponds to a tectonic slice in which a Mesoarchean (ca. 2.87 Ga) metagranite - herein referred to as the Algodoeiro Metagranite - thrust over the metasedimentary rocks of the Espinhaço Supergroup. The Algodoeiro Metagranite consists of leucocratic, peraluminous, magnesian calc-alkaline metagranites that display moderately to strongly fractionated REE patterns with marked negative Eu anomalies. Petrographic and geochemical similarities, particularly REE slopes and multi-element patterns, combined with geochronological constraints, link these rocks to the gneisses of the Guanhães Complex, exposed in the Guanhães basement inlier, further east. Deformation and metamorphism recorded in the Algodoeiro Metagranite are interpreted as syn-to post-collisional in the context of the Brasiliano-Pan-African orogeny. Taken together, the data indicate that the Algodoeiro Metagranite represents a fragment of the SFCP tectonically reworked within the Araçuaí Orogen during the assembly of West Gondwana. This newly identified inlier therefore adds an important piece to the ongoing efforts to refining the tectonic evolution of eastern South America.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"172 ","pages":"Article 105955"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145979090","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}
Pub Date : 2026-03-01Epub Date: 2025-12-31DOI: 10.1016/j.jsames.2025.105938
Andrés Solórzano , Alfonso Encinas , Mónica Núñez-Flores , Gabriel Carrasco , Karina Buldrini , Jorge Campos-Medina , René Bobe
The fossil record of pre-Quaternary continental mammals from Chile remains less well-documented than that of neighboring Argentina and Bolivia. Among the most promising successions is the Miocene Cura-Mallín Formation at Laguna del Laja (37.5°S), which preserves diverse mammalian assemblages spanning nearly 10 million years. One of the rodents previously reported from this locality is Acarechimys, a small octodontoid widely documented in Late Oligocene to Late Miocene continental deposits of South America. However, records from Laguna del Laja were based exclusively on fragmentary and undescribed material, leaving their taxonomic identity uncertain. Here, we describe a Santacrucian (late Early Miocene) occurrence of a caviomorph rodent from Laguna del Laja, represented by a partial mandible preserving m1–m3 and a fragment of the dp4. Dental traits, including a laterally compressed lower incisor and a developed posterior arm of the metaconid, support referral to Acarechimys minutus. This well-dated record provides a stratigraphically constrained occurrence of the species in south-central Chile and narrows the geographic gap between Chilean localities of Chucal in the north and Aysén in the south. The new evidence supports the hypothesis that the Laguna del Laja assemblage was not fully endemic, but rather integrated into the broader Santacrucian biogeographic continuum, reinforcing its value as a key reference point for Neogene faunal and biogeographic studies in the south-central Andes.
与邻国阿根廷和玻利维亚相比，来自智利的前第四纪大陆哺乳动物的化石记录仍然没有得到充分的证明。最有希望的序列是拉古纳德尔拉贾（37.5°S）中新世Cura-Mallín组，它保存了近1000万年的各种哺乳动物组合。在此发现的一种啮齿类动物是Acarechimys，这是一种小型齿状类动物，广泛记录在南美晚渐新世至晚中新世大陆沉积物中。然而，来自拉古纳德尔拉贾的记录完全基于碎片和未描述的材料，使其分类身份不确定。在这里，我们描述了一种来自拉贾湖（Laguna del Laja）的洞穴形啮齿类动物的圣十字期（早中新世晚期），以部分保存的m1-m3下颌骨和dp4的碎片为代表。牙齿特征，包括侧压下门牙和发达的后髁后臂，支持转介到Acarechimys minuth。这一年代准确的记录提供了该物种在智利中南部地层受限的出现，并缩小了智利北部Chucal地区和南部ayssamin地区之间的地理差距。新的证据支持了拉古纳德尔拉贾组合不是完全地方性的假设，而是融入了更广泛的圣克鲁斯生物地理连续体，加强了它作为安第斯山脉中南部新近纪动物和生物地理研究的关键参考点的价值。
{"title":"A Santacrucian record of Acarechimys minutus (Octodontoidea) from Laguna del Laja (Cura-Mallín Formation, Chile; late Early Miocene) and its biogeographic implications","authors":"Andrés Solórzano , Alfonso Encinas , Mónica Núñez-Flores , Gabriel Carrasco , Karina Buldrini , Jorge Campos-Medina , René Bobe","doi":"10.1016/j.jsames.2025.105938","DOIUrl":"10.1016/j.jsames.2025.105938","url":null,"abstract":"<div><div>The fossil record of pre-Quaternary continental mammals from Chile remains less well-documented than that of neighboring Argentina and Bolivia. Among the most promising successions is the Miocene Cura-Mallín Formation at Laguna del Laja (37.5°S), which preserves diverse mammalian assemblages spanning nearly 10 million years. One of the rodents previously reported from this locality is <em>Acarechimys</em>, a small octodontoid widely documented in Late Oligocene to Late Miocene continental deposits of South America. However, records from Laguna del Laja were based exclusively on fragmentary and undescribed material, leaving their taxonomic identity uncertain. Here, we describe a Santacrucian (late Early Miocene) occurrence of a caviomorph rodent from Laguna del Laja, represented by a partial mandible preserving m1–m3 and a fragment of the dp4. Dental traits, including a laterally compressed lower incisor and a developed posterior arm of the metaconid, support referral to <em>Acarechimys minutus</em>. This well-dated record provides a stratigraphically constrained occurrence of the species in south-central Chile and narrows the geographic gap between Chilean localities of Chucal in the north and Aysén in the south. The new evidence supports the hypothesis that the Laguna del Laja assemblage was not fully endemic, but rather integrated into the broader Santacrucian biogeographic continuum, reinforcing its value as a key reference point for Neogene faunal and biogeographic studies in the south-central Andes.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"172 ","pages":"Article 105938"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145886268","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}
Pub Date : 2026-03-01Epub Date: 2025-12-26DOI: 10.1016/j.jsames.2025.105934
Harrizon Lima de Almeida , Jucieny Sousa de Moura Barros
The gold mineralizations of the Borborema Province are structurally controlled and hosted in amphibolite facies metamorphic rock sequences. These gold mineralizations are closely related to the Brasiliano/Neoproterozoic orogeny and classified as orogenic gold deposits. The São Francisco gold deposit (SFGD), located in the Rio Grande do Norte Domain, Borborema Province, has emerged as the most significant gold mine in the region. The SFGD is hosted in biotite schists of the Seridó belt and consists of a planar and elongated, SW-NE-oriented ore shoot spatially associated with F3 antiform fold. The gold occurs both within quartz veins and disseminated in the mica schist, in paragenetic association with pyrite, pyrrhotite, arsenopyrite, and galena. A structural mapping conducted in this study shows that the SFGD occurs in the hinge zone of a F3 fold, which is primarily controlled by an intersection lineation developed during the D3 deformation event. A 3D-dimensional strain analysis was conducted on the mica schists of the area, encompassing different segments of the mineralization-hosting structure. The deformation in the hinge zone and in the limbs of the fold was dominated by constriction strain and flattening strain, respectively. It is proposed that the emplacement and occurrence of the SFGD resulted from the increase in structural permeability in the hinge zone, which, combined with a localized constriction strain regime, enabled the pipe-like channelling of a high volume of hydrothermal fluids. The SFGD represents an alternative model for the formation of saddle reef-type ore shoots in F3 antiform folds hosted in the Seridó belt, Borborema Province.
borborrema省金矿成矿受构造控制，赋存于角闪岩相变质岩层序中。这些金矿化与巴西利亚/新元古代造山运动密切相关，可归类为造山型金矿床。s o Francisco金矿（SFGD）位于borborrema省里约热内卢Grande do Norte Domain，已成为该地区最重要的金矿。SFGD赋存于Seridó带的黑云母片岩中，由一个平面细长的sw - ne向矿床组成，空间上与F3反形褶皱有关。金既赋存于石英脉中，又浸染于云母片岩中，与黄铁矿、磁黄铁矿、毒砂、方铅矿共生。本研究的构造作图表明，SFGD发生在F3褶皱的铰区，主要受D3变形事件期间形成的交点线理控制。对该地区的云母片岩进行了三维应变分析，包括矿化-承载结构的不同段。褶皱铰区和褶皱翼部的变形分别以收缩应变和压扁应变为主。认为SFGD的就位和发生是由于铰链区结构渗透率的增加，加上局部收缩应变状态，使得大量热液形成了管道状通道。SFGD代表了borborrema省Seridó带F3反形褶皱中鞍礁型矿脉形成的另一种模式。
{"title":"Structural control and deformational evolution of the São Francisco gold deposit, Borborema Province (NE Brazil)","authors":"Harrizon Lima de Almeida , Jucieny Sousa de Moura Barros","doi":"10.1016/j.jsames.2025.105934","DOIUrl":"10.1016/j.jsames.2025.105934","url":null,"abstract":"<div><div>The gold mineralizations of the Borborema Province are structurally controlled and hosted in amphibolite facies metamorphic rock sequences. These gold mineralizations are closely related to the Brasiliano/Neoproterozoic orogeny and classified as orogenic gold deposits. The São Francisco gold deposit (SFGD), located in the Rio Grande do Norte Domain, Borborema Province, has emerged as the most significant gold mine in the region. The SFGD is hosted in biotite schists of the Seridó belt and consists of a planar and elongated, SW-NE-oriented ore shoot spatially associated with F<sub>3</sub> antiform fold. The gold occurs both within quartz veins and disseminated in the mica schist, in paragenetic association with pyrite, pyrrhotite, arsenopyrite, and galena. A structural mapping conducted in this study shows that the SFGD occurs in the hinge zone of a F<sub>3</sub> fold, which is primarily controlled by an intersection lineation developed during the D<sub>3</sub> deformation event. A 3D-dimensional strain analysis was conducted on the mica schists of the area, encompassing different segments of the mineralization-hosting structure. The deformation in the hinge zone and in the limbs of the fold was dominated by constriction strain and flattening strain, respectively. It is proposed that the emplacement and occurrence of the SFGD resulted from the increase in structural permeability in the hinge zone, which, combined with a localized constriction strain regime, enabled the pipe-like channelling of a high volume of hydrothermal fluids. The SFGD represents an alternative model for the formation of saddle reef-type ore shoots in F<sub>3</sub> antiform folds hosted in the Seridó belt, Borborema Province.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"172 ","pages":"Article 105934"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145927675","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}
Pub Date : 2026-03-01Epub Date: 2025-12-24DOI: 10.1016/j.jsames.2025.105929
Federico J. Saponara , Maria F. Lajoinie , Mabel E. Lanfranchini , Christopher J. Spencer , Belén Marone
This study looks at the origin and development of anatectic pegmatites in the Paleoproterozoic basement of the Tandilia Belt (TB), Río de la Plata Craton, Argentina. It combines new field observations with petrography, whole-rock geochemistry, and stable isotope (δ18O) data from the Barker and Balcarce regions. The pegmatites, which have granitic and slightly peralkaline compositions, formed mainly during the post-collisional stage from 2026 to 1948 Ma. This occurred under an extensional regime linked to asthenospheric upwelling and they represent the final products of partial melting of metasedimentary and metaigneous rocks through dehydration and fluid-flux melting processes. Field observations show both concordant and discordant intrusions into gneiss, migmatite, amphibolite, granulite, marble, and skarn, which are controlled by tectonic domains and existing structures. Petrographic features include bimodal grain-size distributions, perthitic microcline, heavily sericitized plagioclase, poikilitic and myrmekitic textures, and abundant tourmaline and garnet. These features reflect crystallization from volatile-rich, evolved melts. Geochemical data indicate enrichment in SiO2, K2O, and total alkalis. They also show high levels of LILE (Rb, Th, U), a decrease in HFSE (Nb, Zr, Y), and REE patterns marked by LREE/HREE fractionation and varying Eu anomalies. δ18O values range from +6.5 ‰ to +11.3 ‰, supporting a crustal origin with different degrees of fluid interaction. Higher values in Barker suggest more assimilation from the upper-middle crust, while lower values in Balcarce indicate a stronger influence from mafic lithology and fluid participation. These combined results suggest that the TB pegmatites reflect the late-stage evolution of Paleoproterozoic anatectic magmas. They link the formation to crustal recycling processes and the merging of the Atlantica supercontinent during the 2.2–1.8 Ga interval.
本文研究了阿根廷Río de la Plata克拉通坦迪利亚带（TB）古元古代基底的无晶长伟晶岩的起源和发育。它结合了Barker和Balcarce地区的岩石学、全岩地球化学和稳定同位素（δ18O）数据。伟晶岩主要形成于2026 ~ 1948 Ma的后碰撞阶段，具有花岗质和微过碱性成分。这是在与软流圈上升流有关的伸展状态下发生的，它们是变质沉积岩和变质岩通过脱水和流体通量熔融过程部分熔融的最终产物。野外观测显示，片麻岩、混辉岩、角闪岩、麻粒岩、大理岩和矽卡岩中均有和合型和不和合型侵入，受构造域和现有构造控制。岩石学特征包括：双峰型粒度分布、粗长微斜长石、绢云母斜长石、易绿质和绢云母质织构、丰富的电气石和石榴石。这些特征反映了富含挥发物的熔融物的结晶。地球化学数据表明，SiO2、K2O和总碱富集。它们还显示出高水平的LILE (Rb, Th， U), HFSE （Nb, Zr， Y）的减少，以及以LREE/HREE分异和变化的Eu异常为标志的REE模式。δ18O值在+6.5‰~ +11.3‰之间，表明该区存在不同程度流体相互作用的地壳成因。Barker地区较高的值表明更多的是来自中上地壳的同化作用，而Balcarce地区较低的值表明基性岩性和流体参与的影响更大。这些综合结果表明，结核伟晶岩反映了古元古代深熔岩浆的晚期演化。他们将其形成与2.2-1.8 Ga期间的地壳再循环过程和大西洋超大陆的合并联系起来。
{"title":"Anatectic pegmatites and partial melting evolution in the Paleoproterozoic basement of the Tandilia Belt, Río de la Plata Craton: Insights from Barker and Balcarce regions (Argentina)","authors":"Federico J. Saponara , Maria F. Lajoinie , Mabel E. Lanfranchini , Christopher J. Spencer , Belén Marone","doi":"10.1016/j.jsames.2025.105929","DOIUrl":"10.1016/j.jsames.2025.105929","url":null,"abstract":"<div><div>This study looks at the origin and development of anatectic pegmatites in the Paleoproterozoic basement of the Tandilia Belt (TB), Río de la Plata Craton, Argentina. It combines new field observations with petrography, whole-rock geochemistry, and stable isotope (δ<sup>18</sup>O) data from the Barker and Balcarce regions. The pegmatites, which have granitic and slightly peralkaline compositions, formed mainly during the post-collisional stage from 2026 to 1948 Ma. This occurred under an extensional regime linked to asthenospheric upwelling and they represent the final products of partial melting of metasedimentary and metaigneous rocks through dehydration and fluid-flux melting processes. Field observations show both concordant and discordant intrusions into gneiss, migmatite, amphibolite, granulite, marble, and skarn, which are controlled by tectonic domains and existing structures. Petrographic features include bimodal grain-size distributions, perthitic microcline, heavily sericitized plagioclase, poikilitic and myrmekitic textures, and abundant tourmaline and garnet. These features reflect crystallization from volatile-rich, evolved melts. Geochemical data indicate enrichment in SiO<sub>2</sub>, K<sub>2</sub>O, and total alkalis. They also show high levels of LILE (Rb, Th, U), a decrease in HFSE (Nb, Zr, Y), and REE patterns marked by LREE/HREE fractionation and varying Eu anomalies. δ<sup>18</sup>O values range from +6.5 ‰ to +11.3 ‰, supporting a crustal origin with different degrees of fluid interaction. Higher values in Barker suggest more assimilation from the upper-middle crust, while lower values in Balcarce indicate a stronger influence from mafic lithology and fluid participation. These combined results suggest that the TB pegmatites reflect the late-stage evolution of Paleoproterozoic anatectic magmas. They link the formation to crustal recycling processes and the merging of the Atlantica supercontinent during the 2.2–1.8 Ga interval.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"172 ","pages":"Article 105929"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145886267","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}
Pub Date : 2026-03-01Epub Date: 2025-12-31DOI: 10.1016/j.jsames.2025.105935
Lucca Martins Franco , Miguel Tupinambá , Emanuele Francesco La Terra , Liliane Paiva Panetto , Rogério Guitarrari Azzone
Here, we provide some structural and mineralogical evidence about what happens below a volcanic field during precursor seismic events. Based on outcrops and borehole material, we analyzed volcanic-related structures within the Cretaceous volcanic sequence of the Alto Paranaíba Igneous Province and the underlying Areado Group sandstones in southeastern Brazil, focusing on the role of magmatic volatiles and magmatic fluid circulation. Structural, petrographic, and geochemical data indicate that magma ascent through subvertical conduits generated overpressure conditions, promoting carbonate-rich hydrothermal activity and widespread deformation. The resulting structural assemblage includes normal faults, deformation bands, localized folding, subhorizontal creeping faults, and soft-sediment deformation structures, particularly concentrated at sandstone–volcanic contacts. Geological profiles highlight the mechanical and hydraulic interaction between alkaline rocks and their sedimentary host. Overall, the results indicate that volatile exsolution during magma ascent was a key driver of fluid-assisted brittle deformation and induced seismicity, exerting first-order control on fault development, sediment destabilization, and hydrothermal alteration.
{"title":"Degassing-driven seismicity and deformation: Evidence from the Cretaceous Alto Paranaíba Igneous Province, southeastern Brazil","authors":"Lucca Martins Franco , Miguel Tupinambá , Emanuele Francesco La Terra , Liliane Paiva Panetto , Rogério Guitarrari Azzone","doi":"10.1016/j.jsames.2025.105935","DOIUrl":"10.1016/j.jsames.2025.105935","url":null,"abstract":"<div><div>Here, we provide some structural and mineralogical evidence about what happens below a volcanic field during precursor seismic events. Based on outcrops and borehole material, we analyzed volcanic-related structures within the Cretaceous volcanic sequence of the Alto Paranaíba Igneous Province and the underlying Areado Group sandstones in southeastern Brazil, focusing on the role of magmatic volatiles and magmatic fluid circulation. Structural, petrographic, and geochemical data indicate that magma ascent through subvertical conduits generated overpressure conditions, promoting carbonate-rich hydrothermal activity and widespread deformation. The resulting structural assemblage includes normal faults, deformation bands, localized folding, subhorizontal creeping faults, and soft-sediment deformation structures, particularly concentrated at sandstone–volcanic contacts. Geological profiles highlight the mechanical and hydraulic interaction between alkaline rocks and their sedimentary host. Overall, the results indicate that volatile exsolution during magma ascent was a key driver of fluid-assisted brittle deformation and induced seismicity, exerting first-order control on fault development, sediment destabilization, and hydrothermal alteration.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"172 ","pages":"Article 105935"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145886269","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}
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