Papers by Leonardo Strazzere
El distrito minero Andacollo está ubicado al SO de la localidad homónima, en la provincia de Neuq... more El distrito minero Andacollo está ubicado al SO de la localidad homónima, en la provincia de Neuquén. Se reconocen en el área un conjunto de vetas epitermales con mineralización de Ag ± Au aflorantes en el cerro Las Minas.La veta Buena Vista, motivo del presente trabajo, presenta un rumbo NE-SO, una longitud de 250 m y un espesor promedio de 3,5 m. La roca de caja corresponde a volcanitas con grados variables de alteración hidrotermal. La asociación de alteración en la zona de contacto con la veta está compuesta por cuarzo + sericita (± clorita ± pirita), mientras que en las zonas más alejadas está formada por clorita + minerales arcillosos (± calcita ± pirita). Según las relaciones estratigráficas, la edad de la veta es pre-Carbonífero Superior.La veta está formada por cinco pulsos de relleno hidrotermal entre los que se identificó un evento mineralizante (cuarto pulso) compuesto por pirita, galena, esfalerita, calcopirita, marcasita, argentita y electrum. Desde la superficie hacia...
El Distrito Minero Castano Nuevo, esta localizado en el borde oriental de la Cordillera Frontal d... more El Distrito Minero Castano Nuevo, esta localizado en el borde oriental de la Cordillera Frontal de San Juan, se emplaza en rocas asociadas al magmatismo del Grupo Choiyoi y esta conformado por un conjunto de vetas epitermales de cuarzo/adularia. La veta Dios Protege constituye la estructura principal del distrito y se encuentra emplazada en una falla de rumbo con una leve componente normal y desplazamiento siniestral. Presenta una orientacion general NNE, con buzamiento hacia el O, y a lo largo de su corrida presenta sectores de apertura asociados a inflexiones e intersecciones con otras estructuras. En estos sectores se reconocen los mayores espesores, donde es posible identificar al menos 6 eventos de relleno. Estos eventos constituyen una alternancia entre bechas tipo crackle y brechas tipo cocarda, cuyo desarrollo se encuentra ligado a la relacion entre la velocidad de apertura de la falla y la velocidad de ascenso de los fluidos. Asimismo, las fases minerales que componen cada ...
International Geology Review, 2021
ABSTRACT The Sinemurian Marifil Volcanic Complex at Sierra de Pailemán, located in the east part ... more ABSTRACT The Sinemurian Marifil Volcanic Complex at Sierra de Pailemán, located in the east part of the North Patagonian Region, Argentina, includes five lithofacies and three volcanic events. The volcanic activity begins with subaerial pyroclastic-fall deposits, massive lapilli tuffs with eutaxitic textures, and subaerial silicic domes’ emplacement. The upper part of the sequence is formed by pyroclastic fall deposits that pass to massive lapilli tuffs and rhyolitic lava flows. These lithofacies indicate the collapse of explosive eruption columns, coeval with small silicic domes’ emplacement, and lava-flows’ eruption. The volcanic episode at Sierra de Pailemán was generated during continuous magmatic activity because no erosional or unconformity surfaces were recognized. The Marifil Volcanic Complex’s age at Sierra de Pailemán is 191.2 ± 1.3 Ma (Sinemurian) and belongs to the V0 phase of volcanism. These rocks are high-K rhyolites, possibly produced by partial melting of the lower crust, promoted by fluids derived from a subducted plate in back-arc settings that change to an intraplate setting. The Lu-Hf isotopes suggest the possibility of magma mixing in the source and recycling or re-melting of a more evolved crust related to subduction zones. The Lower Jurassic magmatic activity in the western North Patagonian Region and the Patagonian Cordillera of Argentina and Chile correspond to continental arcs. Graphical abstract
International Geology Review, 2020
The Mencué Batholith, western North Patagonian Massif, includes three major bodies. The Mencué Gr... more The Mencué Batholith, western North Patagonian Massif, includes three major bodies. The Mencué Granodiorite, Cura Lauquén Granite and La Blancura Syenogranite. There are dikes of granitic and basaltic rocks cutting the above-cited rocks. The Mencué Batholith represents several episodes of magmatism, with ages varying between 294 and 239 Ma. The Mencué Granodiorite and the Cura Lauquén Granite are solid-state deformed and are S-type. They have high-K and normal calc-alkaline affinities. These rocks contain significant quantities of subduction-zone chemical components that decrease towards younger lithofacies. La Blancura Syenogranite lack subduction zone chemical components and represent A-type granite, typical of within-plate magmatism. The partial melting of metapelites could be the process of formation of these bodies. The older lithofacies of the Mencué Batholith, found westernmost, display a stronger deformation, but there is a progressive eastward change to younger and mildly deformed bodies and even non-deformed bodies. We conclude that the evolution of the Mencué Batholith start in the Sakmarian-Roadian (Early Permian) period. At this time, a subduction zone was active to the west and its thermal influence affected sedimentary or metamorphic rocks producing S-type granites During the Wordian and Capitanian, (Middle Permian) periods, the Mencué Batholith was mildly deformed, possibly in the process of the vanishing of the deformation and has a minor subduction chemical signature. Between the Wuchiapingian and Olenekia periods, the alkaline facies of the Mencué Batholith show an absence of deformation and the characteristics of within-plate magmatism. The Early Permian magmatic events in the western North Patagonian Massif are represented by the older bodies of the Mencué Batholith and were produced by subduction in the western margin of the Gondwanan continent. The Late Permian-Early Triassic magmatic events show a noticeable decreasing influence of subduction and an increasing influence of within-plate chemical components.
Journal of South American Earth Sciences, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
International Geology Review, 2020
Here we define the Comallo volcanic sedimentary complex of the western North Patagonian Massif. I... more Here we define the Comallo volcanic sedimentary complex of the western North Patagonian Massif. It is composed by two members that include 9 lithofacies and 7 facies associations. The lower member is represented by massive and stratified lapilli tuffs, lithic and tuffaceous breccias, coherent andesite-dacite lava-flows, andesitic breccias, and massive crystalline limestones. The upper member consists of red conglomerates, parallel and cross-stratification sandstones, and mudstones. The lower member is interpreted as having been deposited by dilute and dense pyroclastic currents, block and ash deposits and lava-flow, and hypersaline lacustrine environments. The upper member is considered to have been deposited in fluviatile environments. A new U-Pb age of 192.0 ± 3.0 Ma (Sinemurian) was obtained for this complex. It is coeval with several volcanic sedimentary units that crop out along the western North Patagonian Massif, the Neuquén basin and the Extraandean Chubut in pull-apart or rift depocentres. The movements of the NW-SE strike-slip faults that border the northern and southern limits of the Comallo depocentre made possible the development of a pull-apart basin as well as the volcanism and the fluvial system. This and other coeval units were deposited in similar environmental conditions along the North Patagonian Massif, the Neuquén basin and the extraandean Chubut, indicating a similar tectonomagmatic setting, in a tensional rear-arc during Lower Jurassic times.
International Geology Review, 2019
The northern zone of the Chon Aike Igneous Province, located in the North Patagonian Massif, exhi... more The northern zone of the Chon Aike Igneous Province, located in the North Patagonian Massif, exhibits extensive outcrops of Jurassic volcanic rocks of the Marifil Formation. In the Arroyo Verde area, the initial volcanic stage of the Marifil Formation, that we denominate V0 (192.6 ± 2.5 Ma), includes coulées, megabreccias and lapilli tuffs assigned to plinian-type volcanism. This magmatism was generated by cold-wet-oxidized magmas that resemble those produced in active continental margins and volcanic arcs. The second stage, located unconformably over the first, includes welded lava-like ignimbrites, massive lapilli tuff and rhyolitic lava flow that resemble the Snake River-type volcanism. The magma that produces this volcanic stage exhibit the characteristics of hot-dry-reduced magmas emplaced in intraplate continental environments associated with continental rifting. This stage coincides with the V1 volcanic episode early recorded in the Marifil Formation.
Geoscience Frontiers, 2018
The Marifil Volcanic Complex, exposed in the eastern North Patagonian Massif, Argentina, includes... more The Marifil Volcanic Complex, exposed in the eastern North Patagonian Massif, Argentina, includes up to 550 m of red conglomerates, sandstones, black siltstones, limestones, and reworked tuff of the Puesto Piris Formation. The basal part of this unit, which was deposited in high-gradient topographic relief, is composed of conglomerates and sandstones with thin layers of reworked tuffs. The lithofacies associations of the basal part indicate that the depositional mechanisms were mantled and gravitational flows. The middle part of the unit consists of fine sandstones, limestones, and black siltstones that were deposited in low-energy fluvial and lacustrine environments. The outcrops are located along the NEeSW direction and the major thickest units represented by limestones and siltstones, occur near the southeastern border of this NEeSW depocenter. Since the rhyolitic and trachytic lava flows and tuffs of the Marifil Volcanic Complex are interbedded with the sedimentary sequences of the Puesto Piris Formation, both units are coeval. Zircon UePb age was obtained for a trachytic lava flow (193.4 AE 3.1 Ma) suggesting that sedimentation and volcanism are Sinemurian. This extensional episode was recorded in the eastern, western, and southwestern sectors of the North Patagonian Massif, and is possibly associated with the Gondwana supercontinent breakup.
Geoscience Frontiers, 2016
Permian sedimentary and basic to intermediate volcanic rocks assigned to the Conglomerado del Río... more Permian sedimentary and basic to intermediate volcanic rocks assigned to the Conglomerado del Río Blanco and Portezuelo del Cenizo Formation, lower part of the Choiyoi Group, crop out between the Cordon del Plata, Cordillera Frontal and Precordillera of Mendoza Province, Argentina. The sedimentary rocks are represented by six lithofacies grouped in three facies associations. They were deposited by mantled and gravitational flows modified by high-energy fluvial currents that evolved to low-energy fluvial and lacustrine environments. They constitute the Conglomerado del Río Blanco, which cover unconformably marine Carboniferous sequences. Five volcanic and volcaniclastic facies make up the beginning of volcanic activity. The first volcanic event in the Portezuelo del Cenizo is basaltic to andesitic lava-flows emplaced in the flanks of volcanoes. Lava collapse produced thick block and ash flows. Interbedding in the intermediate volcanic rocks, there are dacites of different geochemical signature, which indicate that the development of acidic volcanism was coetaneous with the first volcanic activity. The geochemistry of these rocks induces to consider that the Choiyoi Group Lower section belongs to a magmatic arc on continental crust. The age of this section is assigned to the lower Permian (277 AE 3.0 Ma, Kungurian age).
Geoscience Frontiers, 2017
The metasedimentary sequence of the Cushamen Formation in the western North Patagonian Massif is ... more The metasedimentary sequence of the Cushamen Formation in the western North Patagonian Massif is 540 m thick and comprises six sedimentary lithofacies associations related to a glacimarine environment. Four of these lithofacies represent distal glacimarine environments, whereas another one was deposited in proximal glacimarine environments, and the last includes subglacial environments. The organization and configuration of these lithofacies associations represent the advance and retreat of the glacier masses. The maximum glacial advance is correlatable with the G2 glacial interval of the Pennsylvanian Pampa de Tepuel, Las Salinas and Valley Chico, formations of the Extraandean Chubut, and the southern part of Neuquén Cordillera. Contemporaneously, in southern Chile there are marine and glacimarine sediments. The chronostratigraphic relationships between the Silurian to Permian units allow five paleogeographic stages to be distinguished. The middle Silurianelate Devonian igneous rocks represent the first magmatic stage. The second stage, which is transitional to the first, is represented by a marine basin that includes the late Devonianeearly Carboniferous Esquel and Río Pescado formations and the Llanquihue Complex. The third stage (earlyelate Carboniferous) includes granitoids of the second magmatic event that partially overlapped the first magmatic igneous belt. The fourth stage belongs to the late Carboniferous sedimentation of the Cushamen and equivalent formations. The extended early Permian magmatism was the last Paleozoic event in the studied area.
Revista de la Asociacion Geologica Argentina
RESUMEN. En las quebradas de Santa Elena y del Telegrafo, Uspallata, Precordillera mendocina, fue... more RESUMEN. En las quebradas de Santa Elena y del Telegrafo, Uspallata, Precordillera mendocina, fueron descriptas rocas volcanicas de edad permotriasica, asignadas al Grupo Choiyoi. En este sector el grupo esta representado por una secuencia volcanica, formada a partir de varios eventos piroclasticos de diferente magnitud, sucedidos en intervalos de tiempos cortos. Se reconocieron ochos eventos volcanicos, integrados por litofacies tales como flujos ignimbriticos parcialmente soldados, flujos ignimbriticos densamente soldados, vitrofiros y perlitas, oleadas piroclasticas y depositos de caidas de tefras y cenizas. La composicion determinada a traves de observaciones petrograficas revela una acidificacion creciente hacia las litofacies superiores, variando gradualmente de fenodacitas a riofenodacitas, finalizando con fenoriolitas. El esquema geologico definido para el area de estudio permite correlacionar dichas unidades con la Formacion Horcajo, descripta para el valle del rio de los Patos en la provincia de San Juan. Los espesores medidos disminuyen notablemente hacia el NNO y el SSE, lo que sugiere que los flujos se movilizaron canalizados en direccion NE-SO. Palabras clave: Grupo Choiyoi, Sucesiones volcanicas, Ignimbritas de alto y bajo grado, Precordillera Mendoza, Argentina.
Revista de la Asociacion Geologica Argentina
RESUMEN. En el yacimiento Mina Ángela se definieron tres diseños de alteración hidrotermal. El de... more RESUMEN. En el yacimiento Mina Ángela se definieron tres diseños de alteración hidrotermal. El de menor temperatura fue generado por fluidos que circularon en forma paralela al contacto existente entre las andesitas brechosas y las coladas andesiticas. Las fallas y fracturas donde posteriormente se depositará la mena se hallarían cerradas. El segundo diseño, representado por la distribución de los minerales del grupo del caolín, indica una circulación preponderantemente descendente de los fluidos y un aumento en las condiciones de acidez de los mismos. En el diseño de mayor temperatura, ligado a la mineralización principal, la alteración hidrotermal transita de clorítica a potásica con aumento de la temperatura y cambios químicos en los fluidos. La circulación de éstos es típicamente ascendente.
localiza un conjunto de rocas volcánicas y sedimentarias que fue asignado a la sección ácida del ... more localiza un conjunto de rocas volcánicas y sedimentarias que fue asignado a la sección ácida del Grupo Choiyoi, alcanzando las segundas 300 m de espesor. Las volcánicas, que representan un periodo altamente explosivo, incluyen dos eventos eruptivos con grandes volúmenes de rocas, siendo el primero generado por pulsos piroclásticos unitarios a los que les siguieron plumas volcánicas sustentadas durante largos periodos con colapsos parciales. El segundo evento eruptivo es correlacionable con cuerpos dómicos que tienen una edad Pérmico inferior alto. El mismo muestra una disminución areal considerable respecto al primero, así como un estadio generalizado de subsidencia en el área estudiada. Las asociaciones sedimentarias del primer evento inter-eruptivo se hallan constituidas por conglomerados, fanglomerados, areniscas, calizas y fangolitas y representan flujos densos, lahares, ambientes fluviales y lagunares. Estos últimos son los que poseen el mayor desarrollo areal y se encuentran representados por calizas donde se reconocen estromatolitos, restos de vermes y palinomorfos. El segundo evento inter-eruptivo está casi exclusivamente representado por sistemas lagunares y posiblemente fue de mayor duración que el primero. La morfología y el espesor de los depocentros fue condicionada por la estructura previa de las Formaciones Bonilla (Cambro-Ordovícico) y Formación Santa Elena (Carbonífero) así como por un sistema de fallamiento generalizado durante los últimos eventos volcánicos del Grupo Choiyoi.
Geoscience Frontiers, 2016
Structural analyses in the northern part of the North Patagonia Massif, in the foliated Caita Có ... more Structural analyses in the northern part of the North Patagonia Massif, in the foliated Caita Có granite and in La Seña and Pangaré mylonites, indicate that the pluton was intruded as a sheet-like body into an opening pull-apart structure during the Gondwana Orogeny. Geochronological studies in the massif indicate a first, lower to middle Permian stage of regional deformation, related to movements during indentation tectonics, with emplacement of foliated granites in the western and central areas of the North Patagonian Massif. Between the upper Permian and lower Triassic, evidence indicates emplacement of undeformed granitic bodies in the central part of the North Patagonian Massif. A second pulse of deformation between the middle and upper Triassic is related to the emplacement of the Caita Có granite, the development of mylonitic belts, and the opening of the Los Menucos Basin. During this pulse of deformation, compression direction was from the eastern quadrant.
Geoscience Frontiers, 2013
Journal of South American Earth Sciences, 2014
In the Cerro Carro Quebrado and Cerro Catri Cura area, located at the border between the Neuquén ... more In the Cerro Carro Quebrado and Cerro Catri Cura area, located at the border between the Neuquén Basin and the North Patagonian Massif, the Garamilla Formation is composed of four volcanic stages: 1) andesitic lavaflows related to the beginning of the volcanic system; 2) basal massive lithic breccias that represent the caldera collapse; 3) voluminous, coarse-crystal rich massive lava-like ignimbrites related to multiple, steady eruptions that represent the principal infill of the system; and, finally 4) domes, dykes, lava flows, and lava domes of rhyolitic composition indicative of a post-collapse stage. The analysis of the regional and local structures, as well as, the architectures of the volcanic facies, indicates the existence of a highly oblique rift, with its principal extensional strain in a NNE-SSW direction (~N10°). The analyzed rocks are mainly high-potassium dacites and rhyolites with trace and RE elements contents of an intraplate signature. The age of these rocks (189± 0.76 Ma) agree well with other volcanic sequences of the western North Patagonian Massif, as well as, the Neuquén Basin, indicating that Pliensbachian magmatism was widespread in both regions. The age is also coincident with phase 1 of volcanism of the eastern North Patagonia Massif (188-178 Ma) represented by ignimbrites, domes, and pyroclastic rocks of the Marifil Complex, related to intraplate magmatism.
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Papers by Leonardo Strazzere