Papers by Reynaldo Charrier
Andean Geology, Jan 7, 1997
4°Arf3 9 Ar mineral dating and whole rock chemical analyses of Miocene to Pliocene Andean granito... more 4°Arf3 9 Ar mineral dating and whole rock chemical analyses of Miocene to Pliocene Andean granitoids near the El Teniente copper deposit (34°S) provide new evidence for rapid Neogene exhumation. This exhumation is attributed to crustal thickening that culminated in the Late Miocene-Early Pliocene coincident with the emplacement of the ore deposit. Three groups of Neogene plutons in the forearc of the active Southern Volcanic Zone (SVZ) are considered. The oldest and westernmost is represented by the La Obra pluton (19.6 ± 0.5 Ma, biotite) which has chemical affinit es with the host Late Oligocene-Early Miocene Coya-Machalí Formation volcanic rocks. Slow cooling of this pluton is required by a 3.4 my difference between biotite and K-feldspar 4°Arf3 9 Ar ages. Modeling shows that this cooling is consistent with an exhumation rate of-0.55 mm/yr between 19.6 Ma and 16.2 Ma. The second group, termed the El Teniente Plutonic Complex, consists of plutons with biotite ages clustering at-11 to 12 Ma and-8 to 9 Ma. These plutons have chemical affinities with the Middle to Late Miocene Teniente Complex (Fare/lones Formation) volcanic rocks whose chemical characteristics suggest that they erupted through a thicker crustthan the Coya-Machalí units. A 0.7 my diffBrence bEtween biotite (8.4±0.3 Ma) and K-feldspar ages in the Nacimiento Río Cortaderal pluton requires an exhumatiol rate of-3 mm/ yr between 8.4 and 7.7 Ma. Although modeled exhumation rates depend on estimates of mineral closure temperatures, paleo-geothermal gradients, and errors in age determinations, a higher exhumation rate forthe NacimientJ Rio Cortaderal pluton than the La Obra pluton is a robust result of modeling. A third group of plutons (Young Plutonic Complex) farther west, is characterized by biotite ages of 6.6 to 5.6 Ma. Their steeper rare earth element patterns and more Enriched isotopic signatures, are consistent with emplacement in a crust even more thickened by Late Miocene compressiolal deformation. An elevated paleo-geothermal gradient, consistentwith the Miocene magmatic-arc environment, best explains the cooling histories of these plutons. Their mineral ages are interpreted as being contro/led by exhumation associated with Grustal thickening due to compressional deformation related to crustal shortening. The data are consistent with a moderate regional deformation associated with eastward shift of the magmatic front between 20 to 16 Ma, and a stronger regional deformation associated with frontal are migration between 8 and 5 Ma.
Eocene Arc Petrogenesis in Central Chile (~3 1 3.5°S) and Implications for the Late Cretaceous–Miocene Andean Setting: Tracking the Evolving Tectonic Regime
The scarce Eocene geological record in the Andean region of central Chile (~33.5°S) is represente... more The scarce Eocene geological record in the Andean region of central Chile (~33.5°S) is represented by the Estratos del Cordón de los Ratones (ECLR) unit. This is a ~450 m thick mainly volcanic continental series, with a bimodal character, that hosts numerous subvolcanic intrusions. The igneous products show compositional features indicating a cogenetic character for the whole suite, relatively juvenile mantle signatures and arc-like affinities. This along with age determinations of ~42 Ma indicate that the unit corresponds to the middle Eocene arc in the region. Geochemical data obtained complement the evolving arc magmatic record throughout Andean evolution. This allows us to track: (i) the earliest Late Cretaceous orogenic event, (ii) neutral tectonic conditions from latest Cretaceous until middle Eocene times, (iii) the Oligocene-early Miocene extensional episode, and (iv) the onset of prevailing compression. The record also indicates that the extensional event started no earlier...
petrogenesis, chronology, provenance and tectonic implications
Journal of Mammalian Evolution, 2021
The fossil record of chinchillid rodents (Hystricomorpha: Caviomorpha) begins in the early Miocen... more The fossil record of chinchillid rodents (Hystricomorpha: Caviomorpha) begins in the early Miocene. However, nearly all remains have thus far been limited to the Lagostominae, which includes the extant plains viscacha (Lagostomus maximus). Here, we describe the first Neogene remains referable to Pan-Chinchillinae (otherwise including extant chinchillas and mountain viscachas, Chinchilla and Lagidium), and refer them to Miochinchilla gen. nov. Miochinchilla differs from extant chinchillines in having obliquely oriented upper molar laminae, sinuous lower molar laminae, a laminar distal lobe of M3, a medial neurovascular sulcus on the floor of the infraorbital foramen delineated by a low lateral crest, a larger and more robust coronoid process, and a complete entepicondylar foramen, thereby significantly adding to the group's recorded morphological diversity. At present, Miochinchilla is only known from the central Andes (southern tropics). The oldest known pan-chinchilline (and possibly chinchilline), Miochinchilla surirense gen. et sp. nov., is represented by many well-preserved remains from Chucal, northern Chile (late early Miocene). More limited material of Miochinchilla plurinacionalis sp. nov. derives from middle Miocene sites in south-central Bolivia (Nazareno and Quebrada Honda). Intralaminar transverse crests, structures not previously recognized in fossil chinchillids, occur in M. surirense but not M. plurinacionalis. M. plurinacionalis further differs from M. surirense in its more oblique laminae and mesiodistally narrower molars. Although Miochinchilla is exclusively closely related to extant chinchillines, its precise relationship to them remains unclear. We report intralaminar transverse crests in some specimens of the lagostomine Prolagostomus, which suggests the parallel origin of this dental feature in pan-chinchillines and lagostomines.
Tectonics, 2020
We document the effects of major mid to Late Cretaceous compression within the volcanic arc of th... more We document the effects of major mid to Late Cretaceous compression within the volcanic arc of the western Gondwanan margin. The thinned Early Cretaceous Andean margin underwent rapid thickening and shortening-related exhumation of magmatic arc rocks during compressional inversion of late Early Cretaceous intra-arc basins. Clastic sedimentary and volcanic rocks recording this phase of initial Andean shortening correspond to the Las Chilcas Formation and are interpreted to have been deposited in a proximal retro-arc position. A detailed analysis of these deposits reveals multiple periods during sustained compressional deformation throughout the latest Early and Late Cretaceous, from 105 Ma to 83 Ma. This deformation is evidenced by the exhumation of older units in the Coastal Cordillera, together with the development of contractional structures and a strong sedimentary response involving deposition of approximately 3 km of synorogenic nonmarine clastic deposits of the Las Chilcas Formation. The structures and associated deposits suggest that the strongest uplift and deformation period occurred from 100 to 95 Ma, whereas subsequent Late Cretaceous deformation was less pronounced, possibly a result of eastward migration of deformation. This tectonic phase coincided with similar coeval synorogenic deposits in Chile and other Andean regions, which have been attributed to initial Andean shortening resulting from a major plate reorganization.
Lithos, 2013
The Upper Jurassic volcanic rocks of the Pre-Cordillera and High Andes of northern Chile (26-31°S... more The Upper Jurassic volcanic rocks of the Pre-Cordillera and High Andes of northern Chile (26-31°S) represent a back-arc magmatic chain that developed during the early Andean subduction stage. After the Callovian, the dominant marine environment of this back-arc basin became continental and restricted volume of basaltic to riolitic rocks erupted along two belts, parallel to the coeval arc. The western belt comprises the Picudo and Algarrobal formations, whereas the eastern belt is represented by the Lagunillas Formation and the Quebrada Vicuñita Beds. New major and trace elements data, along with Nd-Sr and Pb isotope ratios are presented for these volcanic belts and compared to the geochemical features of the Jurassic and Early Cretaceous arc magmatism. Ar-Ar and U-Pb ages constrain the time span for the volcanism between 163.9 ± 1.4 and 148.9 ± 1.2 Ma. Rocks belonging to the western belt, closer to the arc front, have steep multielement patterns, low concentrations of HREE, suggesting the presence of garnet in the source, and a more radiogenic isotopic composition than the arc magmatism. Parental magmas of these back-arc lavas would have been generated through melting of a depleted mantle, although less depleted than the sub-arc mantle, and interacted with minor amounts of Paleozoic crust. The geochemical composition of the rocks belonging to the eastern belt is more heterogeneous and suggests involvement of different magmatic sources, including shallow depleted asthenosphere as well as an OIB-type mantle within the wedge. In spite the fact that the Jurassic Andean arc was built over a continental plate, the architecture of the volcanic chains and geochemical variations observed among the arc and back-arc rocks in northern Chile resemble those in modern island arcs, and thus support the hypothesis that early Andean subduction developed under extensional tectonic conditions
Andean Geology, 2010
La evolución geológica cenozoica del sector central de la Cordillera Principal a ~35ºS, se encuen... more La evolución geológica cenozoica del sector central de la Cordillera Principal a ~35ºS, se encuentra íntimamente relacionada con la evolución de estructuras profundas, las cuales habrían controlado, en distintas etapas de su historia, tanto la depositación de secuencias volcano-sedimentarias como el ascenso y emplazamiento de cuerpos intrusivos. Estudios estratigráficos en el entorno de estas estructuras, permiten confirmar la edad cenozoica de un conjunto de rocas piroclásticas y sedimentarias que subyacen concordantemente a lavas andesíticas de la Formación Abanico (asignada al Eoceno Tardío-Mioceno Temprano a Medio). Se determinó la existencia de cuatro fases intrusivas principales (diorita, granodiorita, pórfido riodacítico y pórfido dacítico, en ese orden de intrusión), cuyos productos afloran siguiendo una franja de orientación norte-sur. La granodiorita fue datada en 7,8±0,4 Ma (K-Ar en biotita). Pórfidos riodacíticos, considerados como facies marginales de la unidad anterior, se dataron en 7,9±0,4 Ma (K-Ar en fenocristales de plagioclasa). Se reconocieron dos estructuras de importancia regional: el Corrimiento El Fierro, y, más al oeste, se definió el Sistema de Fallas Infiernillo-Los Cipreses. En la caracterización de esta última estructura, se utilizó la modelación magnética de secciones como complemento a la información geológica. Se interpreta que el ascenso de las distintas fases intrusivas mencionadas fue controlado por el Sistema de Fallas Infiernillo-Los Cipreses. Este, al igual que el Corrimiento El Fierro, habría actuado como una falla normal de borde de cuenca durante el Eoceno Tardío-Mioceno Medio, controlando la depositación de productos volcánicos y sedimentarios de la Formación Abanico. Ambas fallas fueron reactivadas en modo inverso durante un importante episodio de contracción tectónica y de elevada presión de fluidos inducida por circulación de magmas, en el Mioceno Tardío, focalizando el ascenso de los intrusivos mencionados.
Andean Geology, 2009
Apatite fission track data for Miocene plutons of the western slope of the Principal Andean Cordi... more Apatite fission track data for Miocene plutons of the western slope of the Principal Andean Cordillera in central Chile (33-35°S) define a distinct episode of enhanced crustal cooling through the temperature range of the apatite partial annealing zone (~125-60°C) from about 6 to 3 Ma. This cooling episode is compatible with accelerated exhumation of the plutons at the time of Pliocene compressive tectonism, and mass wasting on the western slope of the Principal Andean Cordillera in central Chile. The timing coincides with the southward migration of the subducting Juan Fernández Ridge and the development of progressive subduction flattening northward of 33°S. It also corresponds to the time of active magmatic-hydrothermal processes and rapid unroofing of the world class Río Blanco-Los Bronces and El Teniente porphyry Cu-Mo deposits. Zircon fission track ages coincide with previous 40 Ar/ 39 Ar dates of the intrusions, and with some of the apatite fission track ages, being coherent with igneous-linked, rapid cooling following magmatic intrusion. The thermochronologic data are consistent with a maximum of about 8 km for Neogene exhumation of the plutons.
Fission track thermochronology of Neogene plutons in the Principal Andean Cordillera of central C... more Fission track thermochronology of Neogene plutons in the Principal Andean Cordillera of central Chile (33-35°S): Implications for tectonic evolution and porphyry Cu-Mo mineralization
How to cite Complete issue More information about this article Journal's homepage in redalyc... more How to cite Complete issue More information about this article Journal's homepage in redalyc.org Scientific Information System
Crustal evolution of the Southern Central Andes (20°S-26°S) since the Jurassic
An overview is given over the tectonic evolution of the Central Andes. Subduction erosion caused ... more An overview is given over the tectonic evolution of the Central Andes. Subduction erosion caused an eastward migration of the magmatic arc of some 200 km since the Jurassic. Within the arcs the tectonic regime changed from sinistral transtension (Jurassicto Early Cretaceous) to dextral transpression (Paleogene) and contraction (Neogene-Quaternary). Magmatic addition led to a volume increase of the continental crust. The Late Cretaceous-Paleogene arc first was subject to arc-normal extension and later underwent arc-normal contraction and arc-parallel strike-slip motions. Since the Oligocene strong shortening in the arc and backarc areas led to the uplift of the Altiplano-Puna-Plateau and to a thickening of the crust to a maximum thickness of ∼ 70 km. Shortening contrasts with Neogene-Quaternary extensional tectonics in the outer forearc, which is subject to tectonic erosion in the subduction zone. Based on GPS measurements the present tectonic regime is characterized by extensional c...
Crustal evolution of the Southern Central Andes (20°S-26°S) since the Jurassic
An overview is given over the tectonic evolution of the Central Andes. Subduction erosion caused ... more An overview is given over the tectonic evolution of the Central Andes. Subduction erosion caused an eastward migration of the magmatic arc of some 200 km since the Jurassic. Within the arcs the tectonic regime changed from sinistral transtension (Jurassicto Early Cretaceous) to dextral transpression (Paleogene) and contraction (Neogene-Quaternary). Magmatic addition led to a volume increase of the continental crust. The Late Cretaceous-Paleogene arc first was subject to arc-normal extension and later underwent arc-normal contraction and arc-parallel strike-slip motions. Since the Oligocene strong shortening in the arc and backarc areas led to the uplift of the Altiplano-Puna-Plateau and to a thickening of the crust to a maximum thickness of ∼ 70 km. Shortening contrasts with Neogene-Quaternary extensional tectonics in the outer forearc, which is subject to tectonic erosion in the subduction zone. Based on GPS measurements the present tectonic regime is characterized by extensional c...
Andean Geology
Lithological heterogeneities in a rock series deformed by the development of a fold-and-thrust be... more Lithological heterogeneities in a rock series deformed by the development of a fold-and-thrust belt (FTB) affects the pattern of the resulting structures. We present a series of analogue experiments to determine the effect caused on the deformation pattern of a FTB by the presence of cohesive bodies, like plutons or basement blocks that oppose greater resistance than the host rocks to contractional deformation. The influence of these bodies on the deformation pattern of the FTB was studied by incorporating discordant bodies with different cohesions within a stratified granular sequence with negligible cohesion. We describe two sets of experiments in which the inserted body presents low (Co1) and high (Co2) cohesion respectively. The experiments show a tendency of the structural pattern to curve around the inserted body and to migrate towards the deformation front or the foreland, even when the cohesive body is not exposed. In the first case (Co1) the thrusts cut across the cohesive ...
Andean Geology
Lithological heterogeneities in a rock series deformed by the development of a fold-and-thrust be... more Lithological heterogeneities in a rock series deformed by the development of a fold-and-thrust belt (FTB) affects the pattern of the resulting structures. We present a series of analogue experiments to determine the effect caused on the deformation pattern of a FTB by the presence of cohesive bodies, like plutons or basement blocks that oppose greater resistance than the host rocks to contractional deformation. The influence of these bodies on the deformation pattern of the FTB was studied by incorporating discordant bodies with different cohesions within a stratified granular sequence with negligible cohesion. We describe two sets of experiments in which the inserted body presents low (Co1) and high (Co2) cohesion respectively. The experiments show a tendency of the structural pattern to curve around the inserted body and to migrate towards the deformation front or the foreland, even when the cohesive body is not exposed. In the first case (Co1) the thrusts cut across the cohesive ...
Se presenta la historia de la fundacion y del desarrollo de las actividades de ensenanza e invest... more Se presenta la historia de la fundacion y del desarrollo de las actividades de ensenanza e investigacion en Geologia en la Universidad de Chile. Estas se iniciaron con Ignacio Domeyko, uno de los fundadores de la Facultad de Ciencias Fisicas y Matematicas y, posterior Rector de la Universidad, entre 1867 y 1883. Como profesor de Geologia fue sucedido por Johannes (Juan) Bruggen, creador del Instituto de Geologia y autor de “Fundamentos de la Geologia de Chile” en 1950. A su retiro lo sucedio su alumno, el ingeniero de minas Jorge Munoz Cristi. En 1952, participo junto con el geografo Humberto Fuenzalida y otro ingeniero de minas, Hector Flores, en la creacion del Curso Especial de Geologo, posteriormente transformado en Escuela de Geologia y, finalmente, en Departamento de Geologia en 1968. El desarrollo de las actividades docentes y de investigacion se vieron favorecidos en gran medida con la participacion de investigadores extranjeros venidos de Alemania, Argentina, Checoslovaquia...
Se presenta la historia de la fundacion y del desarrollo de las actividades de ensenanza e invest... more Se presenta la historia de la fundacion y del desarrollo de las actividades de ensenanza e investigacion en Geologia en la Universidad de Chile. Estas se iniciaron con Ignacio Domeyko, uno de los fundadores de la Facultad de Ciencias Fisicas y Matematicas y, posterior Rector de la Universidad, entre 1867 y 1883. Como profesor de Geologia fue sucedido por Johannes (Juan) Bruggen, creador del Instituto de Geologia y autor de “Fundamentos de la Geologia de Chile” en 1950. A su retiro lo sucedio su alumno, el ingeniero de minas Jorge Munoz Cristi. En 1952, participo junto con el geografo Humberto Fuenzalida y otro ingeniero de minas, Hector Flores, en la creacion del Curso Especial de Geologo, posteriormente transformado en Escuela de Geologia y, finalmente, en Departamento de Geologia en 1968. El desarrollo de las actividades docentes y de investigacion se vieron favorecidos en gran medida con la participacion de investigadores extranjeros venidos de Alemania, Argentina, Checoslovaquia...
Processes leading to construction of the modern Chilean Andes have followed different paths along... more Processes leading to construction of the modern Chilean Andes have followed different paths along the margin. In the northern region, north of ~27oS, after latest Cretaceous to mid-Eocene Incaic tectonic phase contraction remained continuous until present and the magmatic arc remained approximately at the same location, although with a slight eastward shift. In the central region, after the Incaic phase, in late Eocene to latest Oligocene an extensional event occurred south of ~27o S that caused development of the Abanico basin. Geochemical evidence indicates that whereas continuous crustal thickening occurred in northern Chile, considerable crustal thinning occurred in central Chile during formation of the Abanico basin. Here, contraction resumed in early Miocene causing migration of magmatism and deformation to the east along with a progressive increase in crustal thickness. We propose that the ~25 m.y. long interruption of compression during the development of the Abanico basin i...
Processes leading to construction of the modern Chilean Andes have followed different paths along... more Processes leading to construction of the modern Chilean Andes have followed different paths along the margin. In the northern region, north of ~27oS, after latest Cretaceous to mid-Eocene Incaic tectonic phase contraction remained continuous until present and the magmatic arc remained approximately at the same location, although with a slight eastward shift. In the central region, after the Incaic phase, in late Eocene to latest Oligocene an extensional event occurred south of ~27o S that caused development of the Abanico basin. Geochemical evidence indicates that whereas continuous crustal thickening occurred in northern Chile, considerable crustal thinning occurred in central Chile during formation of the Abanico basin. Here, contraction resumed in early Miocene causing migration of magmatism and deformation to the east along with a progressive increase in crustal thickness. We propose that the ~25 m.y. long interruption of compression during the development of the Abanico basin i...
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Papers by Reynaldo Charrier