Low‐grade regional metamorphism in the Mesozoic‐Cenozoic volcanic sequences of the Central Andes

Levi, Beatriz; Aguirre, Luis; Nyström, Jan Olov; Padilla, Humberto; Vergara, Marcos

doi:10.1111/j.1525-1314.1989.tb00611.x

Cited by 58 publications

(37 citation statements)

References 24 publications

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“…The initial volcanics were more tholeiitic, changing to a more calcalkaline character in the younger rocks. The source of the magmas became more depleted with time due to an increase in degree of partial melting, and their compositions were modified by subduction-related fluids and contamination with a progressively thinner and younger crust (Levi 1973;Aguirre et al 1989;Levi et al 1989). The extension and subsidence resulted in low-relief topography close to sea level, in contrast with the present-day convergent Andeantype volcanism at the same latitude.…”

Section: Central Chile Basin (288-358s Lat)mentioning

confidence: 98%

The tectonic regime along the Andes: Present‐day and Mesozoic regimes

Ramos¹

2009

Geological Journal

230

139

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The analyses of the main parameters controlling the present Chile-type and Marianas-type tectonic settings developed along the eastern Pacific region show four different tectonic regimes: (1) a nearly neutral regime in the Oregon subduction zone; (2) major extensional regimes as the Nicaragua subduction zone developed in continental crust; (3) a Marianas setting in the Sandwich subduction zone with ocean floored back-arc basin with a unique west-dipping subduction zone and (4) the classic and dominant Chile-type under compression. The magmatic, structural and sedimentary behaviours of these four settings are discussed to understand the past tectonic regimes in the Mesozoic Andes based on their present geological and tectonic characteristics. The evaluation of the different parameters that governed the past and present tectonic regimes indicates that absolute motion of the upper plate relative to the hotspot frame and the consequent trench roll-back velocity are the first order parameters that control the deformation. Locally, the influences of the trench fill, linked to the dominant climate in the forearc, and the age of the subducted oceanic crust, have secondary roles. Ridge collisions of seismic and seismic oceanic ridges as well as fracture zone collisions have also a local outcome, and may produce an increase in coupling that reinforces compressional deformation. Local strain variations in the past and present Andes are not related with changes in the relative convergence rate, which is less important than the absolute motion relative to the Pacific hotspot frame, or changes in the thermal state of the upper plate. Changes in the slab dip, mainly those linked to steepening subduction zones, produce significant variations in the thermal state, that are important to generate extreme deformation in the foreland.

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Section: Central Chile Basin (288-358s Lat)mentioning

confidence: 98%

The tectonic regime along the Andes: Present‐day and Mesozoic regimes

Ramos¹

2009

Geological Journal

230

139

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“…These rocks were affected by low-grade metamorphism mostly due to the high geothermal gradients induced by crustal thinning (Levi et al, 1989). …”

Section: Accepted Manuscriptmentioning

confidence: 99%

Unraveling the origin of the Andean IOCG clan: A Re-Os isotope approach

Barra

Reich

Selby

et al. 2017

Ore Geology Reviews

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'Unraveling the origin of the Andean IOCG clan : a Re-Os isotope approach.', Ore geology reviews., 81 (Part 1). pp. 62-78. Further information on publisher's website: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. 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. A C C E P T E D M A N U S C R I P T Chilean IOCGs is the result of different events with metals derived from diverse sources i.e., the magmatic-hydrothermal system and basement/host rocks. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPTRhenium and Os concentrations for the various studied deposits vary over a wide range of values at the ppb and ppt level, respectively, with many sulfides and magnetite bearing appreciable no common Os. The Re and Os contents in sulfides (pyrite, IOCGs in China and Australia argue for the involvement of a much more radiogenic crustal source possibly related to non-magmatic oxidized saline brines that leached basement rocks. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPTWe conclude that Andean IOCG (and IOA) deposits in northern Chile were formed mainly by magmatic-hydrothermal processes related to the formation and emplacement of plutonic rocks with moderate contribution from leaching of basement and/or volcanic host rocks. Surface or basin-derived brines as well as sediments appear to play only a minor role in the formation of the Chilean IOCG clan.

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“…Contiene intercalaciones piroclásticas, volcanoclásticas y subordinadamente sedimentarias, las cuales localmente se encuentran fuertemente plegadas. Además, incluye numerosas intrusiones subvolcánicas de la misma edad del volcanismo (Vergara et al, 2004), y presenta una paragénesis de minerales metamórficos de bajo grado bien desarrollada (Levi et al, 1989;Bevins et al, 2003;Fuentes et al, 2002;Fuentes, 2004). Los afloramientos de esta formación forman dos cinturones N-S separados por la Formación Farellones (Fig.…”

Section: Marco Geológicounclassified

El Cenozoico del alto rio Teno, Cordillera Principal, Chile Central: estratigrafia, plutonismo y su relacin con estructuras profundas

Piquer¹,

Castelli²,

Charrier³

et al. 2010

Andgeo

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RESUMEN.La evolución geológica cenozoica del sector central de la Cordillera Principal a ~35ºS, se encuentra ínti-mamente 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. ABSTRACT. The Cenozoic of the upper Teno River, Cordillera Principal, Central Chile: stratigraphy, plutonism and their relation with deep structures. The Cenozoic geologic evolution of the central part of the Cordillera Principal at ~35°S, is intimately related to the geodynamic evolution of deep crustal structures, which during different stages controlled the deposition of volcanosedimentary sequences, and the ascent and emplacement of epizonal intrusions. Newly defined stratigraphy around these structures confirms the Cenozoic age of a group of pyroclastic and sedimentary rocks, which conformably underlie andesitic lavas of the Abanico Formation (assigned to the Late Eocene-Early to Middle Miocene). Intrusive rocks correspond to four main phases (from oldest to youngest: diorite, granodiorite, rhyo-dacitic and dacitic porphyry), which occurs in a North-South trending belt. The granodiorite was dated at 7,8±0,4 Ma (K-Ar in biotite). Rhyo-dacitic porphyries, considered as a marginal lithodeme of the granodiorite, yielded 7,9±0,4 Ma (K-Ar in plagioclase ph...

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Low‐grade regional metamorphism in the Mesozoic‐Cenozoic volcanic sequences of the Central Andes

Cited by 58 publications

References 24 publications

The tectonic regime along the Andes: Present‐day and Mesozoic regimes

The tectonic regime along the Andes: Present‐day and Mesozoic regimes

Unraveling the origin of the Andean IOCG clan: A Re-Os isotope approach

El Cenozoico del alto rio Teno, Cordillera Principal, Chile Central: estratigrafia, plutonismo y su relacin con estructuras profundas

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