Thermochronology of allochthonous terranes in Ecuador: Unravelling the accretionary and post-accretionary history of the Northern Andes

Spikings, Richard; Winkler, Wilfried; Hughes, Richard; Handler, Robert

doi:10.1016/j.tecto.2004.12.023

Cited by 99 publications

(112 citation statements)

References 38 publications

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“…≤60°C at the time indicated by the respective apatite fission track age (Laslett et al, 1987). Broad track length distributions with shorter mean lengths reveal instead that the sample experienced a more complex thermal history, spending a significant amount of time within the partial annealing zone Spikings et al, 2005). Similar principles apply to zircon fission track data, but the lack of well-characterized annealing kinetics of tracks within zircon precludes the determination of a thermal history from the track length distributions.…”

Section: Fission Track Thermochronologymentioning

confidence: 96%

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

Maksaev

Munizaga

Zentilli

et al. 2009

AndGeo

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AbStRACt. 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.

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Section: Fission Track Thermochronologymentioning

confidence: 96%

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

Maksaev

Munizaga

Zentilli

et al. 2009

AndGeo

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“…The tectonic regime for the Northern Andes had a first-order control in the accretion and collision of island arcs and oceanic plateaux (Spikings et al 2005;Vallejo et al 2009). However, a change in the absolute motion of South America at that time increased the convergence rate between the continent and the oceanic pieces, and therefore favoured the collision with island arcs and oceanic plateaux.…”

Section: Beginning Of Chile-type Subductionmentioning

confidence: 99%

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

Ramos¹

2009

Geological Journal

228

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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“…Geophysical (Feininger and Seguin 1983) and geochemical (e.g., Mamberti et al 2003) data indicate the existence of an oceanic plateau basement in the Coastal Plain and under the Western Cordillera of Ecuador upon which various Late Cretaceous and Tertiary arcs were built. In contrast, the basement underneath the Inter-Andean Depression remains elusive due to the thick Tertiary and Quaternary volcanoclastic cover (a zone of tectonic melange has been proposed by Spikings et al 2005). The basement of the Eastern Cordillera consists of metamorphic Paleozoic to Jurassic rocks that would belong to both continental (schists, gneisses, granites) and oceanic (metabasalts) accreted terranes (Aspden and Litherland 1992;Litherland et al 1994).…”

Section: Geological and Geotectonic Settingmentioning

confidence: 99%

Adakite-like volcanism of Ecuador: lower crust magmatic evolution and recycling

Chiaradia

Müntener

Beate

et al. 2009

Contrib Mineral Petrol

138

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In the Northern Andes of Ecuador, a broad Quaternary volcanic arc with significant across-arc geochemical changes sits upon continental crust consisting of accreted oceanic and continental terranes. Quaternary volcanic centers occur, from west to east, along the Western Cordillera (frontal arc), in the Inter-Andean Depression and along the Eastern Cordillera (main arc), and in the Sub-Andean Zone (back-arc). The adakite-like signatures of the frontal and main arc volcanoes have been interpreted either as the result of slab melting plus subsequent slab melt-mantle interactions or of lower crustal melting, fractional crystallization, and assimilation processes. In this paper, we present petrographic, geochemical, and isotopic (Sr, Nd, Pb) data on dominantly andesitic to dacitic volcanic rocks as well as crustal xenolith and cumulate samples from five volcanic centers (Pululagua, Pichincha, Ilalo, Chacana, Sumaco) forming a NW-SE transect at about 0°latitude and encompassing the frontal (Pululagua, Pichincha), main (Ilalo, Chacana), and back-arc (Sumaco) chains. All rocks display typical subduction-related geochemical signatures, such as Nb and Ta negative anomalies and LILE enrichment. They show a relative depletion of fluid-mobile elements and a general increase in incompatible elements from the front to the back-arc suggesting derivation from progressively lower degrees of partial melting of the mantle wedge induced by decreasing amounts of fluids released from the slab. We observe widespread petrographic evidence of interaction of primary melts with mafic xenoliths as well as with clinopyroxene-and/or amphibole-bearing cumulates and of magma mixing at all frontal and main arc volcanic centers. Within each volcanic center, rocks display correlations between evolution indices and radiogenic isotopes, although absolute variations of radiogenic isotopes are small and their values are overall rather primitive (e.g., e Nd = ?1.5 to ?6, 87 Sr/ 86 Sr = 0.7040-0.70435). Rare earth element patterns are characterized by variably fractionated light to heavy REE (La/Yb N = 5.7-34) and by the absence of Eu negative anomalies suggesting evolution of these rocks with limited plagioclase fractionation. We interpret the petrographic, geochemical, and isotopic data as indicating open-system evolution at all volcanic centers characterized by fractional crystallization and magma mixing processes at different lower-to mid-crustal levels as well as by assimilation of mafic lower crust and/or its partial melts. Thus, we propose that the adakite-like signatures of Ecuadorian rocks (e.g., high Sr/Y and La/Yb values) are primarily the result of lower-to mid-crustal processing of mantle-derived melts, rather than of slab melts and slab melt-mantle interactions. The isotopic signatures of the least evolved adakite-like rocks of the active and recent volcanoes are the same as those of Tertiary ''normal'' calc-alkaline magmatic rocks of Ecuador suggesting that the source of the magma did not change 123Contrib Mineral Petrol (2009) 1...

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Thermochronology of allochthonous terranes in Ecuador: Unravelling the accretionary and post-accretionary history of the Northern Andes

Cited by 99 publications

References 38 publications

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

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

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

Adakite-like volcanism of Ecuador: lower crust magmatic evolution and recycling

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