Hudson Volcano (45°54′S, 72°58′W) represents the southernmost central volcano of the South Andean Volcanic Zone (SVZ). It lies about 280 km east of Nazca–Antarctic–South American Plate Triple Junction, where the Chile spreading ridge enters the Chile Trench. Hudson is located on the border of a volcanic gap separating the Southern from the Austral Volcanic Zone (AVZ), which is commonly interpreted as linked to a slab window. The volcano is characterised by a volcano-tectonic depression about 10 km wide, set in a morphological high of the Patagonian Batholith. The scarce pre-caldera products are made up of mafic lavas interbedded with hyaloclastite. The majority of the volcanic products out from the caldera rims consist of thick deposits of lahars or hyaloclastitic breccias, subordinate lava flows and pyroclastic deposits linked to historical large explosive eruptions. Rough volume calculations on pre-caldera and post-caldera products suggest that the caldera formed in steps in the lifetime of the volcano and that it is mainly linked to a volcano-tectonic collapse during partial emptying of the magma chamber. The monogenetic cones surrounding Hudson (Río Ibanez and Murta) erupted primitive basalts that gave important clues on magma sources. The volcanic products of Hudson, with composition ranging from basalts to dacites, have a calc-alkaline signature. Nevertheless, they have distinctly higher K2O, TiO2, Na2O, LILE, HFSE and REE than the calc-alkaline rocks of SVZ. The basaltic lavas from the monogenetic cones show La/Nb, Ba/Nb and Th/Ta significantly lower than the calc-alkaline lavas. Furthermore, they have some ratios as Th/Yb and La/Yb remarkably low, with values approaching those of MORB-like basalts. All the geochemical characteristics of Río Ibanez and Murta cones are very similar to those of the basalts dredged in the Chile Ridge. Geochemical modeling suggests that the Hudson basalts may derive from the basalts erupted at the Río Ibanez centre through an assimilation plus fractional crystallisation process. On the basis of these data, we propose a geodynamical model. In correspondence to the monogenetic centres, close to the border of the incipient opening of the slab window, the magma features are still those of the depleted asthenosphere under the subducting ridge. In this zone, remnant fragments of subducted oceanic crust undergo partial melting processes, while the mantle wedge is deeply modified by subduction-related components. In correspondence to Hudson and the nearby monogenetic centres, the MORB-type primary source component is modified by altered oceanic crust and variably mixed with andesitic magmas having a calc-alkaline signature. A contribution from partial melting of the continental lithosphere may be present in the complex source mixing process at the border of the slab window.
|Autori interni:||GIONCADA, ANNA|
|Autori:||GUTIERREZ F; A. GIONCADA; O. GONZALEZ FERRAN; A. LAHSEN; MAZZUOLI R|
|Titolo:||The Hudson volcano and surrounding monogenetic centres (Chilean Patagonia): an example of volcanism associated with ridge-trench collision environment|
|Anno del prodotto:||2005|
|Digital Object Identifier (DOI):||10.1016/j.jvolgeores.2005.01.014|
|Appare nelle tipologie:||1.1 Articolo in rivista|