SciELO - Scientific Electronic Library Online

vol.34 issue2Evidence of magma-water interaction during the 13,800 years BP explosive cycle of the Licán Ignimbrite, Villarrica volcano (southern Chile)The Ordovician Quebrada Grande Formation, Cordón de Lila (Antofagasta Region, northern Chile): stratigraphicand paleogeographic significance author indexsubject indexarticles search
Home Pagealphabetic serial listing  

Services on Demand




Related links

  • On index processCited by Google
  • Have no similar articlesSimilars in SciELO
  • On index processSimilars in Google


Revista geológica de Chile

Print version ISSN 0716-0208


CALDERON, Mauricio; HERVE, Francisco; CORDANI, Umberto  and  MASSONNE, Hans-Joachim. Crust-mantle interactions and generation of silicic melts: insights from the Sarmiento Complex, southern Patagonian Andes. Rev. geol. Chile [online]. 2007, vol.34, n.2, pp.249-275. ISSN 0716-0208.

A Late Jurassic seafloor remnant of the Rocas Verdes basin in southern Chile, the Sarmiento Complex {ca. 52°S), bears lithological layers with bimodal meta-igneous rocks appropriate for a comprehensive investigation of magma genesis in part of a lateral lithological transition from continental rifting to initial seafloor spreading. Metamorphosed mafic rocks collected from different layers in the ophiolite pseudostratigraphy and a plagiogranite have positive sNd150 values (+ 1 and +2). Granophyres, which are crosscut by ophiolitic mafic dikes, have negative sNd150 values (-5). Dacitic dikes within thick successions of pillow basalt have the least negative sNd150 values (-3 and -4). Although mafic and felsic igneous rocks show contrasting isotopic signatures, thermochemical modeling (EC-AFC) suggests they can share a common origin. Models consider an arbitrary composition of the crustal assimilant (mostly metapelite with an average eNd150 value of-7) and evaluate the feasibility for generation of silicic melts through the interaction of mafic magmas and metasedimentary rocks. A quantitative evaluation of basaltic magma contaminated by crustal wall rocks requires a Ma7 Mc (mass of anatectic melt/ mass of cumulates) ratio of 0.04. Analyses using dikes of dacite (with MaVMc ratios ranging between 0.28-0.35) and granophyres (with MaVMc ratios of 0.63-0.89) require the silicic magmas to contain higher proportions of anatectic melts derived from metamorphic rocks. Isotopic differences among granophyres and dacites could be controlled by eruption dynamics, regional stress field and/or differences in thermal regimes in magma chambers. Bimodal magmatism in the earliest tectonic evolution of the Rocas Verdes basin could reflect regimes of slow extension of the continental crust along the Jurassic southwestern margin of Gondwana

Keywords : Rocas Verdes basin; Sarmiento Complex; Bimodal magmatism; Petrogenesis; Patagonia; Chile.

        · abstract in Spanish     · text in English


Creative Commons License All the contents of this journal, except where otherwise noted, is licensed under a Creative Commons Attribution License