Lithospheric evolution of the Pre- and Early Andean convergent margin, Chile

Verónica Oliveros, Paulina Vásquez, Christian Creixell, Friedrich Lucassen, Mihai N. Ducea, Isabella Ciocca, Javiera González, Mauricio Espinoza, Esteban Salazar, Felipe Coloma, Simone A. Kasemann

Research output: Contribution to journalReview articlepeer-review

44 Scopus citations


The proto-Andean and Early Andean evolution of the southwestern Gondwana margin comprises three stages that differ in their magmatic evolution and deformational style: the Gondwana cycle (~330–280 Ma), the Pre-Andean stage (~280–210 Ma) and the Early Andean Cycle (210–100 Ma). These stages have been traditionally interpreted as the upper crustal response to changes in the tectonic setting which include: Cordilleran-style continental arc (Gondwana cycle), orogenic collapse and possibly slab break-off that led to continental rifting and extensive crustal melting (Pre-Andean stage), and subsequent subduction re-initiation in oceanic arc-style context (Early Andean cycle). The petrological and geochemical characteristics of Carboniferous to Jurassic igneous rocks from this region however do not support the described model. Elemental and Sr-Nd-Pb isotopic data of 86 samples, along with a compilation of ~1230 samples from the literature suggest that subduction was the most likely process by which the magmatic record was generated. Sub-alkaline affinities, LILE enrichment over HFSE, Nb[sbnd]Ta troughs, porphyritic textures and hornblende- and biotite-bearing lithologies are present in all studied units, whereas isotopes suggest that magma sources are a mixture of depleted mantle and variable contribution from the continental crust. Even though the aforementioned features are common to all igneous rocks, some changes point to a decline in the contribution of crustal/lithospheric sources to the magmatism with time. Thus, SiO2, LaN/YbN and 87Sr/86Srinitial exhibit a systematic decrease from ~285 to 150 Ma, whereas the εNdinitial parameter increases in the same period. These changes were accompanied by the shift from dominant compressional (Carboniferous-Early Permian) to transtentional (Middle Permian-Jurassic) stresses in the upper crust, suggesting that the margin went from advancing to retreating due to Pangea reorganization and break-up. Following a potential flat slab event, slab roll-back may have induced extension in the upper crust and lithospheric loss as a consequence of delamination or thermal erosion.

Original languageEnglish (US)
Pages (from-to)202-227
Number of pages26
JournalGondwana Research
StatePublished - Apr 2020

ASJC Scopus subject areas

  • Geology


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