%0 Journal Article
%A Casquet Martín, César
%A Rapela, Carlos W.
%A Pankhurst, R.J.
%A Baldo, Edgardo G.
%A Galindo Francisco, María Del Carmen
%A Fanning, C.M.
%A Dahlquist, Juan A.
%T Fast sediment underplating and essentially coeval juvenile magmatism in theOrdovician margin of Gondwana, Western Sierras Pampeanas, Argentina
%D 2012
%@ 1342-937X
%U https://hdl.handle.net/20.500.14352/43853
%X Metasedimentary high-pressure upper amphibolite facies gneisses (1.2±0.1 GPa and 780±45 °C) at LasChacras, Sierra de Valle Fértil, are tectonically juxtaposed to thewesternmost parts (outboard) of the Famatinian(Early Ordovician) magmatic arc, which underwent syn-plutonic middle crust high-grade metamorphism atlower pressure. U–Pb SHRIMP zircon data suggest that the gneisses contain Famatinian igneous detritus, sothat their sedimentary protoliths were probably deposited in a forearc basin and then rapidly underthrust andaccreted to the lower crust of the arc, essentially coevallywith arc magmatismat 468±4 Ma. Chemically and isotopicallyjuvenile garnetiferous amphibolites within the gneisses are recognised as representing themost primitivemagmas so far observed in this belt, which has often been considered to be a continental arc derived fromisotopically mature sources. This is consistent with the idea that at least part of the dominant Famatinianmagmatism originated in depleted mantle but was heavily contaminated by crustal components.
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