Browsing by Author "Pontoriero, Sandra"

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    Peraluminous Grenvillian TTG in the Sierra de Pie de Palo, Western Sierras Pampeanas, Argentina: Petrology, geochronology, geochemistry and petrogenetic implications
    (ELSEVIER, 2010) Morata, Diego; Castro de Machuca, Brigida; Arancibia, Gloria; Pontoriero, Sandra; Fanning, C. Mark
    Combined petrological, geochemical, isotopic and geochronological data shed light on the origin and evolution of a peraluminous garnet-bearing two-mica granitoid (El Tigre Granitoid: ETG) cropping out in southwestern Sierra de Pie de Palo (31 degrees 31'30 '' S-68 degrees 15'12 '' W), and to constrain the age and petrogenetic conditions of this intrusive event. ETG experienced amphibolite to greenschist facies metamorphism after igneous crystallization, followed by strong deformation restricted to narrow mylonite zones (ETG shear zone) and partial dynamic recrystallization under lower-T conditions. A dextral shear sense is compatible with kinematic observations registered along the NNE striking regional Las Pirquitas overthrust, active at 473 +/- 10 Ma (K/Ar on <2 mu m micaceous fraction for the ETG shear zone). The ETG crops out as small, tabular to lenticular vein-like bodies emplaced into metasedimentary rocks of the Pie de Palo Complex. The ETG ranges from granodiorite to tonalite, with a moderately peraluminous signature (ASI = 1.09-1.33; A/CNK >1.1; normative corundum; low CaO values between 1.72 and 2.41%), plotting mostly in the granite-trondhjemite fields of the Ab-An-Or diagram. The trace element contents show a relatively low abundance of Rb, HFS elements such as Y, Nb, Ta, Ga and Zr, and high concentrations of Ba, Sr, and Sigma LREE. The chondrite-normalized REE pattern has a high slope with [La/Yb](N) = 9.48-55.32 and a negative or absent europium anomaly. Relationships between trace elements suggest the classical setting of granitoids produced in a convergent plate setting.