Middle Devonian monzonitic to granitic magmatism of the Sierra de San Luis, Argentina: crustal growth at the wanning stages of the Achalian orogeny

LÓPEZ DE LUCHI, MÓNICA G.; MARTÍNEZ DOPICO, CARMEN I.

París

Conferencia; Goldschmidt Conference; 2017

European Mineralogical Association

Middle Devonian (393-382 Ma) batholiths are composed of Ito A-type hybrid shoshonite and subordinated high-K series Monzonite (MS) and Granite suites (GS). SiO2(46?62%), Cr, Ni, V, Sc, LILE, LREE, Th, Zr and variable, Sr/Y, (La/Yb)N and (Tb/Yb)N,, smooth Eu/Eu*, moderate Na2O (ca 3.5), and troughs at Nb and Ta for MS rocks suggest a subductionrelated enriched lithospheric mantle source. Sm-Nd data (TDM=0.98-1.08 Ga, εNd(380Ma)=0.66-1.47) and87Sr/86Sri (0.703520-0.704203) are compatible with an enriched mantle source. GS rocks are characterized by relatively moderate Al2O3, CaO, and 87Sr/86Sri, high LILE, Cr, variable Sr/Y, (La/Yb)N and Eu/Eu* and low Rb/Sr (1.5, ASI 1.05-1.18, and Ga/Al 2.63.9, εNd(380Ma)=-3.74 to-3.95 and (87Sr/86Sr)i=0.7107430.712955 which would point to metasedimentary or felsic igneous crustal sources. Middle Devonian magmatism record an episode of crustal growth by enriched mantle derived magma and variable degrees of partial melting of a lower crustal source at the wanning stages of the Achalian orogeny.