New petrographic and chemical data from Upper Palaeozoic-Triassic granitoids from the Frontal Cordillera of Argentina (33°10 to 33°45) are presented. Five stocks with ages from Early Carboniferous to Late Permian were sampled. The rocks are all calc alkaline with the mineralogy of each stock comprising essential plagioclase, alkali-feldspar and quartz with monor biotite and hornblende. Chemically, the rocks are similar to granitoids from the Frontal Cordillera of Chile, although the Argentinian stocks have generally higher K/Rb ratios. REE chondrite-normalized patterns and overall abundances, along with other petrological and geochemical similarities, suggest a common mode of origin for the granitoid stocks. The absence of systematic and wide variations in abundance of compatible trace elements suggest that the stocks represent magmas largely unaffected by extensive high-level fractional crystallization, and that their compositions are controlled primarily at source. Their age, tectonic setting and geochemical trends are consistent with magma pulses generated during crustal extension. The magma source region is considered to be relatively mafic lower crust.
|Number of pages||11|
|Journal||Journal of South American Earth Sciences|
|Issue number||1-2 SPEC. ISS.|
|Publication status||Published - Jan 1996|