Trace and mayor element models of granitoid genesis in the Pampean Ranges, Argentina

RAPELA, C.W.; SHAW, D.M.

GEOCHIMICA ET COSMOCHIMICA ACTA

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 1979 vol. 42 p. 1117 - 1129

0016-7037

Mathematical models for some major and trace elements have been used to test a petrogenetic hypothesis of granitoid rock emplacement at different levels in the metamorphic basement of the Pampean Ranges (Sierra de Quilmes, Argentina). Previous contributions suggested that the second metamorphic event to affect the area reached temperatures high enough to provoke widespread anatexis of the geosynclinal metasediments which make up Sierra de Quilmes. Comparison of the geochemical trends of the granitoids and metamorphic rocks with theoretical models developed for Ca, Na, K, Rb, Sr, suggests the following conclusions: (1) trends in both granitoid and metamorphic rocks fit reasonably well a model of equilibrium partial melting of the metamorphic rocks; (2) major and trace element trends in the metamorphic rocks are as predicted for the solid residues after partial melting; (3) the anatectic liquid after 40% melting was mainly granodioritic; (4) synkinematic and late-kinematic granitoid bodies were formed by fractional crystallization of the granodioritic magma with successive separation of intercumulus liquids; and (5) post-kinematic bodies were formed by equilibrium or quasi-equilibrium crystallization of the granodioritic magma.