Rb-Sr geochronology of granitoid rocks from the Pampean Ranges, Argentina

RAPELA, C.W.; HEAMAN, L.; MCNUTT, R.

JOURNAL OF GEOLOGY

UNIV CHICAGO PRESS

Lugar: Chicago; Año: 1982 vol. 90 p. 574 - 582

0022-1376

A reconnaissance Rb-Sr geochronological investigation of granitoid rocks from the Pampean Range provides a framework whereby four culminations of igneous activity are delineated: granitoids emplaced prior to 500 Ma (pre- and synkinematic bodies), ca. 475 Ma (late kinematic bodies) and ca. 440 and 340 Ma (post-kinematic bodies). A number of the post-kinematic granitoids have disturbed Sr isotope systematics which is related to the formation of microcline megacrysts. The Carboniferous granitoids are distinguished by their high initial Sr ratios (i.e., > 0.710); a feature compatible with an origin involving reworking of upper crust or crustal contamination. There appears to be no systematic E-W migration of granitoid emplacement during the ca. 300 Ma evolution of the basement rocks in the Pampean Ranges.