SM-ND AGES OF MAFIC ROCKS FROM THE COASTAL CORDILLERA AT 24-DEGREES-S, NORTHERN CHILE

We investigated the Sm-Nd systematics of mafic granulite and undeforme d layered gabbro, which form a midcrustal section of the Jurassic magm atic belt in the North Chilean Coast Range, south of Antofagasta. Mine ral isochrons indicate ages between ca. 171 and 150 Ma for the granuli te and an age of ca. 161 Ma for the gabbro. These ages are interpreted as closure time of the Sm-Nd system in the area. The age of metamorph ism is Late-Jurassic. The minimum intrusion age of the protolith of th e granulite is likely Early Jurassic (ca. 200 Ma), but an exact intrus ion age could not be derived from the data. The intrusion age of the g abbro is ca. 185 Ma. Granulite generated from mantle-derived gabbroic magmas has epsilon(Nd200) between 6.28 and 7.05 and the gabbro that in truded the granulite has epsilon(Nd185) between 5.89 and 6.09.