Ion microprobe (SHRIMP) dates complex granulite from Santa Catarina, southern Brazil

Citation
La. Hartmann et al., Ion microprobe (SHRIMP) dates complex granulite from Santa Catarina, southern Brazil, AN AC BRASI, 72(4), 2000, pp. 559-572
Citations number
41
Categorie Soggetti
Multidisciplinary
Journal title
ANAIS DA ACADEMIA BRASILEIRA DE CIENCIAS
ISSN journal
00013765 → ACNP
Volume
72
Issue
4
Year of publication
2000
Pages
559 - 572
Database
ISI
SICI code
0001-3765(200012)72:4<559:IM(DCG>2.0.ZU;2-Z
Abstract
Complex polymetamorphic granulites have been dated in the Santa Catarina gr anulite complex of southern Brazil through SHRIMP study of zircon. This com plex is dominated by intermediate-acid plutonic rocks and contains small vo lumes of mafic and ultramafic rocks, and minor quartzite and banded iron fo rmation. Porphyroblasts of orthopyroxene, clinopyroxene and plagioclase in mafic and acid rocks are interpreted as magmatic remnants in a volumetrical ly dominant granoblastic aggregate (M-1) of the same minerals and hornblend e. Hornblende formed during a later M-2 metamorphic event constitutes rims around pyroxene, but the hornblende is also rimmed by granoblastic simplect ites of orthopyroxene, clinopyroxene, hornblende and plagioclase in a secon d granulite facies event (M-3) Chlorite and epidote occur in shear zones (M -4) This granulite terrain is Dart of a Neoproterozoic craton, because it w as little affected by the Brasiliano Cycle. The two granulite-facies events (M-1 and M-3) are dated by U/Pb zircon SHRIMP at about 2.68 and 2.17 Ga, w hile the magmatic protoliths formed at about 2.72 Ga. The amphibolite facie s event (M-2) probably occurred close to the 2.17 Ga granulitic metamorphis m.