|
|||||
|
|
Fluid inclusions in the Niquelândia and Barro Alto Complexes, Goias State, Brazil |
|
| Authors: | K Török B De Vivo A A Nilson A Lima A Zuppetta |
| Institution: | Department of Geophysics, E?tv?s Loránd University, Budapest, Hungary, HU Dipartimento di Geofisica e Vulcanologia, Universitá di Napoli “Federico II”, Napoli, Italy, IT Departamento Mineralogia e Petrologia, Universidade de Brasilia, Brasilia, Brazil, BR Universitá degli Studi del Sannio, Benevento, Italy, IT |
| Abstract: | Summary ?Fluid inclusions from two Mesoproterozoic, metamorphosed layered intrusive complexes, Niquelandia and Barro Alto, Goiás State, Brazil record multiple fluid influx events from the magmatic to granulitic and retrograde metamorphic stages. 1. The oldest inclusions contain high density CO2 ± N2 ± CH4 and are found as primaries in plagioclase and orthopyroxene in mafic granulite with homogenization temperatures between − 48 and − 28 °C. These inclusions may correspond to the early, magmatic stage. This type was found in samples from both the Niquelandia and the Barro Alto complexes. 2. Intragranular, relatively high density CO2 + N2 inclusions (Th between − 33 and − 26 °C) together with decrepitated and reequilibrated N2 inclusions (Th between − 160 and − 151 °C) in the rock-forming minerals can be associated with the granulite facies metamorphism. Such inclusions were found only in the Barro Alto complex. 3. Transgranular, high density, CO2–N2 inclusions (93% CO2 and 7% N2, according to Raman analysis, with Th between − 66.6 and − 50.4 °C) as well as the low density, secondary CO2 ± N2 ± CH4 inclusions (Th between − 13.0 and + 18.7 °C) and the H2O–NaCl–CaCl2 hypersaline inclusions (with halite dissolution temperature between 132 and 354 °C, and Th between 212 and 490 °C) are attributed to different fluid influx events during the retrograde metamorphism. This inclusion type can be found both in the Niquelandia and in the Barro Alto complexes. The fluid inclusion textures and compositions show several stages of fluid evolution. The fluid inclusion measurements and the geothermobarometric data indicate an anticlockwise P-T path for both the Barro Alto and the Niquelandia complexes. Received October 16, 2000; revised version accepted November 20, 2001 |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ | |