Petrographic and microthermometrical studies of emeralds in the ‘Garimpo’ of Capoeirana,Nova Era,Minas Gerais State,Brazil |
| |
| Authors: | J L de Souza J C Mendes R M da Silveira Bello D P Svisero J V Valarelli |
| |
| Institution: | (1) DEGEO, Universidade Federal de Ouro Preto, Ouro Preto, Minas Gerais, Brazil;(2) IG, Universidade de São Paulo, São Paulo, Brazil |
| |
| Abstract: | Petrographic investigations in the area of the Capoeirana emerald deposit, Minas Gerais State, revealed two main lithostructural units. The first unit is comprised of gneissic rocks of granitic composition belonging to the basement complex, and the second is composed of a highly weathered metasedimentary-metavolcanic sequence represented by metapelitic schists, amphibolites, schists derived from ultramafic rocks, and quartzites. Quartz and pegmatoid veins appear near the contacts between the gneissic rocks and the mineralization metasedimentary-metavolcanic sequence. The emerald mineralization is dominantly concentrated within the intercalations of meta-ultramafic schists near the contact of the pegmatoid veins. Microthermometric studies of the fluid inclusions of the emerald grains indicate that crystallization occurred in the pressure and temperature ranges of 2000 to 2750 bar and 450 to 650 °C, respectively. These data suggest that the mineralizing solutions have had a late hydrothermal-pneumatolytic origin characterized by low pressures, suggestive of the paragenesis talc + tremolite + carbonate + biotite-phlogopite + chlorite of the emerald wall rocks. |
| |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ |
|
