2019-09-242019-09-242000-08-31FERREIRA, Iêda de Oliveira. Geologia e gênese do veio de cristal de rocha do Garimpo da Lagoa, Xambioá – TO. Orientador: Basile Kotschoubey.2000. 86 f. Dissertação (Mestrado em Geologia e Geoquímica) – Centro de Geociências, Universidade Federal do Pará, Belém, 2000. Disponível em: http://repositorio.ufpa.br/jspui/handle/2011/11823. Acesso em:.https://repositorio.ufpa.br/handle/2011/11823The crystal rock occurrences from Xambioá region, situated in the northem part of the Araguaia Belt, are associated with quartzites of the base of the Morro do Campo Formation and schists of the Xambioá Formation, both of the Upper Proterozoic Estrondo Group. The crystal rock occurs mainly as irregular pockets within milky to grayish translucent quartz veins. The “Garimpo da Lagoa” crystal rock vein is hosted by biotite - schists of the Xambioá Formation, displays a general sub-meridian direction and is up to 5 m thick. Petrography and microthermometry of vein samples revealed the presence of two distinct fluids types: 1) oversaturated aqua - carbonic fluids in pseudo - secondary inclusions, containing up to 4 solid phases and 2) aqueous fluids of low to high salinity in secondary inclusions. The aqua — carbonic fluid inclusions contain almost pure CO», with traces of N; due probably due to the presence of carbonatic rocks and graphite in the area. Most fluid inclusions underwent crepitation before they reached Th. Even so, the minimum trapping temperature for these fluids was estimated in 550 to 600º C. It is believed that fluids are basically of deep metamorphic origin, though they also show significant contribution of magma derived solutions. The aqueous fluids were found in three-phase oversaturated, two-phase and monophase inclusions. The solutions contained in the three-phase inclusions revealed a salinity from 30 to 40% in weight of NaCl and a minimum trapping temperature between + 182 and + 321ºC. K is believed that these fluids were injected after the aqua — carbonic ones and were essentially of magmatic origin. Concemning the fluids contained in the two-phase inclusions, were distinguished solutions of low salinity (1,23 to 11,81% in weight of NaCl) and a minimum trapping temperature from + 123,8 to + 150,9ºC, and solutions of high salinity, sub-divided in two categories (a) and (b), mainly based on their morphology. The (a) type revealed a salinity of about 23% in weight of NaCl and a minimum trapping temperature between +130 and 210%, more frequently at + 160ºC, while the (b) type indicated a salinity ffom 20 to 25% in weight of NaCl and a minimum trapping temperature from + 65 to + 114,Sth C, more frequently at + 70ºC. The fluids contained in the monophase inclusions displayed a salinity of 1.91% to 18.22% in weight of NaCl. The solutions trapped in two-phase and monophase inclusions would represent late injections of hydrothermal fluids of magmatic origin, which underwent progressive cooling and composition modifications in agreement with the importance of the contribution of more superficial (meteoric, conate, etc.) waters. During the final phase of the Araguaia Belt evolution, in predominantly distensive conditions, at first aqua — carbonic fluids were injected, that resulted, in formation of a hyaline quartz vein, poor in fluid inclusions. Later on, the vein suffered multiple fracturing phases and aqueous solutions were injected showing a progressive lowering of the temperature and, in a less systematic and less regular way, of the salinity. These late injections were responsible in variable degree for the transformation of the original hyaline quartz into translucent or milky quartz. Pockets which were not affected by these late hydrothermal displays remained as crystal rock. Crystal rock, mainly as third quality chips is used as raw material for production of synthetic crystal. Prismatic, well developped quartz crystals and first quality chips are used in mineral craft for production of adornment pieces, balls, key rings and cut stones. Crystal rock is mainly exported to Belo Horizonte, Sete Lagoas, Governador Valadares, where already cut stones are commercialized , and to São Paulo and Rio de Janeiro, where raw crystals are mainly appreciated.Acesso AbertoGeologiaXambioá - TORochasDissertaçãoCNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIASGEOQUÍMICA E PETROLOGIA