Petrografia dos greisens mineralizados a Sn, Cu, Zn, Pb associados ao plúton Saubinha, Suíte Intrusiva São Lourenço-Caripunas, Rondônia
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Data
2019-11-27
Autores
Ferraz, Renan de Salles Flores Garcia
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Universidade Estadual Paulista (Unesp)
Resumo
Greisens são os depósitos primários de estanho mais comuns na Província Estanífera de Rondônia, sudoeste do Cráton Amazônico. Ocorrem associados principalmente às rochas graníticas das suítes intrusivas São Lourenço- Caripunas (SISLC: ca.1310 Ma), Santa Clara (1082-1074 Ma) e Granitos Últimos de Rondônia (998-974 Ma). No plúton Saubinha (SISLC), os greisens ocorrem em dois morros denominados de serras do Isaac e Irene no distrito mineiro de São Lourenço. Formam corpos lenticulares subparalelos (NNE/s.v.), associados ou não com veios de quartzo, com algumas dezenas de metros de extensão e menos de 2,0 m de espessura. Os greisens são cinza a cinza escuros e apresentam estrutura maciça. A textura é heterogranoblástica, granoblástica com granulação variando de grossa a fina. Os greisens heterogranoblásticos e granoblásticos ocorrem alojados no Biotita-álcali feldspato granito heterogranular e porfirítico e são caracterizados principalmente por cristais ou agregados de cristais maiores quartzo envolvido por cristais menores de quartzo, topázio e mica. Mineralogicamente, os greisens são classificados como topázio-mica-quartzo greisen e mica-topázio-quartzo greisen. O quartzo é cinza e aparece sob dois tipos texturais, como cristais anédricos e límpidos e cristais anédricos com inúmeras inclusões de mica e topázio. A mica ocorre sob dois tipos pleocróicos, com cores verde/pardo e amarelo claro/incolor, o topázio é anédrico e incolor e a cassiterita aparece como cristais subédricos castanho avermelhados dispersos pela rocha. Pseudomorfos de mica pretérita com inclusões de zircão são freqüentes e fluorita roxa e anédrica e agregados de sulfetos (galena, esfalerita e calcopirita) ocorrem em vênulas ou dispersos pela rocha, por vezes com inclusões de mica, quartzo e topázio. A mineralização polimetálica no pluton Saubinha ocorreu através de processos de mineralização hidrotermal oxidada e sulfetada.
Greisens are the most common primary tin deposits in the Província Estanífera de Rondônia, southwest of the Amazonian Craton. They occur mainly associated with the granitic rocks of the São Lourenço-Caripunas intrusive suites (SISLC: ca.1310 Ma), Santa Clara (1082-1074 Ma) and Granitos Últimos de Rondônia (998-974 Ma). In the pluton Saubinha (SISLC), greisens occur on two hills called Isaac and Irene mountain ranges in the São Lourenço mining district. They form sub-parallel lenticular bodies (NNENEE / s.v.), Whether or not associated with quartz veins, some tens of meters long and less than 2.0 m thick. The greisens are gray to dark gray and have massive structure. The texture is heterogranoblastic, granoblastic and more rarely porphyroblastic, with granulation ranging from coarse to fine. Heterogranoblastic and granoblastic greisens are housed in biotite-alkali-feldspar heterogranular granite and are mainly characterized by crystals or aggregates of larger quartz crystals, surrounded by smaller quartz, topaz and mica crystals. . Porphyroblastic greisens, on the other hand, are hosted on biotite-alkali- feldspar porphyritic granite. Larger crystals or aggregates of quartz stand out in a matrix composed of quartz, topaz and mica. Mineralogically, greisens are classified as topaz- mica-quartz greisen and mica-topaz-quartz greisen. Quartz is gray and appears under two textural types, such as clear anhedric crystals and anhedric crystals with numerous inclusions of mica and topaz. Mica occurs under two pleochroic types, green / brown and light yellow / colorless, the topaz is anhydrous and colorless and the cassiterite appears as reddish brown subredic crystals scattered over the rock. Pseudomorphs of past mica with zircon (biotite?) Inclusions are frequent and purple and anhedric fluorite and sulfide aggregates (galena, sphererite and chalcopyrite) occur in venules or dispersed by the rock, sometimes with mica, quartz and topaz inclusions. The polimetalic mineralization in pluton Saubinha occur are associated with hidrothermal mineralzation.
Greisens are the most common primary tin deposits in the Província Estanífera de Rondônia, southwest of the Amazonian Craton. They occur mainly associated with the granitic rocks of the São Lourenço-Caripunas intrusive suites (SISLC: ca.1310 Ma), Santa Clara (1082-1074 Ma) and Granitos Últimos de Rondônia (998-974 Ma). In the pluton Saubinha (SISLC), greisens occur on two hills called Isaac and Irene mountain ranges in the São Lourenço mining district. They form sub-parallel lenticular bodies (NNENEE / s.v.), Whether or not associated with quartz veins, some tens of meters long and less than 2.0 m thick. The greisens are gray to dark gray and have massive structure. The texture is heterogranoblastic, granoblastic and more rarely porphyroblastic, with granulation ranging from coarse to fine. Heterogranoblastic and granoblastic greisens are housed in biotite-alkali-feldspar heterogranular granite and are mainly characterized by crystals or aggregates of larger quartz crystals, surrounded by smaller quartz, topaz and mica crystals. . Porphyroblastic greisens, on the other hand, are hosted on biotite-alkali- feldspar porphyritic granite. Larger crystals or aggregates of quartz stand out in a matrix composed of quartz, topaz and mica. Mineralogically, greisens are classified as topaz- mica-quartz greisen and mica-topaz-quartz greisen. Quartz is gray and appears under two textural types, such as clear anhedric crystals and anhedric crystals with numerous inclusions of mica and topaz. Mica occurs under two pleochroic types, green / brown and light yellow / colorless, the topaz is anhydrous and colorless and the cassiterite appears as reddish brown subredic crystals scattered over the rock. Pseudomorphs of past mica with zircon (biotite?) Inclusions are frequent and purple and anhedric fluorite and sulfide aggregates (galena, sphererite and chalcopyrite) occur in venules or dispersed by the rock, sometimes with mica, quartz and topaz inclusions. The polimetalic mineralization in pluton Saubinha occur are associated with hidrothermal mineralzation.
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Alteração hidrotermal, Greisens, Rondônia, Estanho, Greisen, Petrografia, Petrography, Tin