Diferenças Químicas e Texturais entre os Veios de Quartzo Férteis e Estéreis no Depósito Aurífero Pau-a-Pique (Grupo Aguapeí, Estado de Mato Grosso)

The quartz veins in the Pau-a-Pique gold deposit hosted in Aguapeí Group metassediments have textural, paragenetic and chemical characteristics that provide prospectives criteria for gold. Gold disseminations occur in the quartz vein system and in the hydrothermal halo. The highest gold grades are within quartz veins that have comb, saccaroidal and replacement textures. The barren veins show ribbon and buck textures. Both fertile and barren veins exhibit a lack of correlation between gold grades and of the other elements (As, Fe, Sc and Ta). This behavior indicates that gold grades might be adequate chemical criteria for distinction between barren and the fertile veins. Gold grains appear associated to martite and oxihydroxides pseudomorphs that replace the ore minerals in veins. The mineral assemblage and textures of the quartz veins, suggest a gold remobilization due to Eh-pH fluctuations related to interaction between the ore and the meteoric solutions

Estágios de Mineralização no Depósito Aurífero Pau-a-Pique, Grupo Aguapeí, Sudoeste do Estado de Mato Grosso, Brasil Central - Evidências de Química Mineral e Inclusões Fluidas -

The Pau-a-Pique deposit is a small gold prospect in the Southwestern of the Amazonian Craton (Mato Grosso State, Brazil). Ore types comprise quartz veins and disseminations hosted in the mylonitized metaconglomerate (Fortuna Formation, Aguapeí Group) and amphibole-biotite-chlorite mylonite. The native gold is associated with pyrite, pyrrhotite, chalcopyrite, native silver, galena, hematite, magnetite and martite. The aqueous-carbonic (type 1) and aqueous inclusions (type 2) in the quartz veins suggest that ore genesis is related to metamorphic fluids percolation during the late regional shearing. The ore remobilization was promoted by meteoric fluids, which are preserved as aqueous inclusions (type 3) in quartz veins.