Abstract

CASTANO-DAVILA, Diana Lorena; HERNANDEZ-GONZALEZ, Juan Sebastián; MOLANO-MENDOZA, Juan Carlos  and  RODRIGUEZ-VARGAS, Andrés Ignacio. Mineralogy and fluid-inclusion microthermometry of the vein with Au-Ag ore of La Aurora mine in the northern part of the Zaragoza-Segovia-Remedios mining district (ZSRMD), Colombia. Bol. geol. [online]. 2019, vol.41, n.3, pp.107-125.  Epub Sep 30, 2019. ISSN 0120-0283.  https://doi.org/10.18273/revbol.v41n3-2019005.

The gold mineralization related to the vein of La Aurora mine is part of the Zaragoza-Segovia-Remedios Mining District (ZSRMD), located in the eastern flank of Central Cordillera of Colombia. This mineralization is emplaced in metamorphic rocks from Cajamarca Complex and corresponds to a quartz vein with a paragenetic sequence that defines three mineralizing events: i) Stage I with mineral associations Qz+Py+Ccp+Po, ii) Stage II with paragenesis among minerals such as Qz+Chl+Ser+Cal+Py+Ccp+Gn +Au+Sp+Ant and iii) Stage III with associations among minerals Qz+Ser+Cal+Py+Ccp+Gn+Au+Rt+Sp+Gth+Mrc. Mineralizing fluids with the gold formation (stages II and III) are of low salinity and the temperatures between 165.8°C and 262.9°C. The vein contains two types of biphasic primary fluid inclusions (LV) in quartz of the stage II and one type of secondary fluid inclusions: Type IL with a homogenization temperature (T h) between 165.8°C to 195°C and salinity between 4.3 to 5.9 wt % NaCl eq.; Type IIL with homogenization temperature (T h) between 200°C to 262.9°C and salinity between 5.9 to 11.6 wt % NaCl eq.; Type V are monophase inclusions with sizes smaller than 5 μ. The ratios between gold/silver and other metals are variable, with average values of Au/Ag=1.24, Au/Bi=1.02, Au/Pb=0.01, Au/Zn=0.02, Ag/Bi=0.75, Ag/Pb=0.01 and Ag/Zn=0.03. Physical and chemical properties calculated with the measured data from fluid inclusions and related to the paragenetic sequence, and geochemical analysis suggest that the formation conditions of gold mineralization occurred in shallow crustal levels, possibly in an epithermal system. The Otú- Pericos Fault System possibly controlled the emplacement and spatial distribution of the mineralized vein.

Keywords : Gold mineralization; Zaragoza-Segovia-Remedios Mining District (ZSMD); fluid inclusions; La Aurora mine..

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