Microthermometry from Martha Ag mine and other Jurassic epithermal deposits associated to a caldera environment in the Cerro 1ro de Abril District, Deseado Massif, Argentinean Patagonia.

RUIZ, REMIGIO; PAEZ, GERARDO; GUIDO, DIEGO; RIOS, JAVIER; JOVIC, SEBASTIÁN; SCHALAMUK, ISIDORO

Keystone, CO, USA

Conferencia; Society of Economic Geologists 2010 Conference; 2010

Society of Economic Geologists

The aim of this study is to report the results from microthermometry studies carried outat Martha silver mine and other epithermal manifestations from the Cerro 1ro de AbrilDistrict. The study area is located in the southwestern portion of the Deseado Massif, animportant Au-Ag silver producing region form the southern Argentinean Patagonia.This region is characterized by an extensive plateau composed of intermediate to acidMiddle to Upper Jurassic volcanic rocks of the Bahía Laura Volcanic Complex. This volcanic complex has several genetically related Au-Ag low sulfidation epithermal manifestations with currently four operational mines (Cerro Vanguardia, Martha, Manantial Espejo and San Jose).The Cerro 1ro de Abril District is characterized by an important Jurassic volcanismrelated to the evolution of a 12 km wide volcanic caldera. This volcanism is geneticallyrelated with four NW trending vein systems: Wendy, Argenta, Martha and Malbec.Microthermometry show slightly differences between these vein systems, withrelatively uniform homogeniztion temperatures ranging between 213 and 296° C, and morevariable salinities ranging among 0,9 and 9,5 wt% (NaCl eq.).The base metal stage is present at Martha, Argenta and Malbec, the caldera-relatedtrends, probably influenced by a major magmatic component. There is a northward increasein salinity in these trends. The silver stage is located towards the south of the calderastructure (Wendy and Martha trends) and characterized by low salinities. It is alwayspreceded by a higher temperature stage indicating a cooling path controlling silver-richmineralization.