Volatile Phase Separation in Silicic Magmas at Bajo de la Alumbrera Porphyry Cu-Au Deposit, NW Argentina |
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| Authors: | Anthony C Harris Vadim S Kamenetsky Noel C White David A Steele |
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| Institution: | Centre for Ore Deposit Research, University of Tasmania, Private Bag 79, Hobart, Tasmania 7001, Australia [e-mail: ];Central Science Laboratory, University of Tasmania, Private Bag 74, Hobart, Tasmania 7001, Australia |
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| Abstract: | Abstract. At the Bajo de la Alumbrera porphyry Cu-Au deposit, NW Argentina, several key textural elements preserve evidence for volatile separation. Interconnected miarolitic cavities, while being studied extensively in granites, have now been recognized in intrusions related to porphyry Cu mineralization. Pods of saccharoidal quartz are connected by narrow, anastomosing zones of graphic quartz-alkali feldspar intergrowths and ragged biotite (with lesser apatite and magnetite). Their connectivity can be as much as 15 cm; however, more commonly, the interconnected miarolitic cavities are approximately 1 to 2 mm across and 5 cm or less, long. Features such comb-quartz layered textures and magmatic-hydrothermal veins (P veins), combined with aqueous fluid phase equilibria from fluid inclusions, better constrain physical models of exsolution. We interpret these textures in the context of vapour phase formation, coalescence and accumulation in an evolving silicic magma. Recognition of textures, such as the interconnected miarolitic cavities reported here, may provide a simple exploration tool for porphyry Cu deposits, helping explorers to recognize evidence for a potentially fertile intrusions. |
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| Keywords: | porphyry copper volatiles magma magmatic-hydrothermal miarolitic cavities comb-quartz |
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