Acid sulphate alteration hydrothermal environment

• Main Authors: King George Island, Debbie C. Armstrong
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: volcanic-hosted argillic alteration; acid sulphate-type epithermal system; Antarctica; Barton; Barton Peninsula; Antarc*
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.604.4449; http://www.minersoc.org/pages/Archive-MM/Volume_59/59-396-429.pdf

Volcanic-hosted advanced argillie alteration on Barton Peninsula comprises an assemblage of chalcedonic silica, alunite family minerals, pyrophyllite, pyrite, native sulphur, zunyite and rutile, characteristic of an acid sulphate-type pithermal system. The minerals minamiite, (Na0.36Cao.27K0.1[]0.27)A13(SO4)2(OH)6, and zunyite, Al13SisO2o(OH,F)IsC1, are reported at this locality, and in Antarctica, for the first time. The WNW-striking, 1 km-long zone of alteration is hosted by early Tertiary andesitic rocks and contained in a 1.5 kin-wide depression, rimmed by an arcuate ridge, probably representing a volcanic crater or small caldera structure. Stability relations of minerals in the advanced argillic alteration zone indicate alteration took place under acidic conditions in the near-surface environment. Mineralogical and textural evidence also suggest alteration occurred in a magmatic hydrothermal system, possibly with a magmatic steam component, rather than in a supergene or steam-heated nvironment.