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Very low-grade secondary minerals as indicators of palaeo-hydrothermal systems in the Upper Cretaceous volcanic succession of Hannah Point, Livingston Island, Antarctica

Published inApplied Clay Science, vol. 134, p. 246-256
Publication date2016
Abstract

The Upper Cretaceous basic volcanic succession in Hannah Point, Livingston Island, Antarctica, presents a widespread occurrence of very low-grade secondary minerals. They occur filling amygdules, veins and veinlets, and replacing phenocrysts and groundmass/matrix. The paragenetic associations include minerals such as laumontite, heulandite, stilbite and clinoptilolite; mafic phyllosilicates corresponding to chlorite and smectite mixed layers (compositions ranging from 57% to 84% of chlorite), albite, calcite and minor celadonite. The mineral assemblages indicate, based on laboratory and field studies, these mineral paragenesis temperatures of 150–200 °C and pressures of 600–1.800 bars, which agrees with the calculated equilibrium temperatures of 160–190 °C, using chlorite geothermometry. These burial pressures, which were estimated from paragenesis, cannot be attained considering the present thickness of 500 m of the sequence, because at least 1 km of erosion is required to produce the mineral associations. Based on textural evidence, three successive stages are proposed to explain the genesis of the secondary minerals: (1) mafic phyllosilicates ± celadonite, (2) zeolites and (3) calcite. The characteristics of these stages point to a regional burial metamorphism (stage 1) superimposed by hydrothermal alteration (stages 2 and 3). The mineral paragenetical evolution can be used as a proxy for the prospection of modern geothermal reservoirs by allowing the identification of hydrothermal alteration processes and burial metamorphism.

Citation (ISO format)
BASTIAS SILVA, Miguel Joaquin et al. Very low-grade secondary minerals as indicators of palaeo-hydrothermal systems in the Upper Cretaceous volcanic succession of Hannah Point, Livingston Island, Antarctica. In: Applied Clay Science, 2016, vol. 134, p. 246–256. doi: 10.1016/j.clay.2016.07.025
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ISSN of the journal0169-1317
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