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Emerald from the Habachtal: new observations

journal contribution
posted on 2023-05-20, 14:35 authored by Thomas, R, Paul DavidsonPaul Davidson, Rericha, A
The emerald mineralization in the Habachtal (Austria) is geologically and tectonically complex, and previous investigators have identified fluid inclusion evidence for a hydrothermal/metamorphic origin for the emeralds. In this paper we report the discovery of emeralds with a distinctly different inclusion population including melt inclusions, which demonstrates that at least some and probably most of the emerald mineralization in the Habachtal occurred from an extremely fluid-rich pegmatite-like aluminosilicate melt under supercritical conditions, at high temperatures and moderate pressures (~700 °C, 5 kbar). This conclusion is based on the presence of very highly-ordered graphite, and extremely water-rich melt inclusions in emerald. The Lorentz distribution of MgCO3 against the water concentration is a very robust proof for the supercritical state. We suggest that the purely metamorphic model, based on the extrapolation of fluid inclusion data to the regional metamorphic conditions (550 °C and 5 kbar) by some previous investigators are inconsistent with our finding of high-temperature indications (well-ordered graphite, high-temperature fluid inclusions and melt inclusions). This apparent conflict suggests a more complex situation and requires a re-investigation of the emerald genesis in the Habachtal deposit.

History

Publication title

Mineralogy and Petrology

Volume

114

Pagination

161-173

ISSN

0930-0708

Department/School

School of Natural Sciences

Publisher

Springer-Verlag Wien

Place of publication

Sachsenplatz 4-6, Po Box 89, Vienna, Austria, A-1201

Rights statement

Copyright 2020 Springer-Verlag GmbH Austria, part of Springer Nature

Repository Status

  • Restricted

Socio-economic Objectives

Mineral exploration not elsewhere classified; Expanding knowledge in the earth sciences

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