Publikationsdatum:
2017-07-28
Beschreibung:
Emerald from the Binntal occurrence in the Canton of Valais in Switzerland has been studied to determine its chemical zonation, stable isotopic signatures, depositional-fluid characteristics, pressure-temperature emplacement conditions, and formational model. The emerald is vanadium-rich, with optical and blue cathodoluminescence zoning related to chemical variations, primarily in V 2 O 3 concentrations. The hydrogen isotope signature of the emerald channel fluids is unique and in agreement with previously identified high-altitude (deuterium-depleted) Alpine-age meteoric fluids. Field studies, fluid inclusion analyses, and oxygen isotope thermometry are consistent with a metamorphic formational model for the Binntal emerald at temperatures and hydrostatic pressures ranging from 200 to 400 °C and 100 to 250 Mpa, respectively. This corresponds to formational depths on the order of 4 to 9 km and fluids consistent with a 10–20 Ma CO 2 -dominant fluid with approximate mole percentages of 84.0, 11.9, 1.5, 1.3, 0.3, and 0.5 for CO 2 , H 2 O, CH 4 , N 2 , H 2 S, and NaCl, respectively.
Print ISSN:
0008-4476
Thema:
Geologie und Paläontologie
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