OXYGEN-ISOTOPE SYSTEMATICS OF EMERALD - RELEVANCE FOR ITS ORIGIN AND GEOLOGICAL SIGNIFICANCE

Oxygen isotopic composition of emerald from 62 occurrences and deposit s in the world reveals a wide range in delta(18)O (SMOW) between +6.2 and +24.7 parts per thousand,. The delta(18)O-values for each deposit are restricted and can be used to determine the origin of emerald from the world's most important producers. The delta(18)O-value of emerald appears to be a fingerprint of its origin, especially for gems of exc eptional quality from Colombia (eastern emerald zone, delta(18)O = +16 .8 +/- 0.1 parts per thousand; western emerald zone, delta(18)O = +21. 2 +/- 0.5 parts per thousand), Afghanistan (delta(18)O + 13.5 +/- 0.1 parts per thousand), Pakistan (Swat-Mingora districts, delta(18)O = 15.7 +/- 0.1 parts per thousand), Brazil (Santa Terezinha de Goias, de lta(18)O = + 12.2 +/- 0.1 parts per thousand; Quadrilatero Ferrifero, delta(18)O = + 6.9 +/- 0.4 parts per thousand) and Zimbabwe (Sandawana , delta(18)O = + 7.5 +/- 0.5 parts per thousand,). Furthermore, the O- 18-composition of emerald appears to be a good marker of its geologica l environment because the data suggest that host-rock-buffering of flu id delta(18)O is considerable during fluid-rock interaction.