Decrepitation in gold exploration. A case history from the Cotan prospect, N.T.

Abstract

The decrepitation method is capable of providing information on the abundance of CO 2-rich fluid inclusions in quartz samples by the observation of decrepitation at abnormally low temperatures (below 350°C). The method has been used in extensive regional and detailed studies in the Pine Creek goldfields, where a correlation between Au mineralisation and CO 2 content was observed by comparing analyses of samples from several existing operating mines with various other quartz samples from unmineralised areas throughout the region. An area of interest, defined by the regional scale sampling, was subjected to detailed study and this work delineated an anomalous zone with high CO 2 content which is closely related to a zone of low-level anomalous Au contents in quartz samples. The quartz shows highly variable decrepitation (and consequent CO 2 contents) over small distances, due to the presence of growth zoning and multiple stages of quartz emplacement, as is typical of a high level depositional environment.