Abstract

Quartz from the No. 6 vein of the Lamaque gold mine, Bourlamaque, Quebec, decrepitates when heated, beginning at 80 degrees to 124 degrees C. The measured decrepitation temperatures, when plotted in the plane of the vein, can be contoured in a simple manner. The lower values are near the central part of the vein, where it crosses the principal granodiorite-greenstone contact, and the higher values are around the outer limits of ore in the vein. High grade ore specimens have a relatively rapid rate of decrepitation, low grade specimens have a relatively slow rate. Making the assumptions that the measured decrepitation is due to filling of secondary liquid inclusions trapped during the stage of gold deposition, and that the measured variation of decrepitation is due to variation of pressure during that stage, the contoured data are taken to mean that the later gold-bearing solutions entered the quartz vein at the principal wall rock contact and moved up and down the dip, depositing gold during, and possibly due to, the drop in pressure.

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