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Abstract

A formal classification of the textures of vein quartz has been developed for the gold deposits of North Queensland. It is based on the macroscopic appearance of quartz and discriminates primary growth textures or initial vein fill from superimposed or overprinting textures.

The relative proportions of quartz texture classes in over 200 deposits has been used to define four textural associations which correlate with four gold-mineralizing environments. Quartz veins in the epithermal environment are characterized by multiple generations of chalcedonic, microcrystalline, and comb-textured quartz disposed as crustiform and colloform bands and cockade overgrowths. Porphyry vein quartz is dominated by simple comb textures. Plutonic vein quartz is dominated by euhedral buck and coarse comb textures with common but poorly developed superimposed textures. Slate belt vein quartz is dominated by anhedral buck quartz with well-developed ribbon, stylolite, and spider veinlet superimposed textures. Different deposit styles within each environment, for example, skarns and stockworks in the porphyry environment, have the same quartz texture. As quartz typically deposits through the life of a hydrothermal system, the paragenesis and zoning of quartz textures reflect the overall structural and fluid evolution of the system.

In each environment, gold is associated with specific quartz textural classes. In epithermal veins it is typically in the most complexly overprinted quartz; in porphyry veins it is interstitial to fine comb quartz; in plutonic and slate belt veins it is in superimposed ribbons, fractures, veinlets, and stylolites. Mapping the distribution of quartz textures and recognizing the gold texture associations aids ore shoot definition.

The classification scheme is applicable outside North Queensland and may be adapted to other types of vein deposits. It facilitates comparison between veins, is a useful indicator of the conditions of vein formation, and aids the discrimination of gold-bearing and gold-barren quartz.

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