Orogenic disseminated gold in Phanerozoic fold belts: some examples

摘要

Orogenic gold mineralisation in Phanerozoic fold belts has generally been assumed to be confined entirely to quartz veins. These quartz veins, or 'lodes', commonly yield high gold grades but relatively low tonnages of ore. Furthermore, the ore typically exhibits erratic spatial distribution, creating difficulties in exploration and mining. Consequently, these deposits are traditionally regarded as generally suitable for only relatively small-scale underground mining. However, this 'lode-gold paradigm' has been challenged by the recognition of open-pit, bulk-mineable disseminated gold mineralisation in a number of Phanerozoic fold belts. Features of alteration, physico-chemical characteristics of the ore-bearing fluids and strong structural control in all of the studied occurrences point to a close genetic association with lode gold mineralisation. Thus, the two contrasting styles of mineralisation are both considered to be the products of orogenic gold emplacement in Phanerozoic fold belts.