Gold Grade and Tonnage Models of the Gold Deposits, China

Abstract

Abstract: The gold grade and tonnage modelling is applied to some types of the gold deposits in China, including placer, Archaean lode, slate belt, Carlin, volcanogenic, skarn and Shandong Peninsula, among others. The Shandong Peninsula type denotes the gold deposit, which was formed in an intensely reshaped Archaean greenstone belt. The modelling results show: (1) the Archaean lode gold deposits of China are similar to the Homestake type in gold grades. (2) The Chinese slate belt type gold deposits are marked by moderately lower gold grades but considerably larger ore volumes than the similar type elsewhere. (3) The Carlin style gold deposits of China are identified by higher Au grades but evidently smaller sizes in comparison with their counterparts in western North America. (4) The volcanogenic (continental) style is similar to Sado epithermal veins in gold grade-tonnage models and general characteristics while volcanogenic gold deposits of the oceanic subgroup contrast with Kuroko-type deposits in the gold grade model. But the Chinese volcanogenic (oceanic) subtype (Palaeozoic age) shows similar higher gold grades to those of the Palaeozoic Kuroko-type deposits elsewhere. (5) Porphyry and skarn gold deposits tend to have a large size but low grade. (6) Less than half of the Shandong Peninsula gold deposits are of ore volumes exceeding the 50th intercept of the relevant gold tonnage model, implying possible undiscovered gold deposits with a larger size in the peninsula. (7) In general, Chinese gold deposits of larger sizes tend to have lower gold grades in relation to gold grade models. (8) Gold grade-tonnage models can be effectively influenced by how to include or exclude non-economic gold resources in the modelling. Ore volumes of gold deposits actually to some extent depend on gold grades. Consequently, the way of including or excluding low-grade values may effect a gold grade-tonnage model and cause different interpretation of the modelling results. This is particularly true to the gold deposits, which generally show an inverse correlation between gold grade and tonnage.