The global distribution of zinc mineralisation,an analysis based on a new zinc deposits database

Abstract

This paper presents an analysis of the Global Mineral Occurrences Database (GMOD), a zinc deposits database built by Pasminco Australia Ltd to cover zinc mineral occurrences over the entire globe. The database contains over 14 000 records of which 1700 contain resources information. A resource is taken as the total in-ground resource, including past production and current resources. An economic resource classification has been applied to all deposits with resources which divides them into four categories, high grade zinc deposits, low grade zinc deposits, deposits where Cu–Au is economically more significant than Zn–Pb–Ag and minimum grade zinc deposits. Analysis of the data shows that the total world endowment of zinc metal, defined in resources, is over 881 Mt. North America has the greatest endowment of zinc metal and the most deposits. Africa has the least. Canada, the US, China and Australia are the best endowed countries with Australia having larger and higher grade deposits. The Palaeoproterozoic and the Upper Palaeozoic were together the two greatest zinc producing periods in earth history accounting for 41% of global zinc metal. VHMS deposits are the most numerous ore deposit type, totalling 38% of all deposits in the world with zinc. By comparison, shale-hosted deposits are not numerous but are large and high grade, hosting over 18% of the world's zinc. Zinc oxide deposits (both primary and secondary) host less than 4.5% of the world's zinc. Carbonatehosted deposits of the MVT class provide the highest grade and cleanest (low iron) zinc sulphide concentrates, but include some of the lowest grade zinc deposits and also those with the lowest silver values. Analysis of contained metal and the grade of zinc deposits show that four deposit classes are potentially ‘superior’ from an economic perspective. These are shale-hosted, Irish-type carbonate-hosted, intrusionrelated mantos and Broken Hill type deposits. Together these four classes account for 32% of the world's zinc metal in only 108 deposits or 12% of deposits with resources. Because zinc oxide deposits represent such a small proportion of the world's zinc, future exploration will still have to focus on zinc sulphide deposits and with a significant emphasis on the Palaeoproterozoic and Upper Palaeozoic terranes that have already provided a high proportion of the worlds best zinc deposits.