Geology and discovery of porphyry copper deposits / Геология и открытие медно-порфировых месторождений

Porphyry-type deposits range from Sn or W-(Mo), through Mo with negligible Cu, to Cu deposits with variably associated Au and/or Mo (Seedorff et al., 2005). Most deposits occur in provinces that are associated with Phanerozoic orogenic belts related to convergent plate boundaries (Fig. 1.1). Within this broad deposit-type the focus of this book is on deposits that are mined primarily for Cu and that may contain by-product Au and/or Mo. I will refer to these as porphyry copper deposits, although various attempts have been made to classify them into subtypes (see Section 1.3). I am further restricting my coverage to deposits that are associated with quartz-saturated high-K to medium-K calc-alkalic intrusions. These represent the bulk of economic deposits being mined today. I exclude the silica undersaturated syenitic porphyry Cu-Au deposits because of their limited distribution and small size (see Jensen and Barton, 2000, for a review).

Porphyry copper deposits supply 75% of the world’s Cu, 50% of the Mo, 20% of the Au, most of the Re, and minor Ag, Pd, Te, Se, Bi, Zn, and Pb (Sillitoe, 2010a). Of the world’s 21 largest deposits in terms of contained copper metal, 14 are porphyry copper deposits, six are sediment-hosted copper, and one is an “IOCG” (Olympic Dam) (Sillitoe, 2012). One district (Escondida in Chile) produced 9.5% of the world’s copper in 2007. Porphyry Cu and related skarn deposits in the Grasberg-Ertsberg district contain the world’s second largest concentration of gold. All of these factors explain why porphyry copper deposits are primary exploration targets worldwide. As exploration geologists we need to be familiar with the common features of porphyry copper deposits and what they look like in the fi eld. This is the main focus of this book. <...>