Study of ore-forming theoretical innovation and prospecting breakthrough of magmatic copper–nickel–cobalt sulfide deposits in China

Chinese magmatic copper–nickel–cobalt sulfide deposit is the main source of strategic key metal resources, such as nickel, cobalt and platinum group elements in China, and it is an important deposit type with a future value that needs special attention. This type of deposit comes from the mafic and ultramafic magma formed by the upper mantle, especially the asthenosphere, and the immiscible (liquation) action between sulfide liquid–silicate melt is the main mineralization mechanism. They are mainly formed in two geological settings: the continental rift and the extended environment in the orogenic zone. China is a major producer of magmatic copper–nickel–cobalt sulfide deposits, but compared with the world it is relatively unique. Most magmatic copper–nickel–cobalt sulfide deposits in the world are formed in the ancient craton, and are the result of the mantle plume geodynamics. Archeozoic–early Proterozoic komatiite nickel–cobalt sulfide deposits is a distinct metallogenic characteristics. Ancient komatiite-related nickel–cobalt sulfide deposits have been rarely discovered in China, and their mineralization age is relatively late, mainly in the Neoproterozoic, Early and Late Paleozoic. The Neoproterozoic is represented by the Jinchuan super-large deposit with nickel metal reserves ranked the third in the world, and the Early Paleozoic by the Xiarihamu super-large deposit discovered in the prospecting breakthrough of recent years. The Xiarihamu deposit is also the only super-large magmatic copper–nickel–cobalt sulfide deposit found in the Tethys orogenic belt in the world. Mineralization theory of “big magma–deep immiscibility–injection” and “forming big ore deposits in small intrusive rocks” proposed by Chinese scholars based on China’s prospecting practice has been widely accepted and applied by field geological exploration workers, and has made important prospecting breakthrough discoveries. At the same time, it has been recognized by foreign peers, which changed the traditional metallogenic understanding of magma copper–nickel–cobalt sulfide deposits. The extensive distribution of magmatic copper–nickel–cobalt sulfide deposits in orogenic belts is an important feature of such deposits in China. According to the different evolution of orogenic zones and metallogenic history, it can be divided into two important types: Tethys type and Central Asian type. The Tethys type is represented by the Xiarihamu ore deposit, and it is the product of the Tethys structural transformation, which the Paleo-Tethys cracking after the Proto-Tethys orogeny; the Central Asian type is represented by a large number of the early Permian of the Late Palaeozoic magmatic copper–nickel–cobalt sulfide deposits distributed in the Eastern Tianshan–Beishan and Altai zones of the Central Asian Orogenic belt, which is the result of the dual geodynamics mechanism of plate tectonics and mantle plume. China's magmatic copper–nickel–cobalt sulfide deposit has huge prospecting potential, and the Jinchuan deposit as a result of nappe structure from deep horizontal “sill” thrusted to the surface of the inclined “dyke”, it still has significant prospecting potential in its deep and marginal locations, in which important new ore bodies have been found at both ends of the ore-bearing rock body; more than 10 new ore deposits (points) have been found in East Kunlun and its adjacent areas, where the Xiarihamu deposit is located. In the region, the southeastern margin of Tarim Landmass, the northern margin of Tarim Landmass, the western margin of Yangtze Landmass and the northeast margin of North China Landmass are the exploration prospect areas to strengthen prospecting, while the northern margins of Yangzi Landmass and North China land block are the new prospecting areas for urgent investigation.