Metallogenic theory of 'Southeast Asia-Style' archipelagic arc-basin for the Sanjiang area, southwest China

摘要

Archipelagic arc-basin evolutional model for the transition between ocean and continent has been proposed on the basis of extensively studying of different tectonic settings including ocean, continent, island arc and continental margin in the world, and especially, a comparison between recent arc-basin system in Southeast Asia and geological contents in Qinghai-Tibet Plateau and adjacent area (Pan et al., 1997, 2003, 2004). A series of tectonic units related to subduction of oceanic lithosphere (such as frontal arcs, backarcs, volcanic arcs, oceanic ridges, island chains, seamounts, micro-continents, and corresponding backarc basins, intra-arc basins or marginal sea basins), are defined as an Archipelagic Arc-Basin tectonic system with specific configurations and temporal evolutional features. The Sanjiang area can be divided into three arc-basin systems related to subduction northwards (eastwards) of Tethyan Oceanic lithosphere, i. e., Yidun, Jinshajiang and Ta'niantaweng according to the theory of archipelagic arc-basin system. The theory suggests that large-scale metallogenic process will be occurred during the transition of tectonic regime between ocean and continent, being completed in the process of island arc orogenesis consisting of subduction of back-arc basin, arc-arc collision and arc-continent collision.