149 / 2015-09-08 09:06:37

Magmatism and mineralization comparison among the Siberian, Emeishan and Tarim Permian Large Igneous Provinces in Asia

Magmatic evolution, mineralization, comparison, Permian, Siberian, Tarim and Emeishan LIPs

Siberian, Emeishan and Tarim are three important Early Permian Large Igneous Provinces (LIPs) on the present Eurasian Plate. The Siberian LIP (or the Siberian Traps) in Russia, occurred at 250 Ma during a period of less than 2 Ma, extending over an area of up to 7×106 km2. The Emeishan LIP in SW China, was emplaced close to 260 Ma and exposed in an area of 2.5 × 105 km2. The Tarim LIP in NW China covers an area of more than 2.5 × 105 km2 and has a relatively longer lifespan (from 300 Ma to 280 Ma) than the Siberian and Emeishan LIPs. All of the three LIPs are featured with voluminous continental flood basalts (CFBs) and other spatially and temporally related rocks of different composition and origin (e.g., picrites, ultramafic–mafic dikes and intrusions, syenites, alkali granite). As the predominant rock type, The CFBs in the three LIPs exhibit different geochemical characteristics. Basalts in the Emeishan LIP can be grouped into low-Ti (Ti/Y < 500) and high-Ti (Ti/Y > 500) series, of which the low-Ti series seems to be generated from the enriched continental lithospheric mantle while the high-Ti series are more likely to be from a mantle plume. Similarly, the primary magmas of the Siberian LIP basalts can also be divided into the high-Ti primary plume melts and contaminated low-Ti melts. In the Tarim LIP, however, only high-Ti basalts are found so far and they are more likely to be generated from the sub-continental lithospheric mantle (SCLM) rather than the mantle plume. Several important lines of evidence indicate that all the three LIPs are related to the mantle plume, including the presence of picrites, pre-plume eruption crustal uplift, radial distributed dikes and high potential temperature (1300°C or higher) in the magma source. It is proposed by many authors that both the Siberian and Emeishan LIPs have close relationship with the end-Permian and mass extinction, whereas the Tarim LIP seems to be irrelevant with any mass extinction event due to its relatively long lifespan. The three Early Permian LIPs also share similar mineral systems, enriched in magmatic ore deposits. The Emeishan LIP possesses both Fe-Ti oxide deposits (e.g., Panzhihua) and Cu-Ni-PGE sulfide deposits (e.g., Baimazhai). The Siberian LIP is well known for its world-class Noril'sk–Talnakh Ni–Cu–PGE deposits. So far, only a giant Fe-Ti oxide deposit (Bachu deposit) was found in Tarim, but there are numerous Cu-Ni-PGE sulfide deposits along the East Tianshan area, which may be related to the Tarim LIP. Although lots of studies have been taken in the three Early Permian LIPs, there are still many unknown on their genesis and other aspects. A systematic comparison of the three LIPs will help better understand the genesis of continental LIPs and their genetic relation with the mantle plume.