Geochronology, geochemistry and implications of Au-mineralized porphyries in the Linzhou basin, Gangdese belt, Tibet

Abstract

The Linzhou porphyry bodies are distributed within or along the edge of Linzhou basin, which is located to the south of Namling-Luobadui-Milashan fault in the central Gangdese magmatic arc. The porphyry bodies can be divided into two groups including the early intruded the Sexing Formation, the Dianzhong Formation and the late intruded the upper Linzizong volcanic successions. The single zircon from the early porphyry body (Hutouya) yielded a restrictedly concordant weighted mean 206Pb/238U age of 58.7±1.1 Ma (2σ) and is ascribed to the collisional stage porphyries when India collided with Asia. The early porphyries are geochemically similar to Linzizong volcanic rocks, and are interpreted to the predominately remelting of crustal components, and to a lesser extent, the contributions from subducted oceanic crust were also involved in their generation. The early porphyries with Au mineralization at collisional stage indicate that the collisional stage intrusives (60-50 Ma) in the Gangdese have potential for gold.