Ophiolites in China: their distribution, ages and tectonic settings

Abstract

Abstract Ophiolites are widespread and abundant in China, where they lie along suture zones delineating major tectonic blocks. They range in age from Proterozoic to Tertiary and generally belong to the Palaeo-Asian, Qinling-Qilian-Kunlun, Tethyan and Circum-Pacific systems. A few possible Proterozoic ophiolites may reflect rifting of Rodinia at c. 800–1000 Ma. The Palaeo-Asian ophiolites, which range in age from Cambrian to Carboniferous, crop out abundantly in the northern parts of the country whereas the Qinling-Qilian-Kunlun ophiolites occur in north-central China, along the boundaries of the Tarim, North China and Yangtze blocks. Tethyan ophiolites are confined to southwestern China and Tibet whereas those of the Circum-Pacific belt are found in Taiwan and northeastern China. Chinese ophiolites are typically tectonically disrupted mélanges composed of isolated blocks of peridotite, gabbro and basalt. Sheeted dykes are rare or absent. Many of the ophiolites are compositionally complex, containing mixtures of island-arc tholeiite and boninite with lesser amounts of mid-ocean ridge basalt and ocean-island basalt. Most show evidence of having been formed or assembled in suprasubduction zone environments. However, Palaeo-Tethyan ophiolites generally lack suprasubduction zone signatures and may have formed in small, intracontinental basins. A rapidly expanding database of high-precision age dates and detailed geochemical analyses on Chinese ophiolites is providing new insight into the nature and timing of the tectonic events that shaped this part of Asia.