Holocene volcanism in central Mongolia and Northeast China: Asynchronous decompressional and fluid melting of the mantle

Volcanic eruptions in central Mongolia during the latest Pleistocene and Holocene time preceded an initial Holocene volcanic event of 8740 ± 400 years ago in Northeast China and terminated simultaneously with that event as inferred from 14 C datings. Alkali basaltoid magmatic material from a partially melted (1.5- 3%) mantle source was erupted in the Taryat Basin of central Mongolia, at first along a nearly east-west line of volcanoes, and afterwards material of higher melting (up to 5%) was discharged along the north-northeast line of Khorgo edifices. A material of similar composition was erupted in the Jingpohu area, Northeast China during the period from 5430-4400 BP. Initial liquids of ~2% beneath the Frog Pool volcanic center and ~5% beneath Crater Forest were expressed varying liquids beneath the latter area, yielding final melts of ~5%. The action of the decompressional and the fluid mechanism was followed by in eruptions of, respectively, isotope-homoge- neous magmas in central Mongolia and isotope-heterogeneous magmas depleted in high field strength elements (Nb, Ta, Ti) in Northeast China.