Late Cenozoic intra-plate basalts of the Greater Khingan Range in NE China and Khangai Province in Central Mongolia

Abstract

This paper presents new major and trace element data, Sr-Nd-Pb isotopic ratios and K-Ar ages from volcanic rocks of the Greater Khingan Range of NE China (Nuomin–Keluo and Arxan–Chaihe volcanic fields) and the Khangai volcanic province of Central Mongolia. These data are discussed in correlation with available in literature geological, geochronological, geochemical, isotopic, petrologic and geophysical data from intra-plate volcanic fields of Central and East Asia. All volcanic rocks possess geochemical affinities to intra-plate oceanic and continental basalts. The Nuomin-Keluo samples (2.75 and 0.41 Ma) show enrichment in large ion lithophile elements (LILE) and light rare earth elements (LREE; La/YbN = 43.6–91.5), as well as depletion in heavy REE (HREE), and Nb peaks relative to La and Th (Nb/Lapm = 0.61–1.24; Nb/Thpm = 0.96–1.70) in the multi-element spectra. The Arxan-Chaihe basalts (0.91 and 0.53–0.27 Ma) have lower K, less fractionated REE (La/YbN = 15.7–28.1), but higher Nb peaks (Nb/Lapm = 1.56–1.74; Nb/Thpm = 1.27–1.79), as well as higher epsilon Nd and 206Pb/204Pb, but lower Sr isotopic ratios. The Khangai volcanic province consists of central and peripheral areas, which are dominated by low–alkali and high–alkali varieties, respectively. The central Khangai have lower LREEs and LILEs, and lower Gd/YbN ratios compared to the peripheral Khangai. In the 143Nd/144Nd vs. 87Sr/86Sr diagram, the Nuomin-Keluo and Khangai samples plot close to EM1, whereas the Arxan-Chaihe samples possess less enriched compositions. In Pb isotope diagrams, the Nuomin-Keluo and peripheral Khangai samples plot between DM and EM1, whereas the Arxan-Chaihe and central Khangai samples plot near PREMA. Geochemistry-based melting modeling indicates that all the volcanic rocks were derived from garnet-bearing, probably enriched, mantle sources melted at variable degrees Based on the whole set of new and previous data we suggest that the Great Khingan and Khangai volcanic rocks were probably produced by hydrous mantle plumes generated in the MTZ and ascending from the subducted Pacific slab stored therein. In general, the late Cenozoic intra-plate volcanism in Central and East Asia can be triggered by the material, which has accumulated beneath the Asian continent and metasomatized the mantle underneath since the amalgamation of Laurasia and formation of the Central Asian Orogenic Belt at ca. 300–250 Ma.