Genesis of potassic minerals in the Xiaogulihe-Keluo-Wudalianchi-Erkeshan volcanic rock belt,Northeast China and their geological implications

Xiaogulihe-Keluo-Wudalianchi-Erkeshan potassic volcanic rock belt in Northeast China,one of the well preserved volcanic clusters in China,was characterized by the high contents of potassium,alkali and high K2O/Na2O ratios(1.2) in the rocks and was attributed to high potassium peralkaline volcanic rocks,Based on the research relating compositions,crystallization conditions of potassic minerals(phlogopites,leucites) in hosted volcanic rocks and mantle peridotite xenoliths with magma component and its source,the authors suggested that lithospheric extension in the studied region was responsible for low-degree decompression melting of phlogopite-bearing peridotites in the mantle and the potassic magma experienced leucites crystallization in shallow crust,As magma evolved,the magma tended to be Na-rich and xenomorphic nepheline and sodalite occurred in matrix glass resulting from the crystallization of lots of potassic minerals,The volatile-rich minerals as phlogopite,leucite,aptite,nepheline and sodalite in volcanic rocks and mantle xenoliths also provided the evidence of high abundance of H2O,F,Cl and P in the magma.