The Dariganga volcanic field, located in SE Mongolia near the China border, consists of more than 200 lava and cinder cones of Pleistocene and Holocene age erupted from NE-trending parallel fissures. The cones range in height from 25 to 300 m, and vary from partially eroded to completely preserved. Compositionally they are more soda-rich than the potassium-rich rocks of northern and central Mongolia and consist of basaltic, trachybasaltic, and foiditic rocks. The southern part of the volcanic field, which may be contiguous with the Dolon Nor volcanic field across the border in China, is rich in ultramafic xenoliths.