Abstract:

Ultra-mafic peridotite is  a new type of rock found in the Houxianyu district, Dashiqiao,eastern Liaoning, and named by authors based on molecular components of forsterit, a rock containing excess cations. Cation surplus results in formation of independent Mg-Fe oxides such as forsterit, humite, and magnetite, in ultra-mafic peridotite which occurs as granular and tabular, with the structures of breccia volcanic erupitive, cooled spinifix  pillow lava texture and massive liquation texture.The rock is of lamination with lower part being forsteit and upper part magnetitic humitite, with minor amount of pentlandite forming texture of iron-bearing sponge. Lithological study shows that it is a suit of Mg-rich basic  volcanic rock, equivalent to kamatitie, which provides a great volume of magnesium for the deposition of Mg-rich borate deposit.

Key words: Dashiqiao of eastern Liaoning, ultra-mafic peridotite, kamatitie, borate deposit