GEOLOGICAL CHARACTERISTICS OF THE XUJIATUN GIGANTIC PILLOW LAVA IN YIXIAN COUNTY, WESTERN LIAONING PROVINCE

The Xujiatun gigantic pillow lava in Yixian County of Western Liaoning occurs in the sedimentary interbed of volcanic rocks, which belong to the second subcycle of Yixian cycle. The gigantic pillow lava, characterized by huge pillow bodies (5 to 8 m) and diverse shapes, constitutes a distinctive landscape of volcanic rocks. Each pillow body is generally composed of three parts, i. e. chilled border, transitional belt and core, which distinguish each other in their colors, quantity and size of vesicles and amygdales. Belonging to basaltic andesite, the pillow lava could be petrologically and geochemically compared with the underlying volcanic rocks. The pillow lava was formed as a result of condensation of magma in lake, when it effused again during the intermittent of volcanic activity in the second subcycle. It belongs to continental volcanic rock, which is obviously different from marine basaltic pillow lava.