Abstract:Five different types of amygdaloid complexes were found in vesicular basalt of Puge County, south Sichuan, mainly calcite amygdaloid complex and asphalt (bitumen) amygdaloid complex. The babingtonite amygdaloid complexes are spheroidal with 5~8 mm in diameter. A commonly recognized mineral sequence of the amygdaloid complex from the wall inward is quartz→brunsvigite→babingtonite. The babingtonite crystals are black and lamellar, and are composed of five pinacoids. X-ray micro-diffraction measurements indicate that babingtonite is triclinic, with space group P. Chemical composition analyses show that babingtonite has the following data: SiO2 53.55%, CaO 18.84%, Fe2O3 13.65%, FeO 9.68%, MgO 1.44%, H2O+ 1.74%, and FeO/Fe2O3=0.709, whereas brunsvigite has the data SiO2 33.17%, Al2O3 13.03%, Fe2O3 8.45%, FeO 13.06%, MgO 18.82%, H2O+ 12.12%, CaO 0.87%,and FeO/ Fe2O3=1.55. The evolution of mineral associations in babingtonite amygdaloid complexes suggests that the ore-forming fluids at the late stage converted from Mg- and Fe-rich fluids to Si- and Ca-rich fluids. Babingtonite crystallized in a transitional environment from meta-acid and weak reduction to meta-alkaline and weak oxidation.