摘要
The ~1.74 Ga Damiao massif-type anorthosite complex in the northern margin of the North China Craton hosts a large Fe-Ti-P oxide deposit. Volatiles that were trapped in magnetite, apatite and plagioclase of massive Fe-Ti ore, massive Fe-Ti-P ore and disseminated ore were measured by step heating mass spectrometer at three releasing temperature intervals 200~400 ℃, 400~800 ℃ and 800~1 200 ℃ to obtain major components and C-H-O isotopic composition. It is proposed that the parental magma from which the Damiao anorthosite complex formed may have fractionated under a relatively reduced condition at the beginning. The mantle fluids and surface water may have been involved in the later stage of the magma fractionation and fractioned to increase the oxygen fugacity of the magmas, which in turn, triggered the accumulation of magnetite and apatite to form the Damiao Fe-Ti-P oxide deposit.