LAUSR

Abstract Apatites those shielded as inclusions in igneous minerals are avoided of diffusion effects associated with evolving melts and can record the original volatile and trace element evolutions of the magma. Volatile and trace element compositions of apatites enclosed in high-Al, medium-Al, low-Al amphibole, magmatic biotite, plagioclase, and groundmass from ores, quartz monzonite porphyry (QMP) and its mafic microgranular enclaves (MMEs), and pre-ore coarse-grained quartz diorite porphyry (CQD) were present to evaluate the magmatic processes in the formation of Pulang porphyry Cu-Au deposit. All apatite inclusions are magmatic fluorapatites and occur as early-crystallization phases (940 ∼ 980 ℃), followed by the crystallization sequence of high-Al amphibole, medium-Al amphibole, magmatic biotite, plagioclase, low-Al amphibole (altered medium-Al amphibole) with fluctuating ƒO2 conditions. Compared to the low SO3 ( Given that Sr/Y ratios (2.21 ∼ 3.62) of apatite at Pulang do not vary significantly with changing melt composition (Mg = 119.1 ∼ 528.8 ppm), the Sr/Y and Eu/Eu* ratios of apatite from QMP have confirmed a water-rich, oxidized magma origin, whereas the CQD are originated from a water-poor, reduced source. Besides, the hydrothermal alteration possibly accounts for the abnormally increased Ce/Ce* ratios of altered apatites from CQD and decreased Sr/Y ratios of the low-Al amphibole-hosted apatite from QMP. Therefore, using trace elements as indicators for petrogenetic studies would be more robust for those apatites enclosed in igneous minerals. Our studies demonstrate that apatite inclusions can be linked to discrete periods in the crystallization history of its host phases, thus providing insight into the magma evolution process.