Geochronology and mineral geochemistry of apatite and zircon in the Hutouya Skarn deposit, East Kunlun Mountains, NW China

Consistency between apatite and zircon petrochronology supports the robustness in fingerprinting igneous processes in porphyry systems. In this paper, we systematically investigate geochronology and mineral chemistry of apatite and zircon hosted in syenogranite and monzogranite intrusive rocks in the large Hutouya skarn-type Cu–Pb–Zn–Fe deposit, in order to corroborate their potential chronological monitoring capabilities in fingerprinting igneous processes in porphyry systems. Zircon grains of magmatic origin provide crystallization ages of 224.70 ± 0.61 Ma in the syenogranite and 225.75 ± 0.66 Ma / 226.31 ± 0.78 Ma in the monzogranite, respectively. Apatite yield ages of 229.0 ± 6.6 Ma in syenogranite and 224.3 ± 4.5 Ma / 223.7 ± 3.9 Ma in monzogranite and are within analytical uncertainty of ages displayed by zircon. Geochronology results suggest that the associated hydrothermal mineralization events at Hutouya probably have similar short durations of just a few million years or less. Trace element compositions in the two intrusives indicate the apatite and zircon crystallized under volatile-undersaturated conditions and have primary a magmatic origin. However, in the later volatile-oversaturated stage, the early crystallizing zircon is altered by the fluid phase, and shows distinctive amorphous textures with pores filled with numerous hydrothermal minerals. Accordingly, U–Pb dates of apatite and zircon, as well as corresponding in-situ trace element compositions, can provide constraints on rock formation ages, temperature, oxygen fugacity, magma source, and tectonic background.