Volatile Characteristics of Apatite in Dacite from the Eastern Manus Basin and Their Geological Implications

As one of the youngest back-arc basins, evolutionary behavior magmatic volatiles in Eastern Manus Basin has been poorly studied. Recently, apatite received widespread attention for its powerful function recording information on volatiles. In this paper, by determining major element compositions and primary volatile abundances (F, Cl, SO3) apatites dacite, we analyze before magma eruption Basin, as well their indications oxygen fugacity petrogenesis, so to improve study about evolution region. Experimental data indicate that saturation temperatures range from 935 952 °C. All are with F contents 0.87−1.39 wt.%, Cl 1.24−1.70 SO3 ≤ 0.06 wt.%. Analysis reveals crystallized volatile-undersaturated melts, chemical can be used indicators compositions. According calculations, minimum S concentrations host melts 2−65 ppm or 8−11 ppm. The crystallization separation magnetite caused reduction state relatively low (ΔFMQ = −0.2 ± 0.9) apatites. addition, melt were calculated 185−448 1059−1588 ppm, corresponding H2O 1.4−2.1% 1.2−1.5% (error 30−40%), respectively. high Cl/F ratio samples addition slab-derived fluids mantle source region Basin. High may influenced F-rich sediments, release lawsonite phengite decomposition. appears originate dual influence subduction-released Cl-rich seawater-derived components. Further, it is estimated 14−21% total added directly fluids, higher.