Mizuki Ishida

PhD Candidate

Graduate School of Engineering, the University of Tokyo

Mizuki Ishida is a PhD candidate in the Department of Systems Innovation, Graduate school of Engineering at the University of Tokyo in Japan, under the supervision of Professor Yasuhiro Kato. She earned her B.S. and M.S. degrees in natural resource engineering from the University of Tokyo in 2018 and 2020. She is interested in the factors controlling the mineralizing potential of various areas in Circum-Pacific, which is used in exploration targeting of undiscovered mineral resources. Her current research focuses on elucidating the metal sources of epithermal deposits using trace element and heavy-metal isotope analyses. She was awarded GSDM fellowship in 2018-2019, International Musha-Shugyo grant for short-term exchange at the University of Chile in 2019, the Dean’s award for outstanding graduate research from the department in 2020, and JSPS DC1 Research Fellowship for Young Scientists in 2020-2023.  

Auriferous pyrite formed by episodic fluid inputs in the Akeshi and Kasuga high deposits, Southern Kyushu, Japan.

Pyrite geochemistry has proven useful for tracking changes in the composition and physico chemical conditions of hydrothermal fluids in ore-- forming environments. Here, we investigated the microtextural features and chemical composition of pyrite, a main Aubearing phase in the Akeshi and Kasuga deposits (Southern Kyushu, Japan), to better constrain the ore processes in these high-- forming sulfidation epithermal Au deposits. Despite the widespread distribution of Aubearing pyrite in both deposits, no visible Au minerals coexist with pyrite. However, in situ laser ablation inductively coupled plasma mass spectrometry results show that Au concentrations in pyrite vary from below the detection limit to 41 ppm and are positively correlated with Cu ( r 0.4 ; up to 7400 ppm) and Bi concentrations ( = r and Au concentrations occur in small (< 25 = 0.44; up to 640 ppm). In both deposits, high Cu μ m) anhedral grains of pyrite, which are interpreted to have rapidly crystallized from the oreforming hydrothermal flui reprecipitation textures and thin, concentric, Cu d. In addition, dissolution–- larger (> 25 μ rich overgrowths were identified in a number of m) pyrite grains and aggregates. These abrupt changes in the trace element compositions of pyrite grains likely reco rd episodic metalrich fluid inputs. We also propose that gold adsorption onto growing pyrite surfaces played a key role in the mineralization of these deposits.