Artículos de revistas
Auriferous pyrite formed by episodic fluid inputs in the Akeshi and Kasuga high-sulfidation deposits, Southern Kyushu, Japan
Fecha
2021Registro en:
Mineralium Deposita (2021)
10.1007/s00126-021-01053-4
Autor
Ishida, Mizuki
Romero, Rurik
Leisen, Mathieu
Yasukawa, Kazutaka
Nakamura, Kentaro
Barra Pantoja, Luis Fernando
Reich Morales, Martín Herbert
Kato, Yasuhiro
Institución
Resumen
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
Au-bearing phase in the Akeshi and Kasuga deposits (Southern Kyushu, Japan), to better constrain the ore-forming processes in
these high-sulfidation epithermal Au deposits. Despite the widespread distribution of Au-bearing 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 = 0.44; up to 640 ppm). In both deposits, high Cu and Au concentrations occur in
small (< 25 μm) anhedral grains of pyrite, which are interpreted to have rapidly crystallized from the ore-forming hydrothermal
fluid. In addition, dissolution–reprecipitation textures and thin, concentric, Cu-rich overgrowths were identified in a number of
larger (> 25 μm) pyrite grains and aggregates. These abrupt changes in the trace element compositions of pyrite grains likely
record episodic metal-rich fluid inputs. We also propose that gold adsorption onto growing pyrite surfaces played a key role in the
mineralization of these deposits.