Formation of highly Zn-enriched sulfide scale at a deep-sea artificial hydrothermal vent, Iheya-North Knoll, Okinawa Trough

Tatsuo Nozaki, Toshiro Nagase, Junji Torimoto, Yutaro Takaya, Jun ichiro Ishibashi, Kazuhiko Shimada, Masayuki Watanabe, Yuka Masaki, Koichi Iijima, Kazuya Kitada, Masafumi Saitoh, Takahiro Yokoyama, Keita Akiyama, Noriaki Sakurai, Tomokazu Saruhashi, Masanori Kyo, Hidenori Kumagai, Lena Maeda

研究成果: Article査読

抄録

Artificial hydrothermal vents, created by boreholes that discharge hydrothermal fluids and useful for observing secular changes in mineral precipitates and the chemical compositions of hydrothermal fluids, are periodically cleaned of scale deposits. Here, we report petrographic and geochemical features of hydrothermal scale with a concentric structure and extreme enrichment in Zn, recovered as an intact plug from an artificial hydrothermal vent pipe in the Okinawa Trough. The scale consists of sphalerite with accessory galena and chalcopyrite, and minor cotunnite (PbCl2), barite, an unidentified Zn sulfate, and Bi-rich minerals. It comprises at least five concentric layers alternating between thin, reddish-brown porous layers composed of relatively Fe-rich sphalerite accompanied by galena and chalcopyrite, and coarse-grained, dark gray layers dominated by relatively Fe-poor sphalerite. Cotunnite occurs only in the innermost reddish-brown layer, and barite occurs only in the uppermost and innermost layers. The scale is composed of > 50 wt% Zn, several wt% Fe and Pb, and < 1 wt% Cu, Mn, and Cd, a composition consistent with the solubility of Zn and Cu in a hydrothermal fluid at 304–311 °C and pH 4.7–5.0. We suggest that the concentric layers are related to periodic scale removal operations through which (1) mostly clogged pipe conditions and weak hydrothermal discharge alternate with (2) fully open pipe conditions and vigorous hydrothermal discharge, thus affecting sulfur fugacity and [Cl] and [SO42−] activities in the hydrothermal fluid and leading to the formation of concentric layers of precipitated minerals.

本文言語English
ページ(範囲)975-990
ページ数16
ジャーナルMineralium Deposita
56
5
DOI
出版ステータスPublished - 2021 6

ASJC Scopus subject areas

  • 地球物理学
  • 地球化学および岩石学
  • 経済地質学

フィンガープリント

「Formation of highly Zn-enriched sulfide scale at a deep-sea artificial hydrothermal vent, Iheya-North Knoll, Okinawa Trough」の研究トピックを掘り下げます。これらがまとまってユニークなフィンガープリントを構成します。

引用スタイル