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Progress in Earth and Planetary Science
Fig. 6 | Progress in Earth and Planetary Science

Fig. 6

From: Sr isotopic ratios of hydrothermal fluids from the Okinawa Trough and the implications of variation in fluid–sediment interactions

Fig. 6

Schematic diagram showing two types of hydrothermal circulation in the Okinawa Trough (modified after Kawagucci 2015). Arrows indicate hydrothermal fluid circulation, with color representing the temperature of hydrothermal fluid. a Hydrothermal circulation in contact with sediments at high temperatures and volcanic rocks at moderate temperatures (> 150 °C). Fluid is in contact with sediments at high temperatures, and the sediments supply Sr (e.g., Yonaguni Knoll IV). b Hydrothermal circulation in contact with sediments at low temperatures and volcanic rocks at high temperatures. Sr from volcanic rocks is supplied to hydrothermal fluids (e.g., Iheya North Knoll and Hatoma Knoll). Thus, CH4 is provided by thermogenic CH4 at high temperatures (a) and microbial sources at low temperatures (b)

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