During the fluid's ascent, the temperature decreases; consequently, the high salinity fluid precipitates minerals.
As a consequence of degassing of geothermal fluids (depressurization during ascent) and the cooling of the fluid, measured pH can strongly differ from in situ values affecting calculated multicomponent geothermometer temperatures.
Specimens of serpentinite collected from tectonically emplaced serpentinite blocks along the SAFS show mineralogical and structural evidence of high fluid pressures during ascent from depth.
Since the absolute concentrations of 3He in AOC, oceanic sediment, and ASW are four to six orders of magnitude lower than those in MORB (Zelenski et al. 2012), the high 3He/4He ratios found in the Arima hot springs are attributed to mantle helium incorporated in the fluid upon its ascent in the mantle.
Unfavorably, the determination of dissolved aluminum in geothermal fluids is often interfered by secondary processes during ascent of fluids (precipitation), sampling and sample handling (e.g., coagulant for silica gel formation and incorporation) in the laboratory (Brown 2013).
During ascent, aqueous fluids are also partly used for forming hydrated minerals (Peacock 1993).
In contrast, the fluids supplied to the Oomine Ridge contain CH4 of microbial origin from the shallow sediments through which the fluids passed during their ascent to the seafloor.
The ascent of fluids could induce the seismic burst events near the Da-you-ken-Cing-tian-gang area as shown in Figure 6 (Konstantinou et al. [2007]).
Anticipated processes are the dilution with superficial water during ascent of fluids, the deviation of measured pH from in situ pH (due to degassing and as a function of temperature), as well as the uncertainties of aluminum concentrations (due to precipitations, sampling, sample storage and measurement errors).
The presence of low-temperature forms of serpentine: chrysotile and lizardite, in such serpentinite bodies is considered geologic evidence that these minerals crystallized from solute-laden aqueous fluids that accompanied the ascent of these serpentinites from the serpentinite wedge through depths corresponding to the seismogenic zone of the SAFS.
