Characteristics of Cold Seep Fluids at Subduction Zones

6 Characteristics of Cold Seep Fluids at Subduction Zones 

Ice-like gas hydrates (clathrates) also have been found at numerous sites along the convergent plate margins (e.g., Suess et al. 1997). Methane hydrates are stable in solid form only in a narrow temperature-pressure window (Dickens and Quinby-Hunt 1994 Fig. 14.3 in chapter 14). In theory, Im of methane hydrate can contain up to 164 m of methane gas at standard conditions (Kvenvolden 1993). It has been estimated that the amount of carbon in gas hydrates considerably exceeds the total of carbon occurring in all known oil, gas and coal deposits worldwide (Kvenvolden and McMenamin 1980 Kvenvolden 1988). This raises the possibility that gas hydrates may be a future energy source of global importance. 

A fluid sample collected at a mid-ocean ridge hydro-thermal vent has a temperature of 250°C and Mg concentration of 15 mmol/kg (Fig. 13.9). If the fluid contains 100 ppm Fe at 250°C, what is the likely eon-centration of Fe in the end-member fluid at 350°C  

A 100 m diameter sulfide deposit on the mid-ocean ridge has been drilled to a depth of 25 m. The metal concentrations of the sulfides recovered from the core are 2 wt.% Cu, 5 wt.% Zn, and 15 wt.% Fe, and the samples have a bulk density of 3 g/cml What is the total metal content of the deposit If the 

The average depth of the summit calderas along a submarine volcanic arc in the western Pacific Ocean is about 1000 m. What is the pressure at this depth What is the maximum temperature of a vent fluid discharging at 1000 m, assuming a composition similar to that of mid-ocean ridge vents What is the maximum temperature of vents at 500 m depth  

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