The concentrations of methane and hydrogen in hydrothermal vent fluids issuing from mid-ocean ridges tend to fall into two groups, one with high concentrations of these gases in ultramafic-hosted vent fields and a second group with relatively lower concentrations in basalt-hosted vent fluids. Ultramafic-hosted systems, however, appear to be restricted to slow-spreading ridges and constitute only a fraction of the hydrothermal systems found there. In this note, the hydrothermal fluxes of methane and hydrogen have been calculated by estimating the percentages of the total subsurface hydrothermal circulation that circulate through each type of host rock. Even though the percentage of the total subsurface flow that is affected by serpentinization appears to be rather small (8%), it still appears that this process produces about 70% of the total mid-ocean flux of these gases. The total production of methane and hydrogen is calculated to be about 20 x 10(9) mol yr(-1) and 190 x 10(9) mol yr(-1), respectively. The hydrogen flux is comparable to that most recently calculated on the basis of the rate of hydration of mantle rock in newly formed crust and the stoichiometry of the serpentinization reaction. This suggests that, except for the production of methane, a major portion of the hydrogen produced in the subsurface is not consumed before venting.
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机译：从洋中脊喷出的热液喷出液中的甲烷和氢的浓度倾向于分为两组，一组在超镁铁质喷出液中的这些气体浓度高，另一组在玄武岩喷出液中的浓度相对较低。 。然而，超镁铁质宿主系统似乎仅限于缓慢扩散的山脊，仅占那里发现的热液系统的一小部分。在本文中，甲烷和氢气的水热通量是通过估算在每种类型的岩体中循环的地下总热液循环的百分比来计算的。尽管受蛇纹石化影响的地下总流量的百分比似乎很小（8％），但似乎该过程仍产生了这些气体总中洋通量的约70％。甲烷和氢气的总产量经计算分别约为20 x 10（9）mol yr（-1）和190 x 10（9）mol yr（-1）。根据新形成的地壳中地幔岩石的水合速率和蛇化反应的化学计量，氢通量与最近计算的氢通量相当。这表明，除了甲烷的产生外，地下的大部分氢气在排放前没有被消耗掉。
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