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Origin of Massive Methane Reservoir Identified

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49 minutes ago, Meredith Poor said:

.... “Identifying an abiotic source of deep-sea methane has been a problem that we’ve been wrestling with for many years,” says Jeffrey Seewald a senior scientist at WHOI who studies geochemistry in hydrothermal systems and is one of the study’s authors. 

Of 160 rock samples analyzed from across the world’s oceans, almost all contained pockets of methane.  These oceanic deposits make up a reservoir exceeding the amount of methane in Earth’s atmosphere before industrialization, estimates Frieder Klein, a marine geologist at WHOI and lead author of the study. 

“We were totally surprised to find this massive pool of abiotic methane in the oceanic crust and mantle,” Klein says.

The scientists analyzed rocks using Raman spectroscopy, a laser-based microscope that allows them to identify fluids and minerals in a thin slice of rock. Nearly every sample contained an assemblage of minerals and gases that form when seawater, moving through the deep oceanic crust, is trapped in magma-hot olivine.  As the mineral cools, the water trapped inside undergoes a chemical reaction, a process called serpentinization that forms hydrogen and methane. The authors demonstrate that in otherwise inhospitable environments, just two ingredients⁠—water and olivine⁠—can form methane. 

“Here’s a source of chemical energy that’s being created by geology,” says Seewald.  ...

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(edited)

A very small contributor.

https://en.wikipedia.org/wiki/Serpentinite

 

In the presence of carbon dioxide, however, serpentinitization may form either magnesite (MgCO3) or generate methane (CH4). It is thought that some hydrocarbon gases may be produced by serpentinite reactions within the oceanic crust.

Olivine(Fe,Mg)2SiO4 + watern·H2O + carbon dioxideCO2serpentineMg3Si2O5(OH)4 + magnetiteFe3O4 + methaneCH4

 

 

 

 

(Reaction 2a)

or, in balanced form:

18 Mg2SiO4 + 6 Fe2SiO4 + 26 H2O + CO2 → 12 Mg3Si2O5(OH)4 + 4 Fe3O4 + CH4

 

 

 

 

(Reaction 2a')

Olivine(Fe,Mg)2SiO4 + watern·H2O + carbon dioxideCO2serpentineMg3Si2O5(OH)4 + magnetiteFe3O4 + magnesiteMgCO3 + silicaSiO2

 

 

 

 

(Reaction 2b)

Reaction 2a is favored if the serpentinite is Mg-poor or if there isn't enough carbon dioxide to promote talc formation. Reaction 2b is favored in highly magnesian compositions and low partial pressure of carbon dioxide.

Edited by Enthalpic

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Reading this article raised two questions

On 8/25/2019 at 12:32 PM, ronwagn said:

Why I keep refuting people who think that natural gas is only going to last us 15 years or so. I think a hundred years is a very low estimate.

Ron,

Two things came to mind while reading this article. First, this methane is not concentrated in a pool and would be difficult to access as a resource. Secondly, I am not sure that present technology would allow us to even try to 'reduce to possession' if it is in ultra-deep water. The cost would be astronomical!

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