New evidence for oceans of water deep in the Earth

earths-mantel[1]From Northwestern University  (h/t to Harold Ambler)

Water bound in mantle rock alters our view of the Earth’s composition

Researchers from Northwestern University and the University of New Mexico report evidence for potentially oceans worth of water deep beneath the United States. Though not in the familiar liquid form — the ingredients for water are bound up in rock deep in the Earth’s mantle — the discovery may represent the planet’s largest water reservoir.

The presence of liquid water on the surface is what makes our “blue planet” habitable, and scientists have long been trying to figure out just how much water may be cycling between Earth’s surface and interior reservoirs through plate tectonics.

Northwestern geophysicist Steve Jacobsen and University of New Mexico seismologist Brandon Schmandt have found deep pockets of magma located about 400 miles beneath North America, a likely signature of the presence of water at these depths. The discovery suggests water from the Earth’s surface can be driven to such great depths by plate tectonics, eventually causing partial melting of the rocks found deep in the mantle.

The findings, to be published June 13 in the journal Science, will aid scientists in understanding how the Earth formed, what its current composition and inner workings are and how much water is trapped in mantle rock.

“Geological processes on the Earth’s surface, such as earthquakes or erupting volcanoes, are an expression of what is going on inside the Earth, out of our sight,” said Jacobsen, a co-author of the paper. “I think we are finally seeing evidence for a whole-Earth water cycle, which may help explain the vast amount of liquid water on the surface of our habitable planet. Scientists have been looking for this missing deep water for decades.”

Scientists have long speculated that water is trapped in a rocky layer of the Earth’s mantle located between the lower mantle and upper mantle, at depths between 250 miles and 410 miles. Jacobsen and Schmandt are the first to provide direct evidence that there may be water in this area of the mantle, known as the “transition zone,” on a regional scale. The region extends across most of the interior of the United States.

Schmandt, an assistant professor of geophysics at the University of New Mexico, uses seismic waves from earthquakes to investigate the structure of the deep crust and mantle. Jacobsen, an associate professor of Earth and planetary sciences at Northwestern’s Weinberg College of Arts and Sciences, uses observations in the laboratory to make predictions about geophysical processes occurring far beyond our direct observation.

The study combined Jacobsen’s lab experiments in which he studies mantle rock under the simulated high pressures of 400 miles below the Earth’s surface with Schmandt’s observations using vast amounts of seismic data from the USArray, a dense network of more than 2,000 seismometers across the United States.

Jacobsen’s and Schmandt’s findings converged to produce evidence that melting may occur about 400 miles deep in the Earth. H2O stored in mantle rocks, such as those containing the mineral ringwoodite, likely is the key to the process, the researchers said.

“Melting of rock at this depth is remarkable because most melting in the mantle occurs much shallower, in the upper 50 miles,” said Schmandt, a co-author of the paper. “If there is a substantial amount of H2O in the transition zone, then some melting should take place in areas where there is flow into the lower mantle, and that is consistent with what we found.”

If just one percent of the weight of mantle rock located in the transition zone is H2O, that would be equivalent to nearly three times the amount of water in our oceans, the researchers said.

This water is not in a form familiar to us — it is not liquid, ice or vapor. This fourth form is water trapped inside the molecular structure of the minerals in the mantle rock. The weight of 250 miles of solid rock creates such high pressure, along with temperatures above 2,000 degrees Fahrenheit, that a water molecule splits to form a hydroxyl radical (OH), which can be bound into a mineral’s crystal structure.

Schmandt and Jacobsen’s findings build on a discovery reported in March in the journal Nature in which scientists discovered a piece of the mineral ringwoodite inside a diamond brought up from a depth of 400 miles by a volcano in Brazil. That tiny piece of ringwoodite — the only sample in existence from within the Earth — contained a surprising amount of water bound in solid form in the mineral.

“Whether or not this unique sample is representative of the Earth’s interior composition is not known, however,” Jacobsen said. “Now we have found evidence for extensive melting beneath North America at the same depths corresponding to the dehydration of ringwoodite, which is exactly what has been happening in my experiments.”

For years, Jacobsen has been synthesizing ringwoodite, colored sapphire-like blue, in his Northwestern lab by reacting the green mineral olivine with water at high-pressure conditions. (The Earth’s upper mantle is rich in olivine.) He found that more than one percent of the weight of the ringwoodite’s crystal structure can consist of water — roughly the same amount of water as was found in the sample reported in the Nature paper.

“The ringwoodite is like a sponge, soaking up water,” Jacobsen said. “There is something very special about the crystal structure of ringwoodite that allows it to attract hydrogen and trap water. This mineral can contain a lot of water under conditions of the deep mantle.”

For the study reported in Science, Jacobsen subjected his synthesized ringwoodite to conditions around 400 miles below the Earth’s surface and found it forms small amounts of partial melt when pushed to these conditions. He detected the melt in experiments conducted at the Advanced Photon Source of Argonne National Laboratory and at the National Synchrotron Light Source of Brookhaven National Laboratory.

Jacobsen uses small gem diamonds as hard anvils to compress minerals to deep-Earth conditions. “Because the diamond windows are transparent, we can look into the high-pressure device and watch reactions occurring at conditions of the deep mantle,” he said. “We used intense beams of X-rays, electrons and infrared light to study the chemical reactions taking place in the diamond cell.”

Jacobsen’s findings produced the same evidence of partial melt, or magma, that Schmandt detected beneath North America using seismic waves. Because the deep mantle is beyond the direct observation of scientists, they use seismic waves — sound waves at different speeds — to image the interior of the Earth.

“Seismic data from the USArray are giving us a clearer picture than ever before of the Earth’s internal structure beneath North America,” Schmandt said. “The melting we see appears to be driven by subduction — the downwelling of mantle material from the surface.”

The melting the researchers have detected is called dehydration melting. Rocks in the transition zone can hold a lot of H2O, but rocks in the top of the lower mantle can hold almost none. The water contained within ringwoodite in the transition zone is forced out when it goes deeper (into the lower mantle) and forms a higher-pressure mineral called silicate perovskite, which cannot absorb the water. This causes the rock at the boundary between the transition zone and lower mantle to partially melt.

“When a rock with a lot of H2O moves from the transition zone to the lower mantle it needs to get rid of the H2O somehow, so it melts a little bit,” Schmandt said. “This is called dehydration melting.”

“Once the water is released, much of it may become trapped there in the transition zone,” Jacobsen added.

Just a little bit of melt, about one percent, is detectible with the new array of seismometers aimed at this region of the mantle because the melt slows the speed of seismic waves, Schmandt said.

###

The USArray is part of EarthScope, a program of the National Science Foundation that deploys thousands of seismic, GPS and other geophysical instruments to study the structure and evolution of the North American continent and the processes the cause earthquakes and volcanic eruptions.

The National Science Foundation (grants EAR-0748797 and EAR-1215720) and the David and Lucile Packard Foundation supported the research.

The paper is titled “Dehydration melting at the top of the lower mantle.” In addition to Jacobsen and Schmandt, other authors of the paper are Thorsten W. Becker, University of California, Los Angeles; Zhenxian Liu, Carnegie Institution of Washington; and Kenneth G. Dueker, the University of Wyoming.

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New evidence for oceans of water deep in the Earth
————
It must be steam – algore said:
“…the interior of the earth is extremely hot, several million degrees…”

Fascinating, great reading.

Michael C. Roberts

This may help to explain the formation of asbestiform minerals:
http://en.wikipedia.org/wiki/Asbestos

Gary Pearse

Normal granite magmas contain approx. 5% water by weight. When molten rock intrudes into cooler host rocks, it begins to crystallize and the water is concentrated in a ”cupola” at the top of the intrusion. The water, at about 350C or so generally contains a number of rare elements that aren’t accommodated into the crystal lattices of normal rock-forming silicates (like quartz and feldspar), plus dissolved silica, alkali metals, etc.
Fracturing due to thermal shock and the doming of overhead rocks can result in the formation of rare-metal deposits (Li, Cs, Be, Ta, Nb, rare earth elements, fluorine-bearing minerals, tin, etc.) in the fractures. If, however, the fractures reach the surface, a massive boiling of the water with huge expansion of steam and the rush of rock fragments followed by a viscous lava called rhyolite, usually containing crystals of quartz and feldspar that had formed in the cooling granite, erupts onto the earth’s surface. This one of the most dangerous of volcanoes because of its violent explosivity and the ‘bombs’ it hurls out. Worse, sometimes the viscous lava will freeze in the throat of the volcano as the pressure drops and subsequent activity with the vent plugged can result in a massive explosion destroying the volcano itself.
http://www.universetoday.com/40601/mount-krakatoa/
Krakatoa was the most famous. I was taught that the ‘plug’ in the throat of the volcano was up to 3km long. Basically the whole island blew away leaving a crater in the sea floor. Yeah there is a bit of water down there.
[Same for gold veins in granite and quartz? .mod]

Jimbo

Is that where the missing heat went?

Philip

I need a chemist to explain this part to me:
This water is not in a form familiar to us — it is not liquid, ice or vapor. This fourth form is water trapped inside the molecular structure of the minerals in the mantle rock. The weight of 250 miles of solid rock creates such high pressure, along with temperatures above 2,000 degrees Fahrenheit, that a water molecule splits to form a hydroxyl radical (OH), which can be bound into a mineral’s crystal structure.
So what is bound into this rock is OH, missing the additional H which makes it into water.
To recover water, it would seem that we need to find an additional hydrogen atom from somewhere?

Mike Kogswell

Yep, The Missing Heat Must Be There As We Can’t Find It Anywhere else !! So One Day, Mankind will cause The Planet to Blow apart Like a Neutron star, Instead of just dying out like Pluto did !! And That’s My story & I’m Sticking To It !!

Is this science?

Louis

This is not the first study to suggest that there are oceans of water in the mantle. Back in January, scientists at the University of Liverpool published information to show that deep sea fault zones could transport much larger amounts of water from Earth’s oceans to the upper mantle than previously thought.
“Seismologists at Liverpool have estimated that over the age of Earth, the Japan subduction zone alone could transport the equivalent of up to three and a half times the water of all Earth’s oceans to its mantle.”
The Liverpool study suggested that “the sea water that percolated through the faults reacted with the oceanic rocks to form serpentinite — a mineral that contains water.” The Northwestern University study says the water is stored in ringwoodite. But both studies claim the equivalent of several oceans exist deep in the Earth’s mantle.

Alan Robertson

We have been adding water to the biosphere with each drop of hydrocarbon fuel we burn. In a way, one could say that coal seams are as much a part of the oceans, as the rocks in this study.

Catherine Ronconi

Steven Mosher says:
June 13, 2014 at 5:18 pm
Is this science?
——————–
Yes. Only a Warmunista confused about what science is would ask that question.
It is science because its results are repeatable & it makes testable predictions. Unlike your death cult of man-made global warming.

Philip says:
June 13, 2014 at 4:16 pm
I need a chemist to explain this part to me:
========================================
This wiki page explains Ringwoodite a bit better, with a few links: one which links to this study.
http://en.wikipedia.org/wiki/Ringwoodite

In this case my freshman chemistry deserts me. Wikipedia describes the hydroxyl radical, “The hydroxyl radical, •HO, is the neutral form of the hydroxide ion. Hydroxyl radicals are highly reactive and consequently short-lived; however, they form an important part of radical chemistry”
If the hydroxyl radical is so short lived, how can it exist in the presence of other matter without some sort of combination going on? It sounds like some strange things can occur within the crystal structure of carbon and other elements.

Berényi Péter

Even better. If you mix water (H2O), limestone (CaCO3) and ferrous oxide (FeO) at that pressure and temperature, you get ferric oxide (Fe2O3) and all kinds of alkanes (abiotic deep petroleum) spontaneously. With oceans of water down there, it should be synthesized in prodigious quantities.

Mike T

Catherine, I think Steven Mosher was being sarcastic.

I wonder if some of the hydrogen at this depth could be compressed with carbon to produce methane? if so, the methane might migrate towards the surface and replenish deep natural gas fields. With all that water, it could provide a truly inexhaustible supply of methane.

pat

a fitting tale to post here!
14 June: Guardian: Stuart Clark: Apparent pause in global warming blamed on ‘lousy’ data
European Space Agency scientist says annual sea level rises since 1993 indicate that warming has continued unabated
A widely reported “pause” in global warming may be an artefact of scientists looking at the wrong data, says a climate scientist at the European Space Agency.
Global average sea surface temperatures rose rapidly from the 1970s but have been relatively flat for the past 15 years. This has prompted speculation from some quarters that global warming has stalled.
Now, Stephen Briggs from the European Space Agency’s Directorate of Earth Observation says that sea surface temperature data is the worst indicator of global climate that can be used, describing it as “lousy”.
“It is like looking at the last hair on the tail of a dog and trying to decide what breed it is,” he said on Friday at the Royal Society in London…
Scientists are now trying to simulate the behaviour using computer models. This is difficult because the behaviour of the deep ocean is too poorly known to be reliably included.
“The models don’t have the skill we thought they had. That’s the problem,” said Peter Jan van Leeuwen, director of the National Centre of Earth Observation at the University of Reading…
Another problem in building computer models has been knowing how to compare measurements taken by different satellites…
http://www.theguardian.com/science/2014/jun/13/pause-global-warming-data-sea-level-rises?CMP=twt_gu

pat

disappointed, but not surprised, to hear BBC World Sce give this plenty of time last nite. bit about using IPCC models made me laugh:
AUDIO: FIRST 7 MINS)14 June: BBC Science in Action: Indian Ocean Extreme Weather
Devastating droughts and crippling floods could become many, many, times more frequent in areas as far spread as India, Australia, the east of Africa, and Indonesia. These all border the Indian Ocean, and extreme climate and weather events are predicted to become more common as greenhouse gas emissions continue to increase. This warning comes from scientists in India, China and Japan, who modelled the effects of CO2 on a climate cycle known as the Indian Ocean dipole. Dr Andrew Turner, a lecturer in monsoon systems at the University of Reading in the UK, explains more.
http://www.bbc.co.uk/programmes/p020d8ph
following has link to Nature:
11 June: SMH: Peter Hannam: Climate change to almost triple risk of extreme Indian Ocean weather events
The research, to be published in the journal Nature on Thursday, used 23 climate models and assumed greenhouse gas emissions would continue on their current trajectory…
Earlier this year, research led by Dr Cai identified that global warming would double the incidence of extreme El Ninos, such as 1982-83 and 1997-98, from one in 20 years to one per decade on average…
http://www.smh.com.au/environment/climate-change/climate-change-to-almost-triple-risk-of-extreme-indian-ocean-weather-events-20140611-zs43n.html
12 June: ABC: Karen Palenzuela: Climate change set to triple drought, bushfires and floods in Australia
Dr (Wenju) Cai (CSIRO Marine and Atmospheric Research), who led the research,) said the research, which was funded by the Australian Climate Change Science Program and the Goyder Institute in South Australia, has also raised a deeper line of inquiry around the Indian Ocean Dipole…
http://www.abc.net.au/environment/articles/2014/06/12/4023302.htm

Patrick

“pat says:
June 13, 2014 at 7:33 pm”
The articles at the ABC and SMH state results are based on model outputs. Too funny!

Alan Robertson

Berényi Péter says:
June 13, 2014 at 6:56 pm
Even better. If you mix water (H2O), limestone (CaCO3) and ferrous oxide (FeO) at that pressure and temperature, you get ferric oxide (Fe2O3) and all kinds of alkanes (abiotic deep petroleum) spontaneously. With oceans of water down there, it should be synthesized in prodigious quantities.
________________________
Yes, but it’s “dirty” oil. It could only be transported in rail cars and sold to China.

So what is bound into this rock is OH, missing the additional H
==========
the additional H combines with C from breakdown of limestone (CaCO3) due to heat and subduction, to form hydrocarbons. Methane. Natural gas. Which we are discovering is much more plentiful than can be explained by decomposition of dinosaurs millions of years ago.

If you mix water (H2O), limestone (CaCO3) and ferrous oxide (FeO) at that pressure and temperature, you get ferric oxide (Fe2O3) and all kinds of alkanes (abiotic deep petroleum) spontaneously.
============
exactly!!

thingadonta

those oceans didn’t come from comets.

Billtb52

What’s the consensus on this?

LarryD

thingadonta: “those oceans didn’t come from comets.”
Well, “small comet theory”, 20-30 million tons of water per year for the last 4+ billion years would do it. That rate of influx matches what subduction is estimated to remove.
BTY, the “dinosaur” theory of oil origin is long obsolete, the biotic explanation is sourced from plankton remains accumulating on the bottoms of warm, shallow oceans.
The Greens should hate this news, as noted above, this much water means huge amounts of deep abiotic oil and gas.

Max™

Reminds me of the Baxter novel Flood… it doesn’t work out well.

John F. Hultquist

LarryD says:
June 13, 2014 at 10:13 pm
“BTY, the “dinosaur” theory of oil origin is long obsolete, …

Thanks for ruining my day Larry. Who will tell Dino and the other good folks of Sinclair Oil?
http://www.sinclairoil.com/sinclair_history.html

John F. Hultquist

Fascinating guys. Thanks Anthony, Mods &, as always, commenters.
Looks like solid evidence for the Abiotic Oil Theory.
http://www.youtube.com/watch?v=vdSjyvIHVLw
OR: (put in search box) The Origins of Oil – falsely defined in 1892 .8 mins.
Also :
http://www.youtube.com/watch?v=N-UCoOOq0zY . 5 mins.
OR : (PISB) Abiotic Oil Theory Earth Has An Endless Supply Of Oil
Astounding.
Follow the $money$

Patrick

While sea water percolates through faults to the mantle, is it possible that the reverse happens affecting sea levels?

Rhoda Klapp

We could frack that water, but it could lead to contamination in our gas supply. Cue pics of water streaming from gas taps in somebody’s kitchen.

johnmarshall

Excellent— science at work.

Jaakko Kateenkorva

Excellent. The age of athropocentrisism is coming to an end.

Kelvin Vaughan

Mark and two Cats says:
June 13, 2014 at 2:58 pm
New evidence for oceans of water deep in the Earth
————
It must be steam – algore said:
“…the interior of the earth is extremely hot, several million degrees…”
That’s all our problems solved. Steam generators, steam central heating, steam cars, steam trucks, steam buses and steam trains.

Zaphod Beeblebrox (part time galactic president)

Steam trains?
Nah, they’ll never catch on…

Genesis 7 v 10-11 “And it came to pass after seven days, that the waters of the flood were upon the earth. In the six hundredth year of Noah’s life, in the second month, the seventeenth day of the month, the same day were all the fountains of the great deep broken up, and the windows of heaven were opened.

cedarhill

ferdberple says @ June 13, 2014 at 8:58 pm “..Which we are discovering is much more plentiful than can be explained by decomposition of dinosaurs millions of years ago…”
I think you’re referring to abiotic origins? See
http://en.wikipedia.org/wiki/Abiogenic_petroleum_origin
The study provides another data point. If Kudryavtsev were still alive, it would be interesting how he would interpret their results.

Philip Mulholland

Philip says:
June 13, 2014 at 4:16 pm

To recover water, it would seem that we need to find an additional hydrogen atom from somewhere?

Or alternatively loose one oxygen atom to the host mineral.
2(OH) -> H2O + O

hunter

This is an interesting observation, if it can be confirmed. If it does turn out that there are massive amounts of water tied up deeply in the Earth the implications are huge. It could explain how, after luna was formed by the collision that blew away a substantial amount of the proto-Earht’s crust, oceans formed relatively quickly. This could also give insights on where at least some of natural gas came from.

Rud Istvan

The abiogenesis hypothesis for natural gas and all higher order hydrocarbons has been about as thoroughly debunked as possible given the present state of geochemistry and geophysics. Oil and gas are either formed from marine kerogens or from coal precursor matter (cellulose, hemicellulose, and lignin). In both cases, they are fossil fuels in a literal sense, having originally stored energy created by photosynethesis of sunlight. One way to be sure is literally observing the fossilized remains of the organisms that did the photosynthesizing, which are observable in the source rock (shale) cores extracted as part of the exploration and development process.

Philip Peake

Philip Mulholland: yes, I had wondered about that possibility. It’s an explanation for the abundance of oxygen, although that really only seems to have happened with the appearance of life on earth, not before, so I discounted it.
If water really is being subducted and stripped of a hydrogen atom in the volumes they are talking about, the atmosphere really should have a much higher concentration of hydrogen? No? Even talking into account the leakage into space.
I think the story is overblown. It’s not water that is there it’s a hydroxyl radical somehow being held in a stable state. There would seem to me (non chemist, remember) that there are many other potential reactions that might take place other than combining with hydrogen, which is in pretty short supply, or somewhere finding the energy necessary to split the OH bond to create H2O + H.
Given its reactive nature, I think the doom and gloom crowd should be worried about the potential for several oceans worth of this being released, and it’s potential effect on the environment and the paint finish on their Priuses!

Jbird

Volcanic rock is often very light weight and porous. Is it H2O existing this rock as steam when the magma cools that leaves it this way?

Jbird

Make that “exiting” rather than “existing.” A pox on these automatic spelling corrections!

Lars P.

Rud Istvan says:
June 14, 2014 at 7:55 am
The abiogenesis hypothesis for natural gas and all higher order hydrocarbons has been about as thoroughly debunked as possible given the present state of geochemistry and geophysics.
….
One way to be sure is literally observing the fossilized remains of the organisms that did the photosynthesizing, which are observable in the source rock (shale) cores extracted as part of the exploration and development process.

Nobody contest the fact that there are fossil hydrocarbons from fossilized remains, however this fact does not debunk anything.
There can be various sources for hydrocarbons – see all the hydrocarbons available on other planets …

Berényi Péter

@Rud Istvan June 14, 2014 at 7:55 am

The abiogenesis hypothesis for natural gas and all higher order hydrocarbons has been about as thoroughly debunked as possible […] One way to be sure is literally observing the fossilized remains of the organisms […]

It was not debunked, it was dismissed. There is a difference.
– presence of biomarkers is easily explained by bacteria feeding on upwelling hydrocarbons
– helium in natural gas is inconsistent with biological origin
– dissolved diamondoids in oil is a mystery
– there are hydrocarbon inclusions in diamonds
– all alkanes except methane are only metastable at low pressure (just like diamond)
– no organic material was transformed into higher alkanes in lab ever in a process close to local thermodynamic equilibrium
– spontaneous synthesis of alkanes is demonstrated in the lab at high pressure &. temperature from inorganic precursors
– Titan has hundreds of times more liquid hydrocarbons than all the known oil and natural gas reserves on Earth
In addition to all above now we know for sure there is abundant Hydrogen at depth.

Bob says:
June 13, 2014 at 6:52 pm
In this case my freshman chemistry deserts me. Wikipedia describes the hydroxyl radical, “The hydroxyl radical, •HO, is the neutral form of the hydroxide ion. Hydroxyl radicals are highly reactive and consequently short-lived; however, they form an important part of radical chemistry”
—————————————————————————————————————————
∙OH is known as a “free” radical. Sometimes anions and cations have been called radicals. “The solubility of hydroxide in ringwoodite is important because of the effect of hydrogen upon rheology.” To have water both the OH- and H+ must be present. I don’t know what their proposed structure is, but both are there somewhere.

KRJ Pietersen

I have long felt that the theory of comets as the origin of all water on Earth was about as plausible as CO2 being the be-all-and-end-all of climate variability. So news stories like this interest me greatly. However, it is hardly new news. For example, we can go back as far as 2002 for a similar article published in Science:
http://news.nationalgeographic.com/news/2002/03/0307_0307_waterworld.html
I’m also very interested in the idea that, under the right conditions, water can be created from elemental rock containing hydrogen and oxygen. This is known as primary water. In 1896, Adolf Erik Nordenskjold published an essay, “About Drilling for Water in Primary Rocks,” which won him a nomination for the Nobel Prize in physics. The leading developer of primary water theory and actual wells in the 20th century was Stephen Riess. The Kola Superdeep Borehole faced continual problems encountering vast and wholly unexpected quantities of water at depths of around 7km.
Primary water theory states that water is created within the Earth’s interior and travels toward the surface via fissures and fractures in primary rock. This water represents new additions to the standard hydrological cycle. It can be accessed by drilling into bedrock, often at depths of just 100 to 300 feet. Also referred to as new, juvenile, magmatic or earth-generated water, mention of primary water can be found in modern literature, although it is not generally recognised as significant by the hydrological community. Accordingly, it’s potential to offset the world’s growing water problems remains largely unrealised.
More information for those that may be interested:
http://merlib.org/node/5063

One of the more concise comments on abiotic oil is at http://wattsupwiththat.com/2009/05/15/natural-petroleum-seeps-release-equivalent-of-eight-to-80-exxon-valdez-oil-spills/#comment-132342
doug says:
May 15, 2009 at 1:33 pm
This abiotic theory pops up with irritating regularity.
Yea, there is such a thing as abiotic methane. I can tell you though, from 25 years of looking for and finding oil and gas, that most of what we produce is clearly biotic in origin.
There are complex trace long chain molecules, known as biomarkers present in the oil. They are basically fossils on a molecular level. We can trace these biomarkers directly to the source rock, and often trace then directly to the organism, and determine the age, environment of deposition of the organic matter.
I can show you side by side basins in Indonesia, one with a layer of organic rich black shale deposited in a lake 35 million years ago, and full of the fossil remains of the algea bottriococcus. The other basin lacks the organic rich layer.
Surprise! the basin with the organic layer is full of oil, and the oil is full of the same long chain hydrocarbons as the bottriococus remains. The other basin is barren.
How did those deep mantle hydrocarbons know to migrate into the basin with the algal rich rock?