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IT SOUNDS like a geological magic trick: creating oil and diamonds from water. Aren’t diamonds pure carbon that has been squeezed by enormous pressures in deep Earth? Isn’t oil the result of decayed organic matter (plankton? dinosaurs?) piling up for millennia?
An article in Science published November 8, 2015, by the American Association for the Advancement of Science suggests there could be a more straightforward explanation. “How Buried Water Makes Diamonds and Oil” by Eric Hand has the subtitle, “A new picture of water in the deep Earth predicts surprising chemistry.”
The Earth’s crust varies. It can be 40 miles in depth, yet even so it’s only about 1/100 of the Earth’s radius. Proportionately, the crust is paper thin. As an example, 20 weight Bond paper (the sort in my printer at the moment) is around 0.004 in. thick. An 8-in. globe could simulate this “paper-thin” crust.
Below the solid crust is the mantle making up about 84 percent of the Earth’s volume. This mantle is predominately solid, though in geologic time it behaves like a very viscous fluid. Subjected to the mantle’s extreme pressures, water can dissolve into different ions and give rise to unexpected chemical reactions.
This Deep Earth Water model has been proposed by Dimitri Sverjensky at Baltimore’s Johns Hopkins University. As Eric Hand writes in Science, “Sverjensky has literally taken geochemistry to new depths.”
What’s more, Isabelle Daniel, a mineralogist at Claude Bernard University Lyon 1, in Lyon, France, has devised experimental means of corroborating Sverjensky’s model. As an example, she and colleagues put a single crystal of calcite (limestone) and water into a gold-lined metal cylinder thinner than a human hair. Then the cylinder was squeezed to intense pressures between a pair of diamond-tipped anvils. This mimicked conditions 200 km (125 miles) below the Earth’s surface, well into its mantle.
Cameras recorded the crystal getting smaller and smaller, dissolving into ions of carbonate and bicarbonate. “It’s kind of a love story,” Daniels is quoted as saying, “The water had a tremendous affinity with the minerals down there.”
What about diamonds? Traditional wisdom has it that their carbon comes from organic matter on the sea floor. Instead, postulates Sverjensky, changes of acidity in the water alone can create similar mixes of isotopes. “So diamonds with these isotopic signals may have nothing to do with ancient life,” he says.
Continues Hand’s article, “Even more startling may be the model’s prediction of deep-Earth oil, which Daniel and her colleagues have now validated. They put water and dissolved acetate (vinegar’s main component) in their diamond-anvil apparatus and report, “…as pressures and temperatures ramped up, little oil droplets began emerging from the water.”
It’s not that such petroleum would be accessible for exploitation. However, the results are still exciting. Daniel says, “Previously it was thought that oil was 100% from biotic organisms. What we see here is just starting with minerals deep in the Earth.”
It emphasizes that the science of anything—including diamonds and oil—is never really over. ds
© Dennis Simanaitis, SimanaitisSays.com, 2015