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Earthquakes make gold veins -- pressure changes in Earth crust cause precious metals to deposit

Earthquakes make gold veins -- pressure changes in Earth crust cause precious metals to deposit | Earthquakes | Scoop.it

Scientists have long known that veins of gold are formed by mineral deposition from hot fluids flowing through cracks deep in Earth’s crust. But a study published today in Nature Geoscience has found that the process can occur almost instantaneously — possibly within a few tenths of a second.

 

The process takes place along 'fault jogs' — sideways zigzag cracks that connect the main fault lines in rock, says first author Dion Weatherley, a seismologist at the University of Queensland in Brisbane, Australia.

When an earthquake hits, the sides of the main fault lines slip along the direction of the fault, rubbing against each other. But the fault jogs simply open up. Weatherley and his co-author, geochemist Richard Henley at the Australian National University in Canberra, wondered what happens to fluids circulating through these fault jogs at the time of the earthquake.

 

What their calculations revealed was stunning: a rapid depressurization that sees the normal high-pressure conditions deep within Earth drop to pressures close to those we experience at the surface. For example, a magnitude-4 earthquake at a depth of 11 kilometres would cause the pressure in a suddenly opening fault jog to drop from 290 megapascals (MPa) to 0.2 MPa. (By comparison, air pressure at sea level is 0.1 MPa.) “So you’re looking at a 1,000-fold reduction in pressure,” Weatherley says.

 

Big earthquakes will produce bigger pressure drops, but for gold-vein formation, that seems to be overkill. More interesting, Weatherley and Henley found, is that even small earthquakes produce surprisingly big pressure drops along fault jogs. “We went all the way to magnitude –2,” Weatherley says — an earthquake so small, he adds, that it involves a slip of only about 130 micrometres along a mere 90 centimetres of the fault zone. “You still get a pressure drop of 50%,” he notes.

 

That, Weatherley adds, might be one of the reasons that the rocks in gold-bearing quartz deposits are often marbled with a spider web of tiny gold veins. “You [can] have thousands to hundreds of thousands of small earthquakes per year in a single fault system,” he says. “Over the course of hundreds of thousands of years, you have the potential to precipitate very large quantities of gold. Small bits add up.”

 

Weatherley says that prospectors might be able to use remote sensing techniques to find new gold deposits in deeply buried rocks in which fault jogs are common. “Fault systems with lots of jogs can be places where gold can be distributed,” he explains.

 

But Taka’aki Taira, a seismologist at the University of California, Berkeley, thinks that the finding might have even more scientific value. That’s because, in addition to showing how quartz deposits might form in fault jogs, the study reveals how fluid pressure in the jogs rebounds to its original level — something that could affect how much the ground moves after the initial earthquake.


Via Dr. Stefan Gruenwald
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Earthquakes In The Last Week

Earthquakes In The Last Week | Earthquakes | Scoop.it

This is a shocking resource which shows all of the earthquakes that have happened over one week on a map. The site separates the quakes into colours by strength. It's astonishing to see how many earthquakes happening around the world. Found  via http://twitter.com/@MrsPTeach

 

http://ictmagic.wikispaces.com/Science

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Tony Gough's curator insight, June 14, 2013 9:52 AM

Places hit by eathquakes!

Rescooped by José Miguel Sutherland from @The Convergence of ICT & Distributed Renewable Energy
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Frackers Sued for Causing Earthquakes | AlterNet.org

Frackers Sued for Causing Earthquakes | AlterNet.org | Earthquakes | Scoop.it

It’s become something of a pattern: A quiet town with no history of fault line activity signs a contract with natural gas drillers. Suddenly, it’s beset by minor earthquakes. In Youngstown, Ohio, a recent study  linked a spate of over 100 earthquakes to the process used to dispose of wastewater from hydraulic fracturing, or fracking.

 

In Greenbrier, Arkansas, there weren’t hundreds of small earthquakes, but thousands. A study done in the region also linked their occurence to the arrival in town of wastewater disposal wells. As soon as the Arkansas Oil and Gas commission shut down the wells, the quakes stopped. The residents are suing.

 

According to Reuters, over a dozen residents of Greenbrier have filed five federal lawsuits against the drillers, marking the first legal attempt to link earthquakes to wastewater wells:

 

Click headline to read more--


Via Chuck Sherwood, Senior Associate, TeleDimensions, Inc
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Rescooped by José Miguel Sutherland from World Environment Nature News
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Carbon capture and storage may trigger earthquakes

Carbon capture and storage may trigger earthquakes | Earthquakes | Scoop.it
A common strategy to combating global warming is getting a second look.

Via Maria Nunzia @Varvera
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Four small earthquakes shake Delhi

Four small earthquakes shake Delhi | Earthquakes | Scoop.it

Four earthquakes have shaken homes in the Indian capital, Delhi, sending people running into the streets.

 


Via Ramy Jabbar رامي
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EARHTQUAKE MAGNITUDE 5.9 HIT MEXICO APRIL 22 2013. (ALLEGED METEOR)

PAGINA WEB http://www.gabehash.com/ YOUTUBE http://www.youtube.com/Gabehash (Canal Español) http://www.youtube.com/GabehashTV (English Channel) TWITTER https...
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Rescooped by José Miguel Sutherland from My Umbrella Cockatoo, TIKI
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Stuff They Don't Want You To Know - Manufactured Earthquakes

Earthquakes are terrifying reminders that some of Earth's processes remain beyond human control. So why do some people think scientists can actually create t...

Via Troy Mccomas (troy48)
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Rescooped by José Miguel Sutherland from No Such Thing As The News
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Drilling causes earthquakes in Lancashire

Drilling causes earthquakes in Lancashire | Earthquakes | Scoop.it

It is "highly probable" that test drilling for shale gas triggered two minor earthquakes in Lancashire, a study concludes.


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Underground Carbon Dioxide Injections Triggered Earthquakes in Texas in 2009-2011 | Geophysics | Sci-News.com

Underground Carbon Dioxide Injections Triggered Earthquakes in Texas in 2009-2011 | Geophysics | Sci-News.com | Earthquakes | Scoop.it
A new study correlates 93 small earthquakes near Snyder, Texas between 2009 and 2011 with the underground injection of gas, primarily carbon dioxide.

Via David Simpson
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Are Earthquakes and Fracking Wastewater Injection Wells Related?

Are Earthquakes and Fracking Wastewater Injection Wells Related? | Earthquakes | Scoop.it

Two new papers tie a recent increase in significant earthquakes to reinjection of wastewater fluids from unconventional oil and gas drilling. The first study notes “significant earthquakes are increasingly occurring within the United States midcontinent.” In the specific case of Oklahoma, a Magnitude “5.7 earthquake and a prolific sequence of related events … were likely triggered by fluid injection.”
The second study, of the Raton Basin of Southern Colorado/Northern New Mexico by a U.S. Geological Survey (USGS) team, concludes “the majority, if not all of the earthquakes since August 2001 have been triggered by the deep injection of wastewater related to the production of natural gas from the coal-bed methane field here.”

Both studies are being presented at the annual meeting of the American Geophysical Union this week.
These studies, together with other recent findings, make a strong case that we need national regulations on wastewater injection to prevent induced earthquakes...


Via Lauren Moss
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Andrew S.'s comment, October 20, 2014 9:45 AM
Cool!
Carolyn's curator insight, October 20, 2014 9:59 AM

MORE EARTHQUAKES!

AlaineS's curator insight, October 22, 2014 5:17 PM

Very informative and has specific facts on the topic.

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Earthquakes, tsunamis and volcanoes › Ask an Expert | ABC Science

Earthquakes, tsunamis and volcanoes › Ask an Expert | ABC Science | Earthquakes | Scoop.it

Causes of quakes

Is it possible for anything living to cause an earthquake?
— Megan

 

Yes, people can cause an earthquake through human activity. The most common way is by building a dam. It's very common to get small earthquakes after filling a dam, firstly because of the extra load due to the weight of the water; and then secondly because water seeping down into faults can cause them to move if they're at breaking point. Liquid acts as a lubricant enabling faults to slide more easily.

 

Another way humans can cause earthquakes is with mining - taking material out of the ground also causes little stresses which can results in earthquakes.

 

Pumping oil out can cause earthquakes by changing the stresses underground or because water pumped down to flush the oil out can have a lubricating effect.

 

Another human-related cause of earthquakes is when water is pumped through hot rocks several kilometres underground in order to harness geothermal energy. This can cause little tremors, up to magnitude 3 on the Richter Scale. Scientists use these small earthquakes to trace what is happening underground - they can follow exactly where the water is by following the little earthquakes.

 

— Clive Colins, seismologist, Geoscience Australia

 

Click headline to read more Ask the Expert Q & As--


Via Chuck Sherwood, Senior Associate, TeleDimensions, Inc
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