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ocean1 发表于 2013-3-19 02:08:47 | 显示全部楼层 |阅读模式
转帖来源: OurAmazingPlanet
转帖网址链接: http://www.ouramazingplanet.com/4246-earthquakes-make-gold.html
本帖最后由 jlinwhoi 于 2013-3-19 04:52 编辑

Earthquakes Turn Water Into Gold

Becky Oskin, OurAmazingPlanet Staff Writer
Mar 17, 2013 02:00 PM ET

Earthquakes have the Midas touch, a new study claims.

Water in faults vaporizes during an earthquake, depositing gold, according to a model published in the March 17 issue of the journal Nature Geoscience. The model provides a quantitative mechanism for the link between gold and quartz seen in many of the world's gold deposits, said Dion Weatherley, a geophysicist at the University of Queensland in Australia and lead author of the study.

When an earthquake strikes, it moves along a rupture in the ground — a fracture called a fault. Big faults can have many small fractures along their length, connected by jogs that appear as rectangular voids. Water often lubricates faults, filling in fractures and jogs.

About 6 miles (10 kilometers) below the surface, under incredible temperatures and pressures, the water carries high concentrations of carbon dioxide, silica and economically attractive elements like gold.

Shake, rattle and gold

During an earthquake, the fault jog suddenly opens wider. It's like pulling the lid off a pressure cooker: The water inside the void instantly vaporizes, flashing to steam and forcing silica, which forms the mineral quartz, and gold out of the fluids and onto nearby surfaces, suggest Weatherley and co-author Richard Henley, of the Australian National University in Canberra.

While scientists have long suspected that sudden pressure drops could account for the link between giant gold deposits and ancient faults, the study takes this idea to the extreme, said Jamie Wilkinson, a geochemist at Imperial College London in the United Kingdom, who was not involved in the study.

"To me, it seems pretty plausible. It's something that people would probably want to model either experimentally or numerically in a bit more detail to see if it would actually work," Wilkinson told OurAmazingPlanet.

Previously, scientists suspected fluids would effervesce, bubbling like an opened soda bottle, during earthquakes or other pressure changes. This would line underground pockets with gold. Others suggested minerals would simply accumulate slowly over time.

Weatherley said the amount of gold left behind after an earthquake is tiny, because underground fluids carry at most only one part per million of the precious element. But an earthquake zone like New Zealand's Alpine Fault, one of the world's fastest, could build a mineable deposit in 100,000 years, he said.

Surprisingly, the quartz doesn't even have time to crystallize, the study indicates. Instead, the mineral comes out of the fluid in the form of nanoparticles, perhaps even making a gel-like substance on the fracture walls. The quartz nanoparticles then crystallize over time. [Gold Quiz: From Nuggets to Flecks]

Even earthquakes smaller than magnitude 4.0, which may rattle nerves but rarely cause damage, can trigger flash vaporization, the study finds.

"Given that small-magnitude earthquakes are exceptionally frequent in fault systems, this process may be the primary driver for the formation of economic gold deposits," Weatherley told OurAmazingPlanet.

The hills have gold

Quartz-linked gold has sourced some famous deposits, such as the placer gold that sparked the 19th-century California and Klondike gold rushes. Both deposits had eroded from quartz veins upstream. Placer gold consists of particles, flakes and nuggets mixed in with sand and gravel in stream and river beds. Prospectors traced the gravels back to their sources, where hard-rock mining continues today.

But earthquakes aren't the only cataclysmic source of gold. Volcanoes and their underground plumbing are just as prolific, if not more so, at producing the precious metal. While Weatherley and Henley suggest that a similar process could take place under volcanoes, Wilkinson, who studies volcano-linked gold, said that's not the case.

"Beneath volcanoes, most of the gold is not precipitated in faults that are active during earthquakes," Wilkinson said. "It's a very different mechanism."

Understanding how gold forms helps companies prospect for new mines. "This new knowledge on gold-deposit formation mechanisms may assist future gold exploration efforts," Weatherley said.

In their quest for gold, humans have pulled more than 188,000 tons (171,000 metric tons) of the metal from the ground, exhausting easily accessed sources, according to the World Gold Council, an industry group.
滚滚长江都是水 发表于 2013-3-19 12:22:38 | 显示全部楼层
汤民强 发表于 2013-3-19 20:54:25 | 显示全部楼层
研究称地震具有神奇魔力 能够“点水成金”(图)

新闻来源: 中新网
3月18日电 据美国全国广播公司(NBC)报道,一项最新研究发现,地震具有神奇的魔力,能够使水变成黄金。
领导这个研究项目工作的澳大利亚昆士兰大学地球物理学家威瑟利(Dion Weatherley)说,这项研究为黄金与世界上很多金矿存在石英之间的联系提供了量化机制。
一同领导这个研究项目的澳大利亚国立大学专家亨利(Richard Henley)说,当地震发生时,断层会突然释放大量水分。空隙地带中的水分会突然蒸发,变成蒸汽与石英,产生石英矿与金矿,并随着水流进入距离地面较近的地方。
滚滚长江都是水 发表于 2013-3-19 22:51:34 | 显示全部楼层
本帖最后由 hyangwhoi 于 2013-3-19 23:00 编辑

这个中文报道的记者亟需提高相关专业知识,或者应该找人来咨询一下。什么叫“研究称,当地震发生时,地球会产生断层,水能够加速断层的产生,并填补断裂面”? 基本常识错误。

滚滚长江都是水 发表于 2013-3-19 22:59:12 | 显示全部楼层
这个Flash vaporization倒是让我思考,地震中由于快速运动会产生dilatancy和thermal pressurization,但是vaporization是否会在瞬时改变断层上的摩擦性质?有没有矿物学的人了解相关的知识来说说?
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