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90 million years ago, granite found under the mountains of Sierra Nevada crystallized at cooler temperatures than scientists thought. The new discovery changes virtually everything we know about how the Earth was formed. ( Don Graham | Flickr )
Researchers have discovered that granite-containing minerals crystallize from a molten state at a much lower temperature than we thought before.
about the history of the Earth and how it formed in the crust, mantle and nucleus.
How Granite Forms
Granite is an igneous rock composed largely of quartz and feldspar. It is formed when the melted magma infiltrates cracks in the crust or mantle as it cools on the surface of the Earth.
Granites are directly formed by the geological processes that separated the Earth into three layers: the crust, the mantle and the core. . For this reason, the study of granite formation gives the experts a thorough insight into how the Earth has taken shape.
"Granite minerals record almost the entire history of our planet, from 4.4 billion years ago to today," says Michael Ackerson. The Carnegie Institution for Science in Washington DC
For more than 50 years, geologists have believed that granite is formed at temperatures between 1,200 and 1,300 degrees Fahrenheit (650 and 700 degrees Celsius). A new study, however, turns the tables on this badumption by showing that granite crystallizes at temperatures lower than 300 degrees.
Low temperature crystallization for granite
In a new article published in Nature A team of researchers explains how a laboratory badysis of granite samples collected at the park National Yosemite crystallized at a temperature between 885 and 1,042 degrees Fahrenheit (474 and 561 degrees Celsius).
The team collected granite from the Tuolumne Intrusive Suite. Mbad of granite that is part of the mountains of Sierra Nevada California. They subjected the granite to a test that measures the amount of titanium in the quartz crystal, leading them to the conclusion that granite crystallizes at cooler temperatures.
Melted rock crystallizes into granite as atoms come together to form closely related bonds. Quartz crystals, which comprise the majority of granitic rocks, typically have four oxygen atoms tightly bonded together around a silicon atom. However, under certain conditions, the silicon atom is replaced by a titanium atom. By measuring the amount of titanium present in quartz crystals, the researchers found that granite crystallized at temperatures lower than expected when it formed 90 million years ago [19659013]. By computer model
The results of the laboratory badysis are consistent with the results of a computer model developed by Ackerson to verify the veracity of their study.
The model looks at the changes in titanium concentrations that occur with Temperature. By mapping the titanium concentrations in a quartz crystal cross-section, Ackerson found shifting concentrations in titanium when the crystal was developing from a central point, in the same way that dark circles reveal the aging of crystals. # 39; a tree
Other possibilities, you still have cold crystallization, "says Ackerson. "And it's surprising."
Implications for Science
The discovery has various implications in the scientific and industrial fields. It diverts virtually everything geologists know about the Earth's geothermal gradient, or temperature changes as a function of Earth's depth, and distorts the knowledge of melted materials beneath the surface of the planet.
as Yellowstone National Park will also have to incorporate their results when interpreting their data.
Finally, many minerals of industrial importance, including gold and copper, are found beneath granite. The new findings could help industries better understand where to find minerals for these ores.
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