Then he began probing the minerals with the latest instruments. Wilson and Cline were able to date minerals in 16 samples of rock from Yucca and found no evidence of hydrothermal activity. However, they did find evidence of possible hydrothermal activity 4 million to 5 million years ago. Some double bubbles, called two-phased fluid inclusions, were found in the oldest mineral layers, Wilson said. The two-phased fluid inclusions are generally formed in very hot water, above 300 degrees Fahrenheit.
Fluid inclusions are tiny bubbles of gas and water trapped in the minerals.
We have quite solidly answered all of the questions. Those questions were raised by former Department of Energy geologist Jerry Szymanski, who said in 1983 that deep, hot water periodically intruded into the repository site 1,000 feet beneath the surface of Yucca Mountain. Cline and Wilson plan to publish their final results in April, after more rock samples are dated. UNLV, the U.S. Geological Survey, DOE, the independent Nuclear Waste Technical Review Board and the state of Nevada all contributed scientific information to the study, and all were given oversight of Cline and Wilson's work. Nevada officials, who are opposed to a nuclear repository, said after hearing the results that they still believe that geothermal water entered the mountain in recent geological history.