AGE OF THE EARTH MINERALS AND ROCKS not detected correctly
New research geologists from different countries have shown that the earlier measure the age of rocks and minerals using the isotopes of uranium and samarium were incorrect. The opening force of scientists not only to count the age of the Earth, but also to reconsider many of the physical model.
Geochronology (dating of rocks and minerals) is necessary for researchers to understand the temporal sequence of processes occurring on Earth. For the dating of the events of early history of the planet used isotopes - variations of the same chemical element with different numbers of neutrons in the nucleus.
Many of unstable isotopes of elements: for a specific period for each isotope (a few nanoseconds or hundreds of thousands of years, depending on the stability of the isotope) is its decay into lighter elements. Geochemists to determine the age of rocks or minerals by measuring the ratio of radioactive isotopes found in the samples.
Previously it was thought that the ratio of the isotopes uranium-238 (238U) to uranium-235 (235U), equal to 137.88, the same everywhere. To calculate the age of the sample was sufficient to establish the ratio of these isotopes of uranium in the rock. However, recent research specialist at the Massachusetts Institute of Technology (MIT) and the British Geological Survey (British Geological Survey) gave new results.
In his work, described in the journal Science, scientists rely on high-precision measurements of concentrations of uranium isotopes in the minerals belonging to different eras and found in different regions of the world, including found at the bottom of the ocean and learned from meteorites.
The basis of the study was the analysis of 45 samples of zircon. This mineral was one of the first that were formed during solidification and the subsequent formation of the surface of our planet. Zircon tugoplavok and almost not affected by weathering processes, and thanks to contain uranium is ideal for use in radiometric dating.
The result of the analysis was to obtain a new isotope ratios of uranium 235 and 238, which, as it turns out, is 137.818 +0.045.
The new index will help to refine the age of the samples, the previously set. At first glance, the small difference between 137.88 and 138.82 may in fact represent a significant revision of the age of various breeds. Reduction of age will be greater, the older the rock or mineral.
For example, for the Earth, which is about 4.5 billion years old, which means #39;rejuvenation#39; of 700 000 years.
`The discovery will allow not only more accurately assess the age of the samples, but also multiply our knowledge of many other processes and events in the history of the Earth #39;- says Chenet Blair (Blair Schoene), a geologist at Princeton.
Revision of geochronological indicators taken and the other team of scientists, consisting of the representatives of Japan, the U.S. and Israel. This group specified speed life of another isotope - samarium-146 (146Sm). Samarium - heavy shiny metal that is produced in stars and in its pure form is not found on Earth.
The isotope samarium-146 decays to another metal neodymium-142 (142Nd), which is used for the dating of the samples.
The half-life of samarium-146 was tested four times in the last 60 years, and each time I receive different results. Last physics have converged on the record 103 5000000 years. However, scientists have suspected that this value can also be true.
At this time, researchers have in the reactor samples samarium-146, separating it from the isobars - other isotope with mass number 146 by mass spectrometry accelerator. Measurements were made on the superconducting linear accelerator ATLAS, located at the Argonne National Laboratory (Argonne National Laboratory).
The resulting figure was half-life of 68 million years, which is about 34% less than previously thought. It turns out that the previous dating based on the decay of samarium-146, a deviation from the correct value by millions of years of age!
`Samarium isotopes is so important for the dating of the new data lead us to revise some of the existing physical models associated with the age of the Solar System #39;- concludes Philippe Collon (Philippe Collon), Associate Professor of the University of Notre Dame.
