c equilibrium. However, recent reports that the isotopic composition of many abyssal peridotites are significantly different than mid-ocean ridge basalts call into question the genetic relationship between them and also pose problems for current models for the composition of Earth's upper mantle. In this study, Benjamin L. Byerly and John C. Lassiter compare abyssal peridotites with other samples of the convecting upper mantle and demonstrate that they are indeed representative of the peridotitic upper mantle and are capable of generating mid-ocean ridge basalts. The wide range in the isotopic composition of abyssal peridotites is due to variable amounts of ancient melt extraction from the upper mantle. The common lack of isotopic equilibrium between mid-ocean ridge basalts and associated abyssal peridotites can be accounted for by a lithologically complex upper mantle and selective melting of two of these lithologic domains -- basalt recycled into the upper mantle and peridotite that have isotopic compositions that are similar to mid-ocean ridge basalt.
Seafloor spreading evolution in response to continental growth
N. Coltice et al., Laboratoire de Gologie de Lyon, Universit Lyon 1, Ecole Normale Suprieure de Lyon, Universit de Lyon, 69007 Lyon, France; and Institut Universitaire de France, 103, Bd Saint Michel, 75005 Paris, France; email@example.com. Posted online 10 January 2014, http://dx.doi.org/10.1130/G35062.1.
Seafloor spreading is a cornerstone of plate tectonics theory, proposed in the 1960s. Scientists have reconstructed the evolution of the seafloor in the past 200 million years, driven by the need to estimate crucial geoscience data, like sea level or seafloor heat flow. Going beyond 200 million years was not possible because of lack of data, and because the models to study the dynPage: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Related biology news :1
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