Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5784203 | Lithos | 2017 | 49 Pages |
Abstract
The geochemical signatures (i.e., high Sr/Y and La/Yb ratios) of adakitic rocks in continental settings, which are derived from the continental lower crust rather than from subducted slabs, may reflect high-pressure melting in the lower crust or may be inherited from their sources. The North China Craton (NCC) is an ideal place for investigation of this type of adakites due to its ubiquitous distribution. As an example, we explore the petrogenesis of the Jurassic (~Â 163Â Ma) adakitic rocks in western Liaoning, in the NE part of the NCC, using elemental and Sr-Nd isotopic analysis and crystallization modeling based on Rhyolite-MELTS. The modeling demonstrates that adakitic signatures can be generated by fractional crystallization of magmas within crust of normal thickness (i.e., 33Â km). Partial-melting modeling based on the composition of the lower continental crust shows that only the adakitic rocks from orogenic belts require a thickened crust (i.e., 45Â km). We suggest that continental adakitic rocks are not necessarily linked to high-pressure processes and their use as an indicator of thickened/delaminated continental crust should be regarded with caution.
Keywords
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Geochemistry and Petrology
Authors
Hong-Kun Dai, Jianping Zheng, Xiang Zhou, W.L. Griffin,