Evidence for a Heterogeneous Upper Mantle in the Cabo Ortegal Complex, Spain

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Science  15 Sep 1989:
Vol. 245, Issue 4923, pp. 1231-1233
DOI: 10.1126/science.245.4923.1231


A well-preserved fragment of a heterogeneous upper mantle is present in the Cabo Ortegal Complex (Spain). This section is made of harzburgite containing a large volume of pyroxenite. The pyroxenite is concentrated in a layer 300 meters thick by 3 kilometers long. In this layer, ultramafic rocks, essentially pyroxenite (massive websterite and clinopyroxenite) and minor dunite, alternate without any rhythmicity. Part of this layering is of primary magmatic origin and possibly resulted from crystallization of magmas in dikes intruded into the host peridotite under mantle conditions.

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