Petrology of basic igneous rocks from the floor of the Sulu Sea

Abstract

Major and trace elements, mineral chemistry, and Sr-Nd isotope ratios are reported for representative igneous rocks drilled from the Sulu Basin basement (Site 768) and Cagayan Ridge (Sites 769, 771) during Ocean Drilling Program Leg 124. The data obtained, while confirming the arc-magma affinity for Cagayan Ridge volcanics, further indicate that Sulu Basin back-arc magmatism with MORB/IAT transitional character was also generated from subduction-modified intraoceanic mantle sources. The older (middle Eocene) Celebes Basin oceanic crust, generated by a pure, normal MORB magmatism thus represents a distinct magmatic system with respect to that of the Sulu Sea. -from Authors