Petrology of Sulu basement rocks and Cagayan Ridge volcanics@en

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 Sulu Basin basement rocks, cored for about 220 m beneath late early Miocene pelagic sediments, consist, downhole, of pillow basalts (Unit 1), dolerite (Unit 2), and two-pyroxene microgabbro (Unit 3), followed by pillowed and massive basalts (Units 4, 5, 6, 7, and 8). Basalts and dolerites are relatively homogeneous in petrochemical features, except for LOI and elements such as Na, K, Rb, Cs, Li, and Ti, which suffered intense and variable mobilization due to seawater alteration and low-grade greenschist facies oceanic metamorphism. Ca and Mg contents also appear significantly influenced by halmyrolysis in some samples. […]