Large igneous provinces (LIPs) are constructed when Two objectives of ODP Leg 183 were to sample the copious amounts of mantle-derived magma enter the submarine LIP in as many locations as possible to: (1) Earth’s crust in localized regions. Although the Kerguelen determine the temporal variation in magma production; Plateau and Broken Ridge are now submarine, they (2) constrain the origin and evolution of the volcanic formed as a contiguous, largely subaerial LIP during rocks forming the LIP. Studies of igneous basement Cretaceous time in the eastern Indian Ocean. Subrecovered during Leg 183 complement continuing studies sequently, they were separated by sea-floor spreading of the Cenozoic subaerial lavas that form the Kerguelen beginning in Middle Eocene time along the Southeast Archipelago. This volume includes a collection of papers Indian Ridge (SEIR; Fig. 1). The Kerguelen Archipelago that address these objectives by using data for lavas is a Cenozoic feature constructed on the Northern Kerforming the Kerguelen Plateau, Broken Ridge and Kerguelen Plateau (NKP; Fig. 1). Together with the guelen Archipelago. >82–38 Ma hotspot track formed by the Ninetyeast High-quality radiometric age determinations are critRidge, the Kerguelen Plateau, Broken Ridge and Kerical for understanding rates of LIP formation, their causguelen Archipelago represent >119 Myr of volcanism ative dynamic mantle processes, and their temporal that has been attributed to the Kerguelen mantle plume. relationships to potentially related environmental Although the igneous basement of the Kerguelen Plateau changes. Duncan employs the Ar/Ar technique to had been sampled at Sites 738, 747, 749 and 750 (Fig. determine ages at all of the ODP Leg 183 igneous 1) by Ocean Drilling Program (ODP) Legs 119 and 120, basement drill sites (Fig. 1). In general, ages young Leg 183 was the first leg dedicated to understanding the northwards on the Kerguelen Plateau, from >119 Ma origin and evolution of an oceanic LIP. Five sites (1136, at Site 1136 in the south to >34 Ma at Site 1140 in the 1137, 1138, 1139, 1140) penetrated igneous basement north. Emplacement of the conjugate Central Kerguelen of the Kerguelen Plateau, and at two sites (1141, 1142) Plateau (CKP) and Broken Ridge falls within an >5 Myr the first basement samples were obtained from Broken Ridge (Fig. 1). window from >100 to >95 Ma. An unanticipated result