Secular variability of the thermal regimes of continental flood basalts in large igneous provinces since the Late Paleozoic: Implications for the supercontinent cycle

The thermal regimes of large igneous provinces (LIPs) are addressed in order to evaluate the principal mechanisms of supercontinent breakup. The primary magma solutions and mantle potential temperatures (T-P) determined for flood basalts of LIPs that are associated with Pangea and its breakup are presented. The LIPs are divided into Pangean and post-Pangean based on the amalgamation, rifting, and dispersal stages of Pangea. Among the Pangean LIPs the Oslo Rift (T-P = 1482-1523 degrees C), Emeishan LIP (T-P = 1415-1524 degrees C), and Siberian Traps (T-P = 1440-1538 degrees C) are consistent with a mantle plume thermal regime. The early-Permian Himalayan magmatic province exhibits ambient mantle T-P (1354-1455 degrees C) and consistent with melt derivation from a shallow mantle source. The post-Pangean LIPs, however, exhibit complex T-P relations, and such complexities in the mantle source can be correlated with the dispersal stages of Pangea. The T-P estimates on the Late Triassic Early Jurassic Central Atlantic Magmatic Province (CAMP) (T-P = 1325-1493 degrees C) and Miocene Columbia River Basalt Group (T-P = 1401-1465 degrees C) are consistent with non-plume sources and the slightly elevated T-P relative to the ambient mantle (T-P= 1350 +/- 50 degrees C) is attributed to continental insulation and subduction delamination. The Early Jurassic Karoo-Ferrar LIP (T-P = 1407-1595 degrees C), Early Cretaceous Parana-Etendeka LIP (T-P = 1325-1527 degrees C), and Paleocene North Atlantic LIP (NALIP) (T-P = 1352-1563 degrees C) exhibit both mantle plume and ambient mantle thermal regimes. The T-P estimates of Late Cretaceous-Paleocene Deccan Traps (DLIP) (T-P = 1487-1578 degrees C) and Late Cretaceous Madagascar LIP (T-P = 1509 degrees C) are consistent with a mantle plume related origin. The mantle plume-related LIPs and the LIPs that exhibit both lithospheric and sub-lithospheric components point out that they were emplaced into an already thinned lithosphere. Despite their likely mantle plume origin, plume-induced continental rifting is absent in the Pangean LIPs like Siberian Traps and Emieshan. The LIPs, such as Himalayan magmatic province, CAMP, and Columbia River Basalt Group exhibit significant melt generation and continental rifting without mantle plumes and the rifting process were controlled by plate tectonic processes. The Karoo-Ferrar LIP, Parana-Etendeka LIP, and NALIP show evidence for prior thinned lithosphere and lithosphere-controlled rifting events before the onset of plume magmatism. However, mantle plume events might have accelerated the separation of India and Madagascar but apart from that, there is no other record of plume-induced rifting on both Pangean and post-Pangean LIPs. Rapid dispersal of Pangea and increased rate of subduction along the plate margins are possibly influenced by the thermal energy differences of the plume events at the continental and oceanic LIPs. We posit, based on the thermal state of the LIPs, that mantle plumes act as the source of magma composition and thermal energy rather than the primary driving mechanism of supercontinent rifting, which is controlled by lithospheric processes.