From crustal structure to plate kinematics : the role of Large Igneous Provinces in the Pacific Ocean

• Main Author: Hochmuth, Katharina
• Other Authors: Jokat, Wilfried, Gohl, Karsten, Bach, Wolfgang
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universität Bremen 2016
• Subjects: Large Igneous Provinces; Manihiki Plateau; Ontong Java Nui; Pacific Ocean; crustal structure; plate kinematics; mantle plume; hot spot volcanism; 550; 550 Earth sciences and geology; ddc:550; Danger Islands; Pacific
• Online Access: https://media.suub.uni-bremen.de/handle/elib/1044; https://nbn-resolving.org/urn:nbn:de:gbv:46-00105224-12

The bathymetry of the Pacific Ocean is dominated by three Large Igneous Provinces (LIP): the Ontong Java Plateau, the Hikurangi Plateau and the Manihiki Plateau. Taylor (2006) proposed their joined emplacement as one "Super"-LIP Ontong Java Nui in the early Cretaceous. Petro- logical and geochemical data point to this scenario, but geophysical evidence is sparse. To evaluate the hypothesis of Ontong Java Nui, refraction/wide-angle reflection seismic data was collected in 2012, during the RV Sonne cruise So-224 across the two main sub-provinces of the Manihiki Plateau. The modeling and interpretation of P-wave velocity, S-wave velocity and density profiles across the Manihiki Plateau along with available seismic reflection data aims to enhance our understanding of the crustal structure of the Manihiki Plateau and improve the plate kinematic reconstruction of the western Pacific region during the Cretaceous. If the hypothesis is correct, the Manihiki Plateau exposes break-up margins to all other LIPs of Ontong Java Nui. The Manihiki Plateau itself is fragmented into multiple sub-provinces. The two largest sub-provinces, the High Plateau and the Western Plateaus have been studied in- tensively in this experiment. The crustal structure of the High Plateau is comparable to other LIPs with a high velocity zone (P-wave velocities >7.3 km/s) in the lower crust and a basaltic to gabbroic crust. The crustal thickness is 20 km. Secondary magmatic phases are strong on the High Plateau expressed in multiple volcanic centers. The Danger Islands Troughs are a series of pull-apart basins, which separate the High Plateau from the Western Plateaus. These plateaus have been subject to massive tectonic deformation such as the gradual decrease in crustal thickness from 17.3 km in the East to 9.1 km in the West. Secondary volcanism is limited to fracture zones and low volume seamount volcanism. Since the crustal structure of the Western Plateaus points to a joined emplacement, the "Super"- LIP can be reassembled. The data also ...