The Manihiki Plateau – Magmatic and tectonic evolution of a Large Igneous Province through time.

Pietsch, Ricarda (2015) The Manihiki Plateau – Magmatic and tectonic evolution of a Large Igneous Province through time. (PhD/ Doctoral thesis), Universität Bremen, Bremen, Germany, 125 pp.

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Abstract

The Pacific Plate is highly engraved by volcanism that has formed oceanic plateaus and hotspot chains. The Manihiki Plateau (MP) is a large igneous province (LIP) located in the central Pacific that has an areal extent of 600000 km2. In 2006, Taylor proposed a joint emplacement of the MP with the Ontong Java Plateau, the Hikurangi Plateau and two missing fragments during the Cretaceous in a "Super-LIP" called Ontong Java Nui (OJN). The emplacement of OJN with an aerial extent of 1.1% of the earth’s surface would have had major impacts on Earth’s climate. An investigation of the initital volcanic emplacement history of the Manihiki Plateau and its break-up processes can contribute to a better understanding of LIP-impact on the paleo-climate. Analysis and interpretation of a new, high-resolution multi-channel seismic reflection dataset has provided a detailed and improved volcanic history of the Manihiki Plateau. The new model consists of three volcanic phases instead of the previously assumed two volcanic phases. It includes the initial formation phase (>125 Ma) that formed a spatially localized nucleus, which was extended to the East. The expansion phase (125-116 Ma) erupted massive tholeiitic basalts and break-up processes into the other LIP-fragments occurred. The third phase is a phase of secondary volcanism that leveled out the overall topography and was intense at the tectonically altered margins. Since the late Cretaceous/early Cenozoic, the morphology of the Manihiki Plateau was engraved by tectonic and volcanic features that were strongly related to the kinematics of the Pacific Plate. During the Pleistocene, a major Pacific plate-reorganization occurred that caused changes of inner-lithospheric stress fields. In this study, the origin of the Suvarov Trough has been investigated. Age and spatial extension point towards a cause that is in a good correlation to this major Pleistocene event. Strain within a LIP crust due to applied stress field changes appears to be similar to continental crust and different to the surrounding oceanic crust. During the Cenozoic, the seafloor morphology in the central Pacific is dominated by the formation of age-progressive hotspot seamount chains. Neogene igneous diapirs in the southwestern MP have been investigated within this study. Age and location characteristics support a hotspot origin, which might be related to the Society Islands Hotspot. The characteristic appearance of the diapirs is different to hotspot volcanism within oceanic lithosphere, which can probably be related to the anomalous thick crust of the Manihiki Plateau. The magmatic and tectonic history of the Manihiki Plateau reveals that this LIP acts similar to continental crust on applied external forces, although its chemical composition resembles thick oceanic crust.

Document Type: Thesis (PhD/ Doctoral thesis)
Thesis Advisor: UNSPECIFIED
Projects: Annette-Barthelt-Preis
Date Deposited: 09 Feb 2018 10:22
Last Modified: 09 Feb 2018 10:22
URI: http://oceanrep.geomar.de/id/eprint/41880

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