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Causes and Consequences of Mantle Serpentinization During Passive Margin Formation

Lars H. Rüpke¹, Daniel W. Schmid¹, and Ebbe H. Hartz²
¹GeoModelling Solutions, Hardturmstrasse 120, 8005 Zurich, Switzerland
²Det norske oljeselskap, PB 2070 Vika, 0125 Oslo, Norway

The main goal of this study is to develop a better understanding of the impact of serpentinization reactions on petroleum systems. Serpentinization has a strong effect on the material properties of mantle rocks. Apart from magnetic properties, the main impact is on density. Serpentinite has a much lower density than mantle rocks and this greatly affects the isostatic balance and may lead to uplift. In this study we present the results of integrated basin modeling that resolves the coupled structural, thermal, stratigraphic, and petrological evolutions of passive continental margins. The key objectives are to test whether 1) lower crustal bodies (LCB) imaged along the Norwegian continental margin can be of serpentinized mantle origin, 2) uplift and erosion events could be explained by isostatic adjustments caused by mantle hydration reactions, and 3) sedimentation suppresses water supply to mantle rocks and affects the thermal stability of serpentine at sub-Moho levels.

The causes and consequences of serpentinization reactions during passive margin formation have been explored using a self-consistent tectonostratigraphic modeling approach. The key findings are:

  • Serpentinization reactions can have first order effects on margin evolution as they can cause uplift and erosion as well as temperature changes by latent heat effects.
  • Most concepts and ideas on serpentinization reactions have been developed for sediment-starved margins (e.g. Iberia). We show that sedimentation dampens the impact of serpentinization by limiting water supply and by thermal blanketing effects.
  • Lower crustal bodies along the Norwegian margin may indeed form by serpentinization reactions although the thick sediment cover greatly limits the volume of mantle rocks within the stability limit of serpentine.
  • AAPG Search and Discovery Article #120098©2013 AAPG Hedberg Conference Petroleum Systems: Modeling the Past, Planning the Future, Nice, France, October 1-5, 2012