Faculty candidate seminar - Adrien Arnulf

04/06/2017 - 3:00pm
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DATE:          April 6th, Thursday, 3 p.m.  

LOCATION:     Hubbs Hall 4500
SPEAKER:      Adrien Arnulf, Ph.D.
            University of Texas
TITLE:          Inferring fluid-rock interactions beneath the oceans using modern marine geophysical methods

Fluid-rock interactions play a major role in the structure and evolution of the oceanic plate; from its formation at the ridge, through aging in the abyssal plain, to subduction at the trench. 

Beneath the oceans, submarine volcanism accounts for >80% of Earth’s volcanism, with the vast majority of it taking place along the 65,000 km-long mid-ocean ridge (MOR) spreading system. Needless to say, the MOR system accounts for a large fraction of Earth’s total heat flux. The majority of the total heat loss at MORs occurs through conduction, while a convective process known as hydrothermal circulation influences one third of it. Fluid-rock interactions at hydrothermal vent fields not only influence the chemistry of the oceanic crust and oceans, but also support unique organisms and ecosystems and might have played a crucial role for the early apparition of life. 

In parallel, at convergent margins, slip behavior along the megathrust has been shown to be closely related to the evolution of pore fluid pressures at the plate interface. Fluids released due to mineral dehydration and tectonic loading may play an important role in the onset of seismogenesis, and elevated pore fluid pressures appear to be a key environmental factor promoting shallow transient slip phenomena such as very-low-frequency earthquakes, episodic tremor and slow sleep events. Additionally, sediment accretion and raised fluid expulsion concentrate massive reservoirs of methane and methane hydrates in the accretionary wedge. Those large hydrocarbon reservoirs host a unique microbial biosphere, they present a large economical interest as potential energy resources, and are a societal hazard since increasing ocean temperatures can break down methane ices and modify the stability of continental margins.

In this talk, I will primarily focus on fluid-rock interactions at convergent margins. The core of my presentation will be articulated around results from modern marine geophysical methods across the southern Hikurangi margin, New Zealand. I will discuss the implications of my results for the first-order structure of the overthrusting plate, the distribution of high pore-fluid pressures and the distribution of slow-slip events along the margin. 

Faculty Host:  Jeff Gee  (jsgee@ucsd.edu)
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Hubbs Hall 4500