Abstract
Understanding the physical properties of ultramafic rocks is important for evaluating a wide variety of petrologic models of the oceanic lithosphere, particularly upper mantle and lower crust. Hydration of oceanic peridotites results in increasing serpentine content, which affects lithospheric physical properties and the global bio/geochemical cycles of various elements. In understanding tectonic, magmatic, and metamorphic history of the oceanic crust, interpreting seismic velocities, rock composition, and elastic moduli are of fundamental importance. In this study, we show that as serpentine content increases, density decreases linearly with a slope of 7.85. Porosity of the samples does not show any systematic correlation with serpentine content, as it is more strongly affected by local weathering and erosional processes. We also correlate increase in serpentine content with a linear decline in shear, bulk, and Young’s moduli with slopes of 0.48, 0.77, and 0.45, respectively. Our results show that increase in serpentine content of mantle wedge and forearc mantle contributes to their brittle behavior and result in break-offs, obduction, and overthrusting. Therefore, serpentine content strongly affects tectonic processes at subduction zones, particularly serpentinization may be responsible for formation of weak fault zones. Also, serpentinization of fresh oceanic peridotite in slow and ultra-slow spreading ridges may be responsible for observed discontinuities in thin crust.
Highlights
Understanding the physical properties of ultramafic rocks is important for evaluating the wide variety of petrologic models for the Earth’s upper mantle and lower oceanic crust [1].These properties have a key role in fluid flux and geochemical transport in magmatic systems at mid-oceanic ridges (e.g., [2,3,4]) and subduction zones (e.g., [5,6]), as well as in enhanced geothermal systems (e.g., [7,8])
Our results show that increase in serpentine content of mantle wedge and forearc mantle contributes to their brittle behavior and result in break-offs, obduction, and overthrusting
We show that in serpentinized dunites and pyroxenites as serpentine content increases, density decreases linearly with a slope of 7.85
Summary
Understanding the physical properties of ultramafic rocks (peridotites) is important for evaluating the wide variety of petrologic models for the Earth’s upper mantle and lower oceanic crust [1]. These properties have a key role in fluid flux and geochemical transport in magmatic systems at mid-oceanic ridges (e.g., [2,3,4]) and subduction zones (e.g., [5,6]), as well as in enhanced geothermal systems (e.g., [7,8]). Falcon-Suarez et al, [26] analyzed seismic velocities, electrical resistivity and permeability of four serpentinized peridotite samples from the southern wall of the Atlantis Massif, Mid-Atlantic Ridge, collected during International Ocean Discovery Program (IODP) Expedition 357
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