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Cross-sectional areas of mid-ocean ridge axes bounding the Easter and Juan Fernandez microplates

Content Provider	Springer Nature Link
Author	Pardee, Debra R. Hey, Richard N. Martinez, Fernando
Copyright Year	1998
Abstract	We have calculated cross-sectional areas for the ridges bounding the Easter and Juan Fernandez microplates, 22°–28°S and 31°–35°S, obtaining accurate results where complete bathymetric data exist and estimates in other regions with partial bathymetric coverage and predicted bathymetry. We consider the reliability and usefulness of global predicted bathymetry in these calculations and the possible application of this dataset in other localities. The spreading rates on ridges bounding these microplates span the range from slow to superfast, allowing an investigation of ridge axis inflation over most of the rates active on Earth today. The across-axis areas of the Easter microplate ridge axes range from −29 km$^{2}$ to 7 km$^{2}$, while the Juan Fernandez ridge axis areas range from −27 km$^{2}$ to 8 km$^{2}$. Positive values correlate with regions usually interpreted as magmatically robust. Negative values arise from calculations in areas of propagating rift tips and deep grabens, such as Pito and Endeavor Deeps. Geochemical trends of Easter microplate axial basalts show decreasing MgO toward propagating rift tips and slight positive correlations between variables such as MgO vs. cross-sectional area, Na$_{8.0}$ vs. axial depth, and Na$_{8.0}$ vs. cross-sectional area. We document the decrease in the axial area approaching segment ends and propagating rift tips along both the West and East ridges of the microplates. On the Easter microplate both East and West ridge systems undergo large variations in spreading rate from >130 km Myr$^{−1}$ to <50 km Myr$^{−1}$. Inflation on these ridge segments is highly variable and only weakly correlated with spreading rate. On the Juan Fernandez microplate, West ridge spreading rates vary only between ∼115–140 km Myr$^{−1}$ and are systematically faster than on the East ridge, where rates vary between ∼10–35 km Myr$^{−1}$. Cross axis areas are systematically greater and significantly less variable on the faster spreading West ridge. Overall, compared to oceanic spreading centers bounding major plates with similar spreading rates, the axial areas are smaller on the microplate ridge systems, possibly because their rapidly changing configurations create a lag in the mantle response to the rigid plate boundary.
Starting Page	517
Ending Page	531
Page Count	15
File Format	PDF
ISSN	00253235
Journal	Marine Geophysical Researches
Volume Number	20
Issue Number	6
e-ISSN	15730581
Language	English
Publisher	Kluwer Academic Publishers
Publisher Date	1998-01-01
Publisher Place	Dordrecht
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Geosciences Geophysics/Geodesy Oceanography Offshore Engineering
Content Type	Text
Resource Type	Article
Subject	Geochemistry and Petrology Geophysics Oceanography

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