Mantle flow patterns and magma chambers at ocean ridges: Evidence from the Oman ophiolite

1988 ◽  
Vol 9 (4) ◽  
pp. 293-310 ◽  
Author(s):  
A. Nicolas ◽  
F. Boudier ◽  
G. Ceuleneer
Keyword(s):  
Flow Patterns ◽  
Mantle Flow ◽  
Magma Chambers ◽  
Oman Ophiolite ◽  
Ocean Ridges

scholarly journals Kinematics of mantle flow beneath a fossil Overlapping Spreading Center: The Wuqbah massif case, Oman ophiolite

2002 ◽  
Vol 3 (7) ◽  
pp. 1-20 ◽  
Author(s):  
Jacques Girardeau ◽  
Christophe Monnier ◽  
Patrick Launeau ◽  
Frédéric Quatrevaux
Keyword(s):  
Spreading Center ◽  
Mantle Flow ◽  
Oman Ophiolite

The geochemistry of mafic and ultramafic from the Archaean greenstone belts of Sierra Leone

1983 ◽  
Vol 47 (344) ◽  
pp. 267-280 ◽  
Author(s):  
H. R. Rollinson
Keyword(s):  
Sierra Leone ◽  
Magma Chamber ◽  
Source Region ◽  
Double Diffusion ◽  
Ultramafic Rocks ◽  
Magma Chambers ◽  
Basaltic Rocks ◽  
Ocean Ridges ◽  
Different Depths ◽  
Greenstone Belts

AbstractThe Archaean (c. 2800 Ma) ultramafic rocks in eastern Sierra Leone cut basalt lavas and are mostly olivine-rich cumulates either iron-rich (Fo85–86) and derived from a basaltic or picritic parent, or more magnesian (Fo92–93) derived from an ultramafic melt with c. 18–25 wt. % MgO. In central Sierra Leone the ultramafic rocks are lavas predating tholeiitic basalts.The basalts show a wide variation in Zr/Y, suggesting that garnet was present in the source region of some of these rocks but not others. This implies that melting took place at different depths in the mantle. The REE evidence for basaltic rocks in the upper part of the Nimini belt succession suggests that they were derived from a mantle source region which had already suffered melt extraction. Ti/Zr ratios in the basaltic rocks are also variable and individual belts define different trends on a Ti vs. Zr plot implying that the basaltic rocks evolved in geographically distinct magma chambers. It is likely that the basaltic rocks evolved from a parental liquid with Ti/Zr = 90 via shallow level crystal fractionation. The source region for these rocks therefore had a lower than chondritic Ti/Zr.There are two possible models for the basaltic and ultramafic magmas in the Sierra Leone greenstone belts. First that the ultramafic and basaltic liquids were derived from mantle diapirs of differing size, but originating in the same region of the mantle. Ultramafic liquids were produced in small diapirs, which store large melt fractions, and basaltic liquids in larger diapirs which segregate larger melt fractions. A second model is based upon the double diffusion process suggested for magma chambers at mid-ocean ridges and involves a transient magma chamber from which basalts, derived from parental ultramafic liquids, are erupted, with ultramafic liquids rising directly to the surface when the magma chamber is frozen. The available data does not discriminate between these two models.

Mantle flow patterns at an oceanic spreading centre: The Oman peridotites record

1988 ◽  
Vol 151 (1-4) ◽  
pp. 1-26 ◽  
Author(s):  
G. Ceuleneer ◽  
A. Nicolas ◽  
F. Boudier
Keyword(s):  
Flow Patterns ◽  
Mantle Flow ◽  
Oceanic Spreading

Computing LPO for Geodynamic Models in ASPECT

2020 ◽  
Author(s):  
Magali Billen ◽  
Menno Fraters
Keyword(s):  
Water Content ◽  
Flow Pattern ◽  
Subduction Zones ◽  
Seismic Anisotropy ◽  
Flow Patterns ◽  
Mantle Flow ◽  
Lattice Preferred Orientation ◽  
Axis Alignment ◽  
Geodynamic Models ◽  
Initial Results

<p>When modeling subduction processes, the results are usually constrained by looking at the geological surface expressions, geochemistry and geophysical observations such as tomography and seismic anisotropy. Of these observations, seismic anisotropy is the only type of observation that can potentially be directly linked to the spatial flow pattern in the mantle. Seismic anisotropy in the mantle is due to lattice-preferred orientation (LPO) of olivine minerals. In subduction environments, which can have complex and changing flow patterns, it is not expected that the LPO necessarily aligns with the flow pattern. This is partly due to the fact that it takes time to realign the LPO and partly because the olivine fast axis alignment depends on the water content and the magnitude of stress. To overcome this problem, the LPO must be computed for realistic and end member subduction zones in order to be able to relate seismic anisotropy to mantle flow and thereby slab dynamics.</p><p>There are many ways to compute LPO. For this study we have used DREX (Kaminski et al., 2004), because the underlying method is accurate and fast enough for use in geodynamic models. To achieve a good and native integration with ASPECT (Kronbichler et al., 2012; Heister et al., 2017; Bangerth et al,. 2019), we have rewritten DREX in CPP as a plugin for ASPECT. In this presentation we will show how it was implemented and what the limitations and possibilities are. Furthermore, we will show initial results from 3D subduction models to study the link between seismic anisotropy and mantle flow.</p>

Buoyancy effects on mantle flow under Mid-Ocean Ridges

1993 ◽  
Vol 98 (B7) ◽  
pp. 12191-12205 ◽  
Author(s):  
Wusi Su ◽  
W. Roger Buck
Keyword(s):  
Mantle Flow ◽  
Ocean Ridges
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