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E-MORB
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The nomenclature is confusing and recent studies have shown that among mid-ocean ridge basalts (generally called MORBs) that normal mid-ocean ridge basalts (NMORB) should reflect the statistically usual composition while enhanced MORB (EMORB) and depleted MORB (DMORB) should reflect end-members of the MORB population.
Of particular importance and a subject of ongoing debate is the ubiquity of ``enriched-type'' samples, or E-MORB, which represent a subordinate component of global MORB and are 5 - 10× more ...
These E-MORB subsequently spread away from the AST, and, finally, were preserved on the seafloor through asymmetric construction of the extrusive layer. Taken together, the range of ages of E-MORB at 9-10°N EPR and the geochemical and isotopic mixing trends suggest that enriched melts are continuously supplied to the ridge axis, but because ...
E-MORB, are more evolved than N-MORB from comparable regions of the ocean and there are a higher proportion of E-MORB in the Atlantic (31%) compared to the Pacific (12%) and Galapagos Spreading Center region (7%). Unlike the Atlantic where E-MORB are typically associated with inflated portions of the ridge due to the effects of plume-ridge ...
What is the origin of E-MORB? Three suggestions for the Source of E-MORB: 1. Derived from a deeper more fertile mantle. 2. Depleted upper mantle may be locally fertilized by prior intrusion of magmas from the deeper mantle 3. Mixing occurs laterally along mid-ocean ridges with material from nearby plumes (e.g. Iceland, Galapagos) Note how Sr ...
The E-MORB pattern is characterized by a strong enrichment in the highly incompatible elements and a depletion in the middle to heavy REE, crossing over the REE patterns of the N- and D-MORB. The N-MORB in this study, calculated as the log-normal mean (most typical value) of segments >500 km from a plume, is more enriched than previously ...
The minimum amount of solid recycled MORB-like pyroxenite in a peridotitic (DMM) source required to produce E-MORB is ~10%, while that of the solid primary eclogite precursor to secondary pyroxenite required to produce E-MORB is 16% (see the Supplementary Materials). For N-MORB compositions, intermediate amounts are required (see the ...
As shown in Fig. 15C and D, the Benqu diorite samples plot near the lower continental crust (LCC) and E-MORB standard points and show an evolutionary trend toward an enriched mantle source. ...
The distinctions between N-MORB, E-MORB, and OIB provide valuable insights into the complex processes occurring within the Earth's mantle and the tectonic environments in which volcanism occurs. N-MORB represents the composition of the depleted upper mantle, while E-MORB reflects some enrichment, probably due to subduction-related processes.
Many E-MORB (or "P-MORB") are clearly associated with obvious hot spots or plumes such as Iceland [Schilling, 1973]. Others have been interpreted to be formed by channels or offshoots of plume material into the asthenosphere [Schilling et al., 1985]. But some E-MORB, and this includes many small seamounts, cannot be attributed to input from ...