Geochemistry of lavas from the 2005–2006 eruption at the East Pacific Rise, 9°46′N–9°56′N : implications for ridge crest plumbing and decadal changes in magma chamber compositions
Goss, Adam R.
Perfit, Michael R.
Ridley, W. Ian
Rubin, Kenneth H.
Kamenov, G. D.
Soule, Samuel A.
Fornari, Daniel J.
MetadataShow full item record
KeywordMid-ocean ridge basalt; East Pacific Rise; Eruption; Trace elements; Radiogenic isotopes; Fractional crystallization
Detailed mapping, sampling, and geochemical analyses of lava flows erupted from an ∼18 km long section of the northern East Pacific Rise (EPR) from 9°46′N to 9°56′N during 2005–2006 provide unique data pertaining to the short-term thermochemical changes in a mid-ocean ridge magmatic system. The 2005–2006 lavas are typical normal mid-oceanic ridge basalt with strongly depleted incompatible trace element patterns with marked negative Sr and Eu/Eu* anomalies and are slightly more evolved than lavas erupted in 1991–1992 at the same location on the EPR. Spatial geochemical differences show that lavas from the northern and southern limits of the 2005–2006 eruption are more evolved than those erupted in the central portion of the fissure system. Similar spatial patterns observed in 1991–1992 lavas suggest geochemical gradients are preserved over decadal time scales. Products of northern axial and off-axis fissure eruptions are consistent with the eruption of cooler, more fractionated lavas that also record a parental melt component not observed in the main suite of 2005–2006 lavas. Radiogenic isotopic ratios for 2005–2006 lavas fall within larger isotopic fields defined for young axial lavas from 9°N to 10°N EPR, including those from the 1991–1992 eruption. Geochemical data from the 2005–2006 eruption are consistent with an invariable mantle source over the spatial extent of the eruption and petrogenetic processes (e.g., fractional crystallization and magma mixing) operating within the crystal mush zone and axial magma chamber (AMC) before and during the 13 year repose period. Geochemical modeling suggests that the 2005–2006 lavas represent differentiated residual liquids from the 1991–1992 eruption that were modified by melts added from deeper within the crust and that the eruption was not initiated by the injection of hotter, more primitive basalt directly into the AMC. Rather, the eruption was driven by AMC pressurization from persistent or episodic addition of more evolved magma from the crystal mush zone into the overlying subridge AMC during the period between the two eruptions. Heat balance calculations of a hydrothermally cooled AMC support this model and show that continual addition of melt from the mush zone was required to maintain a sizable AMC over this time interval.
Author Posting. © American Geophysical Union, 2010. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 11 (2010): Q05T09, doi:10.1029/2009GC002977.
Showing items related by title, author, creator and subject.
Navigational infrastructure at the East Pacific Rise 9°50′N area following the 2005–2006 eruption : seafloor benchmarks and near-bottom multibeam surveys Soule, Samuel A.; Ferrini, Vicki L.; Kinsey, James C.; Fornari, Daniel J.; Sellers, Cynthia J.; White, Scott M.; Von Damm, Karen L.; Carbotte, Suzanne M. (American Geophysical Union, 2008-11-06)Four seafloor benchmarks were deployed with ROV Jason2 at frequently visited areas along the northern East Pacific Rise (NEPR) ridge crest near 9°50′N, within the Ridge2000 EPR integrated study site (ISS) bull's eye. When ...
Hydrothermal vent mussel habitat chemistry, pre- and post-eruption at 9°50′North on the East Pacific Rise Nees, Heather A.; Moore, Tommy S.; Mullaugh, Katherine M.; Holyoke, Rebecca R.; Janzen, Christopher P.; Ma, Shufen; Metzger, Edouard; Waite, Tim J.; Yucel, Mustafa; Lutz, Richard A.; Shank, Timothy M.; Vetriani, Costantino; Nuzzio, Donald B.; Luther, George W. (National Shellfisheries Association, 2008-03)Between October 2005 and March 2006, a seafloor volcanic eruption occurred at 9°50′N East Pacific Rise (EPR), establishing a “time zero” for characterizing newly-formed hydrothermal vent habitats and comparing them to ...
Bowles, Julie A.; Gee, Jeffrey S.; Kent, Dennis V.; Perfit, Michael R.; Soule, Samuel A.; Fornari, Daniel J. (American Geophysical Union, 2006-06-08)Placing accurate age constraints on near-axis lava flows has become increasingly important given the structural and volcanic complexity of the neovolcanic zone at fast spreading ridges. Geomagnetic paleointensity of submarine ...