2012, Oceanography 25(1):89–93, http://dx.doi.org/10.5670/oceanog.2012.06
Michael R. Perfit | Department of Geological Sciences, University of Florida, Gainesville, FL, USA
V. Dorsey Wanless | Geology and Geophysics Department, Woods Hole Oceanographic Institution (WHOI), Woods Hole, MA, USA
W. Ian Ridley | Central Mineral and Environmental Resources Science Center, US Geological Survey, Denver, CO, USA
Emily M. Klein | Division of Earth and Ocean Sciences, Nicholas School of the Environment, Duke University, Durham, NC, USA
Matthew C. Smith | Department of Geological Sciences, University of Florida, Gainesville, FL, USA
Adam R. Goss | ExxonMobil Upstream Research Company, Houston, TX, USA
Jillian S. Hinds | Shaw Environmental, Melbourne, FL, USA
Scott W. Kutza | Baxter Pharmaceuticals, Bloomington, IN, USA
Daniel J. Fornari | Geology and Geophysics Department, WHOI, Woods Hole, MA, USA
Basalt lavas comprise the greatest volume of volcanic rocks on Earth, and most of them erupt along the world's mid-ocean ridges (MORs). These MOR basalts (MORBs) are generally thought to be relatively homogeneous in composition over large segments of the global ridge system (e.g., Klein, 2005). However, detailed sampling of two different regions on the northern East Pacific Rise (EPR) and extensive analysis of the samples show that fine-scale mapping and sampling of the ridge axis can reveal significant variations in lava chemistry on both small spatial and short temporal scales. The two most intensely sampled sites within the EPR Integrated Study Site (ISS) lie on and off axis between 9°17'N and 10°N, and from a wide region centered around 9°N where two segments of the EPR overlap (see Fornari et al., 2012, Figure 3, in this issue). The chemical composition of erupted lavas, similar to the genotype of an organism, can be used by igneous petrologists to trace the evolution of magmas from the mantle to the seafloor. The extensive and detailed geochemical studies at the EPR highlight how a thorough understanding of the variability in lava compositions on small spatial scales (i.e., between lava flows) and large spatial scales (i.e., from segment center to segment end and including discontinuities in the ridge crest) can be used in combination with seafloor photography, lava morphology, and bathymetry to provide insights into the magmatic system that drives volcanism and influences hydrothermal chemistry and biology at a fast-spreading MOR.
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