CHARACTERIZING THE INFLUENCE OF MANTLE HETEROGENEITY AND RESULTING MAGMA SUPPLY VARIATIONS ON DETACHMENT FAULTING AT SLOW-SPREADING MID-OCEAN RIDGES

It remains unclear how mantle heterogeneity influences plate tectonics and the generation of new crust through magmatic activity. The Kane-Atlantis Supersegment (21-31˚N) of the Mid-Atlantic Ridge (MAR) is a slow spreading ridge (2.2 cm/yr) and an ideal location for exploring the influence of mantle melting variations on crustal growth, because it is well mapped and heavily sampled. The ridge segment is 800 km long, with 13 second-order segments characterized by a combination of symmetrical normal faults and detachment faulting [Murton & Rona, 2015, Deep Sea Research Pt II, 121, 71-84]. To better characterize small-scale variations in the underlying melt source, we present new geochemical measurements of basaltic glass for a series of dredge and wax core samples retrieved from the Kane-Atlantis segment by the R/V Knorr in 2012. Preliminary radiogenic isotope results are moderately radiogenic (e_Hf = +16 to +18), suggesting a relatively trace element depleted mantle source.

To better characterize the influence of mantle source heterogeneity on ridge structural evolution, we aim to compare and evaluate statistical differences between lavas from segments with clearly identified faulting styles. If the presence or absence of detachment faults along slow-spreading ridge segments is controlled by underlying melt supply, we expect to observe systematic differences between symmetrical and asymmetrical segments, with asymmetrical segments driven by deficits in melt supply, akin to what was suggested at 13-14ºN MAR [Wilson et al., 2013, Geochemistry Geophysics Geosystems, 14, doi:10.1002/ggge.20046]. The details of these differences may then provide constraints on the relationships between trace element heterogeneity and the extent of melting beneath ocean ridges.