Publication Date:
2022-10-26
Description:
Author Posting. © American Geophysical Union, 2018. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Crustal magmatic system beneath the East Pacific Rise (8°200 to 10°100N): Implications for tectonomagmatic segmentation and crustal melt transport at fast-spreading ridges. Geochemistry, Geophysics, Geosystems, 19, (2018): 4584–4611, doi: 10.1029/2018GC007590 .
Description:
Detailed images of the midcrustal magmatic system beneath the East Pacific Rise (8°20′–10°10′N) are obtained from 2‐D and 3‐D‐swath processing of along axis seismic data and are used to characterize properties of the axial crust, cross‐axis variations, and relationships with structural segmentation of the axial zone. Axial magma lens (AML) reflections are imaged beneath much of the ridge axis (mean depth 1,640 ± 185 m), as are deeper sub‐AML (SAML) reflections (brightest events ~100–800 m below AML). Local shallow regions in the AML underlie two regions of shallow seafloor depth from 9°40′–55′N and 8°26′–33′N. Enhanced magma replenishment at present beneath both sites is inferred and may be linked to nearby off‐axis volcanic chains. SAML reflections, which are observed primarily from 9°20′ to 10°05′N, indicate a finely segmented magma reservoir similar to the AML above, composed of subhorizontal, 2‐ to 7 km‐long AML segments, often with stepwise changes in reflector depth from one segment to the next. We infer that these melt bodies are related to short‐lived melt instability zones. In many locations including where seismic constraints are strongest the intermediate scale (~15–40 km) structural segmentation of the ridge axis identified in this region coincides with (1) changes in average thickness of layer 2A (by 10%–15%), (2) changes in average depth of AML (〈100 m), and (3) with the spacing of punctuated low velocity zones mapped in the uppermost mantle. The ~6 km dominant length of multiple AML segments within each of the larger structural segments may reflect the spacing of local sites of ascending magma from discrete melt reservoirs pooled beneath the crust.
Description:
We thank the crew of the MGL0812 expedition aboard R/V Marcus G. Langseth. Special thanks to the Captain M. Landow and technical staff led by R. Steinhaus and Science Officer A. Johnson for their efforts that led to a successful research cruise. We are grateful to D. J. Fornari, D.R. Toomey, and an anonymous reviewer for their comments and suggestions that significantly improved the manuscript. Seismic data from this study are archived with the IEDA MGDS (Mutter et al., 2008) and Academic Suport Portal (ASP) at UTIG (Marjanović et al., 2018). We would also like to thank Vicki Ferrini for Matlab code for manipulating data grids. Software packages Focus and VoxelGeo by Paradigm Geophysical were used for seismic data processing and interpretation. This research was supported by NSF awards OCE0327872 to J. C. M. and S. M. C., OCE‐0327885 to J. P. C., and OCE0624401 to M. R. N.
Description:
2019-05-06
Keywords:
Mid‐ocean ridges
;
Multichannel seismic data
;
Tectonomagmatic segmentation
;
Melt transport
;
East Pacific Rise
Repository Name:
Woods Hole Open Access Server
Type:
Article
