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- Title
Crustal Magmatic System Beneath the East Pacific Rise (8°20′ to 10°10′N): Implications for Tectonomagmatic Segmentation and Crustal Melt Transport at Fast‐Spreading Ridges.
- Authors
Marjanović, Milena; Carbotte, Suzanne M.; Carton, Hélène D.; Nedimović, Mladen R.; Canales, Juan Pablo; Mutter, John C.
- Abstract
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. Key Points: The 2‐D and 3‐D swath seismic data sets are used to characterize crustal magmatic system beneath the East Pacific Rise from 8°20′ to 10°10′NDisruptions in continuity of magma lenses are observed and in places are vertically aligned indicating coincident magmatic segmentationObservations support the hypothesis that third‐order segments represent volcanic/magmatic units extending from seafloor to uppermost mantle
- Subjects
EAST Pacific Rise; MID-ocean ridges; MAGMAS; CRUST of the earth; EARTH'S mantle
- Publication
Geochemistry, Geophysics, Geosystems: G3, 2018, Vol 19, Issue 11, p4584
- ISSN
1525-2027
- Publication type
Article
- DOI
10.1029/2018GC007590