Preliminary analysis of the Knipovich Ridge segmentation: influence of focused magmatism and ridge obliquity on an ultraslow spreading system

Okino, Kyoko; Curewitz, D.; Asada, Miho; Tamaki, Kensaku; Vogt, Peter R.; Crane, Kathleen

doi:10.1016/s0012-821x(02)00790-2

Cited by 73 publications

(87 citation statements)

References 45 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The submarine samples from Jan Mayen Island appear relatively evolved compared to the most magnesian subaerial samples of this study (MgO = 5.1-6.45 vs. 10.6-11.1 wt. %; Table S The Mohns Ridge is an ultraslow-spreading ridge (17 mm yr -1 full-spreading rate; Mosar et al, 2002; Dick et al, 2003) north of Jan Mayen Island with relatively thin crust (~4 km; Klingelhofer et al, 2000;Okino et al, 2002; Ljones et al, 2004; Kandilarov et al, 2008) and mainly characterised by highly oblique spreading expressed as a series of en echelon rift basins (Géli et al, 2012). In contrast, its southern segment (the SMR) has an orthogonal spreading direction and irregular off-axis crustal morphology, with a shallower ridge axis and thicker crust (~10 km; Kandilarov et al, 2012) (Fig.…”

Section: Lettermentioning

confidence: 99%

North Atlantic hotspot-ridge interaction near Jan Mayen Island

Elkins¹,

Hamelin²,

Blichert‐Toft³

et al. 2016

Geochem. Persp. Let.

View full text Add to dashboard Cite

At slow to ultraslow spreading rates along mid-ocean ridges, thicker lithosphere typically impedes magma generation and tectonic extension can play a more significant role in crustal production (Dick et al., 2003). The source of anomalously high magma supply thus remains unclear along ridges with ultraslow-spreading rates adjacent to Jan Mayen Island in the North Atlantic (Neumann and Schilling, 1984;Mertz et al., 1991; Haase et al., 1996;Schilling et al., 1999;Trønnes et al., 1999; Haase et al., 2003;Mertz et al., 2004;Blichert-Toft et al., 2005; Debaille et al., 2009). Here we show that Jan Mayen volcanism is likely the surface expression of a small mantle plume, which exerts significant influence on nearby mid-ocean ridge tectonics and volcanism. Progressive dilution of Jan Mayen geochemical signatures with distance from the hotspot is observed in lava samples from the immediately adjacent Mohns Ridge, and morphological indicators of enhanced magma supply are observed on both the Mohns Ridge and the nearby Kolbeinsey Ridge, which additionally locally overlies a highly heterogeneous, eclogite-bearing mantle source. These morphological and geochemical influences underscore the importance of heterogeneous mantle sources in modifying melt supply and thus the local expression of tectonic boundaries. LetterThe normal accretion process along divergent plate boundaries can be notably altered in hotspot-ridge interaction settings, where elevated mantle temperature anomalies enhance mantle melting, generating unusually thick oceanic crust (e.g., Schilling et al., 1985;Schilling, 1991; Gale et al., 2013 Gale et al., , 2014. Jan Mayen and its immediate environs in the North Atlantic (Fig. 1) include an intraplate, volcanically-active island or hotspot (Jan Mayen Island), positioned at the northern terminus of a small, rifted microcontinent (Jan Mayen Ridge; Johnson and Heezen, 1967; Kodaira et al., 1997; Gaina et al., 2009) and adjacent to two second-order ultraslow-spreading (Dick et al., 2003) ridge segments, the Northern Kolbeinsey Ridge (NKR) and Southern Mohns Ridge (SMR), and the Jan Mayen Fracture Zone, a major fracture zone with ~200 km of transform offset. Although different in key ways, broad geochemical similarities between Jan Mayen Island and Icelandic lavas have suggested the influence of a mantle plume (either a unique Jan Mayen plume or emplaced Icelandic material) on mantle melting beneath Jan Mayen Island (Schilling et al., 1999;Trønnes et al., 1999; Debaille et al., 2009). The absence of a clear hotspot track has led to conflicting, alternate interpretations for Jan Mayen's high magma production rate and enriched chemistry (Imsland, 1986;Maaløe et al., 1986;Thy et al., 1991): cold edge effects near the fracture zone (Mertz et al., 1991; Haase et al., 1996), variably melting source heterogeneities (Mertz et al., 1991; Haase et al., 2003;Mertz et al., 2004), upwelling along a mantle chemical discontinuity (Blichert-Toft et al., 2005), or a locally wet mantle (Haase et al., 2003;Mertz et al., 2004)....

show abstract

Section: Lettermentioning

confidence: 99%

North Atlantic hotspot-ridge interaction near Jan Mayen Island

Elkins¹,

Hamelin²,

Blichert‐Toft³

et al. 2016

Geochem. Persp. Let.

View full text Add to dashboard Cite

show abstract

“…These ridges had been largely unexplored until the 1990s, but significant portions are now mapped, both on and off axis (e.g. Mendel et al 1997;Rommevaux-Jestin et al 1997;Grindlay et al 1998;Sauter et al 2001;Okino et al 2002;Cannat et al 2003Cannat et al , 2006Cochran et al 2003;Dick et al 2003;Michael et al 2003). Because the MidCayman, Mohns and Knipovich ridges are relatively short (,400 km), the range of ultraslow segmentation scales is best investigated on the SWIR and Gakkel ridges.…”

Section: Ultraslow-spreading Ridgesmentioning

confidence: 99%

Tectonic and magmatic segmentation of the Global Ocean Ridge System: a synthesis of observations

Carbotte

Smith

Cannat

et al. 2015

View full text Add to dashboard Cite

Mid-ocean ridges display tectonic segmentation defined by discontinuities of the axial zone, and geophysical and geochemical observations suggest segmentation of the underlying magmatic plumbing system. Here, observations of tectonic and magmatic segmentation at ridges spreading from fast to ultraslow rates are reviewed in light of influential concepts of ridge segmentation, including the notion of hierarchical segmentation, spreading cells and centralized v. multiple supply of mantle melts. The observations support the concept of quasi-regularly spaced principal magmatic segments, which are 30-50 km long on average at fast-to slow-spreading ridges and fed by melt accumulations in the shallow asthenosphere. Changes in ridge properties approaching or crossing transform faults are often comparable with those observed at smaller offsets, and even very small discontinuities can be major boundaries in ridge properties. Thus, hierarchical segmentation models that suggest large-scale transform fault-bounded segmentation arises from deeper level processes in the asthenosphere than the finer-scale segmentation are not generally supported. The boundaries between some but not all principal magmatic segments defined by ridge axis geophysical properties coincide with geochemical boundaries reflecting changes in source composition or melting processes. Where geochemical boundaries occur, they can coincide with discontinuities of a wide range of scales.Discovery and interpretations of mid-ocean ridge (MOR) segmentation: historical review

show abstract

“…spreading rate ) and Knipovich Ridges (up to 16 mm/yr. ; ) have estimated crustal thicknesses of 4 to 8 kin, based on seismic data (Kandilarov et al, 2008;Klingelhofer et al, 2000;Ljones et al, 2004;Okino et al, 2002). The Mohns Ridge spreads NW-SE, which is oblique to the orientation of the axis, and Knipovich Ridge spreading is even more highly oblique (35 -490 obliquity; (Okino et al, 2002)).…”

Section: Geologic Settingmentioning

confidence: 99%

“…; ) have estimated crustal thicknesses of 4 to 8 kin, based on seismic data (Kandilarov et al, 2008;Klingelhofer et al, 2000;Ljones et al, 2004;Okino et al, 2002). The Mohns Ridge spreads NW-SE, which is oblique to the orientation of the axis, and Knipovich Ridge spreading is even more highly oblique (35 -490 obliquity; (Okino et al, 2002)). The ultraslow Knipovich Ridge contains amagmatic as well as magmatic sections, and the ridge axis is located in a series of pull-apart basins along the strike of the ridge that are underlain by small-scale transform structures Bathymetric and topographic profile along the Arctic ridge system, showing sample locations for this study.…”

Section: Geologic Settingmentioning

confidence: 99%

“…The ultraslow Knipovich Ridge contains amagmatic as well as magmatic sections, and the ridge axis is located in a series of pull-apart basins along the strike of the ridge that are underlain by small-scale transform structures Bathymetric and topographic profile along the Arctic ridge system, showing sample locations for this study. (Okino et al, 2002). Gakkel Ridge crust, due to the cold, thick lithosphere underlying ultraslow spreading centers, is extremely thin (5 3 km) and amagmatic in many locations, with local thickening beneath isolated active volcanoes along the ridge axis (Jokat and Schmidt-Aursch, 2007).…”

Section: Geologic Settingmentioning

confidence: 99%

See 1 more Smart Citation

Basalt petrogenesis beneath slow- and ultraslow-spreading Arctic mid-ocean ridges

Elkins¹

2009

View full text Add to dashboard Cite

To explore the ability of melting mafic lithologies to produce alkaline ocean-island basalts (OIB), an experimental study was carried out measuring clinopyroxene (Cpx)-melt and garnet (Gt)-melt partition coefficients during silica-poor garnet pyroxenite melting for a suite of trace elements, including U and Th, at 2.5GPa and 1420-1450'C.Partition coefficients range from 0.0083+0.0006 to 0.020+0.002 for Th and 0.0094+0.0006 to 0.024+0.002 for U in Cpx, and are 0.0032+0.0004 for Th and 0.013+0.002 for U in Gt. Forward-melting calculations using these experimental results to model time-dependent uranium-series isotopes do not support the presence of a fixed quantity of garnet pyroxenite in the source of OIB.To use U-series isotopes to further constrain mantle heterogeneity and the timing and nature of melting and melt transport processes, U-Th-Pa-Ra disequilibria, radiogenic isotopes, and trace-element compositions were measured for the slow-spreading Arctic mid-ocean ridges (MOR). A focused case study of 33 young (<10ka) MOR basalts (MORB) from the shallow endmember of the global ridge system, the Kolbeinsey Ridge ACKNOWLEDGMENTSMy deepest thanks, first and foremost, must go to Ken Sims, who taught me so much of what I know about mid-ocean ridge basalts, uranium-series chemistry, sample preparation, and thinking like a scientist. Ken was the most attentive and caring advisor, checking on me regularly to keep me on task and check in, but letting me take time to myself (and telling me to take vacations) when I needed it. Ken sent me all over the world to learn techniques in the best places from some of the best scientists, he challenged me to think things through, and he made sure I always had the resources I needed to excel. I could never have hoped for a more thoughtful, caring mentor.Glenn Gaetani taught me, step by patient step, how to construct and run my own pistoncylinder experiments. Glenn always had words of encouragement to keep me going despite all the difficult failures experimental work can sometimes entail. I got to see firsthand how methods are tested and developed in an experimental lab, and take part in that process. It was an invaluable learning experience, and it has left me with admiring respect for those lifelong experimentalists who love unwrapping their presents after an experiment is done, and who don't mind taking the occasional shower in coolant or finding anti-seize on the back of their elbow in bed at night.I also want to thank the rest of my committee. Fred Frey, my advisor at MIT, was there to teach me and help me think critically about my research throughout my time in the Joint Program. Jian Lin, from Geodynamics project advisor to exam committee chair to a thesis committee member, provided guidance and always reminded me to think beyond chemistry to the big picture questions involved. Peter Kelemen was always excited to talk about Kolbeinsey data and to share his innovative ideas, and he challenged me in committee meetings to think about everything in more depth. Susan Humph...

show abstract

Preliminary analysis of the Knipovich Ridge segmentation: influence of focused magmatism and ridge obliquity on an ultraslow spreading system

Cited by 73 publications

References 45 publications

North Atlantic hotspot-ridge interaction near Jan Mayen Island

North Atlantic hotspot-ridge interaction near Jan Mayen Island

Tectonic and magmatic segmentation of the Global Ocean Ridge System: a synthesis of observations

Basalt petrogenesis beneath slow- and ultraslow-spreading Arctic mid-ocean ridges

Contact Info

Product

Resources

About