Crustal thickness anomalies in the North Atlantic Ocean basin from gravity analysis

Wang, Tingting; Lin, Jian; Tucholke, Brian E.; Chen, Yongshun John

doi:10.1029/2010gc003402

Cited by 62 publications

(72 citation statements)

References 122 publications

(164 reference statements)

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“…The parameters used in the calculation are the same as in Wang et al . []. This mantle thermal model was then converted to a 3‐D mantle density structure, which was used to calculate gravitational effects.…”

Section: Data Acquisition and Processingmentioning

confidence: 99%

Spatial and temporal variations in crustal production at the Mid‐Atlantic Ridge, 25°N–27°30′N and 0–27 Ma

2015

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We use high-resolution multibeam bathymetry, shipboard gravity, side-scan sonar images, and magnetic anomaly data collected on conjugate flanks of the Mid-Atlantic Ridge at 25°N-27°30′N and out tõ 27 Ma crust to investigate the crustal evolution of the ridge. Substantial variations in crustal structure and thickness are observed both along and across isochrons. Along isochrons within spreading segments, there are distinct differences in seafloor morphology and gravity-derived crustal thickness between inside and outside corners. Inside corners are associated with shallow depths, thin crust, and enhanced normal faulting while outside corners have greater depths, thicker crust, and more limited faulting. Across-isochrons, systematic variations in crustal thickness are observed at two different timescales, one at~2-3 Myr and another at >10 Myr, and these are attributed to temporal changes in melt supply at the ridge axis. The shorter-term variations mostly are in-phase between conjugate ridge flanks, although the actual crustal thickness can be significantly different on the two flanks at any given time. We observe no correlation between crustal thickness and spreading rate. Thus, during periods of low melt supply, tectonic extension must increase to accommodate the full plate separation rate. This extension commonly is concentrated in long-lived faults on only one side of the axial valley, resulting in strong across-axis asymmetries in crustal thickness and seafloor morphology. The thin-crust flank has few volcanic features and exhibits elevated, blocky topography with large-offset, often irregular faults, while the conjugate thicker-crust flank shows shorter-offset, regular faulting, and common volcanic features. The variations in melt supply at the ridge axis most likely are caused either by episodic convection in the subaxial mantle or by variable melting of chemically heterogeneous mantle.

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Section: Data Acquisition and Processingmentioning

confidence: 99%

Spatial and temporal variations in crustal production at the Mid‐Atlantic Ridge, 25°N–27°30′N and 0–27 Ma

2015

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“…(d) The free-air gravity anomaly (FAA) of the study region, with data extracted from the global database of Sandwell et al (2014). Wang et al 2006Wang et al , 2011Zhao et al 2010;Lin & Zhu 2015); H c is the average thickness of the model oceanic crust and ρ w , ρ s , ρ c and ρ m are the densities of sea water, sediment, crust and mantle, respectively (Table 1). Non-Airy-isostatic topography: we then calculated the non-Airyisostatic topography of the Manila Trench (T noniso , Fig.…”

Section: Observational Constraintsmentioning

confidence: 99%

“…(4) Crustal thickness model: finally, we calculated models of crustal thickness variations by downward continuation of the RMBA signals to a constant-reference depth (e.g. Parker 1973; Kuo & Forsyth 1988;Wang et al 2011;Lin & Zhu 2015). The best-fitting parameters in the gravity modeling, including the mantle and crust densities used in the gravity model, were obtained from comparison with available seismic profiles in the SCS (Qiu et al 2001;Yan et al 2001;Hayes & Nissen 2005;Wang et al 2006;Zhao et al 2010 Notes: Symbol ' * ' represents data points with relatively poor constraints on key portions of the across-trench profile and thus were not plotted in Figs 6(c)-(i) and 7-10.…”

Section: A C K N O W L E D G E M E N T Smentioning

confidence: 99%

Intra- and intertrench variations in flexural bending of the Manila, Mariana and global trenches: implications on plate weakening in controlling trench dynamics

Zhang

Lin

Zhou

et al. 2017

Geophysical Journal International

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S U M M A R YWe conducted detailed analyses of a global array of trenches, revealing systematic intra-and intertrench variations in plate bending characteristics. The intratrench variations of the Manila and Mariana Trenches were analysed in detail as end-member cases of the relatively young (16-36 Ma) and old (140-160 Ma) subducting plates, respectively. Meanwhile, the intertrench variability was investigated for a global array of additional trenches including the Philippine, Kuril, Japan, Izu-Bonin, Aleutian, Tonga-Kermadec, Middle America, Peru, Chile, Sumatra and Java Trenches. Results of the analysis show that the trench relief (W 0 ) and width (X 0 ) of all systems are controlled primarily by the faulting-reduced elastic thickness near the trench axis (T m e ) and affected only slightly by the initial unfaulted thickness (T M e ) of the incoming plate. The reduction in T e has caused significant deepening and narrowing of trench valleys. For the cases of relatively young or old plates, the plate age could be a dominant factor in controlling the trench bending shape, regardless the variations in axial loadings. Our calculations also show that the axial loading and stresses of old subducting plates can vary significantly along the trench axis. In contrast, the young subducting plates show much smaller values and variations in axial loading and stresses.

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“…Notes: a) Marion -Zhang et al 14 ; b) Iceland& Azores -Wang et al 5 ; Galapagos -Canales et al 6 ; Marion -Zhang et al 14 . c) Maximum and minimum elevations are measured from shallowest point on axis, or midpoint of Iceland plateau to the rift valley axis point where average depth stabilizes or blocking transform.…”

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Thin crust as evidence for depleted mantle supporting the Marion Rise

Zhou

Dick

2013

Nature

137

106

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The global ridge system is dominated by oceanic rises reflecting large variations in axial depth associated with mantle hotspots. The little studied Marion Rise is as large as the Icelandic, considering length and depth, but has an axial rift rather than a high nearly its entire length. Uniquely, along the SW Indian Ridge systematic sampling allows direct examination of crustal architecture over its full length. Unlike Iceland, peridotites are extensively exposed high over the rise. This shows for the 1 st time that the crust is generally thin, and often missing over a rifted rise. Thus the rise must be largely an isostatic response to ancient melting events that created low-density depleted mantle beneath the ridge rather than thickened crust and/or a large thermal anomaly. The likely origin for the depleted mantle is that emplaced into the African asthenosphere during the Karoo and Madagascar flood basalt events. Following Morgan1 , common wisdom equates oceanic rises to a hot fertile mantle plume producing a flow of plume-derived mantle to the ridge and down the sub-axial asthenospheric channel, resulting in elevated mantle temperature, ridge topography, and thickened igneous crust (the mantle wedge hypothesis, e.g.:2 ). Studies of the Reykjanes Ridge support this, with seismic crust thickening from ~6 km near the Gibbs FZ for 1600 km to ~18 km at the Reykjanes Peninsula e.g.: 3 . The Icelandic Rise, also has a long axial high consistent with such robust magmatism 4 (Table 1). The current consensus is the igneous crust thickens from east to west up the Marion Rise, and indeed up all rises (e.g.: 5 6 ). Basalt sodium contents, like other rises, decrease systematically towards Marion, and are interpreted to represent higher degrees of mantle melting and thicker crust 7 . Dick et al. 8 , however, point out that such correlations can be due to variable mantle temperature, or an increasingly depleted mantle source composition, and do not require thicker crust. The Marion Rise, in particular, has numerous large-offset transforms that would block sub-axial asthenospheric flow (e.g.: 9 ), and its deep rift valley indicates anemic rather than robust magmatism 4 . Niu and O'Hara 10 , though assuming thick crust over rises, suggest the global correlation of basalt chemistry and ridge depth is best explained by mantle composition variations, with many rises supported by depleted chemically buoyant mantle as first proposed by O'hara 11 for the Iceland Rise and Presnall and Helsley 12 for the Azores.2 14 . c) Maximum and minimum elevations are measured from shallowest point on axis, or midpoint of Iceland plateau to the rift valley axis point where average depth stabilizes or blocking transform. d) The 200-km average represents average elevation about the highest or lowest point. e) Iceland average plateau height; crest of Azores Rise, SWIR @ 36°15Ed) MAR @ Charlie Gibbs FZ; axial valley floor, MAR @ 24°N, axial valley floor @61°45'E. e) Depth anomaly calculated for the 200-km averages to eliminate local topographic e...

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Crustal thickness anomalies in the North Atlantic Ocean basin from gravity analysis

Cited by 62 publications

References 122 publications

Spatial and temporal variations in crustal production at the Mid‐Atlantic Ridge, 25°N–27°30′N and 0–27 Ma

Spatial and temporal variations in crustal production at the Mid‐Atlantic Ridge, 25°N–27°30′N and 0–27 Ma

Intra- and intertrench variations in flexural bending of the Manila, Mariana and global trenches: implications on plate weakening in controlling trench dynamics

Thin crust as evidence for depleted mantle supporting the Marion Rise

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