Depleted spinel harzburgite xenoliths in Tertiary dykes from East Greenland: Restites from high degree melting

Bernstein, Stefan; Kelemen, P. B.; Brooks, C. Kent

doi:10.1016/s0012-821x(97)00175-1

Cited by 159 publications

(107 citation statements)

References 70 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The same xenolith suite however also contains a spectrum of peridotite compositions which include lherzolites with variable olivine content (down to 50%) and up to 25% clinopyroxene (Hanghøj et al, 2001). As with the western Greenlandic NAC, Os-isotopic compositions from these eastern Greenlandic NAC xenoliths record Archaean polybaric melt depletion for the harzburgites, initiating at 57 GPa (~210 km) and continuing at 2À3 GPa (65À100 km) (Bernstein et al, 1998). Later refertilization of restites added pyroxene (particularly clinopyroxene) and re-equilibrated the modal mineral and isotopic compositions at high temperatures (up to 980ºC).…”

Section: Overview Of the North Atlantic Craton à Formation Amalgamatmentioning

confidence: 81%

Trace-element abundances in the shallow lithospheric mantle of the North Atlantic Craton margin: Implications for melting and metasomatism beneath Northern Scotland

et al. 2015

View full text Add to dashboard Cite

Bulk rock geochemistry and major-and trace-element compositions of clinopyroxene have been determined for three suites of peridotitic mantle xenoliths from the North Atlantic Craton (NAC) in northern Scotland, to establish the magmatic and metasomatic history of subcontinental lithospheric mantle (SCLM) below this region. Spinel lherzolites from the southernmost locality (Streap Com'laidh) have non-NAC mantle compositions, while the two northern xenolith suites (Loch Roag and Rinibar) are derived from the thinned NAC marginal keel. Clinopyroxene compositions have characteristic trace-element signatures which show both 'primary' and 'metasomatic' origins. We use Zr and Hf abundances to identify ancient cryptic refertilization in 'primary' clinopyroxenes. We suggest that Loch Roag and Rinibar peridotite xenoliths represent an ancient ArchaeanPalaeoproterozoic SCLM with original depleted cratonic signatures which were overprinted by metasomatism around the time of intrusion of the Scourie Dyke Swarm (~2.4 Ga). This SCLM keel was preserved during Caledonian orogenesis, although some addition of material and/or metasomatism probably also occurred, as recorded by Rinibar xenoliths. Rinibar and Streap xenoliths were entrained in Permo-Carboniferous magmas and thus were isolated from the SCLM~200 Ma before Loch Roag xenoliths (in an Eocene dyke). Crucially, despite their geographical location, lithospheric mantle peridotite samples from Loch Roag show no evidence of recent melting or refertilization during the Palaeogene opening of the Atlantic.

show abstract

Section: Overview Of the North Atlantic Craton à Formation Amalgamatmentioning

confidence: 81%

Trace-element abundances in the shallow lithospheric mantle of the North Atlantic Craton margin: Implications for melting and metasomatism beneath Northern Scotland

et al. 2015

View full text Add to dashboard Cite

show abstract

“…This negative buoyancy could create convective instability of the lithosphere, with all or part of the thermal boundary layer foundering into the convecting mantle (e.g., Bird, 1979;Houseman et al, 1981). The thickness and stability of the thermal boundary layer underneath cratons, as indicated seismically and based on xenolith studies, suggest that convective instabilities have not removed large parts of the cratonic upper mantle for several billion years (Jordan, 1975a;Parsons and McKenzie, 1978).…”

Section: Vm15-22 Continuedmentioning

confidence: 99%

Subduction dynamics at the middle America trench : new constraints from swath bathymetry, multichannel seismic data, and 10BE

Kelly¹

2003

View full text Add to dashboard Cite

“…A density difference due to an age difference is mostly confined to depths less than 100 km. Although the density contrast can be slightly increased by increasing the asthenospheric temperature and the plate thickness, Bernstein et al, 1998]. Considering its depleted nature, the continental lithosphere at model distances less than 50 km can be less dense than oceanic mantle despite its greater age and consequently lower temperature [e.g., Jordan, 1988].…”

Section: Mantle Contributionsmentioning

confidence: 99%

“…Kinzler and Grove [1993], Hirose and Kushiro [1993], Baker and Stolper [1994], Kinzler [1997] and Walter [1998]. Bernstein et al, 1998], Siberia [Boyd et al, 1997], and Kaapvaal (Boyd, pers. comm.).…”

Section: Fram and Lesher [1997] Estimated Primary Melts For Various Rmentioning

confidence: 99%

Magmatism and dynamics of continental breakup in the presence of a mantle plume

Korenaga¹

2000

View full text Add to dashboard Cite

This thesis studies the dynamics of mantle melting during continental breakups by geophysical, geochemical, and numerical analyses. The first part focuses on the mantle melting and crustal accretion processes during the formation of the Southeast Greenland margin, on the basis of deep-crustal seismic data. A new seismic tomographic method is developed to jointly invert refraction and reflection travel times for a compressional velocity structure, and a long-wavelength structure with strong lateral heterogeneity is successfully recovered, including 30-to 15-km-thick igneous crust within a 150-km-wide continent-ocean transition zone. A nonlinear Monte Carlo analysis is also conducted to establish the absolute uncertainty of model parameters. The derived crustal structure is first used to resolve the origin of a margin gravity high, with new inversion schemes using both seismic and gravity constraints. Density anomalies producing the gravity high seem to be confined within the upper crust, not in the lower crust as suggested for other volcanic margins. A new robust framework is then developed for the petrological interpretation of the velocity structure of igneous crust, and the thick igneous crust formed at the continentocean transition zone is suggested to have resulted from vigorous active upwelling of mantle with only somewhat elevated potential temperature. In the second part, the nature of mantle melting during the formation of the North Atlantic igneous province is studied on the basis of the major element chemistry of erupted lavas. A new fractionation correction scheme based on the Ni concentrations of mantle olivine is used to estimate primary melt compositions, which suggest that this province is characterized by a large degree of major element source heterogeneity. In the third part, the nature of preexisting sublithospheric convection is investigated by a series of finite element analyses, because the strength of such convection is important to define the "normal" state of mantle, the understanding of which is essential to identify any anomalous behavior of mantle such as a mantle plume. The results suggest that small-scale convection is likely in normal asthenosphere, and that the upwelling velocity in such convection is on the order of 1-10 cm/yr. 271 Introductory NotesThis thesis is composed of three parts, all of which are related to the dynamics of mantle melting during continental breakups. In the first part, rifting magmatism associated with the opening of the North Atlantic (at -60 Ma) is investigated on the basis of deep-crustal seismic data collected across the Southeast Greenland continental margin. A new seismic tomographic method is developed to jointly invert refraction and reflection travel times for a two-dimensional velocity structure (Chapter 1). Several key issues in travel time tomography such as velocity-depth ambiguity and absolute parameter uncertainty are identified, and a practical strategy is presented to resolve them. The derived crustal velocity structure is the...

show abstract

Depleted spinel harzburgite xenoliths in Tertiary dykes from East Greenland: Restites from high degree melting

Cited by 159 publications

References 70 publications

Trace-element abundances in the shallow lithospheric mantle of the North Atlantic Craton margin: Implications for melting and metasomatism beneath Northern Scotland

Trace-element abundances in the shallow lithospheric mantle of the North Atlantic Craton margin: Implications for melting and metasomatism beneath Northern Scotland

Subduction dynamics at the middle America trench : new constraints from swath bathymetry, multichannel seismic data, and 10BE

Magmatism and dynamics of continental breakup in the presence of a mantle plume

Contact Info

Product

Resources

About