We use cookies to ensure that we give you the best experience on our website. You can change your cookie settings at any time. Otherwise, we'll assume you're OK to continue.

Durham University

Department of Earth Sciences


Publication details for Dr Geoff Nowell

Pearson, D.G & Nowell, G.M (2004). Re-Os and Lu-Hf isotope constraints on the origin and age of pyroxenites from the Beni Bousera peridotite massif: implications for mixed peridotite-pyroxenite melting models. Journal of Petrology 45(2): 439-455.

Author(s) from Durham


A suite of pyroxenites from the Beni Bousera peridotite massif, northern Morocco, have been analysed for Re–Os and Lu–Hf isotopic compositions. Measured sections of the massif indicate that pyroxenite layers make up between 1 and 9% by volume of the total outcrop. Clinopyroxenes from two Cr-diopside pyroxenites have unradiogenic Hf isotope compositions (Hfi -7·7 to -8·5) whereas those of the Al-augite suite are more radiogenic (Hfi 9·4 to 25·6). In general, the Nd–Hf isotope compositions of the pyroxenites lie close to the mantle array. One garnet pyroxenite lies significantly below the mantle Hf–Nd isotope array such that it requires an ancient history characterized by high Lu/Hf and Sm/Nd but low Lu/Hf relative to Sm/Nd. As with the Sm–Nd and Rb–Sr systems, parent–daughter and isotopic ratios for the Lu–Hf system have been recently decoupled by a partial melting event associated with transfer of the massif from mantle to crust. This created highly fractionated Sm/Nd and Lu/Hf ratios in many rocks and the pyroxenites can be referred to as ‘residual’. The near-solidus extraction of a siliceous melt from the pyroxenites is also a possible explanation for the orthopyroxene-rich margins to numerous pyroxenite layers, via reaction with peridotite. Pyroxenite Os isotope compositions are much more radiogenic than their host peridotites. In contrast to the non-systematic Nd and Hf model ages, a large portion of the pyroxenite Re–Os model ages cluster between 1·2 and 1·4 Ga, within error of the model ages defined by many Ronda pyroxenites and close to the precise 1·43 ± 0·07 Ga Lu–Hf isochron defined by clinopyroxenes from the peridotites. The Re–Os system thus seems to have been more robust to late-stage melting events that decoupled Sm/Nd and Lu/Hf isotope systematics in the pyroxenites. In contrast to pyroxenites measured from Ronda, some Beni Bousera pyroxenites have relatively radiogenic Os isotope compositions at high Os concentrations (0·18 to >2 ppb), comparable with values reported for some cratonic pyroxene-rich xenoliths. In contrast to cratonic eclogites, most pyroxenites analysed here and those reported in the literature lie close to the mantle Nd–Hf isotope array. The Nd–Sr–Pb–Hf isotopic compositions and stable isotope characteristics of these pyroxenites reflect signatures from recycled oceanic crust and sediment. Hence, mixing of such material, if present within the convecting mantle, with peridotite, could account for some of the heterogeneity seen in oceanic basalts. Small amounts of pyroxenite incorporated into peridotite can also produce the radiogenic Os isotope signatures evident in the source of oceanic basalts. However, these observations alone do not require pyroxenite to be an integral part of the convecting upper-mantle magma source region. The spectrum of Nd, Hf and Os isotope compositions also makes them a suitable component to explain some of the isotopic characteristics of the source regions of ultrapotassic magmas.


Allegre, C. J. & Turcotte, D. L. (1986). Implications of a two
component marble-cake mantle. Nature 323, 123---127.
Beard, B. L. & Johnson, C. M. (1993). Hf isotope composition of late
Cenozoic basaltic rocks from northwestern Colorado, U.S.A.: new
constraints on mantle enrichment processes. Earth and Planetary Science
Letters 119, 495---509.
Becker, H. (2000). Re---Os fractionation in eclogites and blueschists and
the implications for recycling of oceanic crust into the mantle. Earth
and Planetary Science Letters 177, 287---300.
Becker, H., Shirey, S. B. & Carlson, R. W. (2001). Effects of melt
percolation on the Re---Os systematics of peridotites from a Paleozoic
convergent margin. Earth and Planetary Science Letters 188, 107---121.
Blichert-Toft, J. (2001). On the Lu---Hf isotope geochemistry of silicate
rocks. Geostandards Newsletter 25, 41---56.
Blichert-Toft, J., Chauvel, C. & Albarede, F. (1997). Separation of Hf
and Lu for high-precision isotope analysis of rock samples by
magnetic sector-multiple collector ICP-MS. Contributions to Mineralogy
and Petrology 127, 248---260.
Blichert-Toft, J., Albarede, F. & Kornprobst, J. (1999a). Lu---Hf isotope
systematics of garnet pyroxenites from Beni Bousera, Morocco:
implications for basalt origin. Science 283, 1303---1306.
Blichert-Toft, J., Frey, F. & Albarede, F. (1999b). Hf isotope evidence
for pelagic sediments in the source of the Hawaiian basalts. Science
285, 879---882.
Bodinier, J.-L., Merlet, C., Bedini, R. M., Simien, F., Remaidi, M. &
Garrido, C. J. (1996). Distribution of niobium, tantalum, and other
highly incompatible trace elements in the lithospheric mantle: the
spinel paradox. Geochimica et Cosmochimica Acta 60, 545---550.
Carlson, R. W. & Irving, A. J. (1994). Depletion and enrichment
history of sub-continental lithospheric mantle: Os, Sr, Nd and Pb
evidence for xenoliths from the Wyoming craton. Earth and Planetary
Science Letters 126, 457---472.
Carlson, R. W. & Nowell, G. M. (2001). Olivine-poor sources for
mantle-derived magmas: Os and Hf isotopic evidence from potassic
magmas of the Colorado Plateau. Geochemistry, Geophysics, Geosystems 2,
Carlson, R. W., Esperanca, S. & Svisero, D. P. (1996). Chemical and
Os isotopic study of Cretaceous potassic rocks from southern Brazil.
Contributions to Mineralogy and Petrology 125, 393---405.
Chauvel, C. & Blichert-Toft, J. (2001). A hafnium isotope and trace
element perspective on melting of the depleted mantle. Earth and
Planetary Science Letters 190, 137---151.
Davies, G. R., Nixon, P. H., Pearson, D. G. & Obata, M. (1993).
Tectonic implications of graphitised diamonds from the Ronda
peridotite massif, southern Spain. Geology 21, 471---474.
Dowall, D. P., Nowell, G. M. & Pearson, D. G. (2003). A 2-column
procedure for the pre-concentration of Sr, Nd and Hf for isotopic
analysis by plasma ionisation multi-collector mass spectrometry. In:
Holland, J. G. & Tanner, S. D. (eds) Plasma Source Mass Spectrometry:
Applications and Emerging Technologies. Cambridge: Royal Society of
Chemistry, pp. 321---337.
Foley, S. F. (1992). Vein-plus-wall-rock melting mechanisms in the
lithosphere and the origin of potassic alkaline magmas. Lithos 28,
Gibson, S. A., Thompson, R. N. & Dickin, A. P. (2000). Ferropicrites:
geochemical evidence for Fe-rich streaks in upwelling mantle
plumes. Earth and Planetary Science Letters 174, 355---374.
Hauri, E. & Hart, S. R. (1993). Re---Os isotope systematics in HIMU
and EMII ocean island basalts. Earth and Planetary Science Letters 114,
Hauri, E. H. (1996). Major-element variability in the Hawaiian mantle
plume. Nature 382, 415---419.
Hirschmann, M. M. & Stolper, E. M. (1996). A possible role for garnet
pyroxenite in the origin of the ‘garnet signature’ in MORB.
Contributions to Mineralogy and Petrology 124, 185---208.
Irving, A. J. (1974). Geochemical and high pressure experimental
studies of garnet pyroxenite and pyroxene granulite xenoliths from
the Delegate pipes, Australia. Journal of Petrology 15, 1---40.
Jacob, D. E., Bizimis, M. & Salters, V. J. M. (2002). Lu---Hf isotope
systematics of subducted ancient oceanic crust: Roberts Victor
eclogites. Geochimica et Cosmochimica Acta 66S1, A360.
Kellog, L. H. (1992). Mixing in the mantle. Annual Review of Earth and
Planetary Sciences 20, 365---388.
Kornprobst, J. (1969). Le massif ultrabasique des Beni Bouchera (Rif
Interne, Maroc). Contributions to Mineralogy and Petrology 29, 283---322.
Kornprobst, J., Piboule, M., Roden, M. & Tabit, A. (1990).
Corundum-bearing garnet clinopyroxenites at Beni Bousera
(Morocco): original plagioclase-rich gabbros recrystallized at depth
within the mantle? Journal of Petrology 31, 717---745.
Kumar, N., Reisberg, L. & Zindler, A. (1996). A major and trace
element and Sr, Nd and Os isotopic study of a thick pyroxenite layer
from the Beni Bousera ultramafic complex of N. Morocco. Geochimica
et Cosmochimica Acta 60, 1429---1444.
Langmuir, C. H., Klein, E. M. & Plank, T. (1992). Petrological
constraints on melt formation and migration beneath mid-ocean
ridges. In: Phipps Morgan, J., Blackman, D. & Sinton, J. L. (eds)
Mantle Flow and Melt Generation at Mid-Ocean Ridges. Geophysical
Monograph, American Geophysical Union 71, 183---280.
Loubet, M. & Allegre, C. J. (1982). Trace elements in orogenic
lherzolites reveal the complex history of the upper mantle. Nature
298, 809---811.
Lundstrum, C., Gill, J., Williams, Q. & Perfit, M. (1995). Mantle
melting and basalt extraction by equilibrium porous flow. Science 270,
Marcantonio, F., Zindler, A., Elliott, T. & Staudigel, H. (1995). Os
isotope systematics of La Palma, Canary Islands; evidence for
recycled crust in the mantle source of HIMU ocean islands. Earth and
Planetary Science Letters 133(3---4), 397---410.
Nowell, G. M., Kempton, P. D., Noble, S. R., Fitton, J. G.,
Saunders, A. D., Mahoney, J. J. & Taylor, R. N. (1998). High
precision Hf isotope measurements of MORB and OIB by thermal
ionisation mass spectrometry: insights into the depleted mantle.
Chemical Geology 149, 211---233.
Nowell, G. M., Pearson, D. G., Ottley, C. J., Dowall, D. P. &
Schwieters, J. (2003a). Long-term performance characteristics of a
plasma ionisation multi-collector mass spectrometer: the Thermo-
Finnigan Neptune. In: Holland, J. G. & Tanner, S. D. (eds) Plasma
Source Mass Spectrometry. Special Publication of the Royal Society of Chemistry,
London 307---320.
Nowell, G. M., Pearson, D. G., Jacob, D. J., Spetsius, Z. V., Nixon, P.
H. & Haggerty, S. E. (2003b). The origin of alkremites and related
rocks: a Lu---Hf, Rb---Sr and Sm---Nd isotope study. Extended Abstracts,
8th International Kimberlite Conference, Victoria, FLA 0271.
Ottley, C. J., Pearson, D. G. & Irvine, G. J. (2003). A routine procedure
for the analysis of REE and trace elements in geological samples by
ICP-MS. In: Holland, J. G. & Tanner, S. D. (eds) Plasma Source Mass
Spectrometry: Applications and Emerging Technologies. Cambridge: Royal
Society of Chemistry, pp. 221---230.
Pearson, D. G. (1989). The petrogenesis of pyroxenites containing
octahedral graphite and associated mafic and ultramafic rocks of the
Beni Bousera peridotite massif, N. Morocco. Ph.D. thesis, University
of Leeds, 412 pp.
Pearson, D. G. & Nixon, P. H. (1996). Diamonds in young orogenic
belts: graphitised diamonds from Beni Bousera, N. Morocco, a
comparison with kimberlite-derived diamond occurrences and
implications for diamond genesis and exploration. Africa Geoscience
Reviews 3, 295---316.
Pearson, D. G. & Nowell, G. M. (2003). Dating mantle differentiation:
a comparison of the Lu---Hf, Re---Os and Sm---Nd isotope systems in
the Beni Bousera peridotite massif and constraints on the Nd---Hf
composition of the lithospheric mantle. Geophysical Research Abstracts 5,
Pearson, D. G. & Woodland, S. J. (2000). Carius tube digestion and
solvent extraction/ion exchange separation for the analysis of PGEs
(Os, Ir, Pt, Pd, Ru) and Re---Os isotopes in geological samples by
isotope dilution ICP-mass spectrometry. Chemical Geology 165,
Pearson, D. G., Davies, G. R., Nixon, P. H. & Milledge, H. J. (1989).
Graphitized diamonds from a peridotite massif in Morocco and
implications for anomalous diamond occurrences. Nature 338,
Pearson, D. G., Davies, G. R., Nixon, P. H., Greenwood, P. B. &
Mattey, D. P. (1991). Oxygen isotope evidence for the origin of
pyroxenites in the Beni Bousera peridotite massif, North Morocco;
derivation from subducted oceanic lithosphere. Earth and Planetary
Science Letters 102, 289---301.
Pearson, D. G., Davies, G. R. & Nixon, P. H. (1993). Geochemical
constraints on the petrogenesis of diamond facies pyroxenites from
the Beni Bousera peridotite massif, north Morocco. Journal of Petrology
34, 125---172.
Pearson, D. G., Snyder, G. A., Shirey, S. B., Taylor, L. A.,
Carlson, R. W. & Sobolev, N. V. (1995a). Archaean Re---Os age
for Siberian eclogites and constraints on Archaean tectonics. Nature
374, 711---713.
Pearson, D. G., Davies, G. R. & Nixon, P. H. (1995b). Orogenic
ultramafic rocks of UHP (diamond facies) origin. In: Coleman, R. G.
& Wang, X. (eds) Ultrahigh Pressure Metamorphism. Cambridge:
Cambridge University Press, pp. 456---510.
Pearson, D. G., Canil, D. & Shirey, S. B. (2004a). Mantle samples
included in volcanic rocks: xenoliths and diamonds, In: Turekian, K.
& Holland, H. D. (eds) Treatise on Geochemistry, Volume 2: The Mantle
and Core. Amsterdam: Elsevier (in press).
Pearson, D. G., Irvine, G. J., Ionov, D. A., Boyd, F. R. & Dreibus, G. E.
(2004b). Re---Os isotope systematics and Platinum Group Element
fractionation during mantle melt extraction: a study of peridotite
xenoliths from the N. Lesostho and S. Namibian kimberlites, the
Vitim volcanic field and massif peridotites from Beni Bousera.
Chemical Geology Special Volume: Highly Siderophile Elements (in press).
Polve, M. (1983). Les isotopes du Nd et du Sr dans les lherzolites
orogeniques: contribution a la determination de la structure et de la
dynamique du manteau superieur. Ph.D. thesis, Universite Paris 7.
Polve, M. & Allegre, C. J. (1980). Orogenic lherzolite complexes
studied by 87Rb---87Sr: a clue to understand the mantle convection
processes. Earth and Planetary Science Letters 51, 71---93.
Prinzhofer, A., Lewin, E. & Allegre, C. J. (1989). Stochastic melting of
the marble-cake mantle: evidence from local study of EPR at 12
degrees 50 N. Earth and Planetary Science Letters 92, 189---196.
Ravizza, G. & Turekian, K. K. (1992). The osmium isotopic
composition of organic-rich marine sediments. Earth and Planetary
Science Letters 55, 3741---3752.
Reisberg, L. C. & Lorand, J. P. (1995). Longevity of sub-continental
mantle lithosphere from osmium isotope systematics in orogenic
peridotite massifs. Nature 376, 159---162.
Reisberg, L. C., Zindler, A. & Jagoutz, E. (1989). Sr and Nd isotopic
compositions of garnet and spinel bearing peridotites in the Ronda
ultramafic complex. Earth and Planetary Science Letters 96, 161---180.
Reisberg, L. C., Allegre, C. J. & Luck, J.-M. (1991). The Re---Os
systematics of the Ronda ultramafic complex in southern Spain.
Earth and Planetary Science Letters 105, 196---213.
Righter, K. & Hauri, E. H. (1998). Compatibility of rhenium in garnet
during mantle melting and magma genesis. Science 280, 1737---1741.
Roy-Barman, M. & Allegre, C. J. (1995). 187Os/186Os in oceanic island
basalts: tracing oceanic crust recycling in the mantle. Earth and
Planetary Science Letters 129, 145---161.
Roy-Barman, M., Luck, J. M. & Allegre, C. J. (1996). Os isotopes in
orogenic lherzolite massifs and mantle heterogeneities. Chemical
Geology 130, 55---64.
Saal, A. E., Takazawa, E., Frey, F. A., Shimizu, N. & Hart, S. R.
(2001). Re---Os isotope in the Horoman peridotite: evidence for
refertilisation? Journal of Petrology 42, 25---37.
Scherer, E. E., Mezger, K. & Munker, C. (2001). Calibration of the
lutetium---hafnium clock. Science 293, 683---687.
Shirey, S. B. & Walker, R. J. (1998). The Re---Os isotope system in
cosmochemistry and high-temperature geochemistry. Annual Review
of Earth and Planetary Sciences 26, 423---500.
Takazawa, E., Frey, F. A., Shimizu, N., Saal, A. & Obata, M. (1999).
Polybaric petrogenesis of mafic layers in the Horoman peridotite
complex, Japan. Journal of Petrology 40, 1827---1851.
Vervoort, J. D., Patchett, P. J., Blichert-Toft, J. & Albarede, F. (1999).
Relationships between Lu---Hf and Sm---Nd isotopic systems in the
global sedimentary system. Earth and Planetary Science Letters 168,
Walker, R. J., Morgan, J. W., Beary, E. S., Smoliar, M. I.,
Czamanske, G. D. & Horan, M. F. (1997). Applications of the
190Pt---186Os isotope system to geochemistry and cosmochemistry.
Geochimica et Cosmochimica Acta 61, 4799---4807.
Widom, E. & Shirey, S. B. (1996). Os isotope systematics in the Azores:
implications for mantle plume sources. Earth and Planetary Science
Letters 142, 451---465.
Widom, E., Hoernle, K. A., Shirey, S. B. & Schmincke, H. U. (1999).
Os isotope systematics in the Canary Islands and Madeira:
lithospheric contamination and mantle plume signatures. Journal of
Petrology 40, 279---296.
Yaxley, G. M. & Green, D. H. (1998). Reactions between eclogite and
peridotite: mantle refertilisation by subduction of oceanic crust.
Schweizerische Mineralogische und Petrographische Mitteilungen 78, 243---255.
Zindler, A., Staudigel, H., Hart, S. R., Endres, R. & Goldstein, S.
(1983). Nd and Sr isotopic study of a mafic layer from Ronda
ultramafic complex. Nature 304, 226---230.


Special edition: Orogenic lherzolites and mantle processes.