(Algeria): a Record from Mantle Xenoliths

32 Pages·2014·2.44 MB·English

JOURNALOFPETROLOGY VOLUME55 NUMBER11 PAGES2249^2280 2014 doi:10.1093/petrology/egu056
Nature and Evolution of the Lithospheric Mantle
beneath the Hoggar Swell (Algeria): a Record
from Mantle Xenoliths
D
FATNA KOURIM1,2*, JEAN-LOUIS BODINIER1, OLIVIER ALARD1, ow
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ABDERRAHMANE BENDAOUD2, ALAIN VAUCHEZ1 AND loa
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JEAN-MARIE DAUTRIA1 ed
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1GE¤OSCIENCESMONTPELLIER, UNIVERSITE¤ DEMONTPELLIER 2 ANDCNRS, CC 60, PLACEEUGE'NEBATAILLON, h
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23L40A9B5OMROANTOTIPREELLDIEERGCE¤EODDEYXNA0M5,IFQRUAEN,CGEE¤OLOGIEDEL’INGE¤NIEURETPLANE¤TOLOGIE, FSTGAT, BP 32 USTHB,16123 s://ac
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BAB-EZZOUAR, ALGER, ALGERIA e
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RECEIVEDMAY 7,2013; ACCEPTED SEPTEMBER19,2014 .c
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PeridotitexenolithsexhumedbyQuaternaryalkalinemagmatismin veins^wall-rock system.The striking correlations between equilib- y/a
theTahalgha district, southern Hoggar, represent fragments of the riumtemperaturesandtrace-elementenrichmentfavorascenarioin rtic
subcontinental lithospheric mantle beneath the boundary between which the high-temperature peridotites record advective heat trans- le-a
the two major structural domains of the Tuareg Shield: the port along melt conduits, whereas the intermediate- and low- bs
‘PolycyclicCentralHoggar’totheeastandthe‘WesternHoggar,’or temperature lherzolites reflect conductive heating of the host tra
c
‘Pharusian Belt,’ tothe west. Samples were collectedfrom volcanic Mechanical Boundary Layer.This indicates that the lithosphere t/5
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centres located on both sides ofa major lithospheric shear zone at didnotreachthermalequilibrium,suggestingthattheinferredheat- /1
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4835’separating these two domains. Although showingsubstantial ingeventwastransientandwasrapidlyerasedbythermalrelaxation /2
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variations in their deformation microstructures, equilibrium tem- down to the relatively low-temperature present-day geotherm.The 49
peraturesandmodalandchemicalcompositions,thestudiedsamples low-T(59008C)deformedlherzolites(porphyroclastictoequigra- /14
5
do not display any systematic changes of these features across the nular) are characterized by only incipient annealing and LREE- 6
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4835’fault.Theobservedvariationsratherrecordsmall-scalehetero- depletedclinopyroxenecompositions.Theywereonlyweaklyaffected 13
geneities distributed throughout the study area and reflecting the bythe Cenozoiceventsand could represent relativelywell-preserved by
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widespread occurrence of vein conduits and metasomatized wall- samples from rejuvenated Pan-African lithosphere. Extensive u
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rocks related to trans-lithospheric melt circulation during the lithospheric rejuvenation occurred either regionally during the st o
Cenozoic.These features include partial annealing of pre-existing Pan-Africanorogeny,asaresultoflithosphericdelaminationorther- n
2
deformation microstructures, post-deformation metasomatic reac- momechanical erosion after thickening, or more locally along the 9
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tions, and trace-element enrichment, coupled with heating from meridionalshearzones.Thelow-TTahalghalherzolitesarecompar- a
750^9008C (low-temperature lherzolites) to 900^11508C (inter- able with lherzolitesfrom Etangde Lherz, southern France, inter- rch
2
mediate-T lherzolites and high-T harzburgites and wehrlites). preted as lithospheric mantle rejuvenated by melt-induced 0
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Trace-elementmodellingconfirmsthattherangeofrareearthelem- refertilizationduringalatestageoftheVariscanorogeny. 9
ent(REE)variationsobservedintheTahalghaclinopyroxenesmay
beaccountedforby reactive porousflow involvinga singlestage of
basaltic melt infiltration into a light REE (LREE)-depleted KEY WORDS: Hoggar swell; Tuareg Shield; Pan-African orogeny;
protolith.Whole-rock compositions record the final entrapment of mantlexenolith;peridotite;mantlemetasomatism;lithosphererejuven-
disequilibrium metasomatic melts upon thermal relaxation of the ation;rareearthelements
(cid:2) The Author 2014. Published by Oxford University Press. All
rightsreserved.ForPermissions,pleasee-mail:journals.permissions@
*Correspondingauthor.E-mail:[email protected] oup.com
JOURNALOFPETROLOGY VOLUME55 NUMBER11 NOVEMBER2014
INTRODUCTION andits evolutionthroughtime, we undertookapetrologi-
cal study of mantle xenoliths from theTahalgha volcanic
The Hoggar swell in southern Algeria represents the
district,inthesouthernpartoftheHoggarswell.Thisdis-
northern part of theTuareg Shield, whichwas uplifted in
trict is elongated east^west across major sub-meridional
the Eocene (Rougier et al., 2013). In this area, a complex
shear zones separating two major terranes of theTuareg
history of lithospheric evolution can be traced from
Shield: the LATEA (¼ Laouni, Azrou-n-Fad, Tefedest,
Archean to Cenozoic times, also including post-orogenic
Egge¤re¤-Alaksod; Black et al., 1994) domain of the
andintra-plateeventsoflithospherereactivationandreju-
‘Polycyclic Central Hoggar’ to the east and the Isklel
venation. Although the details and timing of these pro-
block of ‘Western Hoggar’, or the‘Pharusian Belt’, to the
cessesarestillamatterofdebate,thereisaconsensusthat
west (Caby, 2003; Lie¤geois et al., 2003).The primary aim
accretionofthelithosphereoccurredmostly viajuxtapos- D
of this study wasto answer a number of keyquestions, as o
ition and amalgamation of lithosphericblocks of different w
ages and origins (Black et al.,1994; Caby, 2003; Lie¤geois follows. nloa
d
et al., 2003). This scenario is, however, mostly based on (1) Are theTuareg Shield crustal terranes connected at e
d
structural,petrological,geochronologicalandgeochemical depth with mantle roots of the same provenance, or fro
studies of exhumedcrustalterranes.The architecture and weretheydecoupledfromeachotherduringthecolli- m
h
compositionofthelithosphericmantlebeneaththeTuareg sional stages of the accretion orby subsequent (post- ttp
s
Shield is poorlyconstrained, and its evolution along with orogenic)delaminationorrejuvenationprocesses? ://a
thegeodynamiceventsrecordedbythecrustalunitsislar- (2) DidthemajorshearzonesoftheTuaregShieldcontrol c
a
d
gely unknown. Lithospheric mantle representsthethicker asthenospheric upwelling during the Cenozoic, as e
m
and stronger part of the continental lithosphere and is proposedby Lie¤geoisetal. (2005), or rather, werethe ic
thereforeexpectedtoplayakeyroleinitsstabilitythrough mantle roots of the shear zones erased by astheno- .ou
p
time.However,wedonotknowtowhatextentthevarious sphere^lithosphereinteractions aswouldbe expected .c
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crustalterranes of theTuareg Shield remainedcoupledto from the impingement of a mantle plume or an m
/p
their mantle roots during lithospheric block accretion upper-mantle diapiric instability (Aı¨t-Hamou et al., e
(see, e.g. Lie¤geois et al., 2005). Continental lithosphere 2000;Beggetal.,2009)? trolo
g
mayalsobethinnedandweakenedastheresultofthermo- (3) Did the Cenozoic lithosphere^asthenosphere events y
/a
chemical erosion or convective removal by upwelling as- culminateinextensiverejuvenationasaresultofcon- rtic
thenosphere. These processes were suggested for the vective removal of the Pan-African lithospheric le
-a
Tuareg Shield, either during the Pan-African orogeny mantle,assuggestedbyBeccaluvaetal.(2007)? b
s
(Ashwal & Burke,1989; Black & Lie¤geois,1993; Lie¤geois tra
c
et al.,2003), or in response to Cenozoic mantle upwelling Combined with trace-element modelling, our results t/5
(Beccaluva et al., 2007), but their regional extent and the provide constraints on the mechanisms of metasomatism 5/1
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degree to which the lithosphere was affected are poorly relatedtotheCenozoicigneousevents.However,ourdata /2
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constrained.Thishasimplicationsforthepresent-daytop- alsoshowthatsomeoftheTahalghaxenolithsarevirtually 4
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ography of the lithosphere^asthenosphere boundary, unaffectedby metasomatism andrecordanoldereventof /1
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whichmayinturncontrolshallowmantlecirculationand lithospheric rejuvenation, probably related to the Pan- 56
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trigger further lithosphere^asthenosphere interactions Africanorogeny. 1
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(King & Anderson, 1998; King et al., 2002; Montagner b
y
etal.,2007; Begget al.,2009; Missenard & Cadoux,2012). gu
AspointedoutbyAbdelsalam etal. (2011) fortheadjacent GEOLOGICAL SETTING es
t o
Saharanmetacraton,bothhigh-resolutionseismicimaging In the northern part of the Tuareg Shield in southern n
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and systematic mantle xenolith studies are needed to fur- Algeria, the Hoggar swell (Fig.1a) is a large (500km(cid:2) 9
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ther constrain the upper mantle structure and evolution 600km) domal structure that became uplifted in the a
beneaththeseareas. Eocene (Rougieret al.,2013), with Precambrianbasement rch
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The few studies devoted to mantle xenoliths from the exhumed through its Paleozoic sedimentary cover. The 0
1
Hoggar swell and adjacent areas (Leblanc et al., 1982; basementanditscoverarelocallyoverlainby Cretaceous 9
Miller & Richter,1982; Dupuy et al.,1986; Dautria et al., deposits and Cenozoic intra-plate volcanism. Altitudes in
1987,1992; Beccaluva etal.,2007)have documentedtheef- the Hoggar swellare often higherthan 2000mandreach
fectsofCenozoicmetasomaticorlithosphericrejuvenation 2018m at Mount Tahat, in the Atakor volcanic massif
events, but did not provide information on regional and (Fig.1b).Thebasement ischaracterizedbyasuccessionof
temporalvariations in mantlelithospherecomposition.To juvenile Pan-African crustal domains alternating with
furtherconstrainthenatureofthelithosphericmantlebe- variably reactivated Archean and Eburnean terranes. It
neaththe Hoggar swell, its relationships withthetectonic was amalgamated during Pan-African orogenesis (900^
structures and crustal terranes observed at the surface, 550Ma)throughtheaccretionof ‘terranes’withradically
2250
KOURIM etal. HOGGARSWELLMANTLEXENOLITHS
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Fig.1. (a)LocationmapoftheHoggarshieldandtheprincipalCenozoicvolcanicfieldsofNorthAfricaand(b)sketchmapofthecentral m
Hoggarshowingthemainbasementterranesandvolcanicprovinces.MainfaultsafterCaby(2003)andLie¤geoisetal.(2003),andagesofvolcan- /p
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ismafterRognonetal.(1981,1983),Aı¨t-Hamou&Dautria(1994),Mazaetal.(1998)andAı¨t-Hamouetal.(2000). tro
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rtic
different lithologies and tectono-metamorphic histories (Lie¤geois et al., 2005). Between these extremes, global le
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(Black et al., 1994; Caby, 2003; Lie¤geois et al., 2003; tomographic imaging favors a scenario involving the up- b
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Ouzeganeetal.,2003).ThisPan-Africaneventcorresponds welling of a relatively shallow (5400km), buoyant, as- tra
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totheamalgamationofCentral Gondwanabycollisionof thenospheric mantle instability (Beggetal.,2009). Several t/5
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microcontinentsandaccretionofislandarcs.Theterranes researchershavesuggestedtheexistenceofsuchconvective /1
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werebrought together during the collisional stages of the instabilities in the upper mantle beneath North Africa, /2
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orogeny, whentheTuareg Shieldwas caughtbetweentwo either as an indirect result of the accumulation of sub- 4
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converging continents: the West African Craton to the ducted Tethyan oceanic slabs in the Transition Zone /1
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west andthe Saharan Metacratontothe east.The 23 ter- (Lustrino & Wilson,2007) or owing to the lateral migra- 56
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ranesthatcomposetheHoggarbasement wereeventually tion of plume mantle from the Afar hotspot (Ebinger & 1
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juxtaposedafterconsiderablestrike-slip(hundredsofkilo- Sleep,1998;Montagneretal.,2007). b
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metres) displacements along sub-meridional megashear The present study is focused on mantle xenoliths from gu
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zones(Blacketal.,1994;Lie¤geoisetal.,1994). the Tahalgha volcanic district, which extends east^west s
t o
IntraplatevolcanismbeganintheLateEoceneorEarly acrossthetectonicblocksoftheLaouni,TefedestandIskel n
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Oligocene (35^30Ma; Aı¨t-Hamou et al.,2000) and lasted terranes,delimitedbynorth^south-andNNE^SSW-trend- 9
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until the Neolithic (Lelubre, 1952). Several volcanic dis- ing shear zones (Fig. 1b). The Paleoproterozoic Laouni a
tricts are distinguished in the Hoggar (Fig. 1b): Ege¤re¤ andTefedestterranesarepartoftheLATEAmicrocontin- rch
(2800km2), Adrar N’Ajjer (2500km2), Atakor (2150km2), ent(Lie¤geoisetal.,2003).Theywerepartiallyremobilized 20
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Tahalgha (1800km2), Manzaz (1500km2), Anahef during Pan-African orogenesis and are composed of mig- 9
(400km2), In Teria (100km2), Djanet (50km2), and In matiticgneisses, anatexites, andhigh-grade metasedimen-
Ezzane (800km2).Various models havebeenproposed for tary rocks (Bertrand et al., 1978; Lie¤geois et al., 2003;
theoriginoftheHoggarswell,rangingfromimpingement Peucat et al., 2003; Bendaoud et al., 2004, 2008). To the
of a deep-seated mantle plume into the lithospheric west of LATEA, the Iskel block is an island arc complex
mantle (Aı¨t-Hamou & Dautria, 1994; Aı¨t-Hamou et al., composed of tonalite^trondhjemite^granodiorite (TTG)
2000) to upwelling of asthenospheric mantle along the units and calc-alkaline granites ranging in age from
meridional shear zones reactivated during the early 850 to 630Ma (Caby, 1982, 2003; Be¤chiri-Benmezrzoug,
stages of collision between Africa and Eurasia 2009).
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JOURNALOFPETROLOGY VOLUME55 NUMBER11 NOVEMBER2014
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Fig.2. (a)DistributionofthexenolithtypesinthewesternpartoftheTahalghavolcanicprovinceand(b)modalcompositionoftheselected u
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Tahalghamantlexenoliths.Inthepiechartsin(a):white,low-temperaturelherzolites;grey,intermediate-temperaturelherzolites;black,high- .c
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temperatureharzburgites(H)andwehrlites(W).In(b):Ol,olivine;Opx,orthopyroxene;Cpx,clinopyroxene;opencircles,low-temperature m
lherzolites (LTL); grey circles, intermediate-temperature lherzolites (ITL); filled diamonds, high-temperature harzburgites (HTH); filled /p
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squares,high-temperaturewehrlites(HTW). tro
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y
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Volcanic activity intheTahalghadistrict startedduring with a hammer between plastic sheets.Two100g splits of rtic
theMiocenewitheruptionofextensivebasalticlavaflows eachcrushedsamplewerefurtherinspectedforextraneous le-a
that formed an up to 100m thick plateau in the eastern materials under abinocular microscope andthen ground bs
and central parts of the district (Dautria, 1988; Fig. 2). inanagatemortartoafinepowder.Mostofthexenoliths tra
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Subsequently, numerous small basaltic strombolian erup- prepared for whole-rock analyses were homogeneous in t/5
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tions occurred during Plio-Villafranchian times, both on hand specimen, except for a few lherzolites and wehrlites /1
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the Miocene basaltic plateau and on the adjacent base- characterized by pervasive small-scale heterogeneities in /2
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ment. In addition, 12 Plio-Villafranchian differentiated theformofmillimetre-tocentimetre-scaleveinsordiffuse 49
lava domes and spines of trachytic to alkaline rhyolitic flamesofCpx(cid:3)amphibole(cid:3)spinel. /14
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compositionwere emplaced inthe centralpartof the dis- Majorelementsinminerals(Table1andSupplementary 6
3
trict (Lie¤geois et al., 2005). Finally, basaltic maars and Data; supplementary data are available for downloading 13
cones were formed during the Paleolithic and Neolithic at http://www.petrology.oxfordjournals.org) were deter- by
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periods scattered along the northern margin of the vol- mined by electron microprobe using a CAMECA-SX100 u
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canic massif. Mantle xenoliths have been found only in at the Microsonde Sud facility (Montpellier, France), st o
the western part of the Tahalgha district in strombolian equipped with five wavelength-dispersive spectrometers. n
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volcaniccones(Fig.2). Operating conditions comprised an acceleration voltage 9
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of 20kV and a 10nA beam current. Major elements in a
rc
whole-rocks (Table 2) were analyzed by inductively h
ANALYTICAL METHODS coupled plasma-optical emission spectroscopy (ICP-OES) 20
1
Eighty-seven mantle xenoliths (ranging from 3 to 25cm atGeoscienceLaboratories(ON,Canada). 9
across) werecollectedfrom13 scoriacones fromthewest- Trace-element contents in whole-rocks (Table 3) were
ern part of the Tahalgha volcanic district (Fig. 2), from analyzed by inductively coupled plasma mass spectrom-
which50representativesampleswereselectedfordetailed etry (ICP-MS) using a quadrupole HP7700X system at
investigation. Afterremovinganybasaltcoatingandwea- Ge¤osciences Montpellier following the procedure
thered rims the xenoliths were sawn into small pieces, described by Ionov et al. (1992) and adapted by Godard
fromwhich one was selected for thin sectionpreparation. et al. (2000) for the analysis of ultra-depleted peridotites.
The rest were carefully checked for any infiltration of The precision and accuracy of the ICP-MS analyses can
basalt or alteration before being crushed to 55^10mm be assessed from the results obtained for the UBN rock
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KOURIM etal. HOGGARSWELLMANTLEXENOLITHS
Table1: Modalcomposition,microstructure,keymineralindicesandequilibriumtemperatures
Sample Block Volcano Microstructure Modalcomposition(vol.%) Fo% Cr#Sp Equilibriumtemperature(8C)
Ol Opx Cpx Sp amph W77 1SD B&K90 1SD
Low-temperaturelherzolites(LTL)
72-35 Iskel Hiri coarse-grainedequigranular 59 27 12 2 1 88(cid:4)9 0(cid:4)112 908 8 891 11
88-20* Iskel AQ coarse-grainedequigranular 62 23 13 3 0 89(cid:4)0 0(cid:4)271 851 10 820 8
80-1 Tefedest KA coarse-grainedequigranular 66 19 12 3 0 89(cid:4)4 0(cid:4)129 806 12 749 12 D
o
w
80-7 Tefedest KA porphyroblastic 60 25 12 3 0 89(cid:4)2 0(cid:4)094 900 13 889 25 n
lo
80-2 Tefedest KA coarse-grainedequigranular 57 27 13 3 0 89(cid:4)2 0(cid:4)108 820 8 766 8 a
d
80-5 Tefedest KA porphyroblastic 61 25 12 2 0 89(cid:4)3 0(cid:4)126 840 17 797 20 ed
60-3 Tefedest AA porphyroblastic 63 22 13 2 0 89(cid:4)1 0(cid:4)108 748 8 768 8 fro
m
AD* Tefedest AD coarse-grainedequigranular 63 27 9 1 0 n.a. n.a. 775 11 701 18 h
40-2* Tefedest AE fine-grainedequigranular 56 28 13 3 0 89(cid:4)2 0(cid:4)094 792 14 730 30 ttp
s
48-25 Tefedest AF fine-grainedequigranular 60 26 11 3 0 89(cid:4)2 0(cid:4)113 808 17 738 17 ://a
30-2 Tefedest AF coarse-grainedequigranular 59 24 13 3 0 89(cid:4)0 0(cid:4)264 884 13 890 3 ca
d
10-4 Tefedest AI coarse-grainedequigranular 59 28 11 2 0 89(cid:4)7 0(cid:4)183 785 19 728 25 e
m
Intermediate-temperaturelherzolites(ITL) ic
.o
72-33 Iskel Hiri coarse-grainedequigranular 61 24 12 2 2 89(cid:4)5 0(cid:4)113 938 12 951 12 u
p
91-4 Iskel AR porphyroblastic 76 16 7 0 1 89(cid:4)8 0(cid:4)299 928 8 954 8 .c
o
91-8 Iskel AR fine-grainedequigranular 71 21 7 0 1 89(cid:4)8 0(cid:4)299 918 8 935 16 m
/p
91-2 Iskel AR porphyroblastic 62 23 12 2 1 89(cid:4)6 0(cid:4)134 930 8 937 12 e
91-5 Iskel AR fine-grainedequigranular 59 25 13 2 0 88(cid:4)6 0(cid:4)116 977 6 1001 6 trolo
g
91-9 Iskel AR porphyroblastic–equigranular 47 32 17 3 0 88(cid:4)9 0(cid:4)103 965 5 987 7 y
/a
88-6 Iskel AQ coarse-grainedequigranular 67 21 9 2 1 89(cid:4)6 0(cid:4)113 947 6 977 8 rtic
88-4 Iskel AQ porphyroblastic 70 18 10 2 0 89(cid:4)4 0(cid:4)088 987 4 977 10 le
-a
88-21 Iskel AQ coarse-grainedequigranular 70 20 6 3 1 89(cid:4)8 0(cid:4)104 937 7 969 6 b
s
88-3 Iskel AQ coarse-grainedequigranular 61 23 14 2 0 89(cid:4)3 0(cid:4)112 937 6 950 6 tra
c
88-22 Iskel AQ coarse-grainedequigranular 48 16 17 2 17 86(cid:4)5 0(cid:4)115 927 8 947 6 t/5
276-2* Tefedest CF porphyroblastic 72 24 3 3 0 n.a. n.a. 987 4 1019 8 5/1
276-35 Tefedest CF fine-grainedequigranular 61 19 14 3 3 86(cid:4)8 0(cid:4)115 974 4 1003 9 1/2
10-1 Tefedest AI coarse-grainedequigranular 56 30 12 2 0 86(cid:4)8 0(cid:4)115 966 12 980 17 24
9
80-3 Tefedest KA coarse-grainedequigranular 41 34 21 4 0 89(cid:4)0 0(cid:4)098 988 6 998 19 /1
4
High-temperatureharzburgites(HTH) 56
3
60-1 Tefedest AA porphyroblastic 86 12 2 0 0 90(cid:4)9 0(cid:4)452 1011 25 1055 21 1
3
40-1 Tefedest AE porphyroblastic 91 8 1 0 0 90(cid:4)2 0(cid:4)372 1015 35 1100 22 b
y
30-3 Tefedest AF porphyroblastic 71 24 4 2 0 85(cid:4)2 0(cid:4)322 1009 13 1065 20 g
u
e
48-9 Tefedest AF porphyroblastic–granuloblastic 58 27 13 2 0 n.a. n.a. 1078 11 1118 10 s
High-temperaturewehrlites(HTW) t on
88-1 Iskel AQ fine-grainedequigranular 72 0 24 4 0 89(cid:4)2 0(cid:4)317 n.d. – n.d. – 29
88-7 Iskel AQ fine-grainedequigranular 73 0 24 2 0 89(cid:4)5 0(cid:4)115 n.d. – n.d. – M
a
276-16 Tefedest CF fine-grainedequigranular 71 5 18 1 4 85(cid:4)0 0(cid:4)208 1032 12 1032 12 rc
h
276-22 Tefedest CF fine-grainedequigranular 61 2 15 2 20 n.a. n.a. 1021 13 1030 12 2
0
1
276-25* Tefedest CF fine-grainedequigranular 67 6 25 0 2 86(cid:4)2 0(cid:4)175 1034 8 996 16 9
48-4 Tefedest AF fine-grainedequigranular 66 4 25 3 2 n.a. n.a. 1021 13 1060 11
48 Tefedest AF fine-grainedequigranular 74 2 18 3 3 84(cid:4)5 0(cid:4)335 1029 14 1072 6
Iskel and Tefedest tectonic blocks refer to the emplacement onto the Tuareg basement of the volcanoes from which the
samples have been collected (Figs 1 and 2); volcano location is shown in Fig. 2. Samples are grouped by rock type as
definedinthetext.Fo%isolivineforsteritecontent;Cr# ¼Cr/(CrþAl)cationic ratioinspinel.W77andB&K90arethe
Sp
average equilibrium temperature calculated for pyroxene cores using the Wells (1977) and Brey & Ko¨hler (1990) formu-
lations, respectively. SD, standard deviation; n.a., not analyzed; n.d., not determined.
*Data from Dautria (1988).
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JOURNALOFPETROLOGY VOLUME55 NUMBER11 NOVEMBER2014
Table2: Whole-rockmajorelementcompositionsoftheselectedTahalghamantlexenolithsanalyzedbyICP-OES,inwt%
Sample Block Volcano SiO TiO AlO FeO MnO MgO CaO NaO KO PO LOI Total #Mg CaO/AlO FeOþTiO
2 2 2 3 2 2 2 5 2 3 2
Low-temperaturelherzolites(LTL)
71-35 Iskel Hiri 45(cid:4)34 0(cid:4)07 3(cid:4)17 8(cid:4)70 0(cid:4)14 39(cid:4)62 2(cid:4)86 0(cid:4)08 0(cid:4)01 0(cid:4)01 –0(cid:4)1 99(cid:4)36 0(cid:4)890 0(cid:4)90 8(cid:4)77
80-1 Tefedest KA 44(cid:4)25 0(cid:4)14 2(cid:4)85 8(cid:4)60 0(cid:4)13 40(cid:4)95 2(cid:4)79 0(cid:4)16 0(cid:4)10 0(cid:4)02 –0(cid:4)12 99(cid:4)06 0(cid:4)895 0(cid:4)98 8(cid:4)74
80-7 Tefedest KA 44(cid:4)91 0(cid:4)10 3(cid:4)11 8(cid:4)74 0(cid:4)14 39(cid:4)89 2(cid:4)95 0(cid:4)11 0(cid:4)03 0(cid:4)01 –0(cid:4)19 99(cid:4)57 0(cid:4)890 0(cid:4)95 8(cid:4)84
80-2 Tefedest KA 45(cid:4)12 0(cid:4)20 3(cid:4)23 8(cid:4)60 0(cid:4)14 39(cid:4)05 3(cid:4)23 0(cid:4)22 0(cid:4)15 0(cid:4)05 –0(cid:4)09 99(cid:4)35 0(cid:4)890 1(cid:4)00 8(cid:4)80
D
80-5 Tefedest KA 45(cid:4)01 0(cid:4)09 3(cid:4)25 8(cid:4)80 0(cid:4)14 39(cid:4)73 2(cid:4)81 0(cid:4)13 0(cid:4)01 0(cid:4)02 –0(cid:4)01 99(cid:4)1 0(cid:4)889 0(cid:4)87 8(cid:4)89 ow
n
60-3 Tefedest AA 44(cid:4)42 0(cid:4)20 2(cid:4)44 9(cid:4)55 0(cid:4)15 39(cid:4)82 2(cid:4)99 0(cid:4)28 0(cid:4)09 0(cid:4)05 0(cid:4)37 99(cid:4)34 0(cid:4)881 1(cid:4)23 9(cid:4)75 lo
a
48-25 Tefedest AF 45(cid:4)33 0(cid:4)07 3(cid:4)15 8(cid:4)45 0(cid:4)14 39(cid:4)69 2(cid:4)96 0(cid:4)12 0(cid:4)02 0(cid:4)07 –0(cid:4)04 99(cid:4)43 0(cid:4)893 0(cid:4)94 8(cid:4)52 d
e
d
30-2 Tefedest AF 44(cid:4)82 0(cid:4)05 3(cid:4)49 8(cid:4)82 0(cid:4)14 39(cid:4)45 3(cid:4)08 0(cid:4)10 0(cid:4)03 0(cid:4)01 0(cid:4)55 99(cid:4)45 0(cid:4)888 0(cid:4)88 8(cid:4)87 fro
10-4 Tefedest AI 45(cid:4)22 0(cid:4)06 3(cid:4)17 8(cid:4)58 0(cid:4)13 39(cid:4)98 2(cid:4)74 0(cid:4)09 0(cid:4)01 0(cid:4)01 0(cid:4)11 99(cid:4)52 0(cid:4)892 0(cid:4)87 8(cid:4)64 m
h
Intermediate-temperaturelherzolites(LTL) ttp
9712--433 IIsskkeell AHRiri 4434(cid:4)(cid:4)8899 00(cid:4)(cid:4)0172 12(cid:4)(cid:4)4939 88(cid:4)(cid:4)7324 00(cid:4)(cid:4)1143 4430(cid:4)(cid:4)9486 12(cid:4)(cid:4)6955 00(cid:4)(cid:4)0160 00(cid:4)(cid:4)0011 00(cid:4)(cid:4)0041 ––00(cid:4)(cid:4)2155 19090(cid:4)(cid:4)117 00(cid:4)(cid:4)899060 01(cid:4)(cid:4)9195 88(cid:4)(cid:4)4769 s://ac
a
91-8 Iskel AR 44(cid:4)59 0(cid:4)08 1(cid:4)72 8(cid:4)59 0(cid:4)14 43(cid:4)13 1(cid:4)64 0(cid:4)06 0(cid:4)00 0(cid:4)04 –0(cid:4)26 98(cid:4)85 0(cid:4)899 0(cid:4)95 8(cid:4)67 de
m
91-2 Iskel AR 45(cid:4)07 0(cid:4)09 2(cid:4)83 8(cid:4)36 0(cid:4)14 40(cid:4)58 2(cid:4)77 0(cid:4)14 0(cid:4)01 0(cid:4)01 –0(cid:4)26 99(cid:4)53 0(cid:4)896 0(cid:4)98 8(cid:4)45 ic
91-5 Iskel AR 44(cid:4)65 0(cid:4)20 3(cid:4)33 9(cid:4)96 0(cid:4)15 38(cid:4)56 2(cid:4)97 0(cid:4)11 0(cid:4)02 0(cid:4)05 –0(cid:4)29 100(cid:4)15 0(cid:4)873 0(cid:4)89 10(cid:4)16 .ou
p
91-9 Iskel AR 45(cid:4)82 0(cid:4)15 4(cid:4)81 8(cid:4)24 0(cid:4)14 36(cid:4)54 4(cid:4)03 0(cid:4)19 0(cid:4)01 0(cid:4)07 –0(cid:4)13 99(cid:4)11 0(cid:4)888 0(cid:4)84 8(cid:4)39 .c
o
88-6 Iskel AQ 44(cid:4)47 0(cid:4)09 2(cid:4)71 8(cid:4)65 0(cid:4)14 41(cid:4)57 2(cid:4)22 0(cid:4)11 0(cid:4)01 0(cid:4)02 –0(cid:4)2 99(cid:4)55 0(cid:4)895 0(cid:4)82 8(cid:4)74 m
/p
88-4 Iskel AQ 44(cid:4)58 0(cid:4)08 2(cid:4)63 8(cid:4)61 0(cid:4)14 41(cid:4)58 2(cid:4)24 0(cid:4)11 0(cid:4)01 0(cid:4)02 –0(cid:4)23 99(cid:4)59 0(cid:4)896 0(cid:4)85 8(cid:4)69 e
tro
88-21 Iskel AQ 45(cid:4)23 0(cid:4)11 3(cid:4)11 8(cid:4)16 0(cid:4)13 40(cid:4)14 2(cid:4)95 0(cid:4)15 0(cid:4)01 0(cid:4)01 –0(cid:4)1 99(cid:4)88 0(cid:4)898 0(cid:4)95 8(cid:4)27 lo
g
88-3 Iskel AQ 45(cid:4)18 0(cid:4)10 3(cid:4)37 8(cid:4)82 0(cid:4)14 39(cid:4)01 3(cid:4)17 0(cid:4)13 0(cid:4)02 0(cid:4)05 –0(cid:4)05 99(cid:4)69 0(cid:4)887 0(cid:4)94 8(cid:4)92 y
/a
88-22 Iskel AQ 43(cid:4)96 0(cid:4)74 3(cid:4)52 10(cid:4)05 0(cid:4)16 36(cid:4)39 4(cid:4)49 0(cid:4)42 0(cid:4)23 0(cid:4)04 0(cid:4)04 99(cid:4)75 0(cid:4)866 1(cid:4)28 10(cid:4)79 rtic
276-35 Tefedest CF 44(cid:4)51 0(cid:4)10 3(cid:4)22 9(cid:4)76 0(cid:4)15 38(cid:4)96 3(cid:4)16 0(cid:4)11 0(cid:4)01 0(cid:4)01 –0(cid:4)1 99(cid:4)77 0(cid:4)877 0(cid:4)98 9(cid:4)87 le
-a
10-1 Tefedest AI 45(cid:4)70 0(cid:4)07 3(cid:4)17 8(cid:4)21 0(cid:4)13 39(cid:4)45 3(cid:4)12 0(cid:4)11 0(cid:4)02 0(cid:4)01 0(cid:4)28 99(cid:4)5 0(cid:4)895 0(cid:4)98 8(cid:4)28 bs
80-3 Tefedest KA 46(cid:4)50 0(cid:4)15 5(cid:4)19 8(cid:4)34 0(cid:4)14 34(cid:4)82 4(cid:4)56 0(cid:4)22 0(cid:4)07 0(cid:4)01 0(cid:4)03 98(cid:4)85 0(cid:4)882 0(cid:4)88 8(cid:4)49 tra
c
High-temperatureharzburgites(HTH) t/5
5
60-1 Tefedest AA 42(cid:4)34 0(cid:4)13 0(cid:4)76 9(cid:4)69 0(cid:4)14 46(cid:4)38 0(cid:4)49 0(cid:4)00 0(cid:4)03 0(cid:4)04 –0(cid:4)16 99(cid:4)53 0(cid:4)895 0(cid:4)64 9(cid:4)82 /1
1
40-1 Tefedest AE 42(cid:4)25 0(cid:4)06 0(cid:4)64 9(cid:4)08 0(cid:4)13 47(cid:4)27 0(cid:4)51 0(cid:4)00 0(cid:4)01 0(cid:4)04 0(cid:4)04 98(cid:4)92 0(cid:4)903 0(cid:4)79 9(cid:4)14 /2
2
4
30-3 Tefedest AF 43(cid:4)96 0(cid:4)09 2(cid:4)53 9(cid:4)52 0(cid:4)15 42(cid:4)63 1(cid:4)01 0(cid:4)04 0(cid:4)04 0(cid:4)02 0(cid:4)19 99(cid:4)47 0(cid:4)889 0(cid:4)40 9(cid:4)61 9
/1
High-temperaturewehrlites(HTW) 4
5
6
88-1 Iskel AQ 42(cid:4)86 0(cid:4)13 3(cid:4)15 8(cid:4)37 0(cid:4)14 38(cid:4)85 5(cid:4)16 0(cid:4)50 0(cid:4)16 0(cid:4)68 –0(cid:4)08 99(cid:4)14 0(cid:4)892 1(cid:4)64 8(cid:4)50 3
1
88-7 Iskel AQ 43(cid:4)60 0(cid:4)10 2(cid:4)93 8(cid:4)40 0(cid:4)15 39(cid:4)78 4(cid:4)38 0(cid:4)47 0(cid:4)09 0(cid:4)09 0(cid:4)05 98(cid:4)94 0(cid:4)894 1(cid:4)49 8(cid:4)51 3 b
276-16 Tefedest CF 43(cid:4)18 0(cid:4)36 2(cid:4)08 11(cid:4)72 0(cid:4)16 38(cid:4)44 3(cid:4)89 0(cid:4)13 0(cid:4)01 0(cid:4)02 0(cid:4)08 100(cid:4)28 0(cid:4)854 1(cid:4)87 12(cid:4)09 y g
u
276-22 Tefedest CF 41(cid:4)34 0(cid:4)75 2(cid:4)27 12(cid:4)34 0(cid:4)18 38(cid:4)51 4(cid:4)18 0(cid:4)22 0(cid:4)14 0(cid:4)06 –0(cid:4)24 100(cid:4)09 0(cid:4)848 1(cid:4)84 13(cid:4)09 e
s
48-4 Tefedest AF 42(cid:4)48 0(cid:4)53 2(cid:4)54 12(cid:4)44 0(cid:4)17 35(cid:4)88 5(cid:4)55 0(cid:4)22 0(cid:4)09 0(cid:4)09 0(cid:4)05 99(cid:4)23 0(cid:4)837 2(cid:4)19 12(cid:4)97 t o
n
48 Tefedest AF 51(cid:4)20 0(cid:4)80 5(cid:4)75 6(cid:4)88 0(cid:4)14 17(cid:4)67 16(cid:4)65 0(cid:4)80 0(cid:4)04 0(cid:4)06 0(cid:4)34 99(cid:4)8 0(cid:4)821 2(cid:4)89 7(cid:4)68 2
9
M
LOI, loss on ignition; Mg#¼Mg/(MgþFe) cationic ratio. arc
h
2
0
1
9
standard (Table 3). Trace elements in clinopyroxene extendedrange(XR-)Element2ICP-MSsystemoperated
(Table 4) were analyzed by laser ablation (LA)-ICP-MS in low-resolution mode at 1350W. The ICP-MS system
at Ge¤osciences Montpellier, usinga GeoLas QþExcimer was tuned daily to maximum sensitivity while keeping
(Compex 102) laser system operating in the deep UV oxide production to its minimum level (ThO/Th (cid:5)1%).
(193nm). Ablations were performed in a pure He atmos- TheNIST612 glass (Pearceetal.,1997) wasusedasanex-
phere (c. 0(cid:4)6lmin^1) using a beam diameter ranging be- ternal standard and CaO content determinedby electron
tween 30 and120mm, withanenergydensityc.15(cid:2)10^3J microprobe was used as an internal standard. Data were
cm^2. The laser ablation platform was linked to an processedusing the GLITTER software package (Griffin
2254
KOURIM etal. HOGGARSWELLMANTLEXENOLITHS
Table3: Whole-rocktrace-elementcompositionsoftheselectedTahalghamantlexenolithsanalyzedbyICP-MS,inppm
Rocktype: Low-temperaturelherzolites(LTL) Intermediate-temperaturelherzolites(ITL)
Sample: 71-35 80-1 80-7 80-2 80-5 60-3 48-25 30-2 10-4 72-33 91-4 91-8 91-2 91-5 91-9 88-6 88-4 88-21
Block: Iskel Tefedest Tefedest Tefedest Tefedest Tefedest Tefedest Tefedest Tefedest Iskel Iskel Iskel Iskel Iskel Iskel Iskel Iskel Iskel
Volcano: Hiri KA KA KA KA AA AF AF AI Hiri AR AR AR AR AR AQ AQ AQ
Rb 0(cid:4)255 0(cid:4)878 0(cid:4)626 1(cid:4)60 0(cid:4)311 35(cid:4)8 3(cid:4)39 16(cid:4)8 11(cid:4)4 0(cid:4)215 0(cid:4)184 0(cid:4)213 0(cid:4)330 0(cid:4)456 0(cid:4)460 0(cid:4)454 0(cid:4)315 0(cid:4)309
Sr 9(cid:4)18 19(cid:4)3 5(cid:4)8 34(cid:4)6 5(cid:4)7 108(cid:4)3 21(cid:4)6 13(cid:4)9 5(cid:4)3 13(cid:4)5 22(cid:4)2 25(cid:4)6 10(cid:4)4 25(cid:4)5 18(cid:4)4 23(cid:4)7 15(cid:4)6 17(cid:4)2 D
o
Y 2(cid:4)52 3(cid:4)63 4(cid:4)01 2(cid:4)98 2(cid:4)81 5(cid:4)01 2(cid:4)09 2(cid:4)47 3(cid:4)52 3(cid:4)31 1(cid:4)80 2(cid:4)11 2(cid:4)59 3(cid:4)53 4(cid:4)19 3(cid:4)57 2(cid:4)25 2(cid:4)95 w
n
Zr 1(cid:4)36 5(cid:4)51 1(cid:4)83 13(cid:4)2 2(cid:4)33 16(cid:4)46 1(cid:4)26 1(cid:4)36 1(cid:4)15 6(cid:4)80 6(cid:4)85 7(cid:4)44 3(cid:4)61 13(cid:4)95 5(cid:4)79 9(cid:4)97 8(cid:4)49 5(cid:4)24 lo
a
Nb 0(cid:4)123 2(cid:4)06 0(cid:4)496 3(cid:4)14 0(cid:4)315 6(cid:4)64 0(cid:4)084 0(cid:4)483 0(cid:4)525 0(cid:4)730 0(cid:4)589 0(cid:4)634 1(cid:4)04 2(cid:4)00 1(cid:4)33 0(cid:4)861 0(cid:4)299 0(cid:4)581 de
d
Cs 0(cid:4)0091 0(cid:4)0090 0(cid:4)0062 0(cid:4)0162 0(cid:4)0166 0(cid:4)183 0(cid:4)0478 0(cid:4)161 0(cid:4)0362 0(cid:4)0044 0(cid:4)0068 0(cid:4)0093 0(cid:4)0229 0(cid:4)0123 0(cid:4)0208 0(cid:4)0053 0(cid:4)0096 0(cid:4)0053 fro
Ba 2(cid:4)66 13(cid:4)6 3(cid:4)70 43(cid:4)8 10(cid:4)4 24(cid:4)7 27(cid:4)0 51(cid:4)97 2(cid:4)18 3(cid:4)86 4(cid:4)95 7(cid:4)83 3(cid:4)25 19(cid:4)5 13(cid:4)5 4(cid:4)52 4(cid:4)62 3(cid:4)97 m
La 1(cid:4)03 1(cid:4)13 0(cid:4)255 2(cid:4)17 0(cid:4)531 2(cid:4)74 1(cid:4)90 0(cid:4)593 0(cid:4)0741 1(cid:4)55 1(cid:4)33 1(cid:4)68 0(cid:4)649 2(cid:4)16 1(cid:4)69 1(cid:4)32 0(cid:4)731 0(cid:4)744 h
ttp
Ce 1(cid:4)39 1(cid:4)97 0(cid:4)466 4(cid:4)31 0(cid:4)965 5(cid:4)69 1(cid:4)88 0(cid:4)862 0(cid:4)140 3(cid:4)62 3(cid:4)78 4(cid:4)52 0(cid:4)855 4(cid:4)80 2(cid:4)83 3(cid:4)13 2(cid:4)10 1(cid:4)25 s
Pr 0(cid:4)119 0(cid:4)216 0(cid:4)062 0(cid:4)497 0(cid:4)118 0(cid:4)595 0(cid:4)117 0(cid:4)097 0(cid:4)021 0(cid:4)468 0(cid:4)555 0(cid:4)647 0(cid:4)0935 0(cid:4)609 0(cid:4)306 0(cid:4)372 0(cid:4)315 0(cid:4)132 ://a
c
Nd 0(cid:4)477 0(cid:4)929 0(cid:4)342 2(cid:4)14 0(cid:4)605 2(cid:4)55 0(cid:4)375 0(cid:4)400 0(cid:4)145 2(cid:4)12 2(cid:4)74 3(cid:4)17 0(cid:4)498 2(cid:4)75 1(cid:4)38 1(cid:4)57 1(cid:4)54 0(cid:4)586 ad
e
Sm 0(cid:4)147 0(cid:4)230 0(cid:4)150 0(cid:4)463 0(cid:4)210 0(cid:4)530 0(cid:4)108 0(cid:4)127 0(cid:4)087 0(cid:4)470 0(cid:4)620 0(cid:4)707 0(cid:4)192 0(cid:4)595 0(cid:4)388 0(cid:4)361 0(cid:4)341 0(cid:4)201 m
Eu 0(cid:4)0659 0(cid:4)0898 0(cid:4)0663 0(cid:4)1584 0(cid:4)0842 0(cid:4)1808 0(cid:4)0482 0(cid:4)0542 0(cid:4)0404 0(cid:4)159 0(cid:4)197 0(cid:4)223 0(cid:4)0810 0(cid:4)201 0(cid:4)144 0(cid:4)141 0(cid:4)127 0(cid:4)0902 ic.o
Gd 0(cid:4)283 0(cid:4)321 0(cid:4)288 0(cid:4)508 0(cid:4)346 0(cid:4)580 0(cid:4)219 0(cid:4)245 0(cid:4)192 0(cid:4)552 0(cid:4)566 0(cid:4)638 0(cid:4)322 0(cid:4)637 0(cid:4)556 0(cid:4)496 0(cid:4)393 0(cid:4)354 up
Tb 0(cid:4)0558 0(cid:4)0569 0(cid:4)0578 0(cid:4)0831 0(cid:4)0673 0(cid:4)0914 0(cid:4)0432 0(cid:4)0503 0(cid:4)0398 0(cid:4)0911 0(cid:4)0749 0(cid:4)0850 0(cid:4)0611 0(cid:4)100 0(cid:4)0990 0(cid:4)0881 0(cid:4)0623 0(cid:4)0659 .co
m
Dy 0(cid:4)420 0(cid:4)407 0(cid:4)445 0(cid:4)563 0(cid:4)498 0(cid:4)589 0(cid:4)342 0(cid:4)398 0(cid:4)315 0(cid:4)606 0(cid:4)424 0(cid:4)474 0(cid:4)461 0(cid:4)659 0(cid:4)721 0(cid:4)623 0(cid:4)408 0(cid:4)488 /p
Ho 0(cid:4)0954 0(cid:4)0891 0(cid:4)1031 0(cid:4)1172 0(cid:4)1124 0(cid:4)1198 0(cid:4)0798 0(cid:4)0929 0(cid:4)0753 0(cid:4)125 0(cid:4)0744 0(cid:4)0840 0(cid:4)104 0(cid:4)133 0(cid:4)159 0(cid:4)137 0(cid:4)086 0(cid:4)109 etro
Er 0(cid:4)292 0(cid:4)256 0(cid:4)306 0(cid:4)343 0(cid:4)344 0(cid:4)333 0(cid:4)243 0(cid:4)290 0(cid:4)227 0(cid:4)358 0(cid:4)196 0(cid:4)221 0(cid:4)315 0(cid:4)381 0(cid:4)475 0(cid:4)399 0(cid:4)247 0(cid:4)325 lo
g
Tm 0(cid:4)0449 0(cid:4)0388 0(cid:4)0480 0(cid:4)0511 0(cid:4)0515 0(cid:4)0470 0(cid:4)0394 0(cid:4)0444 0(cid:4)0358 0(cid:4)0535 0(cid:4)0258 0(cid:4)0297 0(cid:4)0485 0(cid:4)0537 0(cid:4)0719 0(cid:4)0599 0(cid:4)0370 0(cid:4)0496 y
/a
Yb 0(cid:4)253 0(cid:4)249 0(cid:4)317 0(cid:4)339 0(cid:4)348 0(cid:4)305 0(cid:4)213 0(cid:4)300 0(cid:4)240 0(cid:4)288 0(cid:4)168 0(cid:4)189 0(cid:4)332 0(cid:4)349 0(cid:4)473 0(cid:4)333 0(cid:4)206 0(cid:4)273 rtic
Lu 0(cid:4)0495 0(cid:4)0424 0(cid:4)0554 0(cid:4)0581 0(cid:4)0594 0(cid:4)0501 0(cid:4)0433 0(cid:4)0515 0(cid:4)0420 0(cid:4)0549 0(cid:4)0273 0(cid:4)0308 0(cid:4)0571 0(cid:4)0577 0(cid:4)0794 0(cid:4)0654 0(cid:4)0392 0(cid:4)0530 le
Hf 0(cid:4)0603 0(cid:4)111 0(cid:4)0644 0(cid:4)253 0(cid:4)0814 0(cid:4)246 0(cid:4)0447 0(cid:4)0424 0(cid:4)0313 0(cid:4)159 0(cid:4)154 0(cid:4)149 0(cid:4)101 0(cid:4)239 0(cid:4)144 0(cid:4)184 0(cid:4)169 0(cid:4)114 -ab
s
Ta 0(cid:4)006 0(cid:4)134 0(cid:4)032 0(cid:4)203 0(cid:4)012 0(cid:4)340 0(cid:4)002 0(cid:4)003 0(cid:4)0090 0(cid:4)0462 0(cid:4)0287 0(cid:4)036 0(cid:4)0269 0(cid:4)141 0(cid:4)101 0(cid:4)0600 0(cid:4)0297 0(cid:4)0387 tra
Pb 0(cid:4)142 0(cid:4)155 0(cid:4)104 0(cid:4)215 0(cid:4)209 0(cid:4)339 0(cid:4)267 0(cid:4)204 0(cid:4)151 0(cid:4)180 0(cid:4)197 0(cid:4)279 0(cid:4)221 0(cid:4)271 0(cid:4)262 0(cid:4)290 0(cid:4)167 0(cid:4)189 ct/5
Th 0(cid:4)0886 0(cid:4)168 0(cid:4)0261 0(cid:4)286 0(cid:4)0523 0(cid:4)333 0(cid:4)226 0(cid:4)0547 0(cid:4)0114 0(cid:4)152 0(cid:4)0685 0(cid:4)0957 0(cid:4)399 0(cid:4)193 0(cid:4)184 0(cid:4)106 0(cid:4)0306 0(cid:4)0432 5
/1
U 0(cid:4)0516 0(cid:4)0639 0(cid:4)0114 0(cid:4)0875 0(cid:4)0344 0(cid:4)0994 0(cid:4)163 0(cid:4)012 0(cid:4)0273 0(cid:4)0453 0(cid:4)0251 0(cid:4)0335 0(cid:4)0937 0(cid:4)0582 0(cid:4)0918 0(cid:4)0326 0(cid:4)0124 0(cid:4)0175 1
/2
2
4
9
Rocktype: Intermediate-temperaturelherzolites(ITL) High-temperatureharzburgites(HTH) High-temperaturewehrlites(HTW) Ref. /1
4
mat. 56
3
Sample: 88-3 88-22 276-35 10-1 80-3 60-1 40-1 88-1 88-7 276-16 276-22 48-4 48 UBN 1
3
Block: Iskel Iskel Tefedest Tefedest Tefedest Tefedest Tefedest Iskel Iskel Tefedest Tefedest Tefedest Tefedest b
y
Volcano: AQ AQ CF AI KA AA AE AQ AQ CF CF AF AF g
u
e
s
Rb 0(cid:4)581 1(cid:4)729 0(cid:4)144 0(cid:4)993 0(cid:4)830 0(cid:4)520 7(cid:4)823 1(cid:4)761 0(cid:4)886 0(cid:4)218 1(cid:4)813 3(cid:4)438 0(cid:4)936 3(cid:4)10 t on
Sr 28(cid:4)4 83(cid:4)0 13(cid:4)7 17(cid:4)9 18(cid:4)1 31(cid:4)9 429(cid:4)4 114 20(cid:4)7 96(cid:4)6 90(cid:4)1 64(cid:4)5 7(cid:4)52 29
Y 3(cid:4)03 6(cid:4)28 4(cid:4)59 3(cid:4)79 6(cid:4)12 5(cid:4)86 5(cid:4)67 10(cid:4)4 7(cid:4)07 4(cid:4)27 7(cid:4)76 5(cid:4)62 9(cid:4)10 2(cid:4)50 M
a
Zr 2(cid:4)88 29(cid:4)8 4(cid:4)98 6(cid:4)93 3(cid:4)80 17(cid:4)6 17(cid:4)8 27(cid:4)1 21(cid:4)4 16(cid:4)3 26(cid:4)7 32(cid:4)5 27(cid:4)2 3(cid:4)59 rc
h
Nb 0(cid:4)707 5(cid:4)98 0(cid:4)281 1(cid:4)44 2(cid:4)02 1(cid:4)65 2(cid:4)20 8(cid:4)26 7(cid:4)48 0(cid:4)462 5(cid:4)64 6(cid:4)29 0(cid:4)765 0(cid:4)056 2
0
Cs 0(cid:4)0068 0(cid:4)0067 0(cid:4)0028 0(cid:4)0343 0(cid:4)0087 0(cid:4)0044 0(cid:4)2638 0(cid:4)0200 0(cid:4)0080 0(cid:4)0037 0(cid:4)0138 0(cid:4)0257 0(cid:4)0141 11(cid:4)5 19
Ba 8(cid:4)09 29(cid:4)0 2(cid:4)64 5(cid:4)59 10(cid:4)7 23(cid:4)0 53(cid:4)7 35(cid:4)5 113 5(cid:4)23 44(cid:4)5 184 44(cid:4)3 28(cid:4)4
La 1(cid:4)30 2(cid:4)30 1(cid:4)20 1(cid:4)70 1(cid:4)43 1(cid:4)40 1(cid:4)23 34(cid:4)8 2(cid:4)96 0(cid:4)901 5(cid:4)32 5(cid:4)10 2(cid:4)06 0(cid:4)331
Ce 2(cid:4)66 7(cid:4)18 2(cid:4)88 3(cid:4)12 2(cid:4)11 4(cid:4)14 3(cid:4)69 67(cid:4)7 11(cid:4)0 3(cid:4)24 11(cid:4)2 9(cid:4)61 6(cid:4)23 0(cid:4)848
Pr 0(cid:4)287 1(cid:4)25 0(cid:4)371 0(cid:4)307 0(cid:4)209 0(cid:4)560 0(cid:4)522 7(cid:4)217 1(cid:4)931 0(cid:4)579 1(cid:4)330 1(cid:4)362 1(cid:4)089 0(cid:4)122
Nd 1(cid:4)21 6(cid:4)98 1(cid:4)630 1(cid:4)094 0(cid:4)889 2(cid:4)930 2(cid:4)786 28(cid:4)3 10(cid:4)2 3(cid:4)46 6(cid:4)56 6(cid:4)47 6(cid:4)25 0(cid:4)658
Sm 0(cid:4)288 1(cid:4)801 0(cid:4)348 0(cid:4)210 0(cid:4)273 0(cid:4)749 0(cid:4)758 4(cid:4)36 2(cid:4)33 1(cid:4)06 1(cid:4)61 1(cid:4)43 1(cid:4)82 0(cid:4)232
(continued)
2255
JOURNALOFPETROLOGY VOLUME55 NUMBER11 NOVEMBER2014
Table3: Continued
Rocktype: Intermediate-temperaturelherzolites(ITL) High-temperatureharzburgites(HTH) High-temperaturewehrlites(HTW) Ref.
mat.
Sample: 88-3 88-22 276-35 10-1 80-3 60-1 40-1 88-1 88-7 276-16 276-22 48-4 48 UBN
Block: Iskel Iskel Tefedest Tefedest Tefedest Tefedest Tefedest Iskel Iskel Tefedest Tefedest Tefedest Tefedest
Volcano: AQ AQ CF AI KA AA AE AQ AQ CF CF AF AF
Eu 0(cid:4)117 0(cid:4)642 0(cid:4)120 0(cid:4)0839 0(cid:4)119 0(cid:4)264 0(cid:4)276 1(cid:4)365 0(cid:4)815 0(cid:4)360 0(cid:4)552 0(cid:4)496 0(cid:4)685 0(cid:4)0877
Gd 0(cid:4)407 1(cid:4)93 0(cid:4)416 0(cid:4)298 0(cid:4)493 0(cid:4)837 0(cid:4)879 3(cid:4)48 2(cid:4)32 1(cid:4)16 1(cid:4)68 1(cid:4)56 2(cid:4)30 0(cid:4)356 D
o
Tb 0(cid:4)0733 0(cid:4)264 0(cid:4)0709 0(cid:4)0553 0(cid:4)0960 0(cid:4)126 0(cid:4)133 0(cid:4)439 0(cid:4)308 0(cid:4)169 0(cid:4)232 0(cid:4)216 0(cid:4)342 0(cid:4)0634 w
n
Dy 0(cid:4)528 1(cid:4)47 0(cid:4)488 0(cid:4)416 0(cid:4)733 0(cid:4)771 0(cid:4)824 2(cid:4)24 1(cid:4)64 0(cid:4)997 1(cid:4)28 1(cid:4)22 1(cid:4)99 0(cid:4)476 lo
a
Ho 0(cid:4)116 0(cid:4)252 0(cid:4)106 0(cid:4)0961 0(cid:4)167 0(cid:4)149 0(cid:4)159 0(cid:4)370 0(cid:4)277 0(cid:4)176 0(cid:4)218 0(cid:4)217 0(cid:4)357 0(cid:4)1056 d
e
TErm 00(cid:4)(cid:4)0354355 00(cid:4)(cid:4)0671857 00(cid:4)(cid:4)034171 00(cid:4)(cid:4)0248363 00(cid:4)(cid:4)047955 00(cid:4)(cid:4)035942 00(cid:4)(cid:4)0452819 00(cid:4)(cid:4)191371 00(cid:4)(cid:4)0687600 00(cid:4)(cid:4)0453465 00(cid:4)(cid:4)0560054 00(cid:4)(cid:4)5036379 00(cid:4)(cid:4)817192 00(cid:4)(cid:4)3004355 d from
Yb 0(cid:4)295 0(cid:4)369 0(cid:4)302 0(cid:4)293 0(cid:4)496 0(cid:4)336 0(cid:4)368 0(cid:4)581 0(cid:4)416 0(cid:4)315 0(cid:4)334 0(cid:4)327 0(cid:4)520 0(cid:4)307 h
Lu 0(cid:4)0567 0(cid:4)0653 0(cid:4)0509 0(cid:4)0510 0(cid:4)0835 0(cid:4)0542 0(cid:4)0594 0(cid:4)106 0(cid:4)0759 0(cid:4)0464 0(cid:4)0488 0(cid:4)0577 0(cid:4)0876 0(cid:4)0513 ttps
Hf 0(cid:4)078 0(cid:4)708 0(cid:4)100 0(cid:4)0943 0(cid:4)110 0(cid:4)319 0(cid:4)307 0(cid:4)224 0(cid:4)270 0(cid:4)514 0(cid:4)547 0(cid:4)677 0(cid:4)855 0(cid:4)113 ://a
c
Ta 0(cid:4)0342 0(cid:4)414 0(cid:4)0512 0(cid:4)102 0(cid:4)103 0(cid:4)125 0(cid:4)130 0(cid:4)276 0(cid:4)244 0(cid:4)039 0(cid:4)303 0(cid:4)409 0(cid:4)0702 0(cid:4)0191 a
d
Pb 0(cid:4)194 0(cid:4)161 0(cid:4)134 0(cid:4)108 0(cid:4)183 0(cid:4)220 0(cid:4)236 0(cid:4)253 0(cid:4)139 0(cid:4)248 0(cid:4)223 0(cid:4)273 0(cid:4)816 12(cid:4)6 em
Th 0(cid:4)160 0(cid:4)0757 0(cid:4)0526 0(cid:4)156 0(cid:4)381 0(cid:4)109 0(cid:4)0901 1(cid:4)64 0(cid:4)0378 0(cid:4)0662 0(cid:4)439 0(cid:4)496 0(cid:4)0866 0(cid:4)0604 ic
.o
U 0(cid:4)0791 0(cid:4)0321 0(cid:4)0168 0(cid:4)022 0(cid:4)0841 0(cid:4)0290 0(cid:4)0398 0(cid:4)485 0(cid:4)0500 0(cid:4)0351 0(cid:4)124 0(cid:4)124 0(cid:4)0670 0(cid:4)0456 u
p
.c
o
n.a., not analyzed. A representative analysis of the UBN rock standard is also reported. m
/p
e
tro
lo
g
y
/a
etal.,2008).TheprecisionandaccuracyoftheLA-ICP-MS and spinel. However, inthe amphibole-rich xenoliths this rticle
analyses canbe assessed fromthe results obtained for the mineralalso occursasthinveinlets subparalleltothefoli- -a
b
BIR-1Gglass(Table4;Jochumetal.,2005,2006). ation(Fig.3a). stra
No systematic variation in modal compositions or rock c
t/5
typeproportionisobservedbetweenthexenolithlocalities 5
/1
PETROGRAPHY withintheTahalghavolcanicdistrict(Fig.2).However,sig- 1
/2
Modal compositions nificant variations are observed as a function of equilib- 24
9
The studied xenoliths are mostly spinel lherzolites, harz- rium temperature (see below). First of all, amphibole is /1
4
burgites andwehrlites (Fig.2b;Table1); no plagioclase or muchmoreabundantinthehigher-temperature(49008C) 56
garnet was found, even in the rare pyroxenites that were peridotites(2^20%amphibole)thanintheirlow-tempera- 31
3
examined. In addition to olivine (Ol), orthopyroxene ture counterparts (51% amphibole). In addition, perido- by
(Opx), clinopyroxene (Cpx) and spinel (Sp), secondary titesequilibratedat highertemperaturearemorevariable gu
Cpxandamphibole(Amph)arepresent.Lherzoliteshave in modalcompositionthanthose equilibratedat low tem- es
modal proportions of Ol and Opx in the range 41^77% perature.TheCpx/Opxratio,for instance,variesbetween t on
and16^34%, respectively, whereas Cpx varies between 6 0(cid:4)39 and 0(cid:4)63 in the low-temperature peridotites, com- 29
and 21% and Sp isbelow 4%. Amphibolemodalpropor- pared with 0(cid:4)3^1(cid:4)05 in the higher-temperature samples. Ma
tions vary from 0 to 3% except for the amphibole-rich The wider range of modal variation in high-temperature rch
peridotite sample 88-22, which contains 17% amphibole. peridotites istheresultof (1) thehigherabundance (upto 20
1
Harzburgites have much higher olivine contents (68^ 10%) in these rocks of anhedral interstitial grains with 9
91%) and lower Opx and Cpx abundances in the range convexboundaries and/or patchyaggregates of secondary
8^26% and 1^6%, respectively; they are amphibole-free Cpx and amphibole, irregularly distributed at the ex-
andcontain lessthan 2% spinel.Wehrlites have Opx and pense of Opx and commonly associated with corroded
Cpxcontentsintherange2^5%and19^26%,respectively. spinel(Dautria,1988;Fig.3),and(2)thepresenceofmilli-
Theyalwayscontainahighproportionofolivine((cid:6)67%) metre- to centimetre-scale veins or diffuse flames of
and a substantial amount of amphibole ((cid:6)2%, up to Cpx(cid:3)amphibole(cid:3)spinel,atsomeangletothefoliation.
20% in sample 276-22), whereas spinel is below 3%. Inseveralcases,itwasdifficulttodistinguishlherzolites
Amphibole is usually associated with clinopyroxene from wehrlites and it would be more appropriate to
2256
KOURIM etal. HOGGARSWELLMANTLEXENOLITHS
Table4: Clinopyroxenetrace-elementcompositionsoftheTahalghamantlexenolithsanalyzedbyLA-ICP-MS,inppm
Rocktype: Low-temperaturelherzolites(LTL) Intermediate-temperaturelherzolites(LTL)
Sample: 88-20 80-2 80-5 60-3 AD 40-2 48-25 30-2 91-4 91-8 91-2 91-5 91-9
Block: Iskel Tefedest Tefedest Tefedest Tefedest Tefedest Tefedest Tefedest Iskel Iskel Iskel Iskel Iskel
Volcano: AQ KA KA AA AD AE AF AF AR AR AR AR AR
Rb 0(cid:4)0309 0(cid:4)0055 0(cid:4)0191 0(cid:4)0775 – 0(cid:4)0049 0(cid:4)0485 0(cid:4)0055 0(cid:4)0026 0(cid:4)102 n.a. n.a.
D
Sr 2(cid:4)98 16(cid:4)6 6(cid:4)80 10(cid:4)5 1(cid:4)30 2(cid:4)42 17(cid:4)5 1(cid:4)56 310 269 59(cid:4)0 107 51(cid:4)4 o
w
Y 14(cid:4)7 13(cid:4)6 15(cid:4)3 18(cid:4)6 14(cid:4)6 16(cid:4)8 16(cid:4)8 16(cid:4)0 18(cid:4)5 18(cid:4)0 12(cid:4)1 17(cid:4)2 14(cid:4)2 n
lo
Zr 2(cid:4)99 9(cid:4)05 3(cid:4)02 5(cid:4)27 1(cid:4)59 2(cid:4)35 5(cid:4)82 1(cid:4)41 52(cid:4)7 52(cid:4)4 13(cid:4)7 32(cid:4)1 6(cid:4)52 ad
e
Nb 0(cid:4)0396 0(cid:4)0605 0(cid:4)0208 0(cid:4)114 0(cid:4)0273 0(cid:4)0526 0(cid:4)164 0(cid:4)212 0(cid:4)613 0(cid:4)627 2(cid:4)440 1(cid:4)181 1(cid:4)372 d
Cs 0(cid:4)0017 n.a. n.a. 0(cid:4)0041 n.a. n.a. n.a. n.a. n.a. 0(cid:4)0216 n.a. n.a. n.a. fro
m
Ba 0(cid:4)0099 0(cid:4)190 0(cid:4)239 2(cid:4)22 0(cid:4)104 0(cid:4)0375 1(cid:4)20 0(cid:4)0031 0(cid:4)0686 4(cid:4)56 0(cid:4)101 0(cid:4)0120 0(cid:4)0350 h
ttp
La 0(cid:4)0081 0(cid:4)203 0(cid:4)495 0(cid:4)928 0(cid:4)002 0(cid:4)0282 1(cid:4)24 0(cid:4)0369 14(cid:4)3 13(cid:4)9 3(cid:4)61 7(cid:4)07 4(cid:4)10 s
Ce 0(cid:4)081 1(cid:4)05 0(cid:4)252 1(cid:4)31 0(cid:4)0373 0(cid:4)0713 1(cid:4)16 0(cid:4)0666 44(cid:4)6 42(cid:4)9 4(cid:4)99 18(cid:4)7 4(cid:4)23 ://a
c
a
Pr 0(cid:4)070 0(cid:4)248 0(cid:4)075 0(cid:4)200 0(cid:4)038 0(cid:4)0501 0(cid:4)169 0(cid:4)0317 6(cid:4)85 6(cid:4)45 0(cid:4)572 2(cid:4)38 0(cid:4)346 d
e
Nd 0(cid:4)927 1(cid:4)804 0(cid:4)946 1(cid:4)555 0(cid:4)597 0(cid:4)749 1(cid:4)29 0(cid:4)497 31(cid:4)6 29(cid:4)5 2(cid:4)86 9(cid:4)58 1(cid:4)81 m
ic
Sm 0(cid:4)831 0(cid:4)918 0(cid:4)817 1(cid:4)01 0(cid:4)667 0(cid:4)752 0(cid:4)857 0(cid:4)568 6(cid:4)98 6(cid:4)84 1(cid:4)10 2(cid:4)14 0(cid:4)992 .o
u
Eu 0(cid:4)419 0(cid:4)415 0(cid:4)393 0(cid:4)439 0(cid:4)337 0(cid:4)369 0(cid:4)399 0(cid:4)274 2(cid:4)30 2(cid:4)26 0(cid:4)482 0(cid:4)805 0(cid:4)463 p.c
o
Gd 1(cid:4)35 1(cid:4)40 1(cid:4)49 1(cid:4)86 1(cid:4)29 1(cid:4)51 1(cid:4)63 1(cid:4)32 6(cid:4)02 5(cid:4)85 1(cid:4)52 2(cid:4)57 1(cid:4)58 m
Tb 0(cid:4)349 0(cid:4)327 0(cid:4)351 0(cid:4)416 0(cid:4)322 0(cid:4)374 0(cid:4)382 0(cid:4)317 0(cid:4)821 0(cid:4)840 0(cid:4)329 0(cid:4)471 0(cid:4)363 /pe
Dy 2(cid:4)68 2(cid:4)49 2(cid:4)77 3(cid:4)25 2(cid:4)55 2(cid:4)93 2(cid:4)99 2(cid:4)64 4(cid:4)28 4(cid:4)34 2(cid:4)35 3(cid:4)25 2(cid:4)76 tro
lo
Ho 0(cid:4)624 0(cid:4)563 0(cid:4)637 0(cid:4)746 0(cid:4)593 0(cid:4)674 0(cid:4)693 0(cid:4)634 0(cid:4)727 0(cid:4)751 0(cid:4)516 0(cid:4)688 0(cid:4)615 gy
/a
Er 1(cid:4)80 1(cid:4)65 1(cid:4)89 2(cid:4)22 1(cid:4)75 2(cid:4)02 2(cid:4)06 1(cid:4)92 1(cid:4)73 1(cid:4)73 1(cid:4)49 1(cid:4)94 1(cid:4)77 rtic
Tm 0(cid:4)279 0(cid:4)254 0(cid:4)281 0(cid:4)341 0(cid:4)272 0(cid:4)311 0(cid:4)313 0(cid:4)297 0(cid:4)229 0(cid:4)231 0(cid:4)221 0(cid:4)282 0(cid:4)267 le
Yb 1(cid:4)82 1(cid:4)65 1(cid:4)87 2(cid:4)19 1(cid:4)76 2(cid:4)05 2(cid:4)01 1(cid:4)90 1(cid:4)39 1(cid:4)36 1(cid:4)45 1(cid:4)77 1(cid:4)72 -ab
s
Lu 0(cid:4)269 0(cid:4)249 0(cid:4)275 0(cid:4)339 0(cid:4)268 0(cid:4)312 0(cid:4)304 0(cid:4)293 0(cid:4)192 0(cid:4)189 0(cid:4)217 0(cid:4)263 0(cid:4)256 tra
c
Hf 4(cid:4)610 0(cid:4)410 0(cid:4)319 0(cid:4)476 0(cid:4)233 0(cid:4)298 0(cid:4)381 0(cid:4)223 1(cid:4)394 25(cid:4)827 0(cid:4)564 0(cid:4)854 0(cid:4)440 t/5
5
Ta 0(cid:4)0003 0(cid:4)0046 n.a. 0(cid:4)0012 n.a. n.a. 0(cid:4)0040 0(cid:4)0010 0(cid:4)128 0(cid:4)107 0(cid:4)0964 0(cid:4)272 0(cid:4)183 /1
1
Pb 0(cid:4)0236 0(cid:4)0903 0(cid:4)377 0(cid:4)0990 0(cid:4)074 0(cid:4)0830 0(cid:4)261 0(cid:4)0153 0(cid:4)330 0(cid:4)341 0(cid:4)447 0(cid:4)291 0(cid:4)162 /2
2
Th 0(cid:4)0022 0(cid:4)0047 0(cid:4)390 0(cid:4)0854 0(cid:4)000 0(cid:4)0030 0(cid:4)407 0(cid:4)0112 0(cid:4)598 0(cid:4)704 2(cid:4)077 0(cid:4)376 0(cid:4)518 4
9
U 0(cid:4)0036 0(cid:4)0090 0(cid:4)252 0(cid:4)0557 0(cid:4)000 0(cid:4)0026 0(cid:4)206 0(cid:4)0062 0(cid:4)184 0(cid:4)215 0(cid:4)606 0(cid:4)104 0(cid:4)164 /14
5
6
3
1
3
Rocktype:Intermediate-temperaturelherzolites(LTL) High-temperatureharzburgites(HTH) High-temperaturewehrlites(HTW) Ref.glassmaterial b
y
g
Sample: 88-4 88-21 276-35 10-1 60-1 40-1 276-16 276-22 BIR-1G ue
s
Block: Iskel Iskel Tefedest Tefedest Tefedest Tefedest Tefedest Tefedest Av. 1SD t o
n
Volcano: AQ AQ CF AI AA AE CF CF 2
9
M
a
Rb 0(cid:4)0064 0(cid:4)0045 0(cid:4)0026 0(cid:4)0656 1(cid:4)21 1(cid:4)12 0(cid:4)0794 0(cid:4)0139 0(cid:4)239 0(cid:4)005 rc
h
Sr 135 104 84(cid:4)0 57(cid:4)8 100 95(cid:4)0 81(cid:4)2 151(cid:4)5 110 1 2
0
Y 20(cid:4)7 18(cid:4)1 17(cid:4)4 12(cid:4)7 14(cid:4)8 10(cid:4)7 13(cid:4)9 16(cid:4)9 13(cid:4)1 0(cid:4)4 19
Zr 57(cid:4)8 26(cid:4)2 26(cid:4)2 8(cid:4)15 51(cid:4)5 39(cid:4)2 46(cid:4)3 64(cid:4)5 12(cid:4)3 0(cid:4)4
Nb 0(cid:4)628 1(cid:4)441 0(cid:4)620 0(cid:4)943 0(cid:4)522 0(cid:4)597 0(cid:4)617 0(cid:4)321 0(cid:4)538 0(cid:4)013
Cs n.a. n.a. n.a. n.a. 0(cid:4)0779 0(cid:4)0100 0(cid:4)0125 - 0(cid:4)0336 0(cid:4)0057
Ba 0(cid:4)0103 0(cid:4)0506 0(cid:4)0085 0(cid:4)143 10(cid:4)3 0(cid:4)882 0(cid:4)889 0(cid:4)0814 6(cid:4)65 0(cid:4)25
La 8(cid:4)78 5(cid:4)55 9(cid:4)14 5(cid:4)16 2(cid:4)82 2(cid:4)26 3(cid:4)56 13(cid:4)8 0(cid:4)631 0(cid:4)013
Ce 27(cid:4)5 10(cid:4)6 22(cid:4)4 8(cid:4)36 11(cid:4)5 10(cid:4)7 12(cid:4)7 30(cid:4)0 2(cid:4)12 0(cid:4)05
(continued)
2257
JOURNALOFPETROLOGY VOLUME55 NUMBER11 NOVEMBER2014
Table4: Continued
Rocktype:Intermediate-temperaturelherzolites(LTL) High-temperatureharzburgites(HTH) High-temperaturewehrlites(HTW) Ref.glassmaterial
Sample: 88-4 88-21 276-35 10-1 60-1 40-1 276-16 276-22 BIR-1G
Block: Iskel Iskel Tefedest Tefedest Tefedest Tefedest Tefedest Tefedest Av. 1SD
Volcano: AQ AQ CF AI AA AE CF CF
Pr 4(cid:4)06 1(cid:4)14 2(cid:4)89 0(cid:4)691 2(cid:4)10 2(cid:4)30 2(cid:4)32 4(cid:4)07 0(cid:4)403 0(cid:4)007
Nd 18(cid:4)1 4(cid:4)53 12(cid:4)1 2(cid:4)234 11(cid:4)5 13(cid:4)4 12(cid:4)7 19(cid:4)0 2(cid:4)43 0(cid:4)04 D
o
w
Sm 3(cid:4)93 1(cid:4)53 2(cid:4)67 0(cid:4)761 3(cid:4)52 4(cid:4)17 3(cid:4)80 4(cid:4)91 1(cid:4)07 0(cid:4)02 n
lo
Eu 1(cid:4)35 0(cid:4)656 0(cid:4)882 0(cid:4)354 1(cid:4)23 1(cid:4)50 1(cid:4)33 1(cid:4)65 0(cid:4)522 0(cid:4)010 a
d
Gd 3(cid:4)96 2(cid:4)33 2(cid:4)93 1(cid:4)32 3(cid:4)67 3(cid:4)74 3(cid:4)72 4(cid:4)89 1(cid:4)60 0(cid:4)04 ed
Tb 0(cid:4)633 0(cid:4)466 0(cid:4)506 0(cid:4)302 0(cid:4)603 0(cid:4)575 0(cid:4)608 0(cid:4)722 0(cid:4)355 0(cid:4)011 fro
m
Dy 4(cid:4)08 3(cid:4)41 3(cid:4)47 2(cid:4)34 3(cid:4)63 2(cid:4)93 3(cid:4)42 4(cid:4)09 2(cid:4)60 0(cid:4)12 h
Ho 0(cid:4)820 0(cid:4)752 0(cid:4)735 0(cid:4)535 0(cid:4)666 0(cid:4)466 0(cid:4)602 0(cid:4)705 0(cid:4)567 0(cid:4)026 ttp
s
Er 2(cid:4)22 2(cid:4)17 2(cid:4)05 1(cid:4)62 1(cid:4)64 0(cid:4)973 1(cid:4)40 1(cid:4)61 1(cid:4)68 0(cid:4)04 ://a
c
Tm 0(cid:4)322 0(cid:4)318 0(cid:4)299 0(cid:4)244 0(cid:4)228 0(cid:4)110 0(cid:4)176 0(cid:4)202 0(cid:4)255 0(cid:4)011 a
d
Yb 2(cid:4)00 2(cid:4)02 1(cid:4)85 1(cid:4)59 1(cid:4)35 0(cid:4)57 1(cid:4)04 1(cid:4)16 1(cid:4)66 0(cid:4)07 em
Lu 0(cid:4)290 0(cid:4)303 0(cid:4)276 0(cid:4)236 0(cid:4)192 0(cid:4)0711 0(cid:4)135 0(cid:4)154 0(cid:4)255 0(cid:4)010 ic.o
u
Hf 1(cid:4)596 0(cid:4)848 0(cid:4)826 0(cid:4)287 1(cid:4)617 1(cid:4)246 2(cid:4)131 2(cid:4)574 0(cid:4)535 0(cid:4)038 p
.c
Ta 0(cid:4)215 0(cid:4)203 0(cid:4)149 0(cid:4)0763 0(cid:4)0985 0(cid:4)0861 0(cid:4)0905 0(cid:4)0608 0(cid:4)0401 0(cid:4)0018 o
m
Pb 0(cid:4)121 0(cid:4)301 0(cid:4)377 0(cid:4)114 0(cid:4)085 0(cid:4)043 0(cid:4)279 0(cid:4)303 5(cid:4)060 1(cid:4)554 /p
e
Th 0(cid:4)299 0(cid:4)271 0(cid:4)416 0(cid:4)419 0(cid:4)0452 0(cid:4)0607 0(cid:4)203 1(cid:4)017 0(cid:4)0304 0(cid:4)0009 tro
U 0(cid:4)0818 0(cid:4)0783 0(cid:4)127 0(cid:4)105 0(cid:4)0269 0(cid:4)0148 0(cid:4)0714 0(cid:4)316 0(cid:4)0234 0(cid:4)0018 log
y
/a
Single LA-ICP-MS analyses (n(cid:6)3) were averaged for each sample; SD, standard deviation; n.a., not analysed. Average rtic
(n¼3) composition of the BIR-1G glass reference material (Jochum et al., 2005, 2006) is also reported. le
-a
b
s
tra
c
t/5
describe such samples as a continuous gradation from (55%), which are mainly pyroxene, and a reduction in 5
/1
‘marbled’lherzolite towehrlite. Furthermore, these small- their average grain size (52(cid:4)7mm). Conversely, recrystal- 1/2
scaleheterogeneitiesmayberesponsibleforsomeinconsis- lized neoblasts (0(cid:4)05^0(cid:4)2mm) increase in abundance 24
9
tencies between whole-rock and in situ mineral (Fig.4e).The coarse-grainedequigranular microstructure /1
4
compositions. is characterized by rounded Ol and Cpx grains, and a 5
6
3
weak foliation markedby the preferred shape orientation 1
3
Microstructures ofOpx.Alineationisdefinedbyelongated,thoughirregu- b
y
TheTahalghaperidotitesshowacontinuumofmicrostruc- larly shaped, spinelgrains.The fine-grainedequigranular gu
e
tures, from porphyroblastic to equigranular (Fig. 4). At microstructureisdistinguishedbyfurthergrain-sizereduc- s
the thin-section scale, the porphyroblastic microstructure tion of both pyroxene porphyroclasts (51(cid:4)3mm; olivine t on
2
is characterizedbyabimodal grain-size distribution (Fig. porphyroclasts are absent) and neoblasts (Fig. 4c). 9
M
4d). Porphyroclasts of olivineandpyroxene,2mmto1cm Theproportionofthefiner-grained(50(cid:4)05mm)neoblasts a
insize,constitute10(cid:3)3%ofthethinsectionsandaresur- increases and generally exceeds 50% (Fig.4f). All phases rch
roundedbyneoblasts(0(cid:4)05^0(cid:4)2mm)ofthesameminerals. have irregular shapes with interpenetrating boundaries. 20
1
Olivineporphyroclasts have irregular shapeswithaweak As in the coarse-grained microstructure, the spinel has 9
elongation marking the foliation and strong undulate ex- elongatedshapesandisalignedparalleltothelineation.
tinction perpendicular to the grain elongation. Opx and Most of these microstructures show evidence for late
Cpx porphyroclasts have rounded or irregular shapes. staticrecrystallization(annealing).Somegrainsgrowtoa
Opxshowsaweakelongationparalleltooratalowangle larger size and grain shapes tend to be more polygonal,
to the olivine foliation.The largest orthopyroxene grains with a significant proportion of grain boundaries being
sometimes show clinopyroxene exsolution lamellae. The reorganized to form 1208 triple junctions (Fig. 5a). The
transition to the equigranular microstructure (Fig. 4b) is histograms of olivine grain distribution weighted by area
marked by decreasing abundance of porphyroclasts fraction showan increase in olivine neoblasts, from about
2258