Chemical Composition Of The Continental Crust: A Perspective From China
ArticleGeochemical News 14328 April 2010Chemical composition of the continentalcrust: a perspective from ChinaShan GAOa,b,*aState Key Laboratory of Geological Processes and Mineral Resources, Faculty of Earth Sciences, ChinaUniversity of Geosciences, Wuhan, 430074, P.R. ChinabState Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an,710069, P.R. China* corresponding author's email: sgao@263.netAbstractThe chemical composition of the continental crust is critically important for understanding itsformation and evolution and, ultimately, understanding Earth differentiation. Here we provide abrief review of the chemical composition of the continental crust, with an emphasis on studiesfrom China. The upper crustal composition reveals higher transition metal abundances comparedto previous estimates that were based on results from the Canadian Shield. Inter-elementcorrelations in clastic sedimentary rocks can be extended to many immobile as well as mobileelements. The significant correlations place constraints on the concentrations of the rarelyanalyzed elements (B, Be, Bi, Ge, In, Mo, Sb, Sn, Te, Tl, W) in the upper crust. Middle crustalcompositional estimates based on sampling of amphibolite-facies rocks and seismic profilesyield a bulk composition with 62-69% SiO2. The eastern China middle crust composition is moreevolved and shows slightly slower compressional velocity than that of global middle crust. Whilethere is a general consensus that the global lower continental crust is mafic in composition,eastern China is a remarkable exception to this generality with an intermediate bulk lower crustcomposition. The total crust composition of eastern China is also more evolved than the globalmodel and characterized by a significant negative Eu anomaly. Delamination of the lower crustand its underlying lithospheric mantle are suggested to have played an important role in drivingthe continental crust to an evolved composition, loss of the Archean keel, and in producing thelarge volumes of intraplate magmatism in the North China Craton during the Mesozoic.Keywords: Continental crust, chemical composition, seismic velocity, delamination, easternChina1. IntroductionThe composition of the continental crust iscritically important for understanding itsformation and evolution and ultimately,understanding Earth's differentiation, and forquantifying geodynamic processes withinthe Earth (e.g., Taylor and McLennan, 1995,2009; Rudnick, 1995; Gao et al., 1998a;Rundick and Gao, 2003; Hawkesworth andKemp, 2006a, b). It also provides baselinesfor assessing geochemical anomalies inexplorationoforedepositsandCopyright 2010 by the Geochemical orthesereasons,determining the chemical composition of thecontinental crust has been an aim ofgeochemists since the first analyses of rockswere undertaken (Clarke, 1889).The continental crust can be divided intoupper, middle and lower layers and showswidelithologicalandgeochemicalvariations. The upper crust is readilyaccessible for direct sampling and itsS.GaoPage 1Chemical composition of the continental crust: a perspective from China
ArticleGeochemical News 14328 April 2010composition is reasonably well establishedfor the major elements and many lithophiletrace elements. In comparison, thecomposition of the deep (middle and lower)crust is less well established due to itsgeneral inaccessibility. Here we provide abrief review of the chemical composition ofthe continental crust, with an emphasis onstudies from China. For detailed reviews ofcomposition of the continental crust in theglobal context see Rudnick and Gao (2003)and Taylor and McLennan (2009).2. The Upper CrustTwo approaches have generally been used todetermine the composition of the uppercontinental crust (ref. Rudnick and Gao,2003; Taylor and McLennan, 2009). One isto establish weighted averages of thecompositions of rocks exposed at the surfaceby large-scale sampling campaigns. Allmajor-element determinations of upper-crustcomposition rely upon this method. Theother approach is to determine the averageconcentrations of insoluble elements in finegrained clastic sediments and sedimentaryrocks (e.g., shale, mudstone, graywacke,siltstone, loess, and tillite) and use these toinfer the average composition of their sourceregions.2.1 Weighted Averages of Exposed CrustThe Canadian Shield represents the first areain which large-scale sampling of the crustwas undertaken for both major and traceelement analyses (Shaw et al., 1967, 1976,1986; Eade and Fahrig, 1971, 1973). Morerecently, two campaigns of systematic largescale sampling and rock analyses wereundertaken in eastern China in the 1980'sand 1990's for the purpose of studying thechemical composition of the continentalcrust. The first was carried out in theQinling orogen and the adjacent regions ofthe North China Craton and Yangtze Craton.Copyright 2010 by the Geochemical SocietyThe sampling covered an area of 153,200km2 and comprised over 4500 individualrock samples that represented all of the LateArchean to Neogene stratigraphic units, the2/3 of the exposed granitoids, as well as allof the major mafic-ultramafic intrusions inthe study area. These individual rocks wereanalyzed for thirteen major and thirty traceand rare earth elements. The results wereused, in conjunction with seismic velocitiesof the deep crust and surface heat flow, toestimate the composition of the upper, deepand total crust of the Qingling region (Gaoet al., 1992; Zhang et al., 1994).Figure 1(see appendix for larger image)A second round of large-scale sampling wasconducted over most of eastern China,covering a total area of ca 3,300,000 km2(Fig. 1) (Yan et al., 1997; Yan and Chi,1997; Gao et al., 1998b; Zhang et al., 2002).A total of 28,253 individual rocks weresampled, from which 2,718 compositesamples were prepared based on age,lithology and tectonic units. Between sixtythree to seventy-six major and traceelements were analyzed by a variety ofmethods, including elements that are rarelyanalyzed (e.g., Ag, As, Bi, Br, Cd, Cl, F, Ge,Hg, I, In, Mo, PGE, Te, Se, W) (Yan et al.,1997; Yan and Chi, 1997; Gao et al., 1998b;Zhang et al., 2002).S.GaoPage 2Chemical composition of the continental crust: a perspective from China
ArticleGeochemical News 14328 April 2010These studies revealed higher transitionmetal abundances of the upper crustcompared to previous estimates that werebased on results from the Canadian Shieldstudies (Shaw et al., 1967, 1976, 1986; Eadeand Fahrig, 1971, 1973; Taylor andMcLennan, 1985; Wedepohl, 1995). Ahigher transition metal content of the uppercrust has been supported by subsequentstudies of fine-grained clastic sedimentaryrocks (Condie, 1993; Plank and Langmuir,1998; McLennan, 2001; Hu and Gao, 2008;Taylor and McLennan, 2009). Thediscrepancies between the Canadian Shieldand eastern China studies were ascribed todifferential erosion. The present-day surfaceof the Canadian Shield is dominated byamphibolite-facies granitoid gneisses, whichare more typical of middle crust than uppercrust. The uppermost crust of Archeanregions typically contains more maficvolcanic rocks (Gao et al., 1998b). Bycontrast, unmetamorphosed to greenschistfacies rocks are well preserved in easternChina.The influence of erosion on the upper crustcomposition was also demonstrated byCondie (1993), who added a 10 km thicklayer of upper crust in Precambrian areasand a 5 km thick layer of upper crust inPhanerozoic areas to the present upper crustlayer. This restoration model for the uppercontinental crust composition shows aremarkably good agreement with the easternChina upper crust composition in terms ofNb, Rb, Th, Zr, Co, Sc, and V, as well asK2O concentrations. Although the Cr and Niabundances of the restoration model aresignificantly greater than the eastern Chinaestimates, the difference is small comparedto estimates based on the Canadian Shield.We conclude that eastern China surfacesamples are a good representation of theCopyright 2010 by the Geochemical Societyaverage upper continental crust (Gao et al.,1992, 1998b).Another important observation from easternChina is that various thicknesses ofsedimentary cover, including carbonate, arean important component of the uppercontinental crust. Because carbonate andsilicate rocks vary greatly in their chemicalcompositions and since the sedimentarycover in eastern China contains asignificantly higher carbonate proportionwith a carbonate/(pelite sandstone) ratio of0.31-2.23 compared to the global ratio of0.18 (Taylor and McLennan, 1985), theupper crust compositions with and withoutcarbonate are distinct in major elements(e.g., 58.5 vs 65.5% for SiO2 and 7.41 vs3.31 for CaO) (Gao et al., 1998b). However,because carbonates have low abundances oftrace elements, excepting Sr, the twoestimates of the upper crust do not vary inrelative trace element abundances (Yan etal., 1997; Gao et al., 1998b). The majorelement compositions without carbonate arealso similar to previous estimates (Gao etal., 1998b).In addition, trace elements associated withmineralization (e.g., B, Cl, Se, As, Bi, Pd,W, Th, Cs, Ta, Tl, Hg, Au, and Pb) showconsiderable inter-unit variability (by afactor of 2-5) in the upper crust (Gao et al.,1998b).2.2 Fine-Grained Sedimentary RocksEstimates of the upper crustal compositionfrom fine-grained clastic sedimentary rockswere applied by Taylor and McLennan(1985) to trace elements that are immobileduring water-rock interaction and are nothosted in accessory minerals and, thus, arelittlefractionedduringsedimentaryprocessing and diagenesis. Such elementsinclude REE, Y, Th, and Sc. The moreS.GaoPage 3Chemical composition of the continental crust: a perspective from China
ArticleGeochemical News 14328 April 2010mobile elements, such as K, U and Rb, canbe estimated from assumed Th/U, K/U andK/Rb ratios (Taylor and McLennan, 1985).The fine-grained sediment approach hasmore recently been extended to elementssuch as Nb, Ta, Cs and transition metals (Cr,Ni, V, Co and Ti) (McDonough et al., 1992;Plank and Langmuir, 1998; Barth et al.,2000; McLennan, 2001).Figure 2(see appendix for larger image)In a recent study, Hu and Gao (2008)analyzed 48 trace elements by ICP-MS(including the rarely analyzed elements As,B, Be, Bi, Cd, Ge, In, Mo, Sb, Sn, Te, Tl,W) in well-characterized upper crustalsamples (shales, pelites, loess, graywackes,granitoids and their composites) fromAustralia, China, Europe, New Zealand andNorth American. The results reveal thatinter-elementcorrelationsinclasticsedimentary rocks can be extended to manyimmobile as well as mobile elements (e.g.,Ga-In, Th-Sn, Rb-Tl, Th-Tl, Rb-Be, Th-Be,Rb-Ge, Rb-W, Be-Bi, W-Bi, In-Li, B-Te,Fe-transition trace metals) (Fig. 2). Thesignificant (r2 0.6) correlations observed inclastic sediments and sedimentary rocksprovide narrowly constrained uppercontinental crust elemental ratios, which canbe used with abundances for certain keyelements to place constraints on theconcentrations of these rarely analyzedCopyright 2010 by the Geochemical Societyelements in the upper crust. Using the wellestablished upper crustal abundances of La(31 ppm), Th (10.5 ppm), Al2O3 (15.40%),K2O (2.80%) and Fe2O3 (5.92%), thesecorrelations lead to revised upper crustalabundances for B 47 ppm, Li 41 ppm,Cr 73 ppm, Ni 34 ppm, Sb 0.075,Te 0.027 ppm, W 1.4 ppm. Tl 0.53 ppmand Bi 0.23 ppm. No significantcorrelations exist between Mo and Cd andother elements in the clastic sediments andsedimentary rocks, probably due to theirenrichment in organic carbon. If we assumethat these two incompatible elements behavemore or less like REE and Th, theirabundances can be calculated by assumingthe upper continental crust consists of 65%granitoid rocks plus 35% clastic sedimentaryrocks. The validity of this bulk averageapproach for incompatible elements issupported by the similarity of SiO2, Al2O3,La and Th abundances calculated in this waywith their upper crustal abundances given inRudnick and Gao (2003). The upper crustalabundances thus obtained are Mo 0.6 ppmand Cd 0.06 ppm. The data also suggest a 20% increase of the Tm, Yb and Luabundances reported in Rudnick and Gao(2003).In summary, studies of surface samples fromeastern China and clastic sediments establishsignificantlyhigheruppercrustalabundances of transition metals compared tothose based on surface samples from theCanadian Shield. The upper crustalcompositions of the major elements and amajority of trace elements, as well as somekey elemental ratios are well established.Such estimates can form basis of massbalance calculations for the Earth andprovide geodynamic insights (e.g., Rudnicket al., 2000). However, the upper crustalabundances of some elements, notablyS.GaoPage 4Chemical composition of the continental crust: a perspective from China
ArticleGeochemical News 14328 April 2010platinum group elements, noble gases andthe halogens are still highly uncertain.3. The Deep CrustMajor uncertainties in the composition ofthe continental crust lie in the deepcontinental crust and particularly the lowercrust, as it is far less accessible than theupper crust. Four approaches have been usedto infer its composition (ref. Rudnick andGao, 2003): (1) analyses of high-grademetamorphic (amphibolite or granulitefacies) terrains and exposed crustal crosssections in particular; (2) studies ofgranulite-facies xenoliths entrained in fastrising magmas; (3) correlation of measuredseismic velocities of deep crustal rocks withseismic profiles of the crust; and (4) surfaceheat flow measurements.Studies of exposed crustal cross-sectionsand xenoliths indicate that, althoughexceptions exist, the middle crust isdominated by rocks metamorphosed atamphibolite-facies to lower granulite facies,while the lower crust consists mainly ofgranulite-facies rocks (Rudnick and Gao,2003 and references therein). Exposedamphibolite- to granulite-facies terrains andmiddle crustal cross-sections show that,although they contain a wide variety oflithologies, including metasedimentaryrocks, they are dominated by igneous andmetamorphic rocks of the diorite-tonalitetrondhjemite-granodiorite (DTTG) andgranite suites. This is true not only forPrecambrian shields, but also forPhanerozoic crust and continental arcs. Suchrock associations are consistent with theaverage middle crustal P-wave velocities of6.4-6.5 km s-1 seen in all the tectonic settingsexcept for active rifts and some intraoceanic island arcs, which have higheraverage velocities suggesting a more maficcomposition (Rudnick and Fountain, 1995).Copyright 2010 by the Geochemical SocietyMiddle crust compositional estimates basedon sampling of amphibolite-facies rocks andseismic profiles yield a bulk compositionwith 62-69% SiO2. Trace elementcomposition of the middle crust is poorlyconstrained, as systematic trace elementstudies of amphibolite-facies rocks are few.Nevertheless, the estimates of Rudnick andFountain (1995) based on lithologies derivedfrom seismic velocities and Gao et al.(1998b) based on eastern China surfacesampling show a broadly similarcomposition in both major and traceelements, although the eastern China middlecrust composition is more evolved, havinghigher SiO2, K2O, Ba, Li, Zr, and LREE andLaN/YbN and lower total FeO, Sc, V, Crand Co with a significant negative Euanomaly. These differences are expectedbased on the slightly higher compressionalvelocity of Rudnick and Fountain's globalmiddle crust compared to that of easternChina (6.6 vs. 6.4 km s-1: Gao et al., 1998a,b). The consistency is surprising,considering that the two estimates are basedon different sample sets and differentapproaches, one global and the otherregional (Rudnick and Gao, 2003).Like the middle crust, the lower crust alsocontains a wide variety of lithologies, asrevealed by studies of granulite xenoliths,exposed high-pressure granulite terranes andcrustal cross sections. Nevertheless, maficrocks appear to dominate in the lower crustbased on the relatively high seismicvelocities, which are faster than 6.9 km s-1(mostly 7.0 km s-1) for various tectonicunits (Rudnick and Fountain, 1995).S.GaoPage 5Chemical composition of the continental crust: a perspective from China
ArticleGeochemical News 14328 April 2010Hannuoba granulite xenoliths, which havean average SiO2 of 56% (Kern et al., 1995;Liu et al., 2001). This is unlike theworldwide compilations of lower crustalxenoliths, which are predominately mafic(Rudnick and Presper, 1990; Rudnick andFountain, 1995) with an average SiO2 of51.5% (Fig. 3). This conclusion is supportedby results of seismic profiling, whichindicate a distinct two-layered structure tothe lower crust for all of eastern China,except the Qingling orogen (Fig. 4). Theupper lower crust has a mean velocity of 6.7km s-1, suggesting an evolved composition;only the lowermost crust has a meanvelocity that is typical of mafic rocks(average velocity 7.1 km s-1) and iscomparable to the global lower crust. Thebulk lower crust of eastern China has a meanP-wave velocity of 6.82 km s-1 that is slowerthan the global average by 0.2-0.4 km s-1,and is consistent with an intermediate bulkcomposition (Gao et al., 1998a, b). Theslower velocity of the lower crust of easternChina is reinforced by recent compilationsof seismic profiling in China (Li et al.,2006). We conclude that the evolved lowercrust composition of eastern China is wellestablished and is a remarkable featureexceptional to the global continental crust.Figure 3(see appendix for larger image)Figure 4(see appendix for larger image)While there is a general consensus that theglobal lower continental crust is mafic incomposition (ref. Rudnick and Fountain,1995; Christensen and Mooney, 1995),Eastern China is a remarkable exception tothis generality. Studies of exposed lowercrustal cross-section and lower crustalgranulite-facies xenoliths in eastern Chinaindicate a bimodal lithological distributionin the lower crust, with felsic rocks being animportant constituent, as exemplified by theCopyright 2010 by the Geochemical Society4. The total crust composition and itsgeodynamic implicationsThere is a general consensus that the bulkcomposition of the continental crust isandesitic. All estimates of the crustcomposition, including the pioneering workof Clarke (1889), have a total crustal SiO2that falls between 57.1-64.5% (Rudnick andGao, 2003), regardless of the approachesand data sets that have been employed toderive these estimates. Moreover, allestimates show a continental crust that ischaracterized by enrichments in large-ionlithophile elements (e.g., Cs, Rb, Ba and, inS.GaoPage 6Chemical composition of the continental crust: a perspective from China
ArticleGeochemical News 14328 April 2010particular, Pb) and depletions in high-fieldstrength elements (Nb, Ta, Ti). Thesefeatures are therefore considered robust andcan be used to understand the formation andevolution of the continental crust.The continental crust grows primarily by anigneous flux from the mantle, which in mostcases should be basaltic. The demonstrablynon-basaltic composition of the continentalcrust requires some form of crustal recyclingthrough delamination, weathering and/orsubduction (Rudnick, 1995).Europium balance or imbalance in thecontinental crust may be useful forunderstanding the processes by which thecrust evolved (e.g., Gao et al., 1998a;Hawkesworth and Kemp, 2006b). Mantlederived additions to the crust wouldnormally have no Eu anomaly. Intracrustaldifferentiation by granitic magmatism hasled to a prominent negative Eu anomaly inthe granitic upper crust (Eu/Eu* 0.72;Rudnick and Gao, 2003), and shouldproduce a restitic lower crust with acomplementary positive Eu anomaly (Taylorand McLennan, 1985, 2009). However, ifdelamination of the dense mafic lower crustcould occur, and if this crust containedcumulate or residual plagioclase, the totalcrust after delamination would evolvetoward a felsic composition with a negativeEu anomaly. The total crust compositionestimates of Rudnick and Gao (2003) has aweak negative Eu anomaly (Eu/Eu* 0.93),which would accommodate some removal ofplagioclase cumulates/restites, althoughgiven the uncertainties, there is no need tocall upon plagioclase removal from thelower crust.Copyright 2010 by the Geochemical SocietyFigure 5(see appendix for larger image)In contrast to the global average lower crust,the continental crust in eastern China has apronouncednegativeEuanomaly(Eu/Eu* 0.80) (Gao et al., 1998a, b). Theupper and middle crusts of eastern Chinahave Eu/Eu* of 0.73 and 0.78, respectively.Weighted by thickness, the upper plusmiddle crust as a whole has an averageEu/Eu* of 0.75 (Fig. 5). The Hannuobamafic and mafic to felsic granulite xenolithshave almost identical Eu/Eu* of 1.28 and1.30, respectively. If the eastern China lowercrust is assumed to be represented by theaverage Hannuoba granulite xenoliths, theresultant total crust has Eu/Eu* of 0.89 (Fig.5). This magnitude of Eu anomaly isinsufficient to compensate for the negativeEu anomaly of the upper and middle crust soas to produce no Eu anomaly in the totalcrust. The model lower crust is required tohave Eu/Eu* of 1.73 to make a balance,which is far greater than the averageworldwide mafic (Eu/Eu* 1.24) and maficto felsic granulite xenoliths (Eu/Eu* 1.14)(Fig. 5). Delamination of the lower crustS.GaoPage 7Chemical composition of the continental crust: a perspective from China
ArticleGeochemical News 14328 April 2010plus underlying lithospheric mantle has beensuggested to have occurred in eastern Chinabased on studies of Mesozoic high-Mgadakitic magmas, picritic and basaltic lavasand entrained eclogitic xenoliths in theNorth China Craton (Gao et al., 2004, 2008;Xu et al., 2006). Although other models mayalso explain the andesitic composition of thecontinental crust (Rudnick and Gao, 2003;Arculus, 2006; Davidson and Arculus,2006), we conclude that delamination of thedeep lithosphere may have played animportant role in driving the continentalcrust to an evolved composition, loss of theArchean keel, and in producing the largevolumes of intraplate magmatism in theNorth China Craton during the Mesozoic(Gao et al., 2004, 2008; Xu et al., 2006).AcknowledgmentsI dedicate this paper to my graduatesupervisor Prof. Benren Zhang. I thank theteam of eastern China crust compositionstudy for their samples and Mingcai Yanparticularly for helping analysis of thecomposites. I also thank Roberta L.Rudnick, Zhaochu Hu, Yongsheng Liu, andScott McLennan for their comments anddiscussion. I finally thank Yong-Fei Zhengand Stephen C. Komor for editorialhandling. This research is supported by theNational Nature Science Foundation ofChina (Grants 40821061, 90714010,40973020), Chinese Ministry of Educationand State Administration of Foreign ExpertAffairs (B07039) as well as the MOSTspecial funds from the State Key Laboratoryof Continental Dynamics and the State KeyLaboratory of Geological Processes andMineral Resources.ReferencesArculus R.J. (2006) The 'Andesite Model' of continental crust origins. Geochim. Cosmochim. Acta 70 (Issue, 18,Supplement 1), A20.Barth M., McDonough W.F. and Rudnick R.L. (2000) Tracking the budget of Nb and Ta in the continental crust.Chem. Geol. 165, 197-213.Christensen N. I. and Mooney W. D. (1995) Seismic velocity structure and composition of the continental crust: Aglobal view. J. Geophys.Res. 100, 7961-9788.Clarke F.W. (1889) The relative abundance of the chemical elements. Phil. Soc. Washington Bull XI, 131-142.Condie K.C. (1993) Chemical composition and evolution of the upper continental crust: contrasting results fromsurface samples and shales. Chem. Geol. 104, 1-37.Eade K.E. and Fahrig W.F. (1971) Chemical evolutionary trends of continental plates-preliminary study of thecanadian shield. Geol. Sur. Can. Bull. 179, 1-51.Eade K.E. and Fahrig W.F. (1973) Regional, lithological, and temporal variation in the abundances of some traceelements in the canadian shield. Geol. Sur. Canada Paper 72-46, Ottawa, Ontario.Davidson J.P. and Arculus R.J. (2006) The significance of Phanerozoic arc magmatism in generating continentalcrust. In Evolution and Differentiation of the Continental Crust (eds. M. Brown and T. Rushmer), pp. 135-172,Cambridge: Cambridge University Press.Gao S., Zhang B.R., Luo T.C., Li Z.J., Xie Q.L., Gu X.M., Zhang H.F., Ouyang J.P., Wang D.P. and Gao C.L.(1992) Chemical composition of the continental-crust in the Qinling Orogenic Belt and its adjacent North Chinaand Yangtze Cratons. Geochim. Cosmochim. Acta 56, 3933-3950.Gao S., Zhang B.-R., Jin Z.-M., Kern H., Luo T.-C., and Zhao Z.-D. (1998a) How mafic is the lower continentalcrust? Earth Planet. Sci. Lett. 106, 101-117.Gao S., Luo T.-C., Zhang B.-R., Zhang H.-F., Han Y.-W., Hu Y.-K. and Zhao Z.-D. (1998b) Chemical compositionof the continental crust as revealed by studies in East China. Geochim. Cosmochim. Acta 62, 1959-1975.Gao S., Rudnick R.L., Yuan H.L., Liu X.M., Liu Y.S., Xu W.L., Ling W.L., Ayers J., Wang X.C. and Wang Q.H.(2004) Recycling lower continental crust in the North China craton. Nature 432, 892-897.Copyright 2010 by the Geochemical SocietyS.GaoPage 8Chemical composition of the continental crust: a perspective from China
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ArticleGeochemical News 14328 April 2010Zhang G. H., Zhou X. H., Chen S. H., and Sun M. (1998) Heterogeneity of the lower crust: Evidence fromgeochemistry of the Hannuoba granulite xenoliths, Hebei province (in Chinese). Geochemica 27, 153-163.Copyright 2010 by the
The chemical composition of the continental crust is critically important for understanding its formation and evolution and, ultimately, understanding Earth differentiation. Here we provide a brief review of the chemical composition of the continental crust, with an emphasis on studies from China.
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̶The leading indicator of employee engagement is based on the quality of the relationship between employee and supervisor Empower your managers! ̶Help them understand the impact on the organization ̶Share important changes, plan options, tasks, and deadlines ̶Provide key messages and talking points ̶Prepare them to answer employee questions
Dr. Sunita Bharatwal** Dr. Pawan Garga*** Abstract Customer satisfaction is derived from thè functionalities and values, a product or Service can provide. The current study aims to segregate thè dimensions of ordine Service quality and gather insights on its impact on web shopping. The trends of purchases have
Chính Văn.- Còn đức Thế tôn thì tuệ giác cực kỳ trong sạch 8: hiện hành bất nhị 9, đạt đến vô tướng 10, đứng vào chỗ đứng của các đức Thế tôn 11, thể hiện tính bình đẳng của các Ngài, đến chỗ không còn chướng ngại 12, giáo pháp không thể khuynh đảo, tâm thức không bị cản trở, cái được
Le genou de Lucy. Odile Jacob. 1999. Coppens Y. Pré-textes. L’homme préhistorique en morceaux. Eds Odile Jacob. 2011. Costentin J., Delaveau P. Café, thé, chocolat, les bons effets sur le cerveau et pour le corps. Editions Odile Jacob. 2010. Crawford M., Marsh D. The driving force : food in human evolution and the future.
Annual Book of ASTM Standards, Vol. 04.02. 3 For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards volume information, refer to the standard’s Document Summary page on the ASTM website. 4 The boldface numbers in parentheses refer to a list of references at the end of this standard. 1 .
