PowerPoint PresentationSlide 2Liquids and residuum of melted pyroliteInitial Conclusions:Primary magmasSummarySlide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17REE data for oceanic basaltsSlide 19REE data for UM xenolithsThin section #94MC-200Liquids and residuum of melted pyroliteLiquids and residuum of melted pyroliteFigure 10-9 Figure 10-9 After Green and Ringwood (1967).After Green and Ringwood (1967). Earth Planet. Sci. Lett.Earth Planet. Sci. Lett. 2, 151-160. 2, 151-160.Initial Conclusions:Initial Conclusions:Tholeiites favored by shallower meltingTholeiites favored by shallower melting25% melting at 25% melting at <<30 km 30 km  tholeiite tholeiite25% melting at 60 km 25% melting at 60 km  olivine basalt olivine basaltTholeiites favored by greater % partial meltingTholeiites favored by greater % partial melting20 % melting at 60 km 20 % melting at 60 km  alkaline basalt alkaline basaltincompatibles (alkalis) incompatibles (alkalis)  initial melts initial melts30 % melting at 60 km 30 % melting at 60 km  tholeiite tholeiitePrimary magmasPrimary magmasFormed at depth and not subsequently modified by Formed at depth and not subsequently modified by FX or AssimilationFX or AssimilationCriteriaCriteriaHighest Mg# Highest Mg# (100Mg/(Mg+Fe))(100Mg/(Mg+Fe)) really really  parentalparental magmamagmaExperimental results of lherzolite meltsExperimental results of lherzolite meltsMg# = 66-75Mg# = 66-75Cr > 1000 ppmCr > 1000 ppmNi > 400-500 ppmNi > 400-500 ppmMultiply saturatedMultiply saturatedSummarySummaryA chemically homogeneous mantle can A chemically homogeneous mantle can yield a variety of basalt typesyield a variety of basalt typesAlkaline basalts are favored over tholeiites Alkaline basalts are favored over tholeiites by deeper melting and by low % PMby deeper melting and by low % PMFractionation at moderate to high depths can Fractionation at moderate to high depths can also create alkaline basalts from tholeiitesalso create alkaline basalts from tholeiitesPreference forPreference formineral phasemineral phasePreferencePreferencefor meltfor meltPlot of ionic radius vs. ionic charge for trace elements of geological interest. Ionic radii are quoted for eight-fold coordination to allow for comparison between elements. From Rollinson(1993).Ionic chargeIonic chargevs. radiusvs. radiusIncompatibleIncompatible elements commonly elements commonly  two subgroups two subgroups based on the ratio of valence to ionic radius:based on the ratio of valence to ionic radius:Smaller, highly charged Smaller, highly charged high field strength (HFS)high field strength (HFS) elementselements (REE, Th, U, Ce, Pb(REE, Th, U, Ce, Pb4+4+, Zr, Hf, Ti, Nb, Ta), Zr, Hf, Ti, Nb, Ta)Low field strength Low field strength large ion lithophile (LIL)large ion lithophile (LIL) elements elements (K, Rb, Cs, Ba, Pb(K, Rb, Cs, Ba, Pb2+2+, Sr, Eu, Sr, Eu2+2+)) are more are more mobile, particularly if a fluid phase is involvedmobile, particularly if a fluid phase is involved•• CompatibleCompatible elements (small, low valence) include: elements (small, low valence) include: Major elements (Fe, Mg) and trace elements Major elements (Fe, Mg) and trace elements (Ni, Cr, Cu, W, Ru, Rh, Pd, Os, Ir, Pt, and Au)(Ni, Cr, Cu, W, Ru, Rh, Pd, Os, Ir, Pt, and Au)Incompatible elementsIncompatible elementsHREEs are less incompatibleRelative ionic radii for common valencesand coordination numbersCompatible elementsPreference forPreference formineral phasemineral phasePreferencePreferencefor meltfor meltPlot of ionic radius vs. ionic charge for trace elements of geological interest. Ionic radii are quoted for eight-fold coordination to allow for comparison between elements. From Rollinson(1993).Ionic chargeIonic chargevs. radiusvs. radiusTrace ElementsTrace ElementsNote Note magnitude magnitude of of majormajor element element changeschangesFigure 8-2. Harker variation diagram for 310 analyzed volcanic rocks from Crater Lake (Mt. Mazama), Oregon Cascades. Data compiled by Rick Conrey (personal communication). From Winter (2001) An From Winter (2001) An Introduction to Igneous and Metamorphic Introduction to Igneous and Metamorphic Petrology. Prentice Hall.Petrology. Prentice Hall.wt %wt %Figure 9-1.Figure 9-1. Harker Diagram for Crater Lake. From data Harker Diagram for Crater Lake. From data compiled by Rick Conrey. From Winter (2001) An Introduction compiled by Rick Conrey. From Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.to Igneous and Metamorphic Petrology. Prentice Hall.Note Note magnitude magnitude of of tracetrace element element changeschangesTrace ElementsTrace ElementsppmppmppmppmTable 9-6 A brief summary of some particularly useful trace elements in igneous petrologyElementUse as a petrogenetic indicatorNi, Co, Cr Highly compatible elements. Ni (and Co) are concentrated in olivine, and Cr in spinel andclinopyroxene. High concentrations indicate a mantle source.V, Ti Both show strong fractionation into Fe-Ti oxides (ilmenite or titanomagnetite). If they behavedifferently, Ti probably fractionates into an accessory phase, such as sphene or rutile.Zr, Hf Very incompatible elements that do not substitute into major silicate phases (although they mayreplace Ti in sphene or rutile).Ba, Rb Incompatible element that substitutes for K in K-feldspar, micas, or hornblende. Rb substitutesless readily in hornblende than K-spar and micas, such that the K/Ba ratio may distinguish thesephases.Sr Substitutes for Ca in plagioclase (but not in pyroxene), and, to a lesser extent, for K in K-feldspar. Behaves as a compatible element at low pressure where plagioclase forms early, butas an incompatible at higher pressure where plagioclase is no longer stable.REE Garnet accommodates the HREE more than the LREE, and orthopyroxene and hornblende doso to a lesser degree. Sphene and plagioclase accommodates more LREE. Eu2+ is stronglypartitioned into plagioclase.Y Commonly incompatible (like HREE). Strongly partitioned into garnet and amphibole. Spheneand apatite also concentrate Y, so the presence of these as accessories could have asignificant effect. Table 9-6.Table 9-6. After Green (1980). Tectonophys., After Green (1980). Tectonophys., 6363, 367-385. From Winter (2001) An Introduction to Igneous and , 367-385. From Winter (2001) An