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basalt or granite crust feldspar peridotite mantle Iron olivine Chondritic Meteorite + Iron Metal Mantle Xenoliths = Sun Chondritic Meteorites Mantle Xenoliths chondrules cpx oliv opx Solar Composition Refractory Mantle Residues Sun - Chondritic Meteorites - Earth’s Mantle Sun ~ BulkSilicateEarth (~68 wt.%) + Fe-metal core (~31 wt.%) The Earth’s upper mantle is similar in composition to BSE, and is composed of a rock called peridotite, which consists largely of the minerals olivine and orthopyroxene basalt or granite crust peridotite mantle Fe-Ni metallic core SiO2 + MgO + FeO ~ 91% Igneous Petrology Lab 3: The Mantle Source and Primary Magmas Calculation for plotting in Olivine – Clinopyroxene – Quartz Liquidus Projection Apatite = P5+ / 3 Cpx (XYT2O6) = X = (Ca2+ + Na+ + K+) - 5 x Apatite Spinel (Y2+Y3+2O4) = Y3+/2 Opx* (Y2T2O6) = Y/2 = Cr3+/2 + (Al3+ - 2Ti4+ - Na+)/2 . = ((Mg2+ + Fe2+ + Mn2+ + Ni2+ + Co2+) - Spin - Cpx)/2 Si* = Si4+ - 2 x Cpx - 2 x Opx* + Ti4+ If Si* is negative: Oliv (Y2TO4) Si* Opx = - Si* = 00.00 = Opx* - Oliv If Si* is positive: Qtz Oliv Opx = Si* = 0.0 = Opx* In order to plot your points, orthopyroxene must be recalculated as a mixture of olivine and quartz. Partial Melting of the Mantle Solid Source Fertile Mantle Refractory Solid Restite + Refractory Mantle + Cpx-rich Peridotite Lherzolite Olivine-rich Peridotite Harzburgite Whole = Σ Parts Lever Rule: p/R = x/y amount of basalt (P) in fertile mantle = x/(x+y) y ~ 15-20% x R Liquid Oceanic Crust + Basalt opx cpx Clinopyroxene component calculation Calculate an ideal Cpx formula: XYT2O6: cations sum to 4 2 – Si Al - Al(1V) Cr Al(VI) – CrCaTs – Na Na Al(1V) Al(VI) CrCaTs (CaCrAlSiO6) AlCaTs (CaAl2SiO6) Jadeiite (NaAlSi2O6) = = = = = Wo (CaSiO3) En (MgSiO3) Fs (FeSiO3) = (Ca - AlCaTs – CrCaTs)/2 = (1-Wo-Jd) × XMg where = (1-Wo-Jd) × (1-XMg) XMg = Mg/(Fe+Mg) opx cpx Estimation of Pressure or Depth of Origin