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basalt or granite crust. feldspar. peridotite mantle. Iron. olivine. Chondritic Meteorite. = Sun. + Iron Metal. Mantle Xenoliths. Chondritic Meteorites. Mantle Xenoliths. nephelinite. chondrules. cpx. oliv. opx. Refractory Mantle Residues. Solar Composition.

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basalt or

granite crust

feldspar

peridotite

mantle

Iron

olivine

Chondritic

Meteorite

= Sun

+ Iron

Metal

Mantle

Xenoliths


Chondritic

Meteorites

Mantle Xenoliths

nephelinite

chondrules

cpx

oliv

opx

Refractory Mantle Residues

Solar Composition


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

SiO2 + MgO + FeO

~ 91%

basalt or

granite crust

peridotite

mantle

Fe-Ni

metallic

core


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 = Cr3+/2 + (Al3+ - 2Ti4+ - Na+)/2

.

Opx* (Y2T2O6) = Y/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*

Si* = 00.00

Opx = Opx* - Oliv

If Si* is positive:

Qtz = Si*

Oliv = 0.0

Opx = Opx*

In order to plot your points, orthopyroxene must be recalculated as a mixture of olivine and quartz.


Partial Melting of the Mantle Quartz

Solid Source Refractory Solid + Liquid

Restite

Fertile Mantle

Refractory Mantle + Oceanic

Crust

Cpx-rich Peridotite

Lherzolite

Olivine-rich Peridotite + Basalt

Harzburgite

Whole = Σ Parts

Lever Rule: p/R = x/y

amount of basalt (P) in

fertile mantle = x/(x+y)

~ 15-20%

y

x

R


opx Quartz

cpx


Clinopyroxene component calculation Quartz

Calculate an ideal Cpx formula: XYT2O6: cations sum to 4

Al(1V) = 2 – Si

Al(VI) = Al - Al(1V)

CrCaTs (CaCrAlSiO6) = Cr

AlCaTs (CaAl2SiO6) = Al(VI) – CrCaTs – Na

Jadeiite (NaAlSi2O6) = Na

Wo (CaSiO3) = (Ca - AlCaTs – CrCaTs)/2

En (MgSiO3) = (1-Wo-Jd) × XMg where XMg = Mg/(Fe+Mg)

Fs (FeSiO3) = (1-Wo-Jd) × (1-XMg)


opx Quartz

cpx



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