Calculating Nickel Concentration in Olivine
Understanding Partition Coefficient ($K_D$)
The partition coefficient ($K_D$) describes how a specific element distributes between two immiscible phases (in this case, solid olivine and liquid magma) at equilibrium.
The formula is:
$ K_D = \frac{\text{Concentration in Solid}}{\text{Concentration in Liquid}} $
For Nickel (Ni) between olivine and basaltic magma, this is:
$ K_{D(\text{Ni, olivine/melt})} = \frac{C_{\text{Ni, olivine}}}{C_{\text{Ni, melt}}} $
Applying the Formula to Find Ni Concentration
We are given:
- Partition coefficient for Ni, $K_{D(\text{Ni, olivine/melt})} = 5$
- Concentration of Ni in the basaltic magma (melt), $C_{\text{Ni, melt}} = 20$ ppm
We need to calculate the concentration of Ni in the crystallizing olivine ($C_{\text{Ni, olivine}}$).
Rearranging the formula to solve for $C_{\text{Ni, olivine}}$:
$ C_{\text{Ni, olivine}} = K_{D(\text{Ni, olivine/melt})} \times C_{\text{Ni, melt}} $
Substituting the given values:
$ C_{\text{Ni, olivine}} = 5 \times 20 \, \text{ppm} $
$ C_{\text{Ni, olivine}} = 100 \, \text{ppm} $
Therefore, the concentration of Ni in the olivine that crystallizes from this magma is 100 ppm.
Important Questions from Igneous Petrology (Trace Elements/Melting/Evolution)
- Accumulation of which one of the following minerals can explain positive Eu and positive Sr anomalies in the primitive mantle-normalized multielement pattern of an igneous rock?
- Choose the explanation(s) for negative Eu anomalies in upper crustal rocks like granite and granodiorite.
- The modal abundance in an ultramafic rock and the partition coefficients of lutetium (Lu) in clinopyroxene, orthopyroxene, olivine and plagioclase are tabulated below. The bulk distribution coefficient of lutetium ($D_{Lu}$) in the ultramafic rock is ________.
Mineral Modal abundance (%) Partition coefficient Clinopyroxene 45 0.506 Orthopyroxene 40 0.42 Olivine 10 0.045 Plagioclase 05 0.019 - A source rock undergoes melting. Assuming batch melting, $5\%$ partial melting and bulk distribution coefficient of $0.045$, the enrichment factor ($C_L/C_o$) of Rb in the melt will be ________. (Round off to $2$ decimal places)
Choose the CORRECT combination for the following four statements.
Statement I: Anhydrous partial melting of peridotites produces basaltic magma.
Statement II: Hydrous melting of peridotites produces andesitic magma.
Statement III: Congruent melting of minerals produces liquids of compositions identical to the minerals.
Statement IV: Incongruent melting of minerals produces liquids of different compositions and new solids.
