Question

9. To answer this question use Table 1 and 2 given below. Pyrolite was "invented" by Ringwood (1966) by combing the compositions of average peridotite and basalt in a ratio of 3:1 Recalculate the chemical composition of pyrolite in terms of weight percent concentrations of the elements then rank the elements in terms of their abundance. Compare your results to the average composition of the mantle (Table 2) and comment on any similarities and discrepancies. i. ii. Table 1. Estimates of the chemical composition of the Earth's mantle, based on the composition of pyrolite. Oxide wt% SiO2 45.2 MgO 37.5 FeO Al20s 3.5 Cao 3.1 Na2O 0.57 Cr20s 0.43 MnO 0.14 P2Os 0.06 K:0 0.13 Tio2 0.17 8.0 Table 2. Abundance of elements in the Mantle Element Wt% Oxygen Magnesium 22.8 Silicon 6.3 Iron Calcium 2.5 Aluminum 2.4 Other 21

Answer 1

Pyrolite is a rock consisting of about three parts of periotite and one part of basalt.

Its name is derived from the chemical and mineralogic composition of the upper mantle of the earth.

The abundances of the principal mettalic element components are similar to the chondritic meteorites and in the solar photosphere.