Nickel bulk Earth composition

Ringwood A. E., Seifert S., and Wanke H. (1987) A komatiite component in Apollo 16 highland breccias imphcations for the nickel-cobalt systematics and bulk composition of the Moon. Earth Planet. Sci. Lett. 81, 105—117. 

The six most abundant, nonvolatile rock-forming elements in the Sun are Si (100), Mg (104), Fe (86), S (43), Al (8.4), and Ca (6.2). The numbers in parentheses are atoms relative to 100 Si atoms. They are derived from element abundances in Cl-meteorites which are identical to those in the Sun except that Cl-abundances are better known (see Chapter 1.03). From geophysical measurements it is known that the Earth s core accounts for 32.5% of the mass of the Earth. Assuming that the core contains only iron, nickel, and sulfur allows us to calculate the composition of the silicate fraction of the Earth by mass balance. This is the composition of the bulk silicate earth (BSE) or the primitive earth mantle (PM). The term primitive implies the composition of the Earth s mantle before crust and after core formation. 

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