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28,
the amount is very constant near Oc075^o
The elBssnt is concentrated in the
surface regions of the earth j and hence we have used a lower value for the
solar abundance, naiaely 1020, instead of the Urey and Craig value of 2200
or the Wiik value of 25006
This lower titanlian abundance is used after many attempts
to adjust the zir^Kiium and hafhium values to their nei^boring elements and
; yet to maintain the observed ratios of these elements to each other and to
titanium. The loner value of titanium seems to be the most plausible adjustment
that we have been able to make*
It may well be that some other choice will be
more correct as better analjrses become available o
Vanadium, chromium and manganese e
Analyses for these three elements seem to be good aiKi hance the choice
of abundances is not a problerao
Chromitoa is depleted in the earth's surface
regions by a factor of about 8o2 relative to the meteoriteso
Hence we use a
slightly higher value for chromium than the meteoritic value, nanwly, lo8l7
X 10** instead of 1»15 x 10***^ We tse the meteoritic values for vanadium and
manganeseo
Important ratios of elemental abiaidanceso
The titsniuift-BijroonluiB-hafnium ratios appear to be well establlshed«
The
evidence indicates that the ratios ere nearly the same in meteorites and
terrestrial soiDrces» Goldsnhmidt gave about 20 fosr the Ti / Zr ratio and
about 50 for the Zr / Hf ratio by weight in both sources»
Pinson, Ahrens
end Franck (1953) find 33 PPm for Zr in chondritesjand Wiik (1955) finds 06075/S
for Ti, i. ec a ratio of 22o7o We shall use this value and take the atomic
Zr abundanoBS as lA3 of ouj' titanium abundaneeo
The Zr / Hf ratio depends on the extensive investigation of Keva^ and
WQrst-lin (1928, 193li) on the abuMance of hafnium in zirconium fptm many
souzHseso Their values for 2r in the Pultusk and Waconda msteorltes differ