Geology Reference
In-Depth Information
Fig. 5.22 a The
208
Pb/
204
Pb
vs
206
Pb/
204
Pb ratios and
b
207
Pb/
204
Pb vs
206
Pb/
204
Pb
for WEK and other potassic
rocks. (N
-
Morb, after White
et al. 1987; NHRL after Hart,
1984; after Zhang et al. 1995)
(a)
41.0
East African
Rift
40.0
Italy
SE Spain
New South Wales
Leucitites
39.0
West Australia
& Gaussberg
38.0
Micaceous
Kimberlites
Crazy
Mts.
Leucite Hills &
NW Colorado
37.0
Smoky
Butte
36.0
(b)
35.0
East African
West Australia
& Gaussberg
Rift
15.7
Italy
SE Spain
New South Wales
Leucitites
15.6
Leucite Hills &
NW Colorado
Micaceous
Kimberlites
15.5
Crazy
Mts.
15.4
15.3
Smoky
Butte
WEK potassic rocks
Average N-MORB
Sierra Nevada
West & Central Europe
Sunda arc, Indonesia
15.2
15.1
15.0
16.0
17.0
18.0
19.0
20.0
206
204
Pb/
Pb
87
Sr/
86
Sr and very low
143
Nd/
144
Nd from the north western USA. They differ from
most OIBs and Chinese basalts by their higher
87
Sr/
86
Sr and lower
143
Nd/
144
Nd
ratios. The Pb isotopic ratios of Chinese potassic rocks overlap those of K-rich
rocks from Crazy Mountains, NW Colorado, Leucite Hills and Smoky Butte. This
unradiogenic Pb composition is also distinct form OIBs and Chinese alkaline
basalts, most of which plot on the right side of the
'
Geochron
'
.
Search WWH ::
Custom Search