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was found by Roger et al. (1985) to increase progressively with fractionation.
Available data showed marked increase in the low K-series than the high K-series.
In general the
143
Nd/
144
Nd and
87
Sr/
86
Sr ratios have following ranges, respectively:
0.51209
0.71105. The incompatible trace element charac-
teristics of the rocks of Vulsini and adjoining complexes are shown in Fig.
5.9
,
which indicates that lavas of Vulsini, Roccamon
0.51216 and 0.70879
-
-
na and Ernici have coherent
variation in radiogenic isotopes. The K-rich rocks of in-plate regions have a
smoother trace element distribution pattern, but those from Italian lavas show
strong spikes with depletion in Ti, Ta, Nb, and P and they are also high in Rb, K
and Th content.
Ferrara et al. (1985, 1986) made Sr and O isotopic studies of potassic rocks from
Alban Hills and Vulsini volcanic province. Their data are plotted in Fig.
5.10
. The
Vulsini samples were divided into four subgroups: A
*
, A, B, and C. The Group A
rocks are tephritic leucitite to leucite tepherite (SiO
2
= 53 wt%, K
2
O > 6.0 wt%), the
Group A
*
rocks are primitive tephritic leucitites.
Group B and C are saturated or oversaturated with respect to SiO
2
(olivine
shoshonite, shoshonitic andesite and trachytic ignimbrite). All A samples are
undersaturated with respect to SiO
2
. Ferrara et al. (1986) plotted the
87
Sr/
86
Sr ratio
of rocks of Alban Hills, Vulsini Hills, Mount Cimini, Mount Amiata, San Venanzo
and Tuscan (Fig.
5.11
) metasediments as a function of 1/Sr (Fig.
5.11
). They noted
that the lavas of Alban Hills and Mount Vulsini are primitive and may represent the
18
O
versus
87
Sr/
86
Sr ratios for the
Vulsini samples (analysed by
Ferrara et al. for Holm and
Munksgaard 1982)
Fig. 5.10 A plot of
δ
+12
C
+11
+10
+ 9
A
B
+ 8
*
+ 7
ALBAN
HILLS
+ 6
0.710
0.711
0.712
86
87
Sr/
Sr
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