Geology Reference
In-Depth Information
Navajo Province & Two Buttes (Rift Flanks)
1000
US8
89SB232
100
10
Subduction - related
basalts
1
Ba Rb Th
KNbTaLaCe Sr Nd P
Sm Zr
Hf
Ti
Tb
Y
Yb Lu
Fig. 5.19 Chondrite-normalized incompatible-element abundance patterns for representative K-
rich magmas from Rio Grande Rift flanks. Gibbson et al. plotted representative samples from
Navajo Volcanic (US-8) field and samples from Two Buttes (89SB232) in this diagram (after
Gibbson et al. 1993)
field. The 143 Nd/ 144 Nd isotopic ratios
0.70533 and 0.706901 in the Navajo volcanic
for the K-rich ma
c rocks at the rift
flanks are lower than basalts at the rift axis, but
the ratio is higher in Navajo volcanic
field (0.512558
0.512713) and at Two Buttes
-
(0.51231
0.51239).
Some of the lavas in the Espanola Basin have high 87 Sr/ 86 Sr ratio (Gibson et al.
1992), and that may be related to contamination of the magma with 87 Sr
-
rich crust.
-
isotopic and 143 Nd/ 144 Nd ratios in the samples from the rift
The Sr
anks and
shoulder, could be interpreted in the same way. The high 86 Sr/ 87 Sr and low
143 Nd/ 144 Nd ratios of the Two Buttes may also indicate crustal contamination. The
K-rich ma
-
flanks and shoulders are
characterized by high Sr, Nd and Pb. According to Gibson et al. very large
quantities of crust need to be contaminated to obtain these values.
c magmas, which were emplaced on the rift
5.7 Minor Element Contents of Potassic Volcanic Rocks
from N.E. China
The trace element geochemistry of potassic rocks from Wudalianchi, Erkeshan and
Keluo volcanic
east China have been studied by Zhang et al. (1995).
According to them these rocks are characterized by high LILE and LREE contents.
They have relatively low U
fields of north
-
Th, HFSE and HREE contents with normalized La/Ya
ratio of 50.0 - 6.8. For most incompatible elements, the concentration ranges between
olivine leucitites on the one hand and leucite basanites and trachybasalts on the
other, with the exception of Zr, Hf and Ga, which are lower in olivine leucitites.
-
 
 
Search WWH ::




Custom Search