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In-Depth Information
Figure
5.26
shows that the K and EK series lavas of Ringgit Beser plot in a close
cluster on the
18
O versus
87
Sr/
86
Sr diagrams, and slightly displaced from the
MORB
isotopic ratios. Edwards et al. found that the calc series
samples plot away from the K-rich rocks to a lower
field to higher Sr
-
18
O values and
87
Sr/
86
Sr
ratios. The Sr and O oxygen isotopic values of K-rich rocks of Ringgit-Beser
Compex however contrast with those of Muriah located in a back-arc extensional
setting. The REE and Trace Element geochemistry of K
δ
rich silica undersaturated
-
Rocks of Alto Paraniba Igneous Province.
The geochemistry of Potassic rocks of Alto Paranaiba Igneous Province has been
studied by Gibson et al. (1992). They found that Cr and Ni content of these rocks
range between 25 and 2000 and 70
1,530 ppm, respectively. As expected these two
elements have positive correlation with MgO. In the kamafugitic rocks, Sc content
(25
-
145 ppm) shows high abundance. The other incompatible elements such as Ba
(1,500
-
40 ppm) show high concentration.
Gibson et al. plotted the composition of the Alto Paranaiba Igneous Province in a
chondrite-normalized multi-element-diagram (Fig.
5.27
). They observed that these
rocks have relatively smooth patterns with a peak at La, and less H
2
O
6,000) and Th (12
-
-
bearing
samples with (Ba/La)
N
ratios being < 1. The patterns are similar in case of both
extrusive and intrusives rocks with most samples having large troughs at K and Sr.
The lavas of Mata da Corda formation commonly have troughs at P, whereas some
of the intrusives at Limeria (I) and Indaia (I) have trough at Ti. These rocks are
depleted in Ta relative to La (Fig.
5.27
). The ma
-
c potassic rocks of the Alto
Paranaiba igneous province have high enrichment with respect to REE. The La and
Lu concentration is respectively, 1,300 and 11 times the values of chondrites,
10000
Kimberlite &
Kamafugitic Intrusions
Kamafugitic Lavas
1000
100
Presidente Olegario
Carmo do Paranaiba
Carmo do Paranaiba
Tres Ranchos
10
Limeira II
Limeira I
1
Madupitic Olivine
Lamproite Intrusions
Phlogopite Picrite dykes
(related to plutonic
complexes)
1000
100
Serra Negra
Catalao I
10
Mata do Lenco
Bocaina
Catalao II
1
Ba Rb Th K Nb Ta La Ce Sr Nd P Sm Zr Hf Ti Tb Y Yb Lu
Ba Rb Th K Nb Ta La Ce Sr Nd P Sm Zr Hf Ti Tb Y Yb Lu
Fig. 5.27 Chondrite-normalized trace element diagram for K-rich rocks of Alto Paranaiba (after
Gibson et al. 1992)
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