Structural and Tectonic Evolution of K-Rich Silica-Deficient Volcanic Provinces of Different Continents - Origin of Potassium-rich Silica-deficient Igneous Rocks - page 424

(a)

15.8

pelagic
sediments

15.7

15.6

LVC

15.5

NH RL

I : Data from Mediterranean & Europe
II : Data from E. Canaries, Europe & Mediterranean
III : Data from W.Canaries, Madeira, E.Canaries,

Europe and the Mediterranean region

(b)

0.725

Shallow domains
Mediterranean

0.706

0.705

Europe

0.704

E. Canaries
W. Canaries
& Madeira

0.703

LVC

(c)

Shallow domains
W. Canaries
& Madeira

0.5130

E. Canaries

Europe

LVC

0.5125

Mediterranean

0.5120

18.5 19.0 19.5 20.0 20.5

206 204

Pb/ Pb

Fig. 14.4 A plot of 207 Pb/ 204 Pb (a), 87 Sr/ 86 Sr (b) and 143 Nd/ 144 Nd (c) isotopic ratios against
206 Pb/ 204 Pb for different K-rich rocks from eastern Atlantic, western and central Europe. NHRL
The Northern Hemisphere Reference Line, LVC low velocity component (modi ed after Hoernle
et al. 1995)

The tomographic study raised an important question concerning the structure of
the LVA. Does the region represent a large-scale upwelling or a multiple smaller,
discrete upwelling? They concluded that evidence for the presence of LVC is
present in all tectonic environments above the LVA. This includes: