Lake Pavin History, geology, biogeochemistry, and sedimentology of a deep meromictic maar lake

135

12 10 8 6 4 2 0

0

5

10

15

20

25

Ta

Th

200180 160 140120 100 80 60 40 20 005

10

15

20

25

Nb

Th

140 120 100 80 60 40 20 00

5

10

15

20

25

La

Th

14 12 10 8 6 4 2 0

0

510

15

20

25

Hf

Th

60 50 40 30 20 10 00

5

10

15

20

25

Co

Th

450 400 350 300 250 200 150 100 50 005

10

15

20

25

V

Th

CP-Bas-H

CP M-T

Clierzou

Montcineyre

Montchal-Estivadoux

Plinian Pavin

basement contaminated plinian clast

Bomb Pavin

Basement contaminated bomb

MI Puy Beaunit

Contamination trend

Fig. 7.2

Evolution of trace element compositions (ppm) of Pavin group magmas.

Black dots

:

Montcineyre basalts (lava fl

ows);

circled grey dots

: hawaïites of Montchal (lava fl

ows and scoria

fall) and Estivadoux maar (scoria fall); Pavin benmoreites:

dashed circles

(caulifl

ower bombs),

open circles

(plinian clasts).

Crosses

: basement contaminated magmas (+ bombs, × plinian

clast). Chaîne des Puys magma compositions (unpublished data): symbols as in Fig.

7.1

. Dotted

line

: possible contamination trends of Pavin clasts by xenoliths (basement xenoliths or older

basaltic fragments –unpublished data; not represented-) and emitted during the phreato-mag-matic activity

7 Magmatic Evolution of Pavin’s Group of Volcanoes: Petrology, Geochemistry...