bhutan: a magic country with magic geology - metamorphic ... · bhutan: a magic country with magic...

Palaeomagnetic sampling along them major highway of the country

Bhutan: a magic country with magic geology - metamorphic, structural, thermal and rock magnetic history of the Pele La profile

István Dunkl, Eva Schill and J. Florian Wellmann

[Gansser, Geology of the Bhutan Himalaya, 1983]

Geology

Simplified geological map of Bhutan [Grujic et al., 2002]

Geology

Geology

Geology, concept of thermo remanent rock magnetism

[Wellmann, 2004]

Fine, laminated clayey and sandymetasediment with crenulation and oblique schistosity

Biotite schist with well developedcrystals

Orientations of bioties and the schistosity indicate two overprint phases

Skeletal garnet

Euhedral garnets in thegarnet-amphibolite

Tourmalinite

Tourmaline growth (metasomatism)postdates the folding

Mineral chemistry

amphibole

biotite

Al = 4

(MgFe)

(MgFe)

(MgFe)

(MgFe)

(MgFe)

(MgFe)

Al = 6

Al = 2

Si = 7

Si = 6

Si = 5

Si = 4

tot

tot

tot

MuscoviteSiderophyllite

PhlogopiteAnnite

Phengite

01

2345

white mica

Mol. % MgCO in calcite3

Mol

. % F

eCO

in

calc

ite3

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0.00 0.50 1.00 1.50

3248 m3010 m2930 m2735 m

Mg and Fe in the calcite of the marbles. The higher values mean higher peakmetamorphic conditions, but the bulk chemistry plays also some role

U/Pb concordia plots for samples from eastern Bhutan

[Daniel et al., 2003]

Summary P-T-t diagram showing monazite & xenotime ages and estimated peak metamorphic conditions for the uppermost Lesser Himalayan rocks of E. Bhutan

BiotiteWhite micaZircon FT

Ele

vatio

n [m

]

K/Ar and FT zircon age [Ma]

5 10 15 202000

2500

3000

3500

Relation of elevation and radiometric ages