Mineral inclusions in zircon from diamond-bearing marble in the Kokchetav Massif, northern Kazakhstan
Mineral inclusions in zircon from diamond-bearing marble in the Kokchetav Massif, northern Kazakhstan
European Journal of Mineralogy (December 2002) 14 (6): 1103-1108
- Asia
- Central Asia
- chain silicates
- clinopyroxene
- coesite
- Commonwealth of Independent States
- diamond deposits
- diopside
- framework silicates
- high pressure
- inclusions
- Kazakhstan
- Kokchetav Kazakhstan
- Kokchetav Massif
- marbles
- metamorphic rocks
- mineral inclusions
- nesosilicates
- orthosilicates
- P-T conditions
- pressure
- pyroxene group
- silica minerals
- silicates
- ultrahigh pressure
- zircon
- zircon group
Zircon is known to protect inclusions of UHP phases from late-stage overprinting. Matrix diopsides contain abundant exsolved phengite lamellae, whereas the exsolution is absent in the inclusions in zircon. The diopside inclusions contain more K (sub 2) O (< or = 0.56 wt.%) and Ca-Eskola component (< or = 3.5 mol%) than those of the matrix (0.14 wt.% and 2.1 mol.%, respectively). Thus phengite exsolution occurs in matrix pyroxene with low K (sub 2) O and Ca-Eskola components compared to the inclusions in zircon, indicating that decreasing K (sub 2) O and Ca-Eskola components during decompression resulted in the phengite exsolution in diopside. The peak metamorphic P-T conditions of the impure marble are estimated to be 60-80 kbar and 960-1050 degrees C.
