Russian Mineralogical Society
XIII All-Russian conference on thermobarogeochemistry in conjunction with IV APIFIS symposium
Inclusions of magmatic fluids in rocks of ongonite massif Ary-Bulak

RMS-DPI code:  2008-1-31-0
Scientific session:  Fluid inclusions in magmatic minerals as indicators of magmas generation conditions and evolution
Author listing:  Peretyazhko I.S., Tsareva E.A.
Principal author:  Tsareva Elena A.
Language:  Russian
Abstract - Summary 
(short description):
Grains of quartz and topaz from porphyric ongonites contain primary syngenetic melt inclusions (MI) and essentially gaseous fluid inclusions (FI). The residual and re-melted glasses in most MI have alumosilicate composition with a wide range of Si, Al, Na, K, and F contents. In the range 365-390C the liquid disappeared on FI walls. Many FI contained a crystal with size <1-2 m (presumably, NaF), which was not dissolved even at high T and quickly diminished in volume within 10-30 until it completely dissolved at 550-680C. After cooling the crystal appeared in different parts of FI and was again dissolved during heating in the same T range. Such type of crystal solubility can exist only in water-salt systems of PQ type. In addition to primary-secondary MI from fissure zones, rare quartz phenocrysts in aphyric rocks have FI essentially gaseous and with salt brines. Crystal phases (chlorides K, Cs, Na, Mn, Fe and KF, probably, other fluorides) were dissolved in the interval 150-650C before FI homogenization into a liquid. The data on MI and FI indicate that at 600-750C and 400-800 bar porphyric ongonites crystallized from melt with quartz, sanidine, albite and topaz phenocrysts. Features of solutions in FI as well as the enrichment of the fluid-magmatic system with F suggest that low-density fluids of PQ type (similar to system NaF-H2O with insignificant chlorides) impurity took place at the formation of porphyric ongonites. Aphyric rocks rich in Ca and F were formed as a result of fluid-magmatic interaction of quenching products of ongonite melt crystallization and residual immiscible fluoride-calcium and alumosilicate melts. Increasing in contents of Cl, K, Cs, Na, Mn, Fe, Al and KF in the magmatic fluids resulted in the transition from PQ type to supercritical fluids. Inclusions of salt brines and essentially gaseous FI were formed at P-T conditions of liquid-vapour immiscibility existence, characteristic of all supercritical fluids.
Date of presentation:  22/09/2008
RMS-DPI code:  2008-1-31-0
Proceeedings volume 
in the RMS catalogue:
Proceedings of XIII International conference on thermobarogeochemistry and IVth APIFIS symposium. Volume 1.
Pages:  128-131
File of proceedings 
 152 K
Status:  printed
Recieved:  02/06/2008
Accepted:  28/06/2008
Published on-line:  13/02/2009
Permanent address of publication:
Contact author(s):  Peretyazhko, Igor Sergeevich

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