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A melt and fluid inclusion assemblage in beryl from pegmatite in the Orlovka amazonite granite, East Transbaikalia, Russia: implications for pegmatite-forming melt systems

Citation

Thomas, R and Davidson, P and Badanina, E, A melt and fluid inclusion assemblage in beryl from pegmatite in the Orlovka amazonite granite, East Transbaikalia, Russia: implications for pegmatite-forming melt systems, Mineralogy and Petrology, 96, (2) pp. 129-140. ISSN 0930-0708 (2009) [Refereed Article]

DOI: doi:10.1007/s00710-009-0053-6

Abstract

Beryl crystals from the stockscheider pegmatite in the apical portion of the Li-F granite of the Orlovka Massif in the Khangilay complex, a tantalum deposit, contain an assemblage of melt and fluid inclusions containing two different and mutually immiscible silicate melts, plus an aqueous CO2-rich supercritical fluid. Pure H2O and CO2 inclusions are subordinate. Using the terminology of Thomas R, Webster JD, Heinrich W. Contrib Mineral Petrol 139:394-401 (2000) the melt inclusions can be classified as (i) water-poor type-A and (ii) water-rich type-B inclusions. Generally the primary trapped melt droplets have crystallized to several different mineral phases plus a vapor bubble. However, type-B melt inclusions which are not crystallized also occur, and at room temperature they contain four different phases: a silicate glass, a water-rich solution, and liquid and gaseous CO2. The primary fluid inclusions represent an aqueous CO2-rich supercritical fluid which contained elemental sulfur. Such fluids are extremely corrosive and reactive and were supersaturated with respect to Ta and Zn. From the phase compositions and relations we can show that the primary mineral-forming, volatile-rich melt had an extremely low density and viscosity and that melt-melt-fluid immiscibility was characteristic during the crystallization of beryl. The coexistence of different primary inclusion types in single growth zones underlines the existence of at least three mutually immiscible phases in the melt in which the large beryl crystals formed. Moreover, we show that the inclusions do not represent an anomalous boundary layer.

Item Details

Item Type:Refereed Article
Keywords:melt inclusions, fluid inclusions, beryl, pegmatite
Research Division:Earth Sciences
Research Group:Geology
Research Field:Ore Deposit Petrology
Objective Division:Mineral Resources (excl. Energy Resources)
Objective Group:Mineral Exploration
Objective Field:Titanium Minerals, Zircon, and Rare Earth Metal Ore (e.g. Monazite) Exploration
Author:Davidson, P (Dr Paul Davidson)
ID Code:61998
Year Published:2009
Web of Science® Times Cited:22
Deposited By:Centre for Ore Deposit Research - CODES CoE
Deposited On:2010-03-09
Last Modified:2010-04-14
Downloads:0

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