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Water- and Boron-Rich Melt Inclusions in Quartz from the Malkhan Pegmatite, Transbaikalia, Russia
Helmholtz Centre Potsdam, German Research Centre for Geoscience GFZ, Telegrafenberg, D-14473 Potsdam, Germany
Centre of Excellence in Ore Deposits, University of Tasmania, Hobart 7001, Australia
Geological Department, Saint Petersburg State University, St. Petersburg, 199034, Russia
* Author to whom correspondence should be addressed.
Received: 16 August 2012; in revised form: 24 October 2012 / Accepted: 25 October 2012 / Published: 15 November 2012
Abstract: In this paper we show that the pegmatite-forming processes responsible for the formation of the Malkhan pegmatites started at magmatic temperatures around 720 °C. The primary melts or supercritical fluids were very water- and boron-rich (maximum values of about 10% (g/g) B2O3) and over the temperature interval from 720 to 600 °C formed a pseudobinary solvus, indicated by the coexistence of two types of primary melt inclusions (type-A and type-B) representing a pair of conjugate melts. Due to the high water and boron concentration the pegmatite-forming melts are metastable and can be characterized either as genuine melts or silicate-rich fluids. This statement is underscored by Raman spectroscopic studies. This study suggested that the gel state proposed by some authors cannot represent the main stage of the pegmatite-forming processes in the Malkhan pegmatites, and probably in all others. However there are points in the evolution of the pegmatites where the gel- or gel-like state has left traces in form of real gel inclusions in some mineral in the Malkhan pegmatite, however only in a late, fluid dominated stage.
Keywords: melt inclusion; fluid inclusion; gel inclusion; water; boron and cesium determination; pegmatite genesis
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Thomas, R.; Davidson, P.; Badanina, E. Water- and Boron-Rich Melt Inclusions in Quartz from the Malkhan Pegmatite, Transbaikalia, Russia. Minerals 2012, 2, 435-458.
Thomas R, Davidson P, Badanina E. Water- and Boron-Rich Melt Inclusions in Quartz from the Malkhan Pegmatite, Transbaikalia, Russia. Minerals. 2012; 2(4):435-458.
Thomas, Rainer; Davidson, Paul; Badanina, Elena. 2012. "Water- and Boron-Rich Melt Inclusions in Quartz from the Malkhan Pegmatite, Transbaikalia, Russia." Minerals 2, no. 4: 435-458.