Water- and Boron-Rich Melt Inclusions in Quartz from the Malkhan Pegmatite, Transbaikalia, Russia

Minerals

Rainer Thomas²  Paul Davidson¹ 

[1] ARC Centre of Excellence in Ore Deposits, University of Tasmania, Hobart 7001, Australia;;Helmholtz Centre Potsdam, German Research Centre for Geoscience GFZ, Telegrafenberg, D-14473 Potsdam, Germany

关键词: melt inclusion;    fluid inclusion;    gel inclusion;    water;    boron and cesium determination;    pegmatite genesis;   

DOI  :  10.3390/min2040435

来源: mdpi

【 摘 要 】

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.

【 授权许可】

CC BY   
© 2012 by the authors; licensee MDPI, Basel, Switzerland.