Journal
LITHOS
Volume 98, Issue 1-4, Pages 261-274Publisher
ELSEVIER
DOI: 10.1016/j.lithos.2007.05.001
Keywords
trace elements; ICP-MS-LA; corundum; magmatic sapphires; metamorphic sapphires
Categories
Ask authors/readers for more resources
Using ICP-MS-LA analyses, we demonstrate that the use of the Ga/Mg ratio, in conjunction with the Fe concentration, is an efficient tool in discriminating between metamorphic and magmatic blue sapphires. Magmatic blue sapphires found in alkali basalts (e.g. southeastern Asia, China, Africa) are commonly medium-rich to rich in Fe (with average contents between 2000 and 11000 ppm), high in Ga (> 140 ppm), and low in Mg (generally < 20 ppm) with high Ga/Mg ratios (> 10). Conversely, metamorphic blue sapphires found in basalts (e.g. Pailin pastel) and in metamorphic terrains (e.g. Mogok, Sri Lanka, Ilakaka) are characterized by low average iron contents (< 3000 ppm), low Ga contents (< 75 ppm), and high Mg values (> 60 ppm) with low average Ga/Mg ratios (< 10). Basaltic magmatic sapphires have Fe, Ga and Mg contents similar to those obtained for primary magmatic sapphires found in the Garba Tula syenite. This suggests that these both sets of sapphires have a possible common syenitic origin, as previously proposed from other criteria. In addition, plumasite-related sapphires and metamorphic sapphires also exhibit similar composition in trace elements. Based on results from the present study, we suggest that fluid circulations during a metamorphic stage produced metasomatic exchanges between mafic and acidic rocks (plumasite model), thus explaining the high Mg contents and converging Ga/Mg ratios observed in metamorphic sapphires. (c) 2007 Elsevier B.V All rights reserved.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available