Skip to Main Content
Skip Nav Destination
GEOREF RECORD

Tetrahedrally coordinated boron in Li-bearing olenite from "mushroom" tourmaline from Momeik, Myanmar

Andreas Ertl, John M. Hughes, Stefan Prowatke, Thomas Ludwig, Franz Brandstaetter, Wilfried Koerner and M. Darby Dyar
Tetrahedrally coordinated boron in Li-bearing olenite from "mushroom" tourmaline from Momeik, Myanmar
The Canadian Mineralogist (August 2007) 45 (4): 891-899

Abstract

So-called "mushroom" tourmaline, a botryoidal aggregate of pale pink tourmaline crystals, occurs in the Palelni mine, Khetchel village, Molo quarter, Momeik Township, northeast of Mogok, Mandalay Division, Shan State, Myanmar. It has been characterized by crystal-structure determination, electron-microprobe analysis (EMPA), secondary-ion mass spectrometry (SIMS), uranium extraction, and inductively coupled plasma-mass spectrometry (ICP-MS). This sample consists of sprays of radially arranged crystals up to approximately 9 mm in length and approximately 50-150 mu m in diameter. Chemical data show that Al increases, whereas the Mn content decreases, from the center of the aggregate to the pyramidal faces. The composition at the center can be described as a Mn-bearing elbaite with approximately 1.6 wt% MnO. Near the pyramidal faces, the composition of these tourmaline crystallites is relatively Al-rich (up to 43.6 wt% Al (sub 2) O (sub 3) ), and Mn-poor (0.1-0.3% MnO). A crystal-structure refinement of the Li-bearing olenite (near the pyramidal faces), in combination with analytical results, gives the optimized formula (super X) (Na (sub 0.55) Ca (sub 0.08) Pb (sub 0.01) [] (sub 0.36) ) (super Y) (Al (sub 2.13) Li (sub 0.75) Mn (super 2+) (sub 0.01) [] (sub 0.11) ) (super Z) Al (sub 6) (super T) (Si (sub 5.34) B (sub 0.66) )O (sub 18) (BO (sub 3) ) (sub 3) (super V) (OH) (sub 3) (super W) [(OH) (sub 0.50) O (sub 0.26) F (sub 0.24) ], with a 15.7561(6), c 7.0703(5) Aa. The structure refinement yields a relatively high (super [4]) B content (Si (sub 0.87(1)) B (sub 0.13(1)) ), and a {T-O} distance of 1.604 Aa, the shortest observed in natural tourmaline to date. Together with Al-rich tourmalines from other localities, a positive correlation between Al at Y site and (super [4]) B with r (super 2) nearly equal 0.998 was found. Furthermore, this tourmaline aggregate shows a relatively high Pb content (1640 ppm) and a significant Bi content (153 ppm). The REE pattern (Sigma REE: approximately 7.2 ppm) exhibits a weak negative Eu anomaly, a strong positive Tm anomaly, and a positive Tb anomaly. Such a pattern cannot be derived simply from a late-stage fractionated magma of a S-type granite or from differentiated crustal melts alone.


ISSN: 0008-4476
EISSN: 1499-1276
Coden: CAMIA6
Serial Title: The Canadian Mineralogist
Serial Volume: 45
Serial Issue: 4
Title: Tetrahedrally coordinated boron in Li-bearing olenite from "mushroom" tourmaline from Momeik, Myanmar
Affiliation: Universitaet Wien, Geozentrum, Institut fuer Mineralogie und Kristallographie, Vienna, Austria
Pages: 891-899
Published: 200708
Text Language: English
Publisher: Mineralogical Association of Canada, Ottawa, ON, Canada
References: 41
Accession Number: 2007-120664
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 5 tables
N09°00'00" - N28°45'00", E92°00'00" - E101°45'00"
Secondary Affiliation: Miami University, USA, United StatesUniversitaet Heidelberg, DEU, Federal Republic of GermanyNaturhistorisches Museum, AUT, AustriaMount Holyoke College, USA, United States
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Association of Canada. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200749
Close Modal

or Create an Account

Close Modal
Close Modal