|
|
 |
|||||||||||||||||
|
|||||||||||||||||
 |
|||||||||||||||||
| JOURNAL HOME | HELP | FEEDBACK/COMMNET | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Articles |
1 Institute of Mineralogy and Petrography, University of Fribourg, 1700 Fribourg, Switzerland
2 Swiss Federal Institute of Technology, ETH Hönggerberg, Zurich, Switzerland
* e-mail: ferraris{at}unisi.it
Nano- to micro-scale lamellae of ferro-aluminian phlogopite (Phl) within centimetre-size crystals of muscovite (Ms-matrix) from a pegmatite near Gorduno (Lepontine Domain, Central Alps, Switzerland) were discovered using high-resolution transmission (HRTEM) and analytical electron microscopy (AEM). The Msmatrix is a 2M1 polytype with occasional disordered sequences. The Phl lamellae, covering a large range of sizes, are parallel to the basal plane of the host. The interfaces parallel to (001) are straight, whereas the interfaces perpendicular to the basal plane are irregular. The lamellae are concentrated on levels of the Ms-matrix with disordered stacking. The Ms-matrix has close to end-member composition with 0.15 tri-octahedral cations p.f.u. The Phl-lamellae show considerable di-octahedral and eastonite substitution and are zoned, with rims slightly richer in di-octahedral component. The Ms-matrix itself is homogeneously exsolved into two sets of nanometre-sized lamellae at an angle of about 40° to the basal plane.
The Phl-lamellae and the fine, homogeneously nucleated lamellae in the Ms-matrix are exsolutions of a primary pegmatitic muscovite, richer in tri-octahedral component. Micas along the di-tri-octahedral join exsolve with increasing temperature and the composition of the exsolved matrix points to an equilibration temperature of 600°C. The recalculated primary composition points to a crystallisation temperature around 500°C. The nearby, younger Novate intrusion body probably acted as heat source for the post-magmatic increase of temperature.
Key-words: micas, HRTEM, AEM, exsolution, temperature, metamorphic petrology.
This article has been cited by other articles:
|
|
 |
|
  M. D. Ruiz Cruz and C. Sanz de Galdeano EXSOLUTION MICROSTRUCTURES IN NH4-BEARING MUSCOVITE AND ANNITE IN GNEISSES FROM THE TORROX AREA, BETIC CORDILLERA, SPAIN Can Mineral, February 1, 2009; 47(1): 107 - 128. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. D. Ruiz Cruz and C. S. De Galdeano High-temperature ammonium white mica from the Betic Cordillera (Spain) American Mineralogist, July 1, 2008; 93(7): 977 - 987. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. FERRARIS, D. CASTELLI, and B. LOMBARDO SEM/TEM-AEM characterization of micro- and nano-scale zonation in phengite from a UHP Dora-Maira marble: petrologic significance of armoured Si-rich domains European Journal of Mineralogy, June 1, 2005; 17(3): 453 - 464. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. FERRARIS, B. GROBETY, G. L. FRUH-GREEN, and R. WESSICKEN Intergrowth of graphite within phlogopite from Finero ultramafic complex (Italian Western Alps): implications for mantle crystallization of primary-texture mica European Journal of Mineralogy, December 1, 2004; 16(6): 899 - 908. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. B. Clarke and P. A. Bogutyn OSCILLATORY EPITACTIC-GROWTH ZONING IN BIOTITE AND MUSCOVITE FROM THE LAKE LEWIS LEUCOGRANITE, SOUTH MOUNTAIN BATHOLITH, NOVA SCOTIA, CANADA Can Mineral, August 1, 2003; 41(4): 1027 - 1047. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. FERRARIS, A. GULA, G. IVALDI, M. NESPOLO, E. SOKOLOVA, Y. UVAROVA, and A. P. KHOMYAKOV First structure determination of an MDO-2O mica polytype associated with a 1M polytype European Journal of Mineralogy, December 1, 2001; 13(6): 1013 - 1023. [Abstract] [Full Text] [PDF]
|
|
| JOURNAL HOME | HELP | FEEDBACK/COMMNET | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
