|
|
 |
|||||||||||||||||
|
|||||||||||||||||
 |
|||||||||||||||||
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Universidad del Pais, Departamento de Mineralogia y Petrologia, Bilbao, Spain
Pervasive metasomatism that involved the formation of tourmaline-rich rocks and influx of Li, F, and Cs into Ordovician psammo-pelitic metasediments occurred in the Valdeflores area (Caceres, Spain). Numerous Li- and Sn-bearing, mineralized, greisen-type veins also can be observed here, in the vicinity of geochemically specialized granites. Tourmaline-rich rocks appear as: (1) massive, fine-grained, dark green to black rocks; and (2) fine-scale tourmaline-rich laminae, which alternate with quartz-rich layers parallel to the bedding. Electron microprobe analyses indicate that the tourmaline lies mostly within the space defined by the exchange vectors from dravite: FeMg (sub -1) (schorl), []AlNa (sub -1) Mg (sub -1) (foitite), AlOMg (sub -1) (OH) (sub -1) (olenite), and CaMgNa (sub -1) Al (sub -1) (uvite). The Fe/(Fe+Mg) ratio ranges mainly from 0.87 to 0.54 and increases with Al in the Y-site. Analytical results and substitutional relations show an insignificant elbaite component. Mica in the tourmalinized rocks is very fine-grained (mostly <50 mu m). White mica ranges from lithian muscovite-phengite to lepidolite/zinnwaldite, containing up to 8.40 wt% F, 6.0 wt% Li 2 O, and 10.73 wt% FeO. Dark mica shows a variable color and has compositions characterized by relatively high contents of Cs 2 O (1.14-2.78 wt%) and F (1.94-8.08 wt%), with a deficit in K 2 O (5.75-9.04 wt%). Log (f H2O /f HF ) of fluids in equilibrium with biotite in the tourmaline-rich rocks was 4.02-4.17 at T nearly equal 400 degrees C. Log (f H2O /f HF ) values of fluids in equilibrium with topaz (X F nearly equal 0.8) in country rock adjacent to contacts with veins, and in equilibrium with amblygonite-montebrasite (X amb = 0.2) in the veins were about 4.30-4.60 and 6.4-6.7, respectively. These variations denote the existence of gradients in relative a HF more than differences of temperature during metasomatism. The lack of tourmaline in the veins is interpreted to reflect the alkalinity and low Fe-Mg contents in the fluids, which precluded the formation of tourmaline. Consequently, most of the boron was expelled into metasediments where tourmaline was produced as a result.
This record provided courtesy of AGI/GeoRef.
This article has been cited by other articles:
|
|
 |
|
  G. Tischendorf, H.-J. Forster, B. Gottesmann, and M. Rieder True and brittle micas: composition and solid-solution series Mineralogical Magazine, June 1, 2007; 71(3): 285 - 320. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. Roda, P. Keller, A. Pesquera, and F. Fontan Micas of the muscovite - lepidolite series from Karibib pegmatites, Namibia Mineralogical Magazine, February 1, 2007; 71(1): 41 - 62. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. RODA-ROBLES, A. PESQUERA, P. P. GIL-CRESPO, J. TORRES-RUIZ, and P. DE PARSEVAL Mineralogy and geochemistry of micas from the Pinilla de Fermoselle pegmatite (Zamora, Spain) European Journal of Mineralogy, June 1, 2006; 18(3): 369 - 377. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. Roda, A. Pesquera, P. P. Gil-Crespo, J. Torres-Ruiz, and F. Fontan Origin and internal evolution of the Li-F-Be-B-P-bearing Pinilla de Fermoselle pegmatite (Central Iberian Zone, Zamora, Spain) American Mineralogist, November 1, 2005; 90(11-12): 1887 - 1899. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Tischendorf, M. Rieder, H.-J. Forster, B. Gottesmann, and Ch. V. Guidotti A new graphical presentation and subdivision of potassium micas Mineralogical Magazine, August 1, 2004; 68(4): 649 - 667. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. Cerny, P. Cerny, R. Chapman, D. K. Teertstra, and M. Novak Rubidium- and cesium-dominant micas in granitic pegmatites American Mineralogist, November 1, 2003; 88(11-12): 1832 - 1835. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 L. G. MEDARIS Jr., J. H. FOURNELLE, and D. J. HENRY TOURMALINE-BEARING QUARTZ VEINS IN THE BARABOO QUARTZITE, WISCONSIN: OCCURRENCE AND SIGNIFICANCE OF FOITITE AND "OXY-FOITITE" Can Mineral, June 1, 2003; 41(3): 749 - 758. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. KALT, W. SCHREYER, T. LUDWIG, S. PROWATKE, H.-J. BERNHARDT, and A. ERTL Complete solid solution between magnesian schorl and lithian excess-boron olenite in a pegmatite from the Koralpe (eastern Alps, Austria) European Journal of Mineralogy, December 1, 2001; 13(6): 1191 - 1205. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Tischendorf, H.-J. Forster, and B. Gottesmann Minor- and trace-element composition of trioctahedral micas: a review Mineralogical Magazine, April 1, 2001; 65(2): 249 - 276. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Shihua and Y. Jie Actual Fe-Li mica series as a series with {square}VI constant but not with AlIV or AlVI Mineralogical Magazine, August 1, 2000; 64(4): 755 - 775. [Abstract] [Full Text] [PDF]
|
|
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
