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GEOREF RECORD

A three-amphibole assemblage from the Tallan Lake Sill, Peterborough County, Ontario

F. C. Hawthorne, J. L. Griep and L. Curtis
A three-amphibole assemblage from the Tallan Lake Sill, Peterborough County, Ontario
The Canadian Mineralogist (August 1980) 18, Part 3: 275-284

Abstract

Textural relations indicate that gedrite, cummintonite, and hornblende form an equilibrium assemblage. The amphiboles are easily distinguished optically (cummingtonite colourless; gedrite pleochroic with alpha tan, beta pale grey, gamma medium grey; hornblende pleochroic with alpha tan, beta olive green, gamma bluish green). Electron microprobe and unit cell data for the minerals are:123SiO (sub 2) 172TiO (sub 2) 216Al (sub 2) O (sub 3) 269Fe as 318MnO 366MgO 413CaO 452Na (sub 2) O273FeO 000Cummingtonite 12253.88 1740.14 2261.77 27020.74 3220.46 36619.81 4180.80 4620.09000Gedrite 12243.46 1740.58 21814.18 27020.35 3220.49 36615.17 4180.78 4622.02000Hornblende 12243.89 1740.79 21814.42 27014.87 3220.29 36612.37 4189.14 4622.10 117K (sub 2) O 162total 224a(A) 300b(A) 372c(A) 459beta (o)000Cummingtonite 1180.01 15997.72 2169.51 28418.12 3605.32 427101.9000Gedrite 1180.05 15997.07 20818.696(5) 28417.913(4) 3605.278(2) 43590000Hornblende 1180.12 15997.99 2169.832(3) 28418.037(5) 3605.302(1) 427105.01(2) Space groups are C2/m (cummingtonite and hornblende), and Pnma (gedrite). Crystal structure refinement of the hornblende (R for 1098 observed reflections 4.8%) indicates an Fe (super 3+) /(Fe (super 2+) + Fe (super 3+) ) value of (super approx ) 0.15, and considerable Fe (super 2+) at the M4 site; this calcic amphibole is therefore a tschermakitic hornblende, with a substantial amount of the cummingtonite component in solid solution.


ISSN: 0008-4476
EISSN: 1499-1276
Coden: CAMIA6
Serial Title: The Canadian Mineralogist
Serial Volume: 18, Part 3
Title: A three-amphibole assemblage from the Tallan Lake Sill, Peterborough County, Ontario
Affiliation: McMaster Univ., Dep. Geol., Hamilton, ON, Canada
Pages: 275-284
Published: 198008
Text Language: English
Summary Language: French
Publisher: Mineralogical Association of Canada, Ottawa, ON, Canada
References: 37
Accession Number: 1981-052028
Categories: Igneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 anals., 9 tables
N44°00'00" - N44°00'00", W78°00'00" - W78°00'00"
Secondary Affiliation: Univ. Toronto, CAN, Canada
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 1981
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