Abstract
At Napoleon Bay, Baffin Island, fibrous aggregates define the contacts of Mesoproterozoic lamproite dykes with feldspathic wall-rock. The aggregates are composed of nepheline, pectolite and andesine, with fibre extensions along c, b and an indeterminate axis, respectively. Optically continuous, polymineralic fibre bundles are 0.1 to 0.2 mm long at the contact (all three minerals), 0.01 to 0.05 mm long in the wall-rock, but were not found beyond 8 mm from the dykes. Strongly alkaline, hydrothermal solutions, emanating from the dykes, reacted with labradorite in the wall-rock producing the fibrous agregates. Nepheline and pectolite were possibly derived from an unidentified, high-temperature phase that decomposed during cooling. Andesine may have been generated independently. Growth was directed across a set of tension fractures and proceeded with the aid of a thermal gradient as heat was removed continuously through the wall-rock.
Original language | English (US) |
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Pages (from-to) | 51-56 |
Number of pages | 6 |
Journal | European Journal of Mineralogy |
Volume | 13 |
Issue number | 1 |
DOIs | |
State | Published - Jan 1 2001 |
Externally published | Yes |
Keywords
- Andesine
- Baffin Island
- Fibrous aggregates
- Labradorite
- Lamproite
- Mesoproterozoic
- Nepheline
- Pectolite
ASJC Scopus subject areas
- Geochemistry and Petrology