A note on the 201 spacing of some lime-rich alkali.feldspars.from Kangerdlugssuaq, East Greenland
Summary. The values of 20 201 for some homogenized lime-rich fine microper-thites from the Kangerdlugssuaq lkaline intrusion, East Greenland, are investi-gated and found to be consistently high when compared with the values used in the standard curves for estimating the Or content of alkali feldspar...
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| Other Authors: | |
| Format: | Text |
| Language: | English |
| Published: |
1965
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| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.601.5325 http://www.minersoc.org/pages/Archive-MM/Volume_35/35-273-704.pdf |
| Summary: | Summary. The values of 20 201 for some homogenized lime-rich fine microper-thites from the Kangerdlugssuaq lkaline intrusion, East Greenland, are investi-gated and found to be consistently high when compared with the values used in the standard curves for estimating the Or content of alkali feldspars. This deviation, which is approximately proportional to anorthite content, results in anomalously low Or percentages being obtained and is ascribed to a distortion of the structure due to the unusually high calcium content of the microperthites. T HE Kangerdlugssuaq alkaline intrusion, East Greenland, com- prises a series of concentric rings passing gradually from an outer quartz nordmarkite through reduction in quartz to a quartz-free transitional pulaskite, a nepheline-bearing pulaskite, and finally to a nepheline- and sodalite-rich core of foyaite. The intrusion is described by Wager (1965). Whilst investigating the mineralogy of the intrusion some 65 natural alkali feldspars have been studied by X-ray diffraction and single-crystal methods. The majority were taken from average rocks and, ignoring the remainder, which come from veins and pegma- |
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