The Insch layered intrusion
- 1 February 1970
- journal article
- Published by Geological Society of London in Scottish Journal of Geology
- Vol. 6 (1) , 7-25
- https://doi.org/10.1144/sjg06010007
Abstract
Synopsis: The Insch layered intrusion comprises an olivine-rich Lower Zone, followed by an olivine-free (labradorite–2 pyroxene cumulates) Middle Zone, and an olivine-bearing Upper Zone in which alkali feldspar becomes an important constituent. The overall cryptic layering is extreme (Fo 80→5 , An 80→40 , En 82→25 , and Ca 40 Mg 50 Fe 10 to Ca 40 Mg 5 Fe 55 ) but the lower part of the intrusion is hardly exposed and the continuity of the sequence (especially in the range An 80–60 and En 82–52 ) can only be inferred. The total thickness of the intrusion may be as much as 18 000 ft but only the top 3000 ft are known in any detail. The Middle Zone cumulates appear to be intricately associated with later gabbros which may be close in composition to the parent magma of the intrusion.Keywords
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