Editing Geochemistry of the major intrusions - St. Kilda: an illustrated account of the geology

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The geochemical data corroborate field and petrographical evidence suggesting that the major intrusions on St Kilda fall into two major groups. The first, a group of mafic rocks, comprises the Western Gabbro, Cambir Dolerite and the rocks of Glacan Mor, Boreray and Soay. In [[:File:P991873.jpg|(Figure 42)]] this group is characterised by low alkali–lime ratios and in [[:File:P991874.jpg|(Figure 43A)]] by a lack of light REE enrichment. The second group range from mafic to granitic compositions and not only have higher alkali and iron ratios but also contain more K, P and REE's, relatively enriched in the light elements. Several members of this second group appear to be related through fractionation to a parental tholeiitic magma of the Glen Bay type. Relationships among the first group are less clear: if the Conachair Granite is related by fractionation to the Western Gabbro, this might explain the relative depletion of the latter in REE's and low alkali and iron ratios. Further sampling of the breccia EK may reveal rocks intermediate between these two groups, and indeed may indicate components from even more sources.
 
The geochemical data corroborate field and petrographical evidence suggesting that the major intrusions on St Kilda fall into two major groups. The first, a group of mafic rocks, comprises the Western Gabbro, Cambir Dolerite and the rocks of Glacan Mor, Boreray and Soay. In [[:File:P991873.jpg|(Figure 42)]] this group is characterised by low alkali–lime ratios and in [[:File:P991874.jpg|(Figure 43A)]] by a lack of light REE enrichment. The second group range from mafic to granitic compositions and not only have higher alkali and iron ratios but also contain more K, P and REE's, relatively enriched in the light elements. Several members of this second group appear to be related through fractionation to a parental tholeiitic magma of the Glen Bay type. Relationships among the first group are less clear: if the Conachair Granite is related by fractionation to the Western Gabbro, this might explain the relative depletion of the latter in REE's and low alkali and iron ratios. Further sampling of the breccia EK may reveal rocks intermediate between these two groups, and indeed may indicate components from even more sources.
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== [[St. Kilda: an illustrated account of the geology#References|References]] ==
 
== [[St. Kilda: an illustrated account of the geology#References|References]] ==
 
{{EGwalks}}
 
{{EGwalks}}
 
[[Category: 2. Northern Highlands]]
 
[[Category: 2. Northern Highlands]]

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