The geochemistry and significance of plugs intruding the Tertiary Mull-Morvern lava succession, western Scotland

Kerr, Andrew Craig ORCID: https://orcid.org/0000-0001-5569-4730 1997. The geochemistry and significance of plugs intruding the Tertiary Mull-Morvern lava succession, western Scotland. Scottish Journal of Geology 33 (2) , pp. 157-167. 10.1144/sjg33020157

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Abstract

The Tertiary plugs of north Mull and Morvern, can be divided into three broad groups; (1) trachytes and mugearites; (2) diorites and tholeiitic dolerites with < 6 wt. % MgO and; (3) predominantly tholeiitic dolerites with > 6 wt. % MgO. Two trachytic trends are discernible, a low-iron and a high-iron trend. However, only the high-iron trend is found within the Tertiary Mull lava sequence. The origin of these two differentiation trends may be related to the composition of the primary magma, with more tholeiitic magmas fractionating to produce the lower-iron trachytes. The more MgO-rich plugs are invariably tholeiitic and are chemically unlike any of the preserved lavas within the Mull succession. The absence of this composition and of the low-iron trachyte compositions within the lava succession suggests that these magmas were possibly erupted near the top of the lava pile and have since been eroded away. The plugs may have acted as substantial feeders of the lava succession during its later stages of formation, while in the earlier stages the lavas were probably erupted from fissures. The absence of plugs associated with the Skye lavas, contrasts with the Mull and Antrim lava fields, and may be due to the more-intermittent nature of the Tertiary volcanic activity on Skye.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Earth and Environmental Sciences
Subjects:	Q Science > QE Geology
Publisher:	Geological Society
ISSN:	0036-9276
Last Modified:	18 Oct 2022 12:22
URI:	https://orca.cardiff.ac.uk/id/eprint/9577

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