Some relationships resulting from the intimate association of acid and basic magmas

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Abstract
Evidence is presented from Guernsey, Iceland, Ireland, and Scotland that basic and acid magmas have commonly come together. Examples of this are found in surface extrusions and tuffs and in intrusions of various sizes formed at different depths. The basic magma has commonly been chilled against the acid, and the relationships indicate that the acid component was highly mobile; these two facts are thought to be intimately related, in that the mobility of the acid magma is due to the transfer of heat from the basic magma. Consequences discussed include the question of the relative age of contiguous intrusions where basic rock is veined by acid: the age-sequence may be the reverse of that normally postulated. The possibility is also considered that basic magma may occasionally be necessary for the uprise of acid magma to high crustal levels.

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