Composite and Multiple Intrusions of Lamlash-Whiting Bay Region, Arran

Abstract

AbstractIn South-East Arran there are many Kainozoic composite and multiple intrusions, mostly in the form of sills, composed of basic, intermediate, and acid rocks, xenolithic enclosure of, basic members by less basic ones being common. The pyroxene of all the rock types is a normal augite and not a pigeonite. Contact hybridization has played an important role in the partial or complete digestion of xenoliths. The genesis of the different members of the intrusions is attributed to the complex process of deep-seated hybridization of two types of magmatic material of contrasting basic and acid composition. The order of injection of magma is, invariably, from basic to acid, though in the intrusions, the spatial sequence of the rock types varies much; their complicated structures are ascribed to a series of pulsations of contaminated magma with its composition tending progressively in the acid direction.