Partial melting of semipelite and the development of marginal breccias around a late Caledonian minor intrusion in the Grampian Highlands of Scotland

Abstract

SummaryA water saturated melt was developed in the semipelitic Leven Schist in contact with the kentallenitic basic rocks of the Barnamuc intrusion. The partly melted rock consisted of a small volume of granitic melt with relict refractory quartz grains and layers of aluminosilicates. This material could be mobilized and mixed with phenocryst-bearing magma. Sheets of country rock breccia are associated with the mobilization and veins of breccia and mobilized hornfels invade the intrusion. Sheets of igneous rock occur along the contact zone and their emplacement is related to the mobilization of the hornfels. Loss of cohesion between solid country rock and crystallized outer parts of the plug leads to collapse and removal of early formed igneous rocks, accounting for the lack of chilled margins in some intrusions.