Incremental emplacement of the sheeted Glas Bheinn Porphyritic Dolerite, Ardnamurchan, NW Scotland

The <em>c</em>. 58 Ma Ardnamurchan Central Complex represents the deeply eroded roots of an ancient volcanic edifice that purportedly formed during three discrete phases of igneous activity. Although only a relatively small component of the first phase of magmatism (Centre 1), the Glas Bheinn Porphyritic Dolerite provides important insights into igneous emplacement mechanisms and age relationships on Ardnamurchan. New field observations combined with anisotropy of magnetic susceptibility analyses, which allow primary magma flow patterns to be reconstructed, suggest that the Glas Bheinn Porphyritic Dolerite consists of numerous inclined sheet intrusions that, overall, have a flower intrusive structure. Vertically ascending sheets that do not appear to be related to the Centre 1 focus are proposed to have been deflected into the inclined sheets and sills by the load of the overlying volcanic edifice. Cross-cutting relationships further suggest that some sheets of the Glas Bheinn Porphyritic Dolerite are later than several Outer Centre 2 cone sheets. These observations suggest that the Glas Bheinn Porphyritic Dolerite cannot be attributed to Centre 1.

约58 Ma的阿德南默坎中央杂岩体（Ardnamurchan Central Complex）是一处古火山构造经深度剥蚀后的残留根部，据推测其形成历经三期独立的岩浆活动阶段。尽管格拉斯本斑状辉绿岩（Glas Bheinn Porphyritic Dolerite）仅为第一期岩浆作用（中心1）的相对较小组分，却为阿德南默坎地区的岩浆侵位机制与年代学关系提供了关键研究启示。结合可恢复原生岩浆流动模式的磁化率各向异性分析结果的新野外观测表明，格拉斯本斑状辉绿岩由大量倾斜岩脉侵入体构成，整体呈现花状侵位构造。研究认为，与中心1侵位中心无关的垂直上升岩脉，因上覆火山构造的荷载作用而被偏转至倾斜岩脉与顺层岩床中。穿切关系进一步显示，部分格拉斯本斑状辉绿岩的岩脉晚于数处外中心2的锥状岩脉。上述观测结果表明，格拉斯本斑状辉绿岩不能归因于中心1的岩浆活动。