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

The c. 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.

距今约58百万年的阿达姆尔查恩中央杂岩体（Ardnamurchan Central Complex）是一处古老火山构造经深度侵蚀后残留的根部构造，据推测其形成于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）仅占第一期岩浆作用（中心1）的相对较小组分，但其为阿达姆尔查恩地区的岩浆侵位机制与年代学关系提供了重要研究视角。新的野外观测结果结合磁各向异性（anisotropy of magnetic susceptibility）分析——该分析方法可重建原生岩浆流动模式——表明格拉斯本斑状辉绿岩由大量倾斜岩席侵入体构成，整体呈现花状侵入构造。看似与中心1的岩浆焦点无关的垂直上升岩席，被认为是受上覆火山构造的载荷作用而偏转进入倾斜岩席与岩床之中。穿切关系进一步表明，格拉斯本斑状辉绿岩的部分岩席形成时间晚于多个外带中心2锥状岩席。上述观测结果表明，格拉斯本斑状辉绿岩无法归因于中心1岩浆作用。