An Ordovician subvolcanic intrusive complex hosted by Neoproterozoic metasediments crops out at Souter Head about 6km S of Aberdeen, Scotland. The complex is composed mainly of two-mica red granite and breccia with minor dykes of pegmatite, quartz porphyry, felsite and dolerite, and widespread quartz veining, hydrothermal alteration and minor molybdenite mineralisation. Anomalous levels of bismuth (Bi), arsenic (As) and gold (Au) occur in quartz–pyrite veins. The complex has been mapped and the major- and minor-element geochemistry, including rare-earth elements of intrusives and mineralisation, has been determined. These data reveal a complex tectonic, intrusive and hydrothermal history. The intrusives are peraluminous and magnetite-, muscovite- and garnet-bearing. The youngest member, a quartz porphyry, is highly fractionated. There are two stages of hydrothermal activity: the first is linked to the explosive release of volatiles from a granite cupola and breccia formation; and the second, widespread quartz veining. Mo is associated with both stages, and Bi–As–Au anomalies are found in late quartz–pyrite veins. The mineralisation is classified as a granite-related vein-type Mo system. The unique preservation, in the Grampian terrane, of an Ordovician subvolcanic complex may be attributed to pre-Devonian movements on the nearby Dee fault and possibly also the collapse of the magma chamber following the explosive release of volatiles. The combination of large size, poor exposure and abundant multi-stage hydrothermal activity suggests that there is potential for further Mo and possibly Au mineralisation in this complex. Further mineralisation of this style may be present in the NE Grampian terrane.

中文翻译：

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苏格兰阿伯丁郡 Souter Head 次火山复合体的地质：与奥陶纪花岗岩相关的 Mo-(Bi-As-Au) 系统

在苏格兰阿伯丁以南约 6 公里的 Souter Head 出土了一个由新元古代变质沉积物构成的奥陶纪次火山侵入杂岩体。该杂岩主要由二云母红色花岗岩和角砾岩组成，具有伟晶岩、石英斑岩、长长英铁矿和辉绿岩的少量岩脉，以及广泛的石英脉、热液蚀变和少量辉钼矿矿化。异常水平的铋 (Bi)、砷 (As) 和金 (Au) 出现在石英-黄铁矿脉中。对该复合体进行了绘图，并确定了主要和次要元素的地球化学，包括侵入体和矿化的稀土元素。这些数据揭示了复杂的构造、侵入和热液历史。侵入物是过铝和磁铁矿、白云母和石榴石轴承。最年轻的成员是石英斑岩，高度分馏。热液活动有两个阶段：第一个阶段与花岗岩冲天炉和角砾岩地层中挥发物的爆炸性释放有关；第二，广泛的石英脉络。Mo与这两个阶段有关，并且在晚期石英-黄铁矿脉中发现了Bi-As-Au异常。该矿化被归类为花岗岩相关脉型钼系。在格兰屏地体中，奥陶纪次火山复合体的独特保存可能归因于附近迪断层的前泥盆纪运动，也可能归因于挥发物爆炸释放后岩浆房的坍塌。大尺寸、不良暴露和丰富的多阶段热液活动的结合表明，该复合体中存在进一步的 Mo 和可能的 Au 矿化的潜力。