ABSTRACT During the second phase of the Alpine Fault, Deep Fault Drilling Project (DFDP) in the Whataroa River, South Westland, New Zealand, bedrock was encountered in the DFDP-2B borehole from 238.5–893.2 m Measured Depth (MD). Continuous sampling and meso- to microscale characterisation of whole rock cuttings established that, in sequence, the borehole sampled amphibolite facies, Torlesse Composite Terrane-derived schists, protomylonites and mylonites, terminating 200–400 m above an Alpine Fault Principal Slip Zone (PSZ) with a maximum dip of 62°. The most diagnostic structural features of increasing PSZ proximity were the occurrence of shear bands and reduction in mean quartz grain sizes. A change in composition to greater mica:quartz + feldspar, most markedly below c. 700 m MD, is inferred to result from either heterogeneous sampling or a change in lithology related to alteration. Major oxide variations suggest the fault-proximal Alpine Fault alteration zone, as previously defined in DFDP-1 core, was not sampled.

中文翻译：

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DFDP-2B 的基岩地质，中央高山断层，新西兰

摘要 在新西兰西南部 Whataroa 河的高山断层深断层钻探项目 (DFDP) 的第二阶段，在 DFDP-2B 钻孔中遇到了 238.5-893.2 m 测量深度 (MD) 的基岩。对整个岩屑的连续采样和中到微尺度表征确定，钻孔依次采样角闪岩相、Torlesse 复合地层衍生的片岩、原裂岩和糜棱岩，终止于高山断层主滑移带 (PSZ) 以上 200-400 m最大倾角为 62°。增加 PSZ 接近度的最具诊断性的结构特征是剪切带的出现和平均石英晶粒尺寸的减小。成分变化更大的云母：石英+长石，最明显低于c。700 m MD, 推断是由非均质采样或与蚀变相关的岩性变化引起的。主要的氧化物变化表明，没有对先前在 DFDP-1 岩心中定义的靠近断层的高山断层蚀变带进行采样。