This sample displays minerals and textures which are interpreted in the following stages, from earliest to latest: 1. Crystallisation of granitoid Acid magma crystallised to form a banded monzogranitic assemblage of K-feldspar + quartz + plagioclase + biotite + minor others (magnetite, ilmenite, apatite, zircon). The presence of both magnetite and ilmenite suggests that the magma was weakly oxidised. Banding was defined by concentration of biotite and accessories (opaques, apatite, zircon) in subparallel bands several millimetres thick. The origin of the banding remains uncertain, but it is possible it represents magmatic elongation of magmatically equilibrated mafics (either early-crystallised minerals or mafic enclaves from source). 2. Alteration The rock was infiltrated by a small volume of hydrous fluid, which generated new alteration albite + sericite + chlorite + minor hematite + zoisite + ?prehnite. Much of the primary plagioclase was replaced by albite + sericite ± zoisite, leaving some relict primary plagioclase. Mot of the primary biotite was replaced by chlorite ± zoisite, leaving local preserved biotite. Hematite formed by partial replacement of magnetite. Uncommon thin fractures were sealed by chlorite + zoisite.

In thin section, this sample displays a hypidiomorphic granitoid texture with mineralogical banding. K-feldspar is abundant, forming subhedral blocky grains ~1-2 mm in size. All display ‘tartan’ twinning characteristic of microcline. Quartz is moderately abundant. It occurs as anhedral grains ~0.4-2.0 mm in size. Some larger grains are aligned in the trace of banding. All grains display mild deformation in the form of shadowy strain extinction; recrystallisation is absent. Plagioclase formed subhedral equant grains ~0.4-1.5 mm in size. All display partial replacement by optically continuous twinned albite lightly clouded by tiny sericite flecks and uncommon small pale yellow zoisite grains. Clear relict primary plagioclase is preserved in some grain sites, where it displays weak normal compositional zoning. Biotite was moderately abundant. It formed well-shaped small plates ~0.4-1.0 mm long. They are distributed throughout the rock, but are notably more abundant in subparallel bands. Preferred orientation of the biotite plates lies subparallel to the mineralogical banding. Most of the biotite has been selectively replaced by pleochroic green chlorite, and uncommon zoisite and ?prehnite (subradiating, colourless, low to moderate birefringence), leaving relict biotite in some of the plate sites displaying its straw yellow to dark brown pleochroism (moderately oxidised Fe-Mg biotite composition). Rare small biotite plates are also preserved where they formed as small inclusions in quartz grains and hence were shielded from alteration fluid. Opaques occur in minor amount as larger subhedral to anhedral grains (magnetite, see hand sample observation) and smaller bladed grains (ilmenite). Partial replacement of magnetite by hematite is evident under the reflected light. Apatite occurs in minor amount as small stumpy colourless prisms. Some occur in biotite, and others occur at margins of opaque grains. Most occurs in or near biotite in the biotite-rich bands, but some is observed in quartz elsewhere through the rock. Zircon occurs as small stumpy colourless prisms ~100-150 μm in size, displaying the typical high relief and high birefringence of this mineral. Most occur in or near biotite in the biotite-rich bands. Rare thin discontinuous fractures, discordant to banding, are sealed by anhedral zoisite grains and aggregates of small chlorite flakes.