2021/01/11 by Hamish C. Lilley, James M. Scott, Joshua Schwartz +2 · 1 citation
Earth and Planetary Sciences · Computer Science · #Geological and Geochemical Analysis #Geochemistry and Geologic Mapping #earthquake and tectonic studies
paper · doi:10.1080/00288306.2020.1855216
openalex publication_date 2021/01/11 · openalex created_date 2025/10/10 · openalex updated_date 2026/05/21
ABSTRACT The discovery of placer tin in southern Stewart Island caused New Zealand's only known tin‐rush. The source of at least some of the placer tin is greisenised granodiorite and metasedimentary rocks on the crest of the Tin Range. There are three mineralised lithologies: a sericite‐quartz greisen, a quartz‐topaz greisen, and a gahnite‐schist greisen. However, very little cassiterite (SnO2) is observed and instead wolframite ((Fe,Mn)WO4) and gahnite (ZnAl2O4) are common. U‐Pb dating of host early Paleozoic Pegasus Group metasediments indicate the area experienced metamorphism at ∼117 Ma (monazite), with granodiorite emplacement at 107.9 ± 2.2 Ma (zircon). U‐Pb isotope and trace element analysis of xenotime in the mineralised zone reveals three distinct growth phases: one at 107.5 ± 1.8 Ma that overlaps with granodiorite emplacement, and then 94.2 ± 0.9 Ma and 91.6 ± 0.6 Ma. Although it is not clear precisely which growth phase correlates with mineralisation, it must have been a mid‐Cretaceous event and we correlate it with the ∼108 Ma Tin Range Granodiorite. The window of mineralisation, ∼ 108‐92 Ma, means that this event was likely associated with the initiation of thinning of the Zealandia lithosphere as a precursor to separation from Australia and Antarctica.