Cretaceous tungsten-tin mineralisation in the Tin Range, Stewart Island, New Zealand. Issue 2 (3rd April 2022)

• Record Type: Journal Article
• Authors: Lilley, Hamish C.; Scott, James M.; Schwartz, Josh J.; Turnbull, Rose E.; Tulloch, Andy J.
• Is Part Of: New Zealand journal of geology and geophysics. Volume 65:Issue 2(2022)
• Page Start: 283
• Page End: 298
• Publication Date: 2022-04-03
• Subjects: tungsten -- tin -- greisen -- Stewart Island -- U-Pb dating -- monazite -- xenotime; Geology -- New Zealand -- Periodicals; Geology -- Periodicals; Geophysics -- Periodicals; Geofysica; Geologie; Geology; Geophysics; New Zealand; Periodicals; 559.3
• DOI: 10.1080/00288306.2020.1855216
• Languages: English
• ISSNs: 1175-8791

Abstract

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.