Twirligig, Burke River, Westland District, West Coast Region, New Zealandi

Regional Level Types
Twirligig	- not defined -
Burke River	River
Westland District	District
West Coast Region	Region
New Zealand	Country

The study by Cooper (1996) was conducted on various sites in the Burke River area, as part of a swarm of lamphrophyre dykes, 25 kilometres wide, and 110 kilometres long in the vicinity of the Alpine Fault.

The main interest was baotite, which is a rare Ba-Nb-Ti chlorosilicate. It is the first silicate that has quadruple metasilicate rings in its crystal structure. It is found here as widespread in Ba-Sr rich carbonitic and sideritic ferrocarbonatites, and associated fenites, showing as richer in Nb and Fe than previous studied samples of the species. The material is largely pale to dark brown grains and granules up to 0.5 mms.

At the Twirligig (creek) is a norsethite rich sill, in a 2.5 kilometre long carbonatite intrusion zone featuring baotite. The species is found in thin veins of calcite-ankerite carbonatite. The calcite-ankerite carbonatite contains calcite, albite, ankerite, titanian aegirine calcian strontianite, Ba-Ca-Sr LREE carbonates, possibly burbankite, pyrite, sphalerite, galena, chalcopyrite and baotite.

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References