GSV UR2003/10 - Bogong dyke chemistry
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Product description:Abstract Dyke chemistry, petrology and field relationships were used to identify the following dyke magmatic groups and characterise these in terms of mineralisation, age and tectonic setting:
Pegmatite is abundant in schist and gneiss of the Omeo Metamorphic Complex. High levels of tin–tantalum–niobium are confined to pegmatite in the andalusite zone of the metamorphic complex—particularly between Mitta Mitta and Glen Wills. Production is modest, with just 34 t of tin concentrate. High-grade lenses contain percents of tin, with 100s of ppm tantalum–niobium, but do not persist for more than 20 m of outcrop. The main ore mineral is cassiterite and tin–tantalum–niobium–gold–calcium values in the pegmatite show a strong sympathetic relationship, with calcium values between 0.5% and 10%. Mineralised pegmatites have ascended and probably fractionated concentrating these metals. Their distinct chemistry suggests that they have an exotic source, although what this source may be is uncertain. Cainozoic phonolite pipes and dykes that crop out in an 80 km2 area southwest of Harrietville contain high levels of tantalum, niobium and REEs. The pipes are 200–300 m in diameter and dykes up to 500 m long. They trend 310–340° normal to the direction of rifting of the Lord Howe Rise that occurred around 80 Ma. The phonolite plots in the alkaline within plate field and probably formed during rifting by low-degree partial melting of the upper mantle at depths around 90–100 km. Download The downloadable version of this report is supplied in PDF format. Bibliographic Reference Maher, S. & Morand, V.J., 2003. Bogong dyke chemistry. Geological Survey of Victoria Unpublished Report 2003/10. Related products:
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