The Sin Quyen Iron Oxide-Copper-Gold-Rare Earth Oxide Mineralisation of North Vietnam
by
Robert N. McLean, AQ Geological Consultants
Hanoi, Vietnam.
in Porter, T.M. (Ed), 2002 - Hydrothermal Iron Oxide Copper-Gold and Related Deposits: A Global Perspective, PGC Publishing, Adelaide, v. 2, pp 293-301.
ABSTRACT
The Sin Quyen deposit in northern Vietnam is an unusual example of the Fe oxide-Cu-Au-REE group of deposits. Magnetite-orthite-chalcopyrite-gold mineralisation is hosted by extremely altered amphibolite and biotite-gneiss lenses within highly deformed and metamorphosed sediments of the Proterozoic Sin Quyen Formation. The deposit formed in a wide fault zone which acted as a channel for pre-mineralisation amphibolite and granitic dykes, mineralising fluids as well as post mineralisation granite, pegmatite and amphibolite. Metasomatic alteration produced a variety of assemblages predominantly composed of variable amounts of quartz, hastingsite and biotite but also including small zones of hedenbergite-garnet skarn. Alteration is closely associated with magnetite and orthite (allanite) development. Sulphide mineralisation, mainly chalcopyrite and pyrrhotite with lesser pyrite is a later and lower temperature hydrothermal event, although the majority of the sulphides were deposited within the alteration zones.
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