A LA-ICP-MS and SHRIMP U/PB age constraint on the timing of ree mineralisation associated with bushveld granites.
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2011
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Abstract
Monazite occurs in association with fluorite and polymetallic sulphides in brecciated pegmatites emplaced within discordant pipelike
structures, and spatially associated mineralised quartz veins that cut hydrothermally altered Bushveld-age Nebo Granite (Lebowa
Granite Suite) on the farm Houtenbek 194 JR. Mineralisation of this style has been viewed as having a high-temperature origin
related to a late-stage of Bushveld-age granite emplacement. However, early attempts to date Houtenbek monazite in the 1950 to
1960s, using thermal ionisation mass spectrometry, gave a range of very imprecise 207Pb/206Pb ages from isotopically moderately
to strongly discordant grains that cannot be used to confidently make this link. Here we present new high spatial resolution SHRIMP
and LA-ICP-MS weighted mean 207Pb/206Pb ages of 2059.2 ± 3.5 Ma and 2046 ± 10 Ma for a museum specimen of Houtenbek
monazite. These estimates overlap with the 2054 Ma emplacement age of the main phase of the Lebowa Granite Suite. Together
with the monazite REE patterns, which indicate a magmatic origin, the new age determinations reinforce the connection between
REE mineralisation and Bushveld-age granites.
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BUICK, I. S.; LANA, C. de C.; GREGORY, C. A LA-ICP-MS and SHRIMP U/PB age constraint on the timing of ree mineralisation associated with bushveld granites. South African Journal of Geology, v. 114, p. 1-14, 2011. Disponível em: <http://sajg.geoscienceworld.org/content/114/1/1>. Acesso em: 20 de jun. 2017.