The Age of Au–Cu–Pb-bearing Veins in the Poly-orogenic Ubendian Belt (Tanzania): U–Th–total Pb Dating of Hydrothermally Altered Monazite
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Date
2015
Journal Title
Journal ISSN
Volume Title
Publisher
Springer
Abstract
The age of gold–copper–lead mineralization
in the Katuma Block of the Ubendian Belt remains controversial
because of the lack of radiometric ages that correlate
with the age of tectonothermal events of this polyorogenic
belt. Previous studies reported whole rock and
mineral Pb–Pb ages ranging between 1,660 and 720 Ma. In
this study, we report U–Th–total Pb ages of monazite from
hydrothermally altered metapelites that host the Au–Cu–
Pb-bearing veins. Three types of chemically and texturally
distinct types of monazite grains or zones of grains were
identified: monazite cores, which yielded a metamorphic
age of 1,938 ± 11 Ma (n = 40), corresponding to known
ages of a regional metamorphic event, deformation and granitic
plutonism in the belt; metamorphic overgrowths that
date a subsequent metamorphic event at 1,827 ± 10 Ma
(n = 44) that postdates known eclogite metamorphism (at
ca. 1,880 Ma) in the belt; hydrothermally altered poikilitic
monazite, formed by dissolution–precipitation processes,
representing the third type of monazite, constrain the age of
a hydrothermal alteration event at 1,171 ± 17 Ma (n = 19).
This Mesoproterozoic age of the hydrothermal alteration
coincides with the first amphibolite grade metamorphismof metasediments in the Wakole Block, which adjoins with
a tectonic contact the vein-bearing Katuma Block to the
southwest. The obtained distinct monazite ages not only
constrain the ages of metamorphic events in the Ubendian
Belt, but also provide a link between the metamorphism of
the Wakole metasediments and the generation of the hydrothermal
fluids responsible for the formation of the gold–
copper–lead veins in the Katuma Block.
Description
Keywords
Monazite dating, Kibaran orogeny, Crustal thickening, Orogenic gold mineralization, Hydrothermally altered monazite
Citation
Kazimoto, E.O., Schenk, V. and Appel, P., 2015. The age of Au–Cu–Pb-bearing veins in the poly-orogenic Ubendian Belt (Tanzania): U–Th–total Pb dating of hydrothermally altered monazite. Contributions to Mineralogy and Petrology, 169(1), pp.1-18.