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TitleLithogeochemistry, geochronology and geodynamic setting of the Lupa Terrane, Tanzania: implications for the extent of the Archean Tanzanian Craton
AuthorLawley, J M; Selby, D; Condon, D J; Horstwood, M; Millar, I; Crowley, Q; Imber, J
SourcePrecambrian Research vol. 231, 2013 p. 174-193, Open Access logo Open Access
Alt SeriesEarth Sciences Sector, Contribution Series 20120424
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf; html
AreaTanzania, United Republic of
Lat/Long WENS 30.0000 33.5000 -6.0000 -9.0000
Subjectsgeochemistry; geochronology; igneous and metamorphic petrology; lithogeochemistry; Archean; mass spectrometer analysis; terranes; magmatism; uranium lead ratios; uranium lead dating; lithology; petrogenesis; Lupa Terrane; Tanzanian Craton; Ubendian Belt; Precambrian
Illustrationslocation maps; photographs; tables; Concordia diagrams; plots; ternary diagrams
ProgramTargeted Geoscience Initiative (TGI-4) Gold Ore Systems
Released2013 07 01
AbstractHerein we provide new zircon U-Pb ID-TIMS, U-Pb LA-MC-ICP-MS and Lu-Hf LA-MC-ICP-MS results fromthe Lupa Terrane, SW Tanzania, and demonstrate that previously considered Paleoproterozoic granitescomprising the Paleoproterozoic Ubendian Belt are in fact Archean (ca. 2.74 Ga). Disparately older inher-ited zircons (ca. 2.85 Ga) and Lu-Hf zircon model ages (>3.1 Ga) suggest that these Archean granites likelyinteracted with substantially older crust underlying the Lupa Terrane at the Tanzanian cratonic margin.Foliated Archean granites are in turn cut by non-foliated, voluminous and greenschist facies granitic-gabbroic intrusions (1.96-1.88 Ga), which are broadly concomitant with granulite- to amphibolites-faciesrocks that characterize the other lithotectonic terranes comprising the Ubendian Belt. New geochemicalresults suggest that these Paleoproterozoic intrusive phases possess trace element compositions that aretypical of continental magmatic arcs, which is consistent with the crust-magma interaction inferred fromfield relationships and inherited Archean zircons within Paleoproterozoic granitic intrusions. Togetherthe available field and geochemical evidence suggest that the Lupa Terrane was a continental cratonicmargin during the Paleoproterozoic onto which the other Ubendian lithotectonic terranes were accretedand implies at least a 150 km southwest extension of the currently accepted position of the Tanzaniancraton margin. These new results are consistent with re-worked Archean crust reported in other meta-morphic belts enveloping the Tanzanian Craton and seismic tomography studies that suggest significantportions of the Ubendian Belt represent re-worked Archean lithosphere.
Summary(Plain Language Summary, not published)
Rock packages in south west Tanzania are poorly understood. In this contribution we show that rock packages in south west Tanzania are substantially older than previously thought (approximately 1 billion years older), which calls for a reassessment of the geologic history of the area. Our results also contribute to a better understanding of ancient mountain building processes and also have implications for mineral deposits associated with ancient mountain belts.

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