Bingen, B.

Bjerkgård, T.

Boyd, R.

Feito, P.

Henderson, I.H.C.

Hollick, Louise

Jacobs, J.

Jamal, D.

Key, Roger

Lutro, O.

Melezhik, V.A.

Nordgulen, Ø.

Rossi, D.

Sandstad, J.S.

Skår, Ø.

Smethurst, M.

Smith, Richard

Solli, A.

Thomas, Robert James

Tveten, E.

Viola, G.

English

NERC Open Research Archive

Geophysical Research Abstracts, Vol. 8, 06049, 2006SRef-ID: 1607-7962/gra/EGU06-A-06049© European Geosciences Union 2006Crustal architecture in Northern Mozambique: resultsfrom a regional bedrock mapping projectB. Bingen (1), R. Boyd (1), R.J. Thomas (2), T. Bjerkgård (1), P. Feito (3), I.H.C.Henderson (1), L.M. Hollick (2), J. Jacobs (5), D. Jamal (4), R.M. Key (2), O. Lutro(1), V.A. Melezhik (1), Ø. Nordgulen (1), D. Rossi (3), J.S. Sandstad (1), Ø. Skår (1),M. Smethurst (1), R.A. Smith (2), A. Solli (1), E. Tveten (1), G. Viola (1)(1) Geological Survey of Norway, Trondheim, Norway, (2) British Geological Survey, UK, (3)National Directorate for Geology, Mozambique, (4) Eduardo Mondlane University, Maputo,Mozambique, (5) University of Bergen, Bergen, Norway (bernard.bingen@ngu.no)The bedrock geology of Northern Mozambique has been investigated as part of aninfrastructure development program funded by the World Bank and other donors.The project has a significant component of technology transfer and training. Thework involved reconnaissance geological mapping at the 1:250000 scale over 31degree square sheets, acquisition of petrographic, mineralogical, geochemical andgeochronological data, and a survey of mineral resources. The maps integrate resultsfrom a new airborne magnetic and radiometric survey over key areas. The geochrono-logical database includes LA-ICPMS and SIMS U-Pb zircon and monazite data from28 samples, Re-Os sulphide data from one deposit and chemostratigraphic 87Sr/86Srand δ13C data from two carbonate sequences.The region is subdivided into a number of gneiss complexes characterized by distinctlithological, structural and magnetic signatures. The northwesternmost Ponta Messulicomplex, along Lake Niassa, contains a Paleoproterozoic basement and evidence foramphibolite-facies migmatitization at 1954±15 Ma. It is associated with the Txitongagroup, dominated by metasediments and hosting Au-bearing quartz veins controlledby late Pan-African shear zones (ca. 485 Ma and younger). The Unango and Marrupacomplexes consist of granitic and charnockitic gneisses formed between 1065 ±16and 988 ±20 Ma, and intruded by 799 ±8 Ma alkaline granite and 576 ±15 to 475±9 Ma magmatic rocks. The above complexes are juxtaposed along tectonic contacts.Deposition of the carbonate-bearing Geci group, now preserved in tectonic lenses,is estimated between 635 and 595 Ma. Pan-African amphibolite- to granulite-faciesmetamorphism occurred between 560 and 520 Ma. A mylonite along a NE-SW trend-ing sinistral shear zone records late Pan-African escape tectonics at 444 ±5 Ma. TheXixano complex corresponds to a radiometric low, and includes granulites juxtaposedalongside various metasedimentary rocks along greenschist- to amphibolite-faciesshear zones. Granulite-facies metamorphism is dated at 735 ±4 Ma. The Lalamo andMontpuez complexes include abundant metasediments and felsic metavolcanic rocks.Deposition of marble is estimated at ca. 1050-1000 Ma. In the southern part of themap area, the Nampula complex is composed mainly of granitic and charnockitic or-thogneisses, one of which is dated at 1051±13 Ma, with screens of high-grade parag-neiss (Molocue group). The complex is overlain by sillimanite-grade, possibly Neo-proterozoic, metasediments, including meta-conglomerates. The Nampula complex isjuxtaposed with the northern complexes along the prominent WSW-ENE trending Lu-rio structure. The Lurio complex dips to the NNW and structures reflect interferenceof at least two major deformation phases. The Lurio complex is cored by granulitelenses decreasing in abundance to the west. Granulite-facies metamorphism and de-formation is bracketed between 556 ±4 and 536 ±6 Ma. The Lurio complex does notalways correspond to a major lithological break between the Nampula and Marrupacomplexes, and consequently does not have all the attributes of a Pan-African suturezone.On a regional scale, the 1.95 Ga metamorphism in the Ponta Messuli complex linksthis complex with the Usangaran belt of Tanzania. The 1.07–0.99 Ga magmatism inthe Unango complex is coeval with the peak of magmatic activity in the Irumide beltof Zambia, possibly restoring this complex at the margin of the Congo-Tanzania cra-ton before the Pan-African orogeny. The penetrative 560-530 Ma high-grade meta-morphism is related to the collision between the Congo-Tanzania craton and a couplemade by the East-Antarctica and Kalahari cratons. Preservation of 735 ±4 Ma gran-ulites in the Xixano complex is evidence for a polyphase Pan-African assembly on thesouth-eastern side of the Congo-Tanzania craton.

Crustal architecture in Northern Mozambique : results

from a regional bedrock mapping project [abstract]

http://nora.nerc.ac.uk/5601/1/EGU2006-abs.pdf

Crustal architecture in Northern Mozambique : results from a regional bedrock mapping project [abstract]

Abstract

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