The Nampula Subprovince (NSP) of the Mozambique Metamorphic Province covers over 100 000 km2, making it the largest Mesoproterozoic crustal block in northern Mozambique and an important
component of the Neoproterozoic to Cambrian (Pan-African) East African Orogen. It is bounded in the
north by the WSW–ENE trending Lurio Belt. The oldest rocks (Mocuba Suite) are a polydeformed
sequence of upper amphibolite grade layered grey gneisses and migmatites associated with intrusive
TTG and granitic orthogneisses. A sample of banded gneiss, interpreted as a meta-volcanic rock,
yielded a U-Pb SHRIMP zircon date of 1127 ± 9 Ma. Metamorphic rims, dated at ca. 1090 Ma,
probably grew during the emplacement of a later magmatic phase, represented by the tonalitic Rapale
orthogneiss, two samples of which were dated at 1095 ± 19 and 1091 ± 14 Ma respectively. The
earliest (D1) deformation and associated amphibolite-grade metamorphism and migmatisation
recognised, took place at approximately this time. The geochemistry of these rocks suggests that they
were generated in a juvenile, island-arc setting. The Mocuba Suite is interlayered with extensive belts
of meta-pelitic/psammitic, calc-silicate and felsic to mafic meta-volcanic supracrustal gneisses termed
the Molocue Group. U-Pb data from detrital zircons from a calc-silicate paragneiss gave a bimodal age
distribution at ca. 1100 and 1800 Ma, showing derivation from rocks of the same age as the Mocuba
Suite and a Palaeoproterozoic source region. The age of the Molocue Group has been directly
determined by dates of 1092 ± 13 and 1090 ± 22 Ma, obtained from two samples of the leucocratic
(meta-acid volcanic?) Mamala gneiss, one of its major constituent formations. The final phase of
Mesoproterozoic activity is represented by voluminous plutons and sheet-like bodies of foliated
megacrystic granite, augen gneiss and granitic orthogneiss (Culicui Suite) which have A-type granite
geochemical characteristics, and were interpreted to have been generated in a late tectonic,
extensional setting. Three samples from the suite gave identical ages of ca. 1075 Ma. The NSP was
extensively re-worked during the major (D2: Pan-African) collision orogen in Late Neoproterozoic to
Cambrian times, when the major regional fabrics were imposed upon the Mesoproterozoic rocks under
amphibolite grade metamorphic conditions. In the dated samples, this major orogenic event is
represented by metamorphic zircon rims and lower intercept ages of ca 550 to 500 Ma.
The Nampula Subprovince probably made up the NE part of a major Mesoproterozoic mobile belt
which was accreted to the old cratonic nucleus of the Kalahari craton (combined Archaean Kaapvaal-
Zimbabwe-Grunehogna cratons and various Palaeoproterozoic blocks). This mobile belt, fragmented
by Gondwana break-up, consisted of (from west to east) the Namaqua-Natal belt (South Africa), the
Falkland microplate, the Haag Nunatak block (West Antarctica) and the Maudheim (East
Antarctica)(Jacobs et al., 2008). The belt, with a restored length of over 3000 km is a major part of a
worldwide in a system of “Grenvillian” orogens associated with the amalgamation of the
supercontinent of Rodinia (e.g. Li et al., 2008).
The Nampula Block is the largest Mesoproterozoic crustal domain in northern Mozambique, covering
>100,000 km2 and constituting one of the most important components of the southern part of the
Neoproterozoic to Cambrian (“Pan-African”) East African Orogen. The Nampula Block is bounded in the
north by the WSW–ENE-trending Lurio Belt and by younger rocks to the south and east. The oldest
rocks of the Nampula Block, the Mocuba Suite, are a polydeformed sequence of upper amphibolite-grade
layered grey gneisses and migmatites associated with intrusive trondhjemite-tonalite-granodiorite and
granitic orthogneisses.
Abstract Analysis of new lithological, structural, metamorphic and geochronological data from extensive mapping in Mozambique permits recognition of two distinct crustal blocks separated by the Lurio Belt shear zone. Extrapolation of the Mozambique data to adjacent areas in Sri Lanka and Dronning Maud Land, Antarctica permits the recognition of similar crustal blocks and allows the interpretation that the various blocks in Mozambique, Sri Lanka and Antarctica were once part of a mega-nappe, forming part of northern Gondwana, which was thrust-faulted c. 600 km over southern Gondwana during amalgamation of Gondwana at c. 590–550 Ma. The data suggest a deeper level of erosion in southern Africa compared with Antarctica. It is possible that this thrust domain extends, through the Zambezi Belt or Valley, as far west as the Damara Orogen in Namibia with the Naukluft nappes in Namibia, the Makuti Group, the Masoso Suite in the Rushinga area and the Urungwe klippen in northern Zimbabwe, fitting the mega-nappe pattern. Erosional products of the mountain belt are now represented by 700–400 Ma age detrital zircons present in the various sandstone formations of the Transantarctic Mountains, their correlatives in Australia, as well as the Urfjell Group (western Dronning Maud Land) and probably the Natal Group in South Africa.
Council for Geoscience, P/Bag X112, Pretoria, South Africa. (grantham@geoscience.org.za, bingram@geoscience.org.za) Council for Geoscience, Bellville, South Africa.(pmacey@geoscience.org.za) MSSP-Geomap Project, c/o Geological Survey of Papua New Guinea, Port Moresby, Papua New Guinea. (mssp_geomalc@yahoo.com.au) RSES, Australian National University, Canberra, ACT, Australia. (Richard.Armstrong@anu.edu.au) National Institute of Polar Research, Itabashi, Tokyo, Japan. (kshiraishi@nipr.ac.jp; hokada@nipr.ac.jp) Caracle Creek International Consulting Inc. (CCIC), Johannesburg.( abisnath@cciconline.com) Direcao Nacional Geologia, Maputo, Mozambique.(vjmanhica@hotmail.com) 11
Research Article| September 01, 2018 The chemistry of Karoo-age andesitic lavas along the northern Mozambique coast, southern Africa and possible implications for Gondwana breakup G. H. Grantham; G. H. Grantham Department of Geology, University of Johannesburg, P.O. Box 524, Auckland Park, 2006 South Africa e-mail: ghgrantham@uj.ac.za Search for other works by this author on: GSW Google Scholar B.M. Eglington; B.M. Eglington Saskatchewan Isotope Laboratory, University of Saskatchewan, 114 Science Place, Saskatoon, Canada S7N 5E2. e-mail: bruce.eglington@usask.ca Search for other works by this author on: GSW Google Scholar P.H. Macey; P.H. Macey Council for Geoscience, P.O. Box 572, Bellville, 7535 South Africa e-mail: pmacey@geoscience.org.za Search for other works by this author on: GSW Google Scholar B.A. Ingram; B.A. Ingram Council for Geoscience, Private Bag x112, Pretoria, 0001 South Africa Search for other works by this author on: GSW Google Scholar M. Rademeyer; M. Rademeyer Council for Geoscience, Private Bag x112, Pretoria, 0001 South Africa Search for other works by this author on: GSW Google Scholar H. Kaiden; H. Kaiden National Institute of Polar Research, 10-3 Midori-cho, Tachikawa, Tokyo 190-8518, Japan e-mail: kaiden@nipr.ac.jp Search for other works by this author on: GSW Google Scholar V. Manhica V. Manhica Direcção Nacional de Geologia, Maputo, Mozambique e-mail: vjmanhica@hotmail.com Search for other works by this author on: GSW Google Scholar South African Journal of Geology (2018) 121 (3): 271–286. https://doi.org/10.25131/sajg.121.0026 Article history first online: 28 Nov 2018 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation G. H. Grantham, B.M. Eglington, P.H. Macey, B.A. Ingram, M. Rademeyer, H. Kaiden, V. Manhica; The chemistry of Karoo-age andesitic lavas along the northern Mozambique coast, southern Africa and possible implications for Gondwana breakup. South African Journal of Geology 2018;; 121 (3): 271–286. doi: https://doi.org/10.25131/sajg.121.0026 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySouth African Journal of Geology Search Advanced Search Abstract Major, trace, radiogenic isotope and stable isotope data from lavas along the northeastern coast of Mozambique are described. The whole rock composition data demonstrate that the rocks are dominantly andesitic with compositions typical of calc-alkaline volcanic rocks from arc environments. SHRIMP U/Pb data from zircons indicate that the zircons are xenocrystic, having ages of between 500 Ma and 660 Ma, with the age of the lava constrained by Rb/Sr data at ~184 Ma. Strontium, Nd and Pb radiogenic isotope data support an interpretation of extensive mixing between a Karoo age basaltic magma (dolerite) from Antarctica and continental crust similar in composition to the Mozambique basement. Oxygen isotope data also imply a significant crustal contribution to the lavas. Possible tectonic settings for the lavas are at the margin of a plume or from a locally restricted compressional setting during Gondwana breakup processes. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
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