Pan-African pressure-temperature evolution of the Merelani area in the Mozambique Belt in northeast Tanzania

Muhongo, S.; Tuisku, Pekka; Mtoni, Yohana Enock

doi:10.1016/s0899-5362(99)00102-5

Cited by 23 publications

(11 citation statements)

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“…Most granulite facies rocks were subsequently down‐graded to amphibolite facies for which pressures of 5–8 kbar and temperatures of 550–700 °C were recorded. Similar P–T ‐values have been reported for retrogressed graphitic metapelites in the Merelani area of NE Tanzania (Muhongo et al ., 1999).…”

Section: Discussionsupporting

confidence: 85%

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Metamorphic petrology and zircon geochronology of high‐grade rocks from the central Mozambique Belt of Tanzania: crustal recycling of Archean and Palaeoproterozoic material during the Pan‐African orogeny

Sommer

Kröner

Hauzenberger

et al. 2003

Journal Metamorphic Geology

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New data on the metamorphic petrology and zircon geochronology of high-grade rocks in the central Mozambique Belt (MB) of Tanzania show that this part of the orogen consists of Archean and Palaeoproterozoic material that was structurally reworked during the Pan-African event. The metamorphic rocks are characterized by a clockwise P-T path, followed by strong decompression, and the time of peak granulite facies metamorphism is similar to other granulite terranes in Tanzania. The predominant rock types are mafic to intermediate granulites, migmatites, granitoid orthogneisses and kyanite ⁄ sillimanite-bearing metapelites. The meta-granitoid rocks are of calc-alkaline composition, range in age from late Archean to Neoproterozoic, and their protoliths were probably derived from magmatic arcs during collisional processes. Mafic to intermediate granulites consist of the mineral assemblage garnet-clinopyroxene-plagioclase-quartz-biotite-amphibole ± K-feldspar ± orthopyroxene ± oxides. Metapelites are composed of garnet-biotite-plagioclase ± K-feldspar ± kyanite ⁄ sillimanite ± oxides. Estimated values for peak granulite facies metamorphism are 12-13 kbar and 750-800°C. Pressures of 5-8 kbar and temperatures of 550-700°C characterize subsequent retrogression to amphibolite facies conditions. Evidence for a clockwise P-T path is provided by late growth of sillimanite after kyanite in metapelites. Zircon ages indicate that most of the central part of the MB in Tanzania consists of reworked ancient crust as shown by Archean (c. 2970-2500 Ma) and Palaeoproterozoic (c. 2124-1837 Ma) protolith ages. Metamorphic zircon from metapelites and granitoid orthogneisses yielded ages of c. 640 Ma which are considered to date peak regional granulite facies metamorphism during the Pan-African orogenic event. However, the available zircon ages for the entire MB in East Africa and Madagascar also document that peak metamorphic conditions were reached at different times in different places. Large parts of the MB in central Tanzania consist of Archean and Palaeoproterozoic material that was reworked during the Pan-African event and that may have been part of the Tanzania Craton and Usagaran domain farther to the west.

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Section: Discussionsupporting

confidence: 85%

“…Retrogression of these HT/HP rocks to about 6 kbar and about 650 °C has been documented in the gneisses of the Merelani area, NW of Arusha town (Fig. 2) (Muhongo et al ., 1999). Granulite facies rocks have been dated by several workers, and these ages are summarized in Table S1.…”

Section: Geological Setting Petrology and Previous Geochronologymentioning

confidence: 88%

Metamorphic petrology and zircon geochronology of high‐grade rocks from the central Mozambique Belt of Tanzania: crustal recycling of Archean and Palaeoproterozoic material during the Pan‐African orogeny

Sommer

Kröner

Hauzenberger

et al. 2003

Journal Metamorphic Geology

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“…U-Pb zircon ages of c. 715 and 695 Ma that were originally interpreted to date granulite facies metamorphism (Maboko et al 1985;Muhongo & Lenoir 1994) are now believed to reflect igneous emplacement ages. Geothermobarometry on the granulites documents deep-crustal metamorphism at pressures ->9-12kbar, with counterclockwise, isobaric cooling paths (Muhongo & Tuisku 1996;Maboko 1997;Appel et al 1998;Muhongo et al 1999).…”

Section: Pan-african Orogenesismentioning

confidence: 97%

Proterozoic geochronology and tectonic evolution of southern Africa

Hanson

2003

157

129

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The Precambrian foundation of southern Africa consists of Archaean cratonic nuclei surrounded by belts formed during three separate Proterozoic orogenic episodes. Crust that formed or was reworked at 2.05-1.8Ga is represented by orogenic belts (e.g. Kheis-Magondi, Ubendian-Usagaran) that partly wrap the ancient craton margins or form extensive basement in younger belts. Orogenic belts formed at 1.35-1.0Ga record arc magmatism and collisional events during assembly of the Rodinia supercontinent. The Namaqua-Natal Belt defines a major convergent plate boundary active at this time along the southern margin of the Archaean Kaapvaal Craton, and the western part of this belt is inferred to link with a largely buried, NE-trending orogen present in the Kalahari region. Orogenesis in the same time frame farther north is recorded by the Kibaran and Irumide Belts, which are separated by the Palaeoproterozoic Bangweulu Block but are inferred to have undergone a linked tectonic evolution. East of the Irumide Belt, extensive Mesoproterozoic arc crust occurs in Malawi and Mozambique, although strong Neoproterozoic overprinting of the arc rocks makes their original relations unclear. Breakup of Rodinia is signalled by widespread Neoproterozoic alkaline and bimodal magmatism associated with rift zones which, in some cases, evolved into major ocean basins. Subsequent amalgamation of Gondwana led to collisional orogenesis culminating at 575-505 Ma in the Mozambique and West Congo-Kaoko-Gariep-Saldania Belts along the present eastem and western margins of southern Africa. Coeval deformation in the interconnecting, transcontinental Damara-Lufilian-Zambezi Orogen may reflect destruction of linked rifts and narrow ocean basins driven by farfield stresses from the collisional plate margins.

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“…To the south, it shows an intricate morphostructural zone dominated by the Kilombero valley that forms an asymmetrical depression, 30-40-km-wide, extending at N10ЊE over 200 km from 6Њ30Ј to 8ЊS. Over most of its length, it is bounded by elongate crystalline basement massifs of the Proterozoic Mozambique belt (Hepworth, 1972;Muhongo et al, 1999). To the east, the Kilombero valley is separated from the undulating plains of the Selous-Luwegu coastal basin by smooth relief (generally less than 900 m) of the Uluguru basement massif.…”

Section: General Rift Structure Of Central Tanzaniamentioning

confidence: 99%

Neogene-Holocene rift propagation in central Tanzania: Morphostructural and aeromagnetic evidence from the Kilombero area

Gall

Gernigon

Rolet

et al. 2004

Geo. Society Am. Bull.

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Based on field studies supplemented by remote sensing and aeromagnetic data from central Tanzania, a Phanerozoic structural history for the region can be developed and placed in a broader rift context. The major contribution of this work is the recognition of rift morphology over an area lying 400 km beyond the southern termination of the Eastern, or Kenya, Rift. The most prominent rift structures occur in the Kilombero region and consist of a wide range of uplifted basement blocks fringed to the west by an east-facing half-graben that may contain 6-8 km of sedimentary strata. Physiographic features and river drainage anomalies suggest that Holocene/Neogene deformation occurs along both rift-parallel and transverse faults, in agreement with the seismogenic character of a number of oblique faults. The present-day rift pattern of the Kilombero extensional province re- †

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Pan-African pressure-temperature evolution of the Merelani area in the Mozambique Belt in northeast Tanzania

Cited by 23 publications

References 5 publications

Metamorphic petrology and zircon geochronology of high‐grade rocks from the central Mozambique Belt of Tanzania: crustal recycling of Archean and Palaeoproterozoic material during the Pan‐African orogeny

Metamorphic petrology and zircon geochronology of high‐grade rocks from the central Mozambique Belt of Tanzania: crustal recycling of Archean and Palaeoproterozoic material during the Pan‐African orogeny

Proterozoic geochronology and tectonic evolution of southern Africa

Neogene-Holocene rift propagation in central Tanzania: Morphostructural and aeromagnetic evidence from the Kilombero area

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