Comparison of the metamorphic history of the Monapo Complex, northern Mozambique and Balchenfjella and Austhameren areas, S?r Rondane, Antarctica: Implications for the Kuunga Orogeny and the amalgamation of N and S. Gondwana

摘要

Reconstructions of Gondwana place Dronning Maud Land, Antarctica (DML) adjacent to N. Mozambique prior to fragmentation. The Monapo Complex outlier klippen overlying the Nampula Terrane in N. Mozambique has been correlated with rocks in eastern and central DML. Metamorphic assemblages and P-T conditions from the two areas are compared as well the timing of metamorphism. Granulite grade assemblages preserved in the Monapo Complex suggest P-T conditions of ~900. °C and >10. kb. Textures vary with reactions typical of isothermal decompression, isobaric cooling and hydration being recognized but also include equilibrium assemblages. P-T estimates from four samples suggest initial inversion of high pressure assemblages from at least ~10. kb and ~900. °C to mid-crustal levels where near isobaric cooling and hydration at between ~4-7. kb and 550-700. °C is recognized. Granulite grade assemblages from Balchenfjella in eastern S?r Rondane, DML suggest initial P-T conditions of ~900. °C and >10. kb. Textures vary with reactions typical of decompression, cooling and hydration being recognized but also include equilibrium assemblages. P-T estimates from four samples suggest initial inversion of high pressure assemblages from at least ~10. kb and ~900. °C to mid-crustal levels where retrogression at between ~6-7. kb and 600-700. °C is recognized.SHRIMP zircon data from six samples from eastern S?r Rondane show episodic zircon growth over a period from ~630. Ma to ~530. Ma with five metamorphic pulses being defined. Undeformed granitic intrusions with ages of ~550. Ma intrude S?r Rondane. SHRIMP zircon data from samples from alkaline intrusions and mafic granulites in the Monapo Complex yield crystallization and metamorphic ages of ~635. Ma and 570-590. Ma respectively. The complex is intruded by granitic veins with ages of ~550. Ma.The similarities in metamorphic mineral assemblages, P-T estimates and zircon geochronology data indicate a common geological history between S?r Rondane and the Monapo Complex of northern Mozambique. This common history is interpreted to result from both areas being part of a mega-nappe structure which was emplaced in a transpressional setting involving collision between N. Gondwana (comprising rocks of the East African Orogeny) and south Gondwana (comprising the Nampula Terrane of northern Mozambique and the Maud Province of western Dronning Maud Land) along the Damara-Zambesi-Lurio-CDML collision boundary.Other erosional remnants of this nappe include the Mugeba Complex in northern Mozambique, the Kataragama klippe in Sri Lanka, the Urungwe klippe in Zimbabwe, the Masosa Suite and Mavhuradohna Complex in western Mozambique and NE Zimbabwe.