Percorrer por autor "Albardeiro, Luís"
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- The age and depositional environments of the lower Karoo Moatize Coalfield of Mozambique: insights into the postglacial history of central GondwanaPublication . Fernandes, Paulo; Hancox, Philip John; Mendes, Márcia; Pereira, Zélia; Rodrigues Lopes, Gilda Maria; Marques, João; Jorge, Raul Carlos Godinho Santos; Albardeiro, LuísThe Moatize Coalfield belongs to a network of continental Karoo basins of central Mozambique, known as the Zambezi Basin. Palynological and sedimentological studies were performed on four coal exploration boreholes to determine the age, depositional settings, and overall geological evolution of its extensive coal deposits. Clastic formations recognised in this coalfield, in ascending order, are the Vu´zi, Moatize and Matinde formations. Palynomorph assemblages indicate that the Moatize Coalfield succession ranges from Roadian (lower Guadalupian) to Changhsingian (upper Lopingian) in age. Two main depositional phases are identified, whose initiation and development are attributed to regional tectonic events and climate amelioration. The first phase formed towards the end of the deglacial period, characterised initially by fan deltas, represented by the upper Vu´zi Formation, and the shift to lake–delta environments, represented by the lower part of the Moatize Formation. This phase took place from Roadian to the Wordian times. The lake–delta settings indicate a sediment aggradation trend with high subsidence rates in the lake basin, which, together with the associated post-glacial climate amelioration, led to the accumulation of coal deposits in swamps of the delta top and lake margins. The second depositional phase took place from Capitanian to Changhsingian times and related to fluvial environments initiated by uplift that reorganised the depocenter into alluvial plains characterised by bedload dominated rivers (braided) and overbank floodplains. Results obtained in this study provide critical information for the onset of the deglaciation events and the age of coal deposits in this part of Gondwana, important for wider stratigraphic correlation of these events in Africa and throughout the Gondwana.
- Detrital zircon U-Pb geochronology of the moatize and n'condédzi coalfields, zambezi karoo basin of Mozambique: implications for provenance, sediment dispersal and basin evolutionPublication . Fernandes, Paulo; Jorge, Raul C. G. S.; Albardeiro, Luís; Chew, David; Drakou, Foteini; Pereira, Zélia; Marques, JoãoDetrital zircon U-Pb geochronology of the Moatize and N'Condedzi coalfields in the Zambezi Karoo Basin of Mozambique provides key insights into the regional provenance, sediment dispersal pathways and basin evolution. Borehole cores from the two coalfields reveal a stratigraphy spanning the early Roadian (middle Permian) to the Carnian (Upper Triassic). The Permian sandstones of the Moatize Coalfield (MC) yield three detrital zircon populations, with ages ranging from 1150 to 950 Ma, 900-780 Ma and 650-490 Ma. In contrast, the Permian sandstones of the N'Condedzi Coalfield (NC) have only one population, which ranges from 1150 to 950 Ma. During the Permian, the provenance area for the NC was the Tete-Chipata Terrane and Malawi Complex (1150-950 Ma) to the north-northeast. In the MC, the detrital zircon populations of the early lake delta depositional setting (Roadian to Wordian) indicate a main provenance in the Zambezi Belt (900-780 Ma) located to the south of the MC, with minor sourcing from the Nampula Block (1150-950 Ma and 650-490 Ma) to the east. The transition from a lake delta to an alluvial depositional setting is attributed to a major tectonic event in the MC, which involved the formation of a braided channel belt. Sandstones from this braided channel belt yield three detrital zircons populations (650-490 Ma, 900-780 Ma and 1150-950 Ma), indicating provenance from both the Zambezi Belt and the Nampula Block. The overlying sandstones in the MC show only a minor population from the Zambezi Belt (900-780 Ma), implying a shift in provenance to the Nampula Block that was likely induced by tectonics. The absence of detrital zircon populations of 900-780 Ma and 650-490 in the Permian sandstones of NC implies that the two coalfields were not connected during the mid to late Permian. It is likely that an intra-rift horst (the Mesoproterozoic Gabbro-Anorthosite Tete Suite) separated the two coalfields. The Lower Triassic sandstones of the NC yield a main detrital zircon population indicating provenance from the TeteChipata Terrane and Malawi Complex (1150-950 Ma). A minor population at 650-490 Ma is linked to increased aridity at the Permian - Triassic boundary, which caused expansion of the watershed across the Tete-Chipata Terrane and the Malawi Complex. The Upper Triassic sandstones in the NC yield a 1150-950 Ma detrital zircon population, indicating provenance from the Tete-Chipata Terrane and Malawi Complex and a return to the source-to-sink conditions seen in the mid to late Permian.