Evidences for multiple remagnetization of Proterozoic dykes from Iguerda inlier (Anti-Atlas Belt,Southern Morocco)     

Marta Neres  Pedro F. Silva  Moha Ikenne  Sofia Martins  Ahmid Hafid  João Mata  Francisco Almeida  Nasrrddine Youbi  Moulay A. Boumehdi 《Studia Geophysica et Geodaetica》2016,60(4):700-730

No paleomagnetic data exist for Paleo-Mesoproterozoic times of the West African Craton (WAC). Therefore, paleogeographic reconstructions for such old geological times are difficult to constrain. Gaps on the sedimentary record and intense remagnetizations are the major problems that paleomagnetic studies come across. Recent geochronological results for dyke swarms that intrude several Proterozoic inliers of WAC in the Anti-Atlas Belt (southern Morocco) revealed ages between Paleoproterozoic and early Neoproterozoic, opening for the first time a window of opportunity to conduct paleomagnetic studies and tentatively infer about the paleoposition of WAC during Proterozoic. On this scope we conducted a paleomagnetic study on seven Proterozoic dykes of the Iguerda inlier. The meaning of the obtained paleomagnetic directions was evaluated by rock magnetic and mineral analyses, complemented by petrographic observations. Our samples record the presence of a complex history of remagnetization, mostly assigned to several Phanerozoic thermal/chemical events, in particular to the late stages of Pan African orogeny (s.l.), to the Late Carboniferous Variscan orogeny, and even to more recent events. The recognized remagnetization processes are related to widespread metamorphic events under greenschist facies followed by low-temperature oxidation, both responsible for the formation of new magnetic phases, like magnetite and hematite. These events obliterated the primary (magmatic) thermo-remanent magnetization and promoted multiple remagnetizations of the dykes, thermally and chemically. For only one dyke the presence of primary magnetization is possible to infer, though not to confirm, and would place WAC at an equatorial position around 1750 Ma.  相似文献   

The zircon evidence of temporally changing sediment transport—the NW Gondwana margin during Cambrian to Devonian time (Aoucert and Smara areas,Moroccan Sahara)     

Gärtner  Andreas  Youbi  Nasrrddine  Villeneuve  Michel  Sagawe  Anja  Hofmann  Mandy  Mahmoudi  Abdelkader  Boumehdi  Moulay Ahmed  Linnemann  Ulf 《International Journal of Earth Sciences》2017,106(8):2747-2769

International Journal of Earth Sciences - Detrital zircon provenance studies are an established tool to develop palaeogeographic models, mostly based on zircon of siliciclastic rocks and isotope...  相似文献