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S U M M A R YDuring remagnetization, chemical changes limited to moderate grain growth from pre-existing single domain (SD) grains do not modify the palaeomagnetic direction carried by these grains. Palaeomagnetic direction from new SD grains, on the contrary, is that of the magnetic field during remagnetization. The resulting direction becomes intermediate between the directions carried by previous and new SD grains, as it appears often in case of a partial magnetic overprint. If the growth of pre-existing grains is more important, these grains become large multidomain (MD) and loose the primary magnetization. Stable magnetization is then only related to the new SD grains, which carry the total remagnetization. In the Illizi basin (Saharan platform), these different cases of partial or total magnetic overprint have been observed, resulting from palaeomagnetic studies of different Palaeozoic and Mesozoic formations.

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