Авторы: Shaar R., Ron H., Tauxe L.

2010 г.

Earth & Planet.Sci.Lett.

     The Middle-Eastern copper slag is a promising newmaterial for studying intensity variations in the geomagnetic field with high resolution and precision. The purpose of this study is to test the accuracy of archaeointensity estimates determined using copper slag by addressing two questions: 1) “Does slagmaterial display themagnetic properties required for valid Thellier experiments?” and 2) “What is the accuracy of the archaeointensity estimates derived fromThellier-style experiments on optimal samples?” Weaddress the first question through a comprehensive microscopic andmagnetic study of representative archaeological slag samples in order to identify the properties responsible for optimal behavior in Thellier experiments. To address the second question, we reproduced slag samples in the laboratory under controlled magnetic fields and analyzed them using the same IZZI paleointensity technique used for the ancient slag. Microscopic analyses of the archaeological slag show that ferromagnetic phases occur as three-dimensional dendritic structures whose branches consist of submicronelongated particles. Magnetic analyses show that these dendrites behave as an assemblage of shape-controlled, single-domain-like particles and that theirmagnetization is thermoremanent.Weconclude that slagmaterial can be magnetically suitable for valid Thellier experiments. The laboratory-produced slag material demonstrated similar magnetic and mineralogical properties as the archaeological slag. IZZI experiments showed that nonlinear TRM acquisition, even at field strengths similar to Earth's, and TRM anisotropy are important factors to monitor during paleointensity studies of slag material. Anisotropy and non-linearity are probably related to the dendritic shape of the oxide grains. Intensity estimates derived from three laboratory-produced slag samples demonstrated accuracy to within ~5% after applying the required corrections.

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