Cooling rate effects on the magnetization of volcanic rocks: Some implications for paleointensity determination
Effects of variation of cooling rate in the acquisition of thermoremanent magnetization (TRM) are analyzed on a suite of volcanic rocks. We use a three-step cooling rate experimental procedure applied at three distinct temperatures of TRM acquisition. Sixteen selected, thermally stable samples from...
| Autores: | , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2006 |
| País: | México |
| Institución: | UNIVERSIDAD NACIONAL AUTÓNOMA DE MÉXICO |
| Repositorio: | Geofísica Internacional |
| Idioma: | español inglés |
| OAI Identifier: | oai:revistagi.geofisica.unam.mx:article/224 |
| Acceso en línea: | http://revistagi.geofisica.unam.mx/index.php/RGI/article/view/224 |
| Access Level: | acceso abierto |
| Palabra clave: | Ritmo de enfriamiento paleointensidad rocas volcánicas magnetismo de rocas Cooling rate paleointensity volcanic rocks rock magnetism |
| Sumario: | Effects of variation of cooling rate in the acquisition of thermoremanent magnetization (TRM) are analyzed on a suite of volcanic rocks. We use a three-step cooling rate experimental procedure applied at three distinct temperatures of TRM acquisition. Sixteen selected, thermally stable samples from Late Quaternary lava flows were given a pTRM (300°C) at a slow cooling rate. The acquired intensities were measured at room temperature. A second pTRM was applied to the same specimens using a fast cooling rate, and the acquired intensities were measured at room temperature. Finally a third pTRM was induced as in the first step, using a slow cooling rate. The procedure was repeated to create pTRM’s at higher temperatures of 450° and 550°C. Corresponding percent variations between magnetization intensities acquired at slow-fast and at slow-slow cooling rates were calculated to investigate the influence of cooling rate on TRM intensity acquisition, and on TRM acquisition capacity. We observe values as high as 300 % in the former case (300 °C). Intensity of the ancient geomagnetic field obtained from volcanic rocks could be overestimated by at least 15% due to a variation in cooling rate normally employed in the laboratory, as compared to slower rates found in nature. |
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