Abstract
The Thellier method is classical but is still regarded as the most reliable method for paleointensity determination. Recently, many types of additional protocols have been advocated to ensure reliability and make laboratory work more laborious and time-consuming. An automated system coupling a magnetometer and an electric furnace is now of prime importance to cope with the increasing demand. Here, we describe a graphics-based program for controlling a fully automatic system combining a spinner magnetometer and a thermal demagnetizer, and for acquiring and processing the magnetization data. A single fluxgate sensor, which can measure the vector magnetization by spinning and translating a standard-sized 1-in. specimen, was calibrated with a rotatable reference specimen that can make the magnetization parallel or perpendicular to the spinning axis. By placing a cooling chamber between the furnace and the sensor for the updated system, the specimen can be heated up more efficiently to ensure an identical thermal history for the double heatings of the Thellier method. The direction of the vector magnetization was precisely obtained as well as the intensity, the results being comparable with those from an ordinary spinner magnetometer. We present an application of the fully automatic system for a Thellier measurement on a recent lava flow, which took about 24 h for approximately ten-step double heatings without manual operation.
Highlights
With the increasing interest in past geomagnetic field intensities, much more reliable and abundant paleointensity determinations are required in recent years (e.g., Dunlop 2011)
Concluding remarks An automated three-component spinner magnetometer equipped with a thermal demagnetizer TSpin is utilized for routine operations for Thellier paleointensity experiments with a LabVIEW controlling software
A Thellier measurement that is very laborious and time-consuming can be performed overnight without any user intervention. This enables a larger number of Thellier measurements to be made, in which uninterpretable results are often obtained
Summary
With the increasing interest in past geomagnetic field intensities, much more reliable and abundant paleointensity determinations are required in recent years (e.g., Dunlop 2011). In an ordinary spinner magnetometer with a fluxgate sensor, a specimen is rotated about a single axis, and the orientation needs to be manually changed for measuring the three components of magnetization. A standard-sized paleomagnetic specimen is translated along the spinning axis; the axial magnetization can be measured as well as the in-plane components perpendicular to the spinning axis.
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