Thermal Resolution of Unblocking Temperatures (TROUT): A Method for "Unmixing" Multi‐Component Magnetizations.

Some rocks contain multiple remanence "components," each of which preserves a record of a different magnetic field. The temperature ranges over which these remanence components unblock can overlap, making it difficult to determine their directions. We present a data analysis tool called Thermal Resolution Of Unblocking Temperatures (TROUT) that treats the process of thermal demagnetization as a function of temperature (or alternating field demagnetization as a function of coercivity). TROUT models the unblocking temperature/coercivity distributions of components in a demagnetization experiment, allowing these distributions to overlap. TROUT can be used to find the temperatures/coercivities over which paleomagnetic directions change and when two directional components overlap resulting in curved demagnetization trajectories. When applied to specimens given multi‐component Thermoremanent Magnetizations (TRMs) in the laboratory, the TROUT method estimates the temperature at which the partial TRMs were acquired to within one temperature step, even for specimens with significant overlap. TROUT has numerous applications: knowing the temperature at which the direction changes is useful for experiments in which the thermal history of a specimen is of interest (e.g., emplacement temperature of pyroclastic deposits, re‐heating of archaeological artifacts, reconstruction of cooling rates of igneous bodies). The ability to determine whether a single component or multiple components are demagnetizing at a given temperature is useful for choosing appropriate ranges of temperatures to use in paleodirection/intensity experiments. Finally, the width of the range of temperature overlap may be useful for inferring the composition, grain size and domain state of magnetic mineral assemblages. Plain Language Summary: Rocks can contain records of multiple magnetization events or "components," which can tell researchers about their history. For example, if a cooled lava flow was later reheated by another lava flowing over the top of it, it will have two magnetic components for each of the cooling events. Sometimes, these components can be hard to separate from one another correctly, making it difficult to reconstruct the rocks' history. In this paper, we present a data analysis tool called Thermal Resolution of Unblocking Temperatures (TROUT) which can analyze experimental data and automatically pick out the different components. We tested TROUT on several data sets where rocks were given multiple magnetic components in the laboratory, and it accurately picks out the correct components in most cases. These test cases indicate that TROUT will be useful as an automatic tool for many applications where researchers want to know about the history of rocks they are studying. Key Points: Multi‐component demagnetization experiments can exhibit curved demagnetization data which may be difficult to interpretThermal Resolution of Unblocking Temperatures (TROUT) is a method for resolving the temperature/coercivity distributions, directions and magnitudes of components in demagnetization dataTROUT accurately estimates the temperature specimens were reheated to in laboratory experiments with curved demagnetization data [ABSTRACT FROM AUTHOR]