Several paleomagnetic studies have been conducted on five Main Group pallasites: Brenham, Marjalahti, Springwater, Imilac, and Esquel. These pallasites have distinct cooling histories, meaning that their paleomagnetic records may have been acquired at different times during the thermal evolution of their parent body. Here, we compile new and existing data to present the most complete time-resolved paleomagnetic record for a planetesimal, which includes a period of quiescence prior to core solidification as well as dynamo activity generated by compositional convection during core solidification. We present new paleomagnetic data for the Springwater pallasite, which constrains the timing of core solidification. Our results suggest that in order to generate the observed strong paleointensities (∼65–95 μT), the pallasites must have been relatively close to the dynamo source. Our thermal and dynamo models predict that the Main Group pallasites originate from a planetesimal with a large core (>200 km) and a thin mantle (<70 km).

中文翻译：

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主要群陨石的时间分辨古地磁记录：大核、薄幔母体的证据

已经对五个主要群 pallasites 进行了几项古地磁研究：Brenham、Marjalahti、Springwater、Imilac 和 Esquel。这些pallasites具有不同的冷却历史，这意味着它们的古地磁记录可能是在其母体热演化过程中的不同时间获得的。在这里，我们汇编了新的和现有的数据，以提供最完整的时间分辨的小行星古地磁记录，其中包括核心凝固之前的一段静止期以及核心凝固过程中成分对流产生的发电机活动。我们提供了 Springwater pallasite 的新古地磁数据，它限制了岩心凝固的时间。我们的结果表明，为了产生观察到的强古强度（~65-95 μT），pallasites 必须相对靠近发电机源。我们的热模型和发电机模型预测，主群陨石起源于具有大核心（>200 公里）和薄地幔（<70 公里）的星子。