Magnetite magnetofossils record biogeochemical remanent magnetization in hydrogenetic ferromanganese crust
Magnetite magnetofossils record biogeochemical remanent magnetization in hydrogenetic ferromanganese crust
复制标题
磁铁矿磁化石记录了水化铁锰地壳中的生物地球化学剩磁
作者：
Yuan Wei;Zhou Huaiyang;Yang Zhenyu;James R. Hein;Yang Qunhui
铁锰结壳中保存的自然反磁化和地磁极性反转记录以及高分辨率磁性地层学分析的应用已得到成功的证实。然而，由于含铁沉淀物或矿物被认为是氧化物和/或氢氧化物沉淀从环境氧化海水或碎屑矿物，铁磁性矿物的磁性和成因机制仍然存在争议，此外，NRM的起源不清楚。在这里，我们表明，纳米级磁铁矿晶体中发现的铁锰结壳从太平洋和中国南海的磁小体化石的基础上，其狭窄的尺寸范围，链排列，化学纯度和晶体学的完善，如透射电子显微镜所示。此外，我们的新数据，从岩石的磁性和电子顺磁共振分析，结合以前报道的微磁性地层序列，表明趋磁细菌和他们的尸体遗骸有助于地球化学的铁锰结壳的再磁化。此外，这些结果为以前未被认识到的深海铁的地球化学循环途径提供了证据。
Records of natural remanent magnetization (NRM) and geomagnetic polarity reversals preserved within ferromanganese (Fe-Mn) crusts, together with the application of fine-resolution magnetostratigraphic analysis, have been successfully demonstrated. However, because Fe-bearing precipitates or minerals are thought to be either oxides and/or hydroxides precipitated from ambient oxic seawater or detrital minerals, the magnetic properties of the ferromagnetic minerals and the genetic mechanisms remain controversial; moreover, the origin of the NRM is unclear. Here, we show that nanometer-scale magnetite crystals found in Fe-Mn crusts from the Pacific Ocean and South China Sea are magnetosome fossils based on their narrow size range, chain arrangement, chemical purity, and crystallographic perfection, as indicated by transmission electron microscopy. Furthermore, our new data from rock magnetic and electron paramagnetic resonance analyses, combined with a previously reported micro-magnetostratigraphic sequence, indicate that magnetotactic bacteria and their post-mortem remains contribute to a biogeochemical remanent magnetization of Fe-Mn crusts. In addition, the results provide evidence for a previously unappreciated pathway for the biogeochemical cycling of iron in the deep ocean.