Iron is the most abundant redox-sensitive element on the Earth's surface, and the oxidation state, mineral host, and crystallinity of Fe-rich phases in sedimentary systems can record details of water-rock interactions and environmental conditions. However, we lack a complete understanding of how these Fe-rich materials are created, maintained, and oxidized or reduced in sedimentary environments, particularly those with mafic sources. The catchment of Lake Towuti, Indonesia, is known to contain a wide range of abundant crystalline Fe oxide, and the lake has a long sedimentary history. Here, we study a ∼100 m long drill core from the lake to understand patterns of sedimentation and how young iron-rich sediments are affected by diagenesis through geologic time. We use visible/near infrared and Mössbauer spectroscopy, X-ray diffraction, bulk chemistry measurements, and statistical cluster analysis to characterize the core sediment. We find that the core sediment can be divided into three statistically different zones dominated by Mg serpentine, Al clay minerals, and Fe²⁺ carbonate, respectively. The entire core is rich in nanophase Fe, and elemental correlations and Fe mineralogy vary between these zones. The nanophase Fe is highly complex with both ferrous and ferric components, and contributes to, but does not dictate, variations in sediment color. We propose that the distinctive zones are the result of structural basin changes (notably river capture and shifting drainage patterns), and diagenetic overprinting caused by deep burial of reactive Fe. This complex record has implications for disentangling depositional and diagenetic trends in other mafic lacustrine systems.

中文翻译：

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印度尼西亚 Towuti 湖 100 m 钻芯中的铁矿物学和沉积物颜色反映了集水区和成岩条件

铁是地球表面最丰富的氧化还原敏感元素，沉积系统中富铁相的氧化态、矿物宿主和结晶度可以记录水岩相互作用和环境条件的细节。然而，我们对这些富含铁的材料如何在沉积环境中产生、维持、氧化或还原缺乏完整的了解，尤其是在那些具有镁铁质来源的环境中。众所周知，印度尼西亚 Towuti 湖的流域含有广泛丰富的结晶氧化铁，该湖的沉积历史悠久。在这里，我们研究了湖中约 100 米长的钻芯，以了解沉积模式以及年轻的富含铁的沉积物如何通过地质时间受到成岩作用的影响。我们使用可见光/近红外和穆斯堡尔光谱、X 射线衍射、大量化学测量和统计聚类分析来表征核心沉积物。我们发现岩心沉积物可以分为三个统计上不同的区域，以 Mg 蛇纹石、Al 粘土矿物和 Fe 为主²⁺碳酸盐，分别。整个核心富含纳米相铁，这些区域之间的元素相关性和铁矿物学各不相同。纳米相 Fe 与亚铁和三价铁成分高度复杂，有助于但不决定沉积物颜色的变化。我们认为独特的区域是构造盆地变化（特别是河流捕获和排水模式转移）以及反应性铁的深埋引起的成岩叠印的结果。这一复杂的记录对解开其他镁铁质湖泊系统中的沉积和成岩趋势具有重要意义。