Concretionary nodule formation is a subaerial process common to both Earth and Mars. The resulting nodules contain information about particular paleoclimatic cycles. However, their genesis and the mineralogical and geochemical effects of climate change on nodule formation have not well constrained so far, limiting their applications to paleoclimatic reconstruction. Since the late Pleistocene, the Qaidam Basin in the northern Tibetan Plateau has been subjected to extreme drought, resulting in a vast area of playas with a diverse eolian morphology that resembles the surface of Mars. Recently, a massive carbonate nodule field was discovered on an ancient diluvial platform in the northwest Qaidam Basin. Detailed analyses revealed that an early period of aragonite precipitation (251 kyr before present) provided seeding material for the later growth of nodule bodies during a period of ∼100 kyr. The highly unstable hydrologic and geochemical conditions during this period led to the growth of high‐Mg calcite zones with varied elemental contents (e.g., Mn), crystal patterns, and porosity levels within the nodule bodies. The δ¹³C and δ¹⁸O values increased by 3‰ and 6‰, respectively, from the cores to the rims of the measured nodules. Rayleigh distillation model suggested that 50% of the H₂O and 25% of the dissolved CO₂ had been removed during nodule growth in response to the drought. These results show that nodules formed in hyperarid environments can record important hydrologic information, which may provide insights for paleo‐environment studies on Mars by examining the formation of nodules in Gale Crater.

中文翻译：

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青藏高原北部柴达木西北部高干旱地区碳酸盐岩结核的大规模沉积

结节性结节形成是地球和火星共同的空中过程。形成的结核包含有关特定古气候周期的信息。然而，到目前为止，它们的成因以及气候变化对结核形成的矿物学和地球化学作用还没有得到很好的限制，从而限制了它们在古气候重建中的应用。自更新世晚期以来，青藏高原北部的柴达木盆地遭受了极度干旱，导致大面积的普拉亚斯风化形态类似于火星表面。最近，在柴达木盆地西北部的一个古老的洪积台地上发现了一块巨大的碳酸盐结核田。详细的分析表明，文石的早期沉淀（之前存在251 kyr）为约100 kyr期间的结节体后期生长提供了播种材料。在此期间，高度不稳定的水文和地球化学条件导致了高镁方解石带的生长，其方解石体内的元素含量（例如，Mn），晶体图案和孔隙度水平各不相同。δ¹³ C和δ ^18个O值增加3‰和6‰，分别从芯到所测量的结节的轮辋。瑞利蒸馏模型表明，响应于干旱，在结核生长期间已除去了50％的H ₂ O和25％的溶解的CO ₂。这些结果表明，在高干旱环境中形成的结核可以记录重要的水文信息，这可以通过检查大风火山口中的结核形成来为火星的古环境研究提供见识。