Cave environment allows long-term processes of rock weathering and chemical deposition that cannot occur on Earth surface directly exposed to meteoric and external biochemical agents. Apart from the common carbonate speleothems, chemical precipitation from infiltration water can also produce phosphate-rich formations usually occurring as parietal dark crusts or spheroidal nodules. Despite the potential purposes of these kind of deposits as paleoenvironmental proxies, they have been still poorly investigated by cave scientists. Monte Corchia cave (NW Tuscany, Central Italy) is one of the most studied caves in the world, particularly for paleoclimate reconstructions from calcite speleothems. Several samples of parietal formations were collected in relict phreatic and epiphreatic passages at different altitudinal levels that reflect different evolution stages of this large cave system. Samples were analyzed by diffractometry and SEM-EDS possibly revealing the occurrence of hydroxyapatite or fluorapatite mixed with Fe/Mn incrustations and allogenic clastic particles. Crusts often cover the entire section of relict phreatic or epiphreatic passages and can be related to precipitation during waterfilled phases. Phosphate nodules are almost entirely composed by hydroxyapatite or fluoroapatite and could be the result of long-term chemical (or bio-chemical) precipitation in air-filled environments.

中文翻译：

---

Alpi Apuane（意大利中部）Monte Corchia洞穴中富含磷酸盐的顶壳和结节的组成和结构

洞穴环境允许岩石风化和化学沉积的长期过程，而直接暴露于陨石和外部生化试剂的地球表面则不会发生这种情况。除了常见的碳酸盐鞘脂，渗透水的化学沉淀还可以产生富含磷酸盐的地层，通常以壁顶暗结皮或球状结节的形式出现。尽管这类沉积物有可能作为古环境的替代物，但洞穴科学家对其进行的研究仍然不多。Monte Corchia洞穴（意大利中部西北托斯卡纳）是世界上研究最多的洞穴之一，尤其是用于方解石蛇眼石的古气候重建。在不同海拔高度的遗留潜水道和上传道中收集了一些顶叶形成的样本，这些高度反映了这个大型洞穴系统的不同演化阶段。通过衍射分析和SEM-EDS分析样品，可能显示出混合有Fe / Mn结壳和同质碎屑颗粒的羟基磷灰石或氟磷灰石的存在。结壳通常覆盖着遗物潜水道或上生通道的整个部分，并且可能与充水阶段的降水有关。磷酸盐结核几乎完全由羟基磷灰石或氟磷灰石组成，并且可能是在充满空气的环境中长期化学（或生化）沉淀的结果。通过衍射分析和SEM-EDS分析样品，可能显示出混合有Fe / Mn结壳和同质碎屑颗粒的羟基磷灰石或氟磷灰石的存在。结壳通常覆盖着遗物潜水道或上生通道的整个部分，并且可能与充水阶段的降水有关。磷酸盐结核几乎完全由羟基磷灰石或氟磷灰石组成，并且可能是在充满空气的环境中长期化学（或生化）沉淀的结果。通过衍射分析和SEM-EDS分析样品，可能显示出混合有Fe / Mn结壳和同质碎屑颗粒的羟基磷灰石或氟磷灰石的存在。结壳经常覆盖着遗物潜水道或上生通道的整个部分，并且可能与充水阶段的降水有关。磷酸盐结核几乎完全由羟基磷灰石或氟磷灰石组成，并且可能是在充满空气的环境中长期化学（或生化）沉淀的结果。