The building blocks of Titan and Enceladus are believed to have formed in a late-stage circumplanetary disk (CPD) around Saturn. Evaluating the evolution of the abundances of volatile species in this disk as a function of the migration, growth, and evaporation of icy grains is then of primary importance to assess the origin of the material that eventually formed these two moons. Here we use a simple prescription of Saturn’s CPD in which the location of the centrifugal radius is varied, to investigate the time evolution of the icelines of water ice, ammonia hydrate, methane clathrate, carbon monoxide, and dinitrogen pure condensates. To match their compositional data, the building blocks of both moons would have had to form in a region of the CPD situated between the icelines of carbon monoxide and dinitrogen at their outer limit, and the iceline of methane clathrate as their inner limit. We find that a source of dust at the location of centrifugal radius does not guarantee the replenishment of the disk in the volatiles assumed to be primordial in Titan and Enceladus. Only simulations assuming a centrifugal radius in the range 66–100 Saturnian radii allow for the formation and growth of solids with compositions consistent with those measured in Enceladus and Titan. The species are then able to evolve in solid forms in the system for longer periods of time, even reaching an equilibrium, thus favoring the formation of Titan and Enceladus’s building blocks in this region of the disk.

土卫六和土卫二的构造块被认为是在土星周围的一个晚期行星行星盘（CPD）中形成的。因此，根据冰粒的迁移，生长和蒸发来评估该盘中挥发性物种的丰度演变对于评估最终形成这两个卫星的物质的起源至关重要。在这里，我们使用土星CPD的简单处方（其中离心半径的位置发生变化）来调查水冰，氨水合物，甲烷包合物，一氧化碳和纯二氮冷凝物的冰线的时间演变。为了匹配它们的成分数据，必须在CPD的外边界一氧化碳和二氮冰线之间的区域中形成两个卫星的构造块，甲烷的冰线笼罩着它们的内在极限。我们发现，在离心半径位置处的尘埃来源不能保证在Titan和Enceladus中被认为是原始的挥发物中磁盘的补充。只有模拟假设离心半径在66–100土星半径范围内，才能形成和生长与土卫二和土卫六测量的成分一致的固体。然后，这些物种能够在系统中以固态形式演化更长的时间，甚至达到平衡，从而有利于在该磁盘区域形成Titan和Enceladus的构造块。我们发现，在离心半径位置处的尘埃来源不能保证在Titan和Enceladus中被认为是原始的挥发物中磁盘的补充。只有模拟假设离心半径在66–100土星半径范围内，才能形成和生长与土卫二和土卫六测量的成分一致的固体。然后，这些物种能够在系统中以固态形式演化更长的时间，甚至达到平衡，从而有利于在该磁盘区域形成Titan和Enceladus的构造块。我们发现，在离心半径位置处的尘埃来源不能保证在Titan和Enceladus中被认为是原始的挥发物中磁盘的补充。只有在假定离心半径在66-100土星半径范围内的模拟条件下，才能形成和生长与土卫二和土卫六中测得的成分一致的固体。然后，这些物种能够在系统中以固态形式演化更长的时间，甚至达到平衡，从而有利于在该磁盘区域形成Titan和Enceladus的构造块。