In order to understand the effect of fluid-induced alteration on the Sm-Nd isotope systematic in apatite, a series of fluid/apatite reaction experiments, which involve reacting the well-characterized Durango fluorapatite with CO₂ ± CaCO₃-, NaF- or HCl ± CaCl₂-bearing solutions with a known ¹⁴³Nd/¹⁴⁴Nd ratio, were conducted at 800 or 600 °C at 200 MPa. In experiments involving CO₂-H₂O ± CaCO₃, the fluorapatite grains did not react with the solution, such that the Sm-Nd isotopic system was undisturbed. In experiments involving NaF, the fluorapatite grains were partially to completely altered. During the alteration process, REE mobilization was retarded via the coupled substitution Na⁺ + REE³⁺ = 2Ca²⁺ due to the high activity of Na in the fluid. Because the REE were not mobilized, the ¹⁴⁷Sm/¹⁴⁴Nd ratios remained constant. However, the ¹⁴³Nd/¹⁴⁴Nd ratios were slightly altered due to small degrees of Nd isotopic exchange between the fluid and fluorapatite. In experiments involving HCl ± CaCl₂, the fluorapatite grains were partially altered, and the REE were variably leached from the altered fluorapatite. Leaching of REE was accompanied by an increase in the ¹⁴⁷Sm/¹⁴⁴Nd ratio, which is related to the higher compatibility of Sm in the fluorapatite structure and the lower mobility of Sm in Cl-bearing fluids. Although the ¹⁴⁷Sm/¹⁴⁴Nd ratios were strongly affected, the ¹⁴³Nd/¹⁴⁴Nd ratios experienced only a small change, which is related to the slow rate of transport for Nd between reaction-front fluid and bulk fluid. In general, the experimental results indicate that fluid chemistry is the main factor controlling the response of the Sm-Nd isotopic system to fluid-induced alteration. The ¹⁴⁷Sm/¹⁴⁴Nd ratio of apatite can be highly modified, and in turn the Sm-Nd isotopic system is disturbed when the fluids are rich in ligands that are able to facilitate REE mobilization and fractionation. Therefore, a thorough evaluation of the fluid-rock history, along with the conjectured fluid chemistry, is necessary before using apatite Sm-Nd isotopes as geological indicators.

为了了解流体诱导的变化对磷灰石中Sm-Nd同位素的系统影响，进行了一系列流体/磷灰石反应实验，其中包括将特征明确的Durango氟磷灰石与CO ₂ ±CaCO _3-，NaF-或CO _2进行反应。在800或600°C和200 MPa下，以¹⁴³ Nd / ¹⁴⁴ Nd的已知比率添加HCl±CaCl ₂溶液。在涉及CO ₂ -H ₂ O±CaCO _{3的实验中}，氟磷灰石晶粒不与溶液反应，因此Sm-Nd同位素系统不受干扰。在涉及NaF的实验中，氟磷灰石晶粒被部分或完全改变。在蚀变过程中，由于流体中Na的高活性，通过偶合取代Na ⁺ + REE ³⁺ = 2Ca ²⁺阻碍了REE的动员。由于未动员稀土元素，因此¹⁴⁷ Sm / ¹⁴⁴ Nd的比率保持恒定。但是，由于流体和氟磷灰石之间的Nd同位素交换程度较小，因此¹⁴³ Nd / ¹⁴⁴ Nd的比率略有变化。在涉及HCl±CaCl _2的实验中，氟磷灰石晶粒发生了部分改变，并且从改变后的氟磷灰石中浸出了REE。稀土元素的浸出伴随着¹⁴⁷ Sm / ¹⁴⁴ Nd比的增加，这与氟磷灰石结构中Sm的较高相容性和含Cl流体中Sm的较低迁移率有关。尽管¹⁴⁷ Sm / ¹⁴⁴ Nd的比值受到严重影响，但¹⁴³ Nd / ¹⁴⁴Nd比率仅发生很小的变化，这与Nd在反应前沿流体和本体流体之间的缓慢传输速率有关。通常，实验结果表明，流体化学是控制Sm-Nd同位素系统对流体诱导的变化的响应的主要因素。磷灰石的¹⁴⁷ Sm / ¹⁴⁴ Nd比可以被高度修饰，并且当流体中富含能够促进REE动员和分离的配体时，Sm-Nd同位素系统就会受到干扰。因此，在使用磷灰石Sm-Nd同位素作为地质指示剂之前，有必要对流体岩石历史以及推测的流体化学进行全面评估。