Neogene dolomites are common in island settings, and they have been used to understand the complex processes of dolomitization. The island of Bonaire was one of the first locations where the concept of reflux dolomitization was applied. Given this historical significance, here we re-evaluate the importance and nature of reflux using a previously unstudied set of outcrops in Bonaire. Mio-Pliocene units in Seru Grandi in northwestern Bonaire show well-defined bodies of dolomite that extend along clinoform surfaces beneath a subhorizontal erosional unconformity. The dolomite distribution suggests early dolomitization as a result of fluids moving downwards through a succession of subtidal facies, as expected from the reflux model. However, non-stoichiometric compositions, weak ¹⁸O enrichment, low trace element concentrations and the sedimentological context of the dolomites suggest that refluxing fluid was more likely to be mesohaline in composition rather than hypersaline as previously proposed. In addition, our findings suggest that the fluids did not dolomitize the succession uniformly, but rather elongate bodies of dolomite were developed within selected clinoforms through different events. This variability may be due to temporal changes in the flux, chemistry of reactive fluids and textural changes of original sediment, whereas downdip trends may reflect evolution of magnesium exchange efficiency with distance from the brine source and reactivity of the rock.

新近系白云岩在岛屿环境中很常见，它们已被用来了解白云石化的复杂过程。博内尔岛是最早采用反流白云石化概念的地区之一。考虑到这一历史意义，在这里我们使用以前未研究的博奈尔岛露头集重新评估回流的重要性和性质。博内尔岛西北部Seru Grandi的Mio-Pliocene单元显示出清晰的白云岩体，它们沿水平下侵蚀不整合面下方的斜交形表面延伸。如回流模型所预期的，白云岩的分布表明早期白云石化是由于流体通过一系列潮下相向下移动所致。然而，非化学计量组成，弱¹⁸O富集，低痕量元素浓度和白云岩的沉积学背景表明，回流流体的成分更可能是中卤，而不是先前提出的高盐。此外，我们的发现表明，这些流体不能均匀地白云石化演替，而是通过不同的事件在选定的斜形岩中形成了细长的白云岩体。这种变化可能是由于通量的时间变化，反应性流体的化学性质以及原始沉积物的质地变化所致，而下倾趋势可能反映了镁交换效率随距盐水源的距离和岩石反应性的变化。