Apatite may be a common accessory mineral in coal seams, but interpretation of its origins can vary from syndepositional mineral detritus, early precipitation during diagenesis, and post coalification precipitation and replacement from hydrothermal or other fluids. It is hypothesised that paragenesis is reflected in the modes of occurrence in different stratigraphic units of the Late Permian in the Bowen Basin. From samples analysed in this study, apatite in the youngest unit, the Rangal Coal Measures, most commonly occurs as pore-apatites (i.e. apatites infilling preserved plant cell cavities of fusinite and semifusinite macerals and commonly associated with kaolinite) and less commonly as fracture-apatites (i.e. apatites infilling micro-fractures) and detrital-apatites intermixed with the organic coal layers (Detrital-B). In the tuffaceous Fort Cooper Coal Measures and equivalents, apatite occurs more commonly as detrital-apatites intermixed with the lithic layers (Detrital-A) (Detrital. Within the basal unit, the Moranbah Coal Measures and its equivalents, the mode is commonly encrusting-apatites (i.e. small apatite crystallites encrusting silicate minerals). Almost all apatites in the coal samples tested by electron microprobe microanalysis (EPMA), regardless of stratigraphic location and mode, are fluorapatite. Although there are some locality-driven enrichments, the minor and trace-element chemistry vary more so by mode of occurrence. For comparison, apatites from dykes intersecting the coal measures and from tuffs were also added to the study. These had lower fluorine (F) but measurable chlorine (Cl) contents and are enriched in light rare earth elements (LREE), similar to the Durango apatite that is of magmatic origins. Most of the detrital-A apatites are also enriched in LREE similar to the tuff-apatites, but with variable enrichment in the rare earth and yttrium elements. Detrital-B apatites have minimal Cl but also show the magmatic LREE trend. The pore- and fracture-apatites exhibited two trends. In the samples from tuffaceous coals (e.g., Fort Cooper Coal Measures), the pore- and fracture apatites tended to follow the magmatic LREE trend. In the Rangal Coal Measures, the pore- and fracture-apatites have elevated F contents, minimal Cl contents and depleted LREE contents (or Middle REE enrichment). Depletion of LREE could occur through leaching in an acidic environment, which is suggested by the abundance of kaolinite. Apatite precipitates under more neutral conditions although pore-apatites are commonly considered “early” and fracture-apatites “late” or post coalification. Their geochemical similarity suggests they have similar fluid origins and/or timing, with geothermal fluids moving through the porosity afforded by the structured inertinite group macerals and fractures. Verification of that geothermal source still requires further work and a technique that can analyse the isotopic composition—e.g., carbon (¹³C/¹²C), oxygen (¹⁸O/¹⁶O) and strontium (⁸⁷Sr/⁸⁶Sr)—of micron-sized crystals in situ.

磷灰石可能是煤层中常见的辅助矿物，但是其来源的解释可能与沉积矿物碎屑，成岩过程中的早期沉淀以及煤化后的沉淀以及水热流体或其他流体的替代有关。假设在Bowen盆地晚二叠世不同地层单元的发生方式中反映了共生作用。从这项研究中分析的样品中，最年轻的单元（Rangal Coal措施）中的磷灰石最常以孔隙磷灰石的形式出现（即，磷灰石充填了Fusinite和Semi-fusinite的矿物中保留的植物细胞腔，并且通常与高岭石相关）。磷灰石（即填充微裂缝的磷灰石）和碎屑磷灰石与有机煤层（碎屑B）混合在一起。这些具有较低的氟（F）但可测量的氯（Cl）含量，并富含轻稀土元素（LREE），类似于岩浆来源的杜兰戈磷灰石。与碎屑磷灰石相似，大多数碎屑A磷灰石也富含LREE，但稀土元素和钇元素的富集程度却不同。碎屑B磷灰石具有最小的Cl，但也显示出岩浆LREE趋势。孔隙磷灰石和断裂磷灰石表现出两种趋势。在含凝性煤的样品中（例如Fort Cooper煤系），孔隙和裂缝性磷灰石趋向于沿岩浆LREE趋势。在Rangal Coal措施中，孔隙和裂缝性磷灰石具有较高的F含量，最小的Cl含量和贫乏的LREE含量（或中等REE富集）。在酸性环境中浸出可能会导致LREE耗尽，高岭土的丰富性暗示了这一点。磷灰石在更中性的条件下析出，尽管通常将孔磷灰石视为“早期”，而将断裂磷灰石“视为晚期”或后煤化。它们的地球化学相似性表明它们具有相似的流体成因和/或时间，地热流体穿过结构化的惰化岩群的微晶岩和裂缝所提供的孔隙度。验证该地热源仍需要进一步的工作，并且需要一种能够分析同位素组成的技术，例如碳（地热流体穿过结构化的惰质岩层和裂缝所提供的孔隙度。验证该地热源仍需要进一步的工作，并且需要一种能够分析同位素组成的技术，例如碳（地热流体穿过结构化的惰质岩层和裂缝所提供的孔隙度。验证该地热源仍需要进一步的工作，并且需要一种能够分析同位素组成的技术，例如碳（原位为微米级晶体的¹³ C / ¹² C），氧气（¹⁸ O / ¹⁶ O）和锶（⁸⁷ Sr / ⁸⁶ Sr）。