Fault‐controlled hydrothermal dolomitisation in tectonically complex basins can occur at any depth and from different fluid compositions, including ‘deep‐seated’, ‘crustal’ or ‘basinal’ brines. Nevertheless, many studies have failed to identify the actual source of these fluids, resulting in a gap in our knowledge on the likely source of magnesium of hydrothermal dolomitisation. With development of new concepts in hydrothermal dolomitisation, the study aims in particular to test the hypothesis that dolomitising fluids were sourced from either seawater, ultramafic carbonation or a mixture between the two by utilising the Cambrian Mount Whyte Formation as an example. Here, the large‐scale dolostone bodies are fabric‐destructive with a range of crystal fabrics, including euhedral replacement (RD1) and anhedral replacement (RD2). Since dolomite is cross‐cut by low amplitude stylolites, dolomitisation is interpreted to have occurred shortly after deposition, at a very shallow depth (<1 km). At this time, there would have been sufficient porosity in the mudstones for extensive dolomitisation to occur, and the necessary high heat flows and faulting associated with Cambrian rifting to transfer hot brines into the near surface. While the δ18Owater and 87Sr/86Sr ratios values of RD1 are comparable with Cambrian seawater, RD2 shows higher values in both parameters. Therefore, although aspects of the fluid geochemistry are consistent with dolomitisation from seawater, very high fluid temperature and salinity could be suggestive of mixing with another, hydrothermal fluid. The very hot temperature, positive Eu anomaly, enriched metal concentrations, and cogenetic relation with quartz could indicate that hot brines were at least partially sourced from ultramafic rocks, potentially as a result of interaction between the underlying Proterozoic serpentinites and CO2‐rich fluids. This study highlights that large‐scale hydrothermal dolostone bodies can form at shallow burial depths via mixing during fluid pulses, providing a potential explanation for the mass balance problem often associated with their genesis.

中文翻译：

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评估新的断层控制的热液白云石化模型：来自加拿大西部沉积盆地寒武纪白云岩的见解

在构造复杂的盆地中，断层控制的热液白云石化可以发生在任何深度，来自不同的流体成分，包括“深层”、“地壳”或“盆地”卤水。然而，许多研究未能确定这些流体的实际来源，导致我们对热液白云石化镁的可能来源的认识存在空白。随着热液白云石化新概念的发展，该研究特别旨在以寒武纪怀特山地层为例，验证白云石化流体来源于海水、超基性碳酸盐化或两者的混合物的假设。在这里，大型白云岩体具有一系列晶体结构的结构破坏性，包括自面体置换（RD1）和正面体置换（RD2）。由于白云岩被低振幅缝合线横切，白云石化被解释为在沉积后不久发生在非常浅的深度（<1 公里）。此时，泥岩中将有足够的孔隙度以发生广泛的白云石化，并且与寒武纪裂谷相关的必要的高热流和断层将热卤水转移到近地表。虽然 RD1 的 δ18Owater 和 87Sr/86Sr 比值与寒武纪海水相当，但 RD2 在这两个参数中都显示出更高的值。因此，尽管流体地球化学的各个方面与海水的白云石化一致，但非常高的流体温度和盐度可能暗示与另一种热液流体混合。非常热的温度，正 Eu 异常，富集的金属浓度，与石英的共生关系表明，热卤水至少部分来自超基性岩，这可能是下伏元古代蛇纹岩和富含 CO2 的流体相互作用的结果。这项研究强调，大型热液白云岩体可以通过流体脉冲期间的混合在浅埋深处形成，为通常与其成因相关的质量平衡问题提供了潜在的解释。