Magmatic Ni–sulfide ore deposits are generally associated with basaltic to komatiitic igneous rocks that originate by partial melting of the mantle, which is usually modelled as a uniform four-phase peridotite. Existing models accept that the key metal contributors to mantle melts are olivine (Ni) and sulfide (Cu, platinum group elements (PGEs) and minor Ni). However, melting in the mantle commonly begins in volumetrically minor mantle assemblages such as hydrous pyroxenites that occur as veins in the peridotite mantle, which are rich in the hydrous minerals phlogopite, amphibole and apatite. The contribution of hydrous pyroxenites to the metal endowment of mantle melts may have been underestimated or overlooked in the past, partly because evidence of their input is partially erased as melting intensifies to involve peridotite.

Here, we compile new results from experiments and natural rocks which demonstrate that the hydrous minerals such as phlogopite, amphiboles and apatite all have high partition coefficients for Ni (3–20) and may be important repositories for Ni in mantle sources of igneous rocks. This implies that hydrous minerals hosted in metasomatic mantle lithologies such as hydrous pyroxenites may be important contributors to some magmatic Ni–sulfide ore systems. Hydrous pyroxenites contain hydrous minerals in large modal abundances up to 30–40 vol% in addition to clinopyroxene and a few vol% of oxide phases, such as rutile and ilmenite. These mantle lithologies are commonly associated with cratonic and continental regions, where low-temperature, low-degree volatile-rich melts commonly modify lithospheric peridotite mantle, depositing variable hydrous pyroxenites.

The lower melting temperatures of hydrous minerals in hydrous pyroxenite lithologies also means that the generation of magmatic ore deposits may not require a major thermal perturbation such as a plume, as the melting temperatures of hydrous pyroxenites lie around 300–350 °C lower than dry peridotites. Partial melts of hydrous pyroxenite are more voluminous at low temperatures than melts of peridotite would be. Furthermore, it is argued in the following that they would contain similar or even higher concentrations of Ni. Thus, predictive exploration models should consider domains of the lithospheric mantle where hydrous pyroxenites may be localised and concentrated, as they may have been episodically melted throughout the long-lived geological evolution of cratonic blocks, yielding Ni-rich melts that may be hosted in conduits of varying size and geometry at various crustal levels.

岩浆镍硫化物矿床通常与玄武岩到科马提岩火成岩有关，这些火成岩起源于地幔的部分熔融，通常被建模为均匀的四相橄榄岩。现有模型认为，地幔熔体的关键金属贡献者是橄榄石 (Ni) 和硫化物（Cu、铂族元素 (PGE) 和少量 Ni）。然而，地幔中的熔化通常始于体积较小的地幔组合，例如橄榄岩地幔中以矿脉形式出现的含水辉石岩，富含含水矿物金云母、角闪石和磷灰石。水合辉石岩对地幔熔体金属禀赋的贡献在过去可能被低估或忽视，部分原因是随着熔融加剧涉及橄榄岩，其输入的证据被部分抹去。

在这里，我们汇总了实验和天然岩石的新结果，表明金云母、角闪石和磷灰石等含水矿物都具有高的镍分配系数（3-20），可能是火成岩地幔源中镍的重要储存库。这意味着交代地幔岩性中的含水矿物（例如含水辉石岩）可能是某些岩浆镍硫化物矿石系统的重要贡献者。除了单斜辉石和少量 vol% 的氧化物相（例如金红石和钛铁矿）外，含水辉石岩还含有高达 30-40 vol% 的大模态丰度的含水矿物。这些地幔岩性通常与克拉通和大陆地区有关，这些地区的低温、低度、富含挥发分的熔体通常会改变岩石圈橄榄岩地幔，沉积可变的含水辉石岩。

含水辉石岩岩性中含水矿物的较低熔化温度也意味着岩浆矿床的生成可能不需要诸如羽流之类的主要热扰动，因为含水辉石岩的熔化温度比干燥橄榄岩低约 300–350 °C 。水合辉石岩的部分熔体在低温下比橄榄岩的熔体体积更大。此外，下文认为它们将含有相似甚至更高浓度的镍。因此，预测勘探模型应考虑岩石圈地幔的区域，其中含水辉石岩可能局部化和集中，因为它们可能在克拉通块体的长期地质演化过程中不定期地熔化，产生可能存在于管道中的富镍熔体在不同地壳层面具有不同的尺寸和几何形状。