The lower crustal domain of the Ivrea‐Verbano Zone (NW Italy) hosts five ~300‐m‐wide pipe‐like ultramafic intrusions that are metasomatized and exhibit Ni‐Cu‐PGE sulphide mineralization. To better constrain the role of metasomatism in the ore genesis, we studied the best‐preserved pipe at Valmaggia which was emplaced 249 Myrs ago. Phlogopite ⁴⁰Ar/³⁹Ar analyses show that the pipe was infiltrated by metasomatic fluids derived from the subcontinental lithospheric mantle (SCLM) in two pulses at ~208 Ma and ~189 Ma which introduced sulphides into the pipe. Consequently, the pipe repeatedly acted as a preferred path for mass transfer from the SCLM into the lower crust over >60 Myrs (i.e., emplacement to second metasomatic pulse). Uplifted block margins, such as the Ivrea‐Verbano Zone, are potentially important exploration targets for magmatic sulphides. We argue that exploration strategies should focus on structures such as pipes that can focus metasomatic agents during ascent through the lithosphere.

中文翻译：

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关于通过岩石圈的长期质量转移在下地壳中形成岩浆状硫化物系统的过程：意大利伊夫雷亚韦尔巴诺区瓦尔马吉亚管道的见解

Ivrea-Verbano区（意大利西北部）的下地壳区域有5个约300米宽的管状超镁铁质侵入体，这些侵入体已交代并表现出Ni-Cu-PGE硫化物矿化作用。为了更好地限制交代作用在矿石成因中的作用，我们研究了Valmaggia保存最完好的管子，该管子放置于249 Myrs之前。金云母⁴⁰ Ar / ³⁹氩气分析表明，该管道被亚大陆岩石圈地幔（SCLM）衍生的交代流体以〜208 Ma和〜189 Ma的两个脉冲渗透，从而将硫化物引入了管道。因此，该管反复地作为质量从SCLM传递到> 60 Myrs的下地壳的首选路径（即，放置到第二交代脉冲）。Ivrea-Verbano带等区块边缘的隆起可能是岩浆硫化物的潜在重要勘探目标。我们认为勘探策略应该集中在诸如管道之类的结构上，这些结构可以在岩石圈上升过程中集中变质作用剂。