Abstract Scapolite, a volatile-bearing framework silicate, is found in pegmatites and leucosomes spatially associated with (ultra)-high pressure ((U)HP) eclogites in the Nordoyane domain of the Western Gneiss Region (WGR), Norway. The field relationships, petrology, and stable isotope geochemistry of scapolite-bearing rocks offer insights into the role of fluids in partial melting of WGR gneisses during the Scandian orogeny. Three types of scapolite pegmatite are distinguished based on mineralogy, texture, and scapolite chemistry. The most abundant Type 1 pegmatites are associated with dioritic to granodioritic migmatites, including local diatexite, developed in dioritic to granitoid orthogneisses. They are zoned from scapolite+quartz cores to hornblende+plagioclase rims, and concentrated in low-strain areas including boudin necks between disaggregated eclogite bodies. They are interpreted as late-stage differentiates of the (grano)dioritic migmatites, which also contain accessory scapolite in leucosomes. Type 2 and 3 pegmatites also contain coarse-grained scapolite but lack hornblende-rich selvages; Type 2 scapolites are texturally and chemically distinct from other varities. Type 1 and 3 pegmatites and host rock migmatites contain meionitic scapolite with high S- and C– contents, whereas Type 2 pegmatites contain marialitic scapolite with high Cl-contents. The pegmatites crystallised at amphibolite-facies conditions, ca. 750–800 °C and 1 GPa. Scapolites in Type 1, 2, and 3 pegmatites and host rock leucosomes share similar δ13C (−7.9 to −2.2‰) and δ34S (−1.1 to 5.7‰) compositions, interpreted to indicate a common source of volatile components. Comparison with literature data suggests a mantle source for the S and C in the scapolite-forming fluids. We propose that infiltration of mantle-derived fluids into the Baltican continental slab during subduction or the early stages of exhumation drove partial melting in subducted Baltican crust.

中文翻译：

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来自挪威西部片麻岩地区 Nordøyane 超高压域的方柱石伟晶岩：由地幔衍生流体的渗透驱动的部分熔融

摘要 方柱石是一种含挥发物的骨架硅酸盐，在挪威西部片麻岩地区 (WGR) 的 Nordoyane 域中与（超）高压 ((U)HP) 榴辉岩空间相关的伟晶岩和白质体中发现。含方柱石的岩石的场关系、岩石学和稳定同位素地球化学提供了对斯堪的亚造山运动期间流体在 WGR 片麻岩部分熔融中的作用的见解。根据矿物学、质地和方柱石化学可以区分三种类型的方柱石伟晶岩。最丰富的 1 型伟晶岩与闪长岩至花岗闪长岩混合岩伴生，包括在闪长岩至花岗岩类正片麻岩中发育的局部透闪岩。它们从方柱石+石英核到角闪石+斜长石边缘分区，并集中在低应变区域，包括离散榴辉岩体之间的布丁颈。它们被解释为（花岗岩）闪长混合岩的晚期分化，其在白质体中还含有辅助方柱石。2 型和 3 型伟晶岩也含有粗粒方柱石，但缺乏富含角闪石的边棱；2 型方柱石在结构和化学上与其他品种不同。1 型和 3 型伟晶岩和母岩混合岩含有 S- 和 C- 含量高的减数粒状方柱石，而 2 型伟晶岩含有高 Cl 含量的海长石方柱石。伟晶岩在角闪岩相条件下结晶，约。750–800 °C 和 1 GPa。1 型、2 型和 3 型伟晶岩中的方柱石和母岩白质体具有相似的 δ13C（-7.9 至 -2.2‰）和 δ34S（-1.1 至 5.7‰）组成，解释为指示挥发性成分的常见来源。与文献数据的比较表明形成方柱石的流体中 S 和 C 的地幔来源。我们认为，在俯冲或剥脱的早期阶段，地幔衍生的流体渗入波罗的海大陆板块导致了俯冲波罗的海地壳的部分熔融。