The Seiland Igneous Province (SIP) is a large province of mafic and ultramafic (UM) complexes interpreted to be relics of a giant plumbing system feeding the Ediacaran Central Iapetus Magmatic Province. The Reinfjord Ultramafic Complex (RUC) is one of the four major ultramafic complexes of the SIP. The RUC has a younger dunite core surrounded by wehrlite and lherzolite embedded in country rocks consisting of layered gabbros with sub-horizontal layering and metamorphosed sedimentary rocks. Here, we develop a 3D subsurface model for the RUC using high-resolution magnetic and gravity data and extensive petrophysical measurements from oriented surface samples and drill core samples. Our model indicates that the RUC narrows in depth, extending a minimum of 1.4 km below sea level, and plunges eastwards below the country rock. This model allows us to decipher the lithologic heterogeneities, and the depth and lateral extent of ultramafic rocks, which we interpret in the context of the geologic history of the area. The RUC is spatially separated from other UM complexes of the SIP and the result of this study indicates a smaller depth extent. Combining these findings with the previously reported distribution of the SIP rocks based on the regional gravity data, we propose that the uplift of the crustal block hosting the RUC is larger than for ultramafic complexes in the northwestern part of the SIP.

中文翻译：

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根据高分辨率磁力、重力和岩石物理数据研究大型岩浆管道系统根区的结构：Reinfjord 超镁铁质复合体

塞兰火成岩省 (SIP) 是一个由镁铁质和超镁铁质 (UM) 杂岩组成的大省，被解释为为埃迪卡拉中央土卫八岩浆省提供水源的巨型管道系统的遗迹。 Reinfjord 超镁铁杂岩 (RUC) 是 SIP 的四大超镁铁杂岩之一。 RUC 具有较年轻的纯橄榄岩核心，周围环绕着嵌在围岩中的韦尔岩和二辉橄榄岩，围岩由具有次水平层理的层状辉长岩和变质沉积岩组成。在这里，我们使用高分辨率磁力和重力数据以及来自定向表面样本和钻芯样本的广泛岩石物理测量结果，为 RUC 开发了 3D 地下模型。我们的模型表明，RUC 的深度变窄，至少延伸到海平面以下 1.4 公里，并向东陷入围岩之下。该模型使我们能够破译岩性非均质性以及超镁铁质岩石的深度和横向范围，我们在该地区的地质历史背景下对此进行解释。 RUC 在空间上与 SIP 的其他 UM 综合体分离，本研究的结果表明深度范围较小。将这些发现与先前报道的基于区域重力数据的 SIP 岩石分布相结合，我们认为 RUC 所在的地壳块体的隆起大于 SIP 西北部的超镁铁杂岩。