Portrait of a giant deep-seated magmatic conduit system: The Seiland Igneous Province

Abstract

The Seiland Igneous Province (SIP), Northern Norway, contains >5000 km 2 of mafic, ultramafic intrusions with minor alkaline, carbonatite and felsic rocks that were intruded into the lower continental crust at a depth of 25 to as much as 35 km.The SIP can be geochemically and temporally correlated to numerous dyke swarms throughout Scandinavia at 560-610 Ma, and is linked to magmatic provinces in W-Greenland and NE-America that are collectively known as the Central Iapetus Magmatic Province (CIMP).

Magnetic Mineralogy and Petrophysical Properties of Ultramafic Rocks: Consequences for Crustal Magnetism

“…Previous authors have reported local serpentinization in surface exposures of the ultramafic rocks (Emblin, ; Grant et al, ; Larsen et al, ). However, there is one area of pervasive serpentinization of the CS dunites, which is associated with a fault trending east‐west at 70°07′N that crosscuts all formations (Figure ), here termed the Storvannet fault.…”

“…The ULS has cyclic units consisting of a dunitic cumulate layer (Fo 85.1–77.4 ; Emblin, ) that gradually taper into wehrlitic cumulates. The later intrusion of the CS into the wehrlitic cumulates led to the assimilation of large volumes of the ULS under the formation of replacive dunites (Larsen et al, ). More than 50% of the surface outcrop of the RUC is CS, which consists of olivine cumulates (>90%) with less than 10% clinopyroxene.…”

“…The SIP has an exposed area of more than 5,000 km 2 and an estimated minimum volume of~17,000 km 3 of Ediacaran mafic and ultramafic rocks (Pastore et al, 2016;Pastore, Fichler, & McEnroe, 2018). The SIP was emplaced at approximately 570-560 Ma at depths of 25-35 km (Larsen et al, 2018;Roberts, 2007;Roberts et al, 2006). It is part of the Central Iapetus Magmatic Province and is composed of several ultramafic complexes including the Nordre Bumansfjord, Melkvann, Kvalfjord, and the Reinfjord complexes (Bennett et al, 1986;Larsen et al, 2018;Oosterom, 1954;Robins & Gardner, 1975;Yeo, 1984).…”

“…Map of the Seiland Igneous Province in northern Norway modified after Larsen et al (). The ultramafic complexes are indicated in green.…”

“…(a) Geological map of the Reinfjord Ultramafic complex (modified after Larsen et al, ). The sampling locations are indicated in black dots, and drill core locations are indicated by the red circles.…”