Anatomy of a deep crustal volcanic conduit system; The Reinfjord Ultramafic Complex, Seiland Igneous Province, Northern Norway

Grant, Thomas B.; Larsen, Rune B.; Anker-Rasch, Lars; Grannes, Kim Rune Bragstad; Iljina, M.; McEnroe, Suzanne A.; Nikolaisen, Even; Schanche, Mona; Øen, Endre

doi:10.1016/j.lithos.2016.02.020

Cited by 29 publications

(41 citation statements)

References 54 publications

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“…The olivine has varying grain sizes, from >1 mm to smaller grains (~100–200 μm). In the ULS there are similar grain sizes of olivine (15–40%) with more abundant clinopyroxene (60–85%), in agreement with Grant et al (). Clinopyroxene grains commonly contain exsolution lamellae of orthopyroxene.…”

Section: Resultssupporting

confidence: 90%

“…There is a cluster of high‐density samples in the surface samples above 3.3 g/cm 3 , and in the drill core samples above 3.2 g/cm 3 . Locally, in the drill core, there are crosscutting centimeter‐sized fractures with serpentinite minerals (Grant et al, ), which may be the explanation of the lowest density values.…”

Section: Resultsmentioning

confidence: 99%

“…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.…”

Section: Geologymentioning

confidence: 95%

“…The assemblage depends on the composition of the ultramafic cumulates, and the host rock at each location. Generally, the MZ is dominated by clinopyroxene and orthopyroxene, with smaller amounts of olivine and plagioclase (Emblin, ; Grant et al, ). In this paper, we further subdivided the MZ depending on the adjacent host rock, gneiss (MZ_gneiss), or gabbro (MZ_gabbro).…”

Section: Geologymentioning

confidence: 99%

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

Maat

McEnroe

Church

et al. 2019

Geochem Geophys Geosyst

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Magnetic properties from the Reinfjord Ultramafic Complex, in northern Norway, which formed as part of a deep magmatic conduit system, have been investigated to determine the magnetic signature of ultramafic rocks now exposed at the surface and deeper in the lower crust. The dominant carriers in these ultramafic rocks are a chrome‐spinel with Fe‐rich exsolution blebs and exsolution lamellae of magnetite in clinopyroxene. Except locally, in a fault zone and in discrete small fractures, these rocks show only minor to no alteration. We infer that the magnetic oxides characterized here are representative of pristine magnetic carriers in similar rocks deeper in the crust. These oxides can be stable in lower crustal, possibly upper mantle, depths when temperatures are below the Curie temperature of magnetite, taking into account pressure effects. These ultramafic rocks are candidates for potential sources of long‐wavelength anomalies.

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Section: Resultssupporting

confidence: 90%

Section: Resultsmentioning

confidence: 99%

Section: Geologymentioning

confidence: 95%

Section: Geologymentioning

confidence: 99%

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

Maat

McEnroe

Church

et al. 2019

Geochem Geophys Geosyst

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“…While non-cryogenic sensors cannot offer the dynamic range and low-field sensitivity of SQUIDs, they are sufficient to measure the magnetic response of rock samples containing abundant magnetic particles. The sample shown in Figure 1 is a paleomagnetic core (25 mm diameter, 22 mm height) of a serpentinized dunite from the Reinfjord ultramafic intrusion (Grant et al, 2016) in northern Norway, with the scan acquired at 100 µm height. It contains extensive alteration at the micro-and macro-scale, including a near-vertical talc vein that intersects the top surface as indicated in Figure 1b and reflects a high degree of serpentinization.…”

Section: Experimental Setup and Capabilitiesmentioning

confidence: 99%

Magnetic Field Surveys of Thin Sections

Church

McEnroe

2018

ASEG Extended Abstracts

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SUMMARYScanning magnetic microscopy (SMM) maps the magnetic field generated by petrologic thin sections or polished rock surfaces at the sub-mm scale, creating the possibility to resolve the contribution of individual grains and mineral phases to bulk magnetic signal. The instrument developed at NTNU has the capability to measure both remanence properties and, uniquely, the magnetic response in a field of known magnitude and direction. A series of case studies are presented to examine the capabilities of the microscope and to describe applications to the study of crustal magnetism. The use of well-characterized samples allows signals in magnetic scans to be attributed to grains of known composition, including the discrimination of signal associated with discrete oxides and assemblages of exsolved oxides in silicates, which can be observed to have differing directions of magnetisation. The ability of this instrument to image in fields mimicking those experienced in the crust allows the observation of the induced magnetic response, both qualitatively in the form of changes in magnetization direction, and quantitatively by varying experimental conditions. This capability gives SMM the ability to map both remanent response and generate a map of susceptibility, and provides a powerful new tool for the examination of bulk magnetic response in the Earth's crust.

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