Pastore, Z. (1),

McEnroe, S. (1), Fichler, C. (1), ter Maat, G. (1), Church, N. (1),

Michels, A. (1), Oda H. (2), Larsen, R. (1)

(1) Norwegian University of Science and

Technology (NTNU), Department of Geoscience and Petroleum, Trondheim,

Norway. (2) Geological Survey of Japan, National Institute of

Advanced Industrial Science and Technology (AIST).



anomalies are observed on multiple scales, from the planetary to the

submillimeter scale. Investigations of these anomalies can lead to

information on the nature of their sources and the processes that

generate them.

The resolvable size of the source causing the anomaly strongly depends

on the magnetic survey design, which varies with the target. Here we

used 3D magnetic modeling to investigate the sources of the magnetic

anomalies on three distinct scales.

In the first study aeromagnetic and gravity data are modelled

revealing the deep crustal structure and the magnetization of the

rocks forming the Seiland Igneous Province (SIP), the largest complex

of mafic and ultramafic rocks in northern Norway, and one of the few

examples in the world of a well preserved deep-seated magmatic

plumbing system.

In the second study ground and helicopter-borne magnetic data are used

in combination with gravity data to explore one of the major

ultramafic complexes of the SIP, the Reinfjord Ultramafic complex.

Here, the magnetic anomalies do not match the mapped lithological

boundaries, but are correlated with changes in magnetic properties and

densities. In particular, the deviating densities and magnetic

susceptibilities at the northern side of the complex are interpreted

to be due to serpentinization. This alteration can significantly

enhance the rock magnetic properties and therefore change the nature

of the magnetic anomaly.

The third study investigates the magnetic anomalies at a submillimeter

scale combining scanning magnetic microscopy with other microscopy

techniques, rock magnetic methods and magnetic modeling. Three thin

sections magnetic scans, of a pristine dunite sample and of two

serpentinized samples from the Reinfjord Ultramafic Complex are

investigated. We apply a forward and inverse modeling approaches on

the magnetic anomaly maps acquired over the thin sections to

characterize the natural remanent magnetization of discrete magnetic

minerals within the samples in terms of intensities and direction. The

application of magnetic modeling in the three studies gave different

degree of information on the magnetic petrology of the sources, and

helped refining the geological interpretation.