D. Livelybrooks et al., INVERSION OF ELECTROMAGNETIC INDUCTION DATA FOR THE IAPETUS SUTURE ZONE IN THE UK, Physics of the earth and planetary interiors, 81(1-4), 1993, pp. 67-84
The Iapetus Suture Zone (ISZ), corresponding to the join between the E
uropean crust of northern England and the North American derived crust
of Scotland, has been examined by numerous seismic and induction expe
riments over a 20 year period. The University of Edinburgh electromagn
etic (EM) induction group is in the process of building a database com
prising magnetotelluric and magnetic variation stations from this regi
on. In this paper we present 2D inversions of selected induction sites
along roughly north-south traverses across the ISZ in northern Englan
d and southern Scotland. The first inversion involves both the transve
rse electric (TE) and transverse magnetic (TM) modes for 10 audio-magn
etotelluric (approximately 100-0.1 Hz) sites. Care has been taken to r
emove the effects of static shifts. This inversion resolves a conducti
ve feature beginning under the southern Northumberland Trough at depth
s of 10 km, dipping to the south below the Alston Block. In the second
inversion, 12 longer-period magnetic variation sites were added to th
e original data set, improving the resolution of this feature, which c
orrelates well with a dipping bright reflector detected by the North E
ast Coast (NEC) seismic reflection experiment. In addition, the Southe
rn Uplands anomaly is imaged. No north-dipping, mid-to deep-crustal co
nductor is observed which would correlate to north-dipping Palaeozoic
subduction under Laurentia.