Magma transport in sheet intrusions of the Alnö carbonatite complex, central Sweden

Transcription

1 Supplementary Information Magma transport in sheet intrusions of the Alnö carbonatite complex, central Sweden Authors: *Magnus Andersson 1, Bjarne S.G. Almqvist 1, Steffi Burchardt 1, Valentin R. Troll 1, Alireza Malehmir 1, Ian Snowball 1, and Lutz Kübler 2 1: Department of Earth Sciences, Uppsala University, Uppsala, Sweden 2: Geological Survey of Sweden, Uppsala, Sweden address of the corresponding author (M. Andersson): magnus.andersson@geo.uu.se This file includes Supplementary Figures S1 to S5 and Table S1 to S2. 1(9)

2 a) 40 Fine grained n=43 b) Frequency Paramagnetic Ferromagnetic Km (µsi) Frequency 40 Medium-coarse grained n= bimodal Km (µsi) Supplementary Figure S1 Bulk magnetic susceptibility. (a) Fine grained carbonatite and (b) mediumcoarse grained carbonatite show bimodality in the distribution of magnetic susceptibility. Number of samples is indicated by n. Susceptibility values above ~2000 µsi are dominated by ferromagnetic (senso lato) minerals. a) b) c) Km (µsi) Pj T 0 1 man man man man1301 man1302 man1303 man1304 man1305 man1306 man1307 man1308 man1309 man1310 man1311 man1312 man1313 man1314 man1315 man1316 man1317 man1318 man1319 man1320 man1321 man1322 man1323 man1324 man1325 man1326 man1327 man1328 man1329 man1330 man1332 man1333 man1334 man1335 man1336 man1338 man1339 man1340 man1341 man1342 Supplementary Figure S2 Boxplot of mean bulk magnetic susceptibility (K m ), degree of anisotropy (P j ) and shape factor (T) for each sampling location. Locations with carbonatite are marked with blue colour. 2(9)

3 Supplementary Figure S3 Typical features visible in outcropping dykes. (a) Carbonatite dyke injected into fenite wall rock. (b) Carbonatite dyke cross-cutting another carbonatite dyke. (c) Indication of simple shear in a carbonatite dyke is provided by rotation of competent pyroxenite wallrock fragments. 3(9)

4 a) man1301 k1 (WE ) Western Eastern k2 (WE ) k3 (WE ) n W = 7, n E = 14 b) man1302 SW NE k1 (SWNE ) k2 (SWNE ) k3 (SWNE ) n SW = 6, n NE = 5 c) man1313 k1 (SouthernNorthern ) k2 (SouthernNorthern ) k3 (SouthernNorthern ) n N = 5, n S = 5 d) man1329 k1 (Southern ) k2 (Southern ) Southern k3 (Southern ) n S = 4 e) man1332 Northern k1 (Northern ) k2 (Northern ) k3 (Northern ) n N = 7 Supplementary Figure S4 AMS data and indications of flow directions. This figure shows the magnetic lineation and foliation of carbonatite samples that were collected close to dyke s at five locations; man1301, man1302, man1313, man1329, and man1332. For each location two lower hemisphere equalarea projections (Schmidt net) with principal susceptibility axes (k 1, k 2, and k 3 ; left hand images) as well as their mean axis and confidence ellipses (centre images) are presented. Flow direction is indicated in the 4(9)

5 right hand images, except for man1313; for man1301 and man1302 it is a horizontal view along the strike of the dyke and for man1329 and man1332 it is a map view. In the centre part of each subfigure the mean axis and great circles (magnetic foliations) are plotted, as well as a dotted line indicating the attitude of the dyke. In the calculations presented here the assumption with vertical dykes has been made. Although this could only be directly measured in the field for site man1302, it can be inferred that dykes in other locations are very close to vertical (sub vertical). (a) In man1301 the magnetic foliations dip steeply inward at both s of the dyke. The bisector of the angle between k 3 axes in the opposite s of the dyke indicates the flow direction; for man1301 that indicates a downward flow. (b) At man1302 a pattern similar to man1301 is observed. Both (a) and (b) may have imbrication that indicates steep downward flow, using the mean flow vector method described by Geoffroy et al. 5. (c) The method used in (a) and (b) failed for location man1313 as the magnetic foliation has the same orientation at both s. As only one dyke wall was outcropping in the locations man1329 (d) and man1332 (e), respectively, a method using only one dyke wall was used, as described by Geoffroy et al.(2002) 5. In the flow calculation the assumption that the dyke was vertical has been made. 5(9)

6 a) b) man1301 Zone axes man1301 k 1 c) d) man1302 Zone axes man1302 k 1 Supplementary Figure S5 Zone axes and the principle axes k 1. In order to test the possibility of overprinting (superposition) of the magnetic fabrics the zone axis method has been used. This technique compares the intersection of magnetic foliations (zone axes) for all mutual combinations of samples in a population with the distribution of the magnetic lineations in the same population. If the zone axes and the magnetic lineations coincide this is an indication that more than one magnetic fabric has been recorded in the rock, i.e. overprinting has occurred. (a) and (b) show the zone axes and k 1, respectively, for carbonatite in location man1301. The majority of the zone axes plot in the same area as most k 1 which indicate that overprinting has occured. (c) and (d) show a similar pattern which indicates that overprinting may have occurred also in location man1302. All the plots are lower hemisphere equal-area projections of a Schmidt net and the contouring is made with counting areas of 1 % of the net area and contour intervals of 2 %. 6(9)

7 Supplementary Table S1 Oriented rock samples collected on Alnö island. Some samples were taken as oriented blocks from which cores were drilled in laboratory. These are marked by * in front of n cores. n cores : is the number of cores drilled at a location (except for locations with block samples), n samples : is the total number of subsamples from a location, Bt is biotite, and Kfsp is alkali feldspar. Site EastNorth Rock type n cores n samples (SWEREF99) man Carbonatite, fenite man Carbonatite, fenite, ijolite man Nepheline syenite 4 11 man Nepheline syenite 2 3 man Pyroxenite 2 5 man Fenite 2 5 man Fenite 2 4 man Pyroxenite 3 5 man Ijolite rich in pyroxene 3 8 man Carbonatite, ijolite 5 11 man Nepheline syenite 4 7 man Fenite, ijolite rich in pyroxene 2 4 man Carbonatite 4 10 man Nepheline syenite 3 5 man Nepheline syenite 4 8 man Nepheline syenite 3 8 man Nepheline syenite 4 8 man Nepheline syenite 2 2 man Nepheline syenite 2 4 man Carbonatite, carbonatite rich in pyroxene, 3 8 pyroxenite man Carbonatite rich in pyroxene 2 5 man Carbonatite rich in Bt 2 5 man Carbonatite rich in Bt, Kfsp, and pyroxene 3 4 man Fenite 3 6 man Nepheline syenite 3 6 man Carbonatite rich in Bt 6 17 man Fenite 2 7 man Carbonatite man Carbonatite man Carbonatite man Carbonatite 8 26 man Carbonatite (silicosövite) 6 17 man Ijolite 2 3 man Pyroxenite, carbonatite 2 3 man Pyroxenite, ijolite 5 13 man Fenite 4 10 man Carbonatite, carbonatite with pyroxene and Bt 3 7 man Fenite, pyroxenite 4 5 man Carbonatite, fenite 3 5 man Fenite, ijolite 6 16 man Ijolite *1 12 man Migmatite *1 10 man Fenite *1 8 man Nepheline syenite *1 17 man Carbonatite *1 13 man Carbonatite *1 8 man Fenite (quartz-free) *1 7 man Pyroxenite *1 12 7(9)

8 Supplementary Table S2 Geological and magnetic data summerized for locations with carbonatite. The data are grouped according to the clustering in Figure 5. Location Samples EastNorth Local orientation of dyke Rock (SWEREF99) Macroscopic foliation Miscellaneous Location within dyke man1301 (a) Carbonatite Follow local attitude of Western dyke, winding man1301 (b) Carbonatite, carb. rich in Follow local attitude of Eastern biotite dyke, winding man1302 (a) Carbonatite (dipdip.dir.) SW (subvertical) man1302 (b) Carbonatite (dipdip.dir.) Centre of dyke (subvertical) man1302 (c) Carbonatite (dipdip.dir.) NE (subvertical) man Carbonatite man1313 (a) Carbonatite Northern man1313 (b) Carbonatite Southern man ,1-2, Carb, carb rich in pyroxene, carb. rich in biotite man Carbonatite rich in biotite (dipdip.dir.) man1328 (a) 1, Carbonatite to man1328 (b) 2, 4-8, Carbonatite to man1329 (a) 6-11, Carbonatite (±10 ) Sinistral sense of shear man1329 (b) Carbonatite Southern man1329 (c) 12, Carbonatite (±10 ) man1330 (a) 10-11, 13, Carbonatite ~ (dipdip.dir.) man1330 (b) 3-4, 7-8, Carbonatite ~ (dipdip.dir.) 12 man1332 (a) Carbonatite ~ (dipdip.dir.) Sinistral sense of shear (see Fig. S3c) man1332 (b) Carbonatite ~ (dipdip.dir.) man Carbonatite (silicosövite) man Carbonatite, carb. with pyroxene and biotite Northern 8(9)

9 Supplementary Table S2 continued Location N Kaver (SI) Pjaver Taver K1dK1i K2dK2i K3dK3i K1 K2 K3 man1301 (a) man1301 (b) man1302 (a) man1302 (b) man1302 (c) man man1313 (a) man1313 (b) man man man1328 (a) man1328 (b) man1329 (a) man1329 (b) man1329 (c) man1330 (a) man1330 (b) man1332 (a) man1332 (b) man man (9)