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Palaeomagnetic dating of fluid flow events along the Moine Thrust Fault, Scotland
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SCIENCE ~OlRECT ELSEVIER
e
Joumal of Geochemical Exploration 78 79 (2003) 45-49
JOURNAL OF
GEOCHEMICAL EXPLORATION www.elsevier.com/locate/jgeoexp
Abstract
Palaeomagnetic dating of fluid flow events along the Moine Thrust Fault, Scotland R.D. Elmore a'*, R. Blumsteina, M. Engel a, J. Pamell b aSchool of Geology and Geophysics, University of Oklahoma, 100 E. Boyd. St., Norman, OK 73019, USA bDepartment of Geology and Petroleum Geology, University of Aberdeen, King's College, Aberdeen AB24 3UE, Scotland, UK
Abstract Palaeomagnetic results suggest that several fluid flow events caused alteration and hematite authigenesis in the Moine Thrust Zone, northwest Scotland, between the Late Palaeozoic and Middle Tertiary. Precambrian Torridonian sandstone and Lewisian gneiss in the fault zone on the Isle of Skye contain a Tertiary magnetization interpreted to be the result of hydrothermal fluids associated with Tertiary intrusions. Samples of the Dumess Formation limestone (Cambrian), Torridon Group and quartzites (Cambrian) in and near the fault zone to the north contain a Late Palaeozoic to Triassic magnetization residing in hematite and interpreted to be related to hydrothermal fluids. This magnetization and associated alteration in the Moine Thrust Zone are direct evidence for post-orogenic activity, in which the thrusts vented excess heat during regional crustal extension. © 2003 Elsevier Science B.V. All rights reserved. Keywords: Fluids; Moine Fault; Remagnetization;Palaeomagnetism
1. Introduction, geological setting and methods Faults can act as barriers to flow or they can be conduits for flow thereby controlling the distribution o f diagenetic alteration and mineralization. The influence o f faults on fluid flow, however, is still poorly understood. In this study, a preliminary palaeomagnetic investigation was undertaken to test if palaeomagnetic methods could be used to date and help determine the origin o f fluids, which migrated along the Moine Thrust Zone, Scotland. Samples were
* Corresponding author. TeL: +1-405-325-3101; fax: +1-405325-3140. E-mail address: [email protected](R.D. Elmore).
collected in and around the fault zone in several units. The Moine Thrust extends from the Isle o f Skye to the Dumess area in northwest Scotland (Fig. 1). Previous studies have shown that it accommodated crustal shortening during Caledonian deformation and ceased movement toward the end of the orogeny at ca. 425 Ma (e.g., Kelley and Powell, 1985). On Skye, samples were collected from altered Torridonian Precambrian sandstone and Lewisian gneiss (Archean) in the fault zone at Loch Meodal (Fig. 1). To the north, samples were collected from the Durness Formation limestone (Cambrian) near Durness and reddish "pipe rock" quartzites (Cambrian) from the Eriboll Formation at Conival near the fault zone. Samples were also collected from the Dumess Formation limestone near Kishom and the Torridon
0375-6742/03/$ - see front matter © 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0375-6742(03)00069-4
46
Abstract
q)
N
0
20 km
Fig. 1. Location of the sampling sites along and near the Moine or associated thrust faults. Shaded box on inset map shows location of the study area in northwest Scotland. K, Kishom; BB, Bealach na Ba; C, Conival; LM, Loch Meodal; D, Durness.
Group sandstone at Bealach na Ba, both near the Kishorn fault. Cores for palaeomagnetic studies were collected with a portable drill and oriented with an inclinometer and Brunton compass. Standard palaeomagnetic specimens were subjected to thermal demagnetization (e.g., Woods et al., 2002) and the directional data was analyzed using Fisher (1953) statistics.
2. Results and interpretations
The Torridon Group sandstone (Lml) and Lewisian gneiss (Lm2) sites in the fault zone on Skye contain a ChRM with southerly declinations and steep negative inclinations (Figs. 2A and 3; Table 1). The ChRMs are similar to directions from Tertiary igneous rocks on Skye (Dagley et al., 1990), as well as directions interpreted to be Tertiary in altered Jurassic sedimentary rock (Woods et al., 2002) and Torridonian sandstones (Ports, 1990) on Skye. The steep pole position (latitude: 79 °, longitude: 124 °) is consistent with a Tertiary age of remagnetization. To the north, the Durness Formation limestone near Dumess and the Torridon Group sandstone at Bealach na Ba contain a ChRM with southerly declinations and shallow to moderate negative inclinations (Figs. 2B, D and 3; Table 1). The ChRM in the Conl site has steeper inclinations and is tentatively included with this group (Figs. 2C and 3). A regional tilt test on these sites indicates that the grouping is better in geographic coordinates, suggesting that the magnetization is post tilting (Table 1). The preliminary pole position (latitude: 47 °, longitude: 174 °) is close to the Late Palaeozoic to Triassic part of the apparent polar wander path (Fig. 4). Torsvik and Sturt (1987a) also report Late Palaeozoic magnetizations in rocks in the Moine Thrust Zone. The K12 site has relatively steep inclinations that could be a Tertiary component, another component between the Tertiary and Late Palaeozoic, or a vector addition of the other two components. The lack of significant decay by alternating field demagnetization and thermal decay to above 580 °C in most specimens suggests that both the Tertiary and the Late Palaeozoic magnetizations reside in hematite. The maximum demagnetization temperatures for the magnetizations are too high for the components to have been acquired by a thermoviscous remagnetization mechanism and they are therefore interpreted to be chemical remanent magnetizations
(CP,Ms). Thermal demagnetization indicates that the specimens contain a characteristic remanent magnetization (ChRM) with southerly declinations and shallow to steep negative inclinations (Fig. 2). The site mean directions in geographic coordinates are streaked between a steep negative and shallow inclination (Fig. 3).
Some samples of Torridon Group sandstones from Bealach na Ba also contain a magnetization residing in hematite with easterly declinations and steep down inclinations at high temperatures after removal of the southerly component (Fig. 2D). This magnetization is similar to other magnetizations reported from the Torridon Group (e.g., Potts, 1990; Torsvik and Sturt,
47
Abstract
,Up
A
C
W, Up Ticks=0.05mA/M
, N Dn
N Ticks=0.1 mA/M DR
W, Up
B
V r,Up
D
300 660
660
,N Ticks=0.05mA/M Ticks=0.5mA/M
in
Fig. 2. Orthogonal projections of the demagnetization of representative specimens from (A) altered Lewisian gneiss at the Moine fault contact with the Torridonian at Loch Meodal, (B) limestone from the Durness Formation near Dumess, (C) quartzite from Conival and (D) Torridon Group sandstone from Bealach na Ba. Open symbols: vertical component and solid symbols: horizontal component. Demagnetization temperatures in °C. 1987b) and it is interpreted as a primary magnetization or an early remagnetization. Preliminary petrographic and geochemical studies indicate that hydrothermal fluids have altered the rocks in the fault zone. The limestone and quartzite (silica-cemented quartzarenite), for example, are stained red by authigenic hematite.
3. Discussion
The Late Palaeozoic-Triassic CRM is found in rocks in and near the thrust zone. We hypothesize that fluids, which moved through the fault zone, caused the hematite authigenesis/recrystalization and remag-
netization. This CRM is found in rocks that also contain kaolin mineralization (J. Parnell, unpublished data) that formed from hydrothermal fluids. Kaolin abundance increases in the vicinity of the Moine Thrust Zone and the high-temperature polytype dickite is present along the thrust plane. Preliminary petrographic studies indicate that the kaolin and authigenic hematite are intergrown at some localities suggesting they are coeval. Our preliminary interpretation is that the palaeomagnetic results date the fluid flow and kaolin mineralization. The fluid flow event could also be related to other Late Palaeozoic fluid flow events that caused dolomitization along the Highland Boundary Fault (Elmore et al., 2002) and dolomite veins in the Dalradian schist
48
Abstract
N
W
E
S Fig. 3. Equal area plot of site mean directions for the components with southerly declinations and moderate to steep inclinations. Open symbols: negative inclinations. in w e s t - c e n t r a l Scotland (Parnell et al., 2000). The fluid flow event could also be related to a dense s w a r m o f Late C a r b o n i f e r o u s - E a r l y Permian dykes that are abundant near the southern extent o f the M o i n e Thrust (Rock, 1983). There was an active hydrothermal system associated with the large Tertiary intrusions on Skye (e.g., Ferry, 1985). The C R M with steep inclinations in the M o i n e Fault Z o n e on Skye suggests that these hydrothermal fluids also migrated along the fault in the Tertiary. In summary, the results from rocks in and near the M o i n e Thrust Z o n e suggest that there were at least
150 ° Fig. 4. Apparent polar wander path for Europe (Van der Voo, 1993) with the pole positions for the Late Palaeozoic and Tertiary CRMs. Square: component with southerly declinations and steep negative inclinations, circle: component with southerly declinations and shallow to moderate negative inclinations. two post-orogenic fluid flow events. O n the Isle o f Skye, a Tertiary C R M was caused by hydrothermal fluids associated w i t h Tertiary intrusions. A Late Palaeozoic to Triassic C R M in samples o f the Durness F o r m a t i o n limestone, Torridon Group and quartzites in and near the fault zone to the north could be related to hydrothermal fluids. This magnetization and associated alteration in the M o i n e Thrust Z o n e are direct e v i d e n c e for p o s t - o r o g e n i c activity, in w h i c h the
Table 1 Preliminary palaeomagnetic data Site
N/No
In situ dec (°)
In situ inc (°)
k
~95 (°)
Tilted dec (°)
Lml Lm2 K12 DUR4 CON1 BB1 MEAN LM1/LM2
6/6 3/3 4/4 2/2 4/4 5/5 2/2 3/3
187.3 189.8 203.5 186.5 174.5 177.6 188.6 179.8
- 70.2 -60.6 -49.7 -23.2 - 40.6 - 19.1 - 65.4 - 27.7
60.8 123.0 36.3 486 50.0 13.9 . 41.1
8.7 11.2 15.5 11.4 13.1 21.3 . 19.5
. 222.2 195.3 207.2 172.2
MEAN
.
Tilted inc (°)
~95 (°) -
.
. 192.0
k
. -41.1 -40.2 - 3.4 - 27.3 . - 24.4
-
. 36.2 486 50.2 13.9
15.5 11.4 13.1 21.3
10.8
39.5
Lithology TorSS SCH LS LS QTZSS
(DUR4, Conl, BB1) N/No, number of demagnetized specimens versus number of specimens with direction; dec, declination; inc, inclination; k, precision parameter; e95, cone of 95% confidence. A tilt correction for sites LM1 and LM2 could not be determined because bedding was obscured in the fault zone. TorSS, Torridon Group sandstone; SCH, Lewisian gneiss; LS, Limestone; QTZSS, quartzite.
Abstract
thrusts v e n t e d excess heat during r e g i o n a l crustal extension.
Acknowledgements Funding was p r o v i d e d b y D e p a r t m e n t o f E n e r g y grant D E - F G 0 3 - 9 6 E R 1 4 6 4 3 to R D E and M H E .
References Dagley, E, Mussett, A.E., Skelhorn, R.R., 1990. Magnetic polarity stratigraphy of the Tertiary igneous rocks of Skye, Scotland. Geophys. J. Int. 101,395-409. Elmore, R.D., Parnell, J., Engel, M., Woods, S., Abraham, M., Davidson, M., 2002. Paleomagnetic dating of fluid-flow events in dolomitized Caledonian basement rocks, central Scotland. Geofluids 2, 299-314. Ferry, J.M., 1985. Hydrothermal alteration of Tertiary igneous rocks from the Isle of Skrye, northwest Scotland: I. Gabbros. Cont. Mineral. Petrol. 91,264-282. Fisher, R.A., 1953. Dispersion on a sphere. Proc. R. Soc. Lond., Set. A 217, 295-305.
49
Kelley, S.E, Powell, D., 1985. Relationships between marginal thrusting and movement on major internal shear zones in the Northern Highland Caledonides, Scotland. J. Sttuct. Geol. 7, 161-174. Parnell, J., Baron, M., Davidson, M., Elmore, D., Engel, M., 2000. Dolomitic breccia veins as evidence for extension and fluid flow in the Dalradian of Argyll. Geol. Mag. 137, 447-462. Ports, G.J., 1990. A palaeomagnetic study of recumbently folded and thermally metamorphosed Torridon Group sediments, Eishort anticline, Skye, Scotland. J. Geol. Soc. Lond. 147, 999-1007. Rock, N.M.S., 1983. The Permo-Carboniferous camptonite monchiquite dyke-suite of the Scottish Highlands and Islands: distribution, field and petrological aspects. Report of the Institute of Geological Sciences, No. 82/14. Torsvik, T.H., Sturt, B.A., 1987a. Multiphase magnetic overprints in the Moine Thrust Zone. Geol. Mag., 63-82. Torsvik, T.H., Sturt, B.A., 1987b. The origin and stability of remanence and the magnetic fabric of the Torridonian Red Beds, NW Scotland. Scott. J. Geol. 1, 23-28. Van der Voo, R., 1993. Paleomagnetism of the Atlantic, Tethys and Iapetus Oceans. Cambridge Univ. Press, Cambridge, 411 pp. Woods, S., Elmore, R.D., Engel, M., 2002. Paleomagnetic dating of the smectite-to-illite conversion: testing the hypothesis in Jurassic sedimentary rocks, Skye, Scotland. J. Geophys. Res. 107 (10.1029/2000JB000053), EPM 2-1-12.
SCIENCE ~OlRECT ELSEVIER
e
Joumal of Geochemical Exploration 78 79 (2003) 45-49
JOURNAL OF
GEOCHEMICAL EXPLORATION www.elsevier.com/locate/jgeoexp
Abstract
Palaeomagnetic dating of fluid flow events along the Moine Thrust Fault, Scotland R.D. Elmore a'*, R. Blumsteina, M. Engel a, J. Pamell b aSchool of Geology and Geophysics, University of Oklahoma, 100 E. Boyd. St., Norman, OK 73019, USA bDepartment of Geology and Petroleum Geology, University of Aberdeen, King's College, Aberdeen AB24 3UE, Scotland, UK
Abstract Palaeomagnetic results suggest that several fluid flow events caused alteration and hematite authigenesis in the Moine Thrust Zone, northwest Scotland, between the Late Palaeozoic and Middle Tertiary. Precambrian Torridonian sandstone and Lewisian gneiss in the fault zone on the Isle of Skye contain a Tertiary magnetization interpreted to be the result of hydrothermal fluids associated with Tertiary intrusions. Samples of the Dumess Formation limestone (Cambrian), Torridon Group and quartzites (Cambrian) in and near the fault zone to the north contain a Late Palaeozoic to Triassic magnetization residing in hematite and interpreted to be related to hydrothermal fluids. This magnetization and associated alteration in the Moine Thrust Zone are direct evidence for post-orogenic activity, in which the thrusts vented excess heat during regional crustal extension. © 2003 Elsevier Science B.V. All rights reserved. Keywords: Fluids; Moine Fault; Remagnetization;Palaeomagnetism
1. Introduction, geological setting and methods Faults can act as barriers to flow or they can be conduits for flow thereby controlling the distribution o f diagenetic alteration and mineralization. The influence o f faults on fluid flow, however, is still poorly understood. In this study, a preliminary palaeomagnetic investigation was undertaken to test if palaeomagnetic methods could be used to date and help determine the origin o f fluids, which migrated along the Moine Thrust Zone, Scotland. Samples were
* Corresponding author. TeL: +1-405-325-3101; fax: +1-405325-3140. E-mail address: [email protected](R.D. Elmore).
collected in and around the fault zone in several units. The Moine Thrust extends from the Isle o f Skye to the Dumess area in northwest Scotland (Fig. 1). Previous studies have shown that it accommodated crustal shortening during Caledonian deformation and ceased movement toward the end of the orogeny at ca. 425 Ma (e.g., Kelley and Powell, 1985). On Skye, samples were collected from altered Torridonian Precambrian sandstone and Lewisian gneiss (Archean) in the fault zone at Loch Meodal (Fig. 1). To the north, samples were collected from the Durness Formation limestone (Cambrian) near Durness and reddish "pipe rock" quartzites (Cambrian) from the Eriboll Formation at Conival near the fault zone. Samples were also collected from the Dumess Formation limestone near Kishom and the Torridon
0375-6742/03/$ - see front matter © 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0375-6742(03)00069-4
46
Abstract
q)
N
0
20 km
Fig. 1. Location of the sampling sites along and near the Moine or associated thrust faults. Shaded box on inset map shows location of the study area in northwest Scotland. K, Kishom; BB, Bealach na Ba; C, Conival; LM, Loch Meodal; D, Durness.
Group sandstone at Bealach na Ba, both near the Kishorn fault. Cores for palaeomagnetic studies were collected with a portable drill and oriented with an inclinometer and Brunton compass. Standard palaeomagnetic specimens were subjected to thermal demagnetization (e.g., Woods et al., 2002) and the directional data was analyzed using Fisher (1953) statistics.
2. Results and interpretations
The Torridon Group sandstone (Lml) and Lewisian gneiss (Lm2) sites in the fault zone on Skye contain a ChRM with southerly declinations and steep negative inclinations (Figs. 2A and 3; Table 1). The ChRMs are similar to directions from Tertiary igneous rocks on Skye (Dagley et al., 1990), as well as directions interpreted to be Tertiary in altered Jurassic sedimentary rock (Woods et al., 2002) and Torridonian sandstones (Ports, 1990) on Skye. The steep pole position (latitude: 79 °, longitude: 124 °) is consistent with a Tertiary age of remagnetization. To the north, the Durness Formation limestone near Dumess and the Torridon Group sandstone at Bealach na Ba contain a ChRM with southerly declinations and shallow to moderate negative inclinations (Figs. 2B, D and 3; Table 1). The ChRM in the Conl site has steeper inclinations and is tentatively included with this group (Figs. 2C and 3). A regional tilt test on these sites indicates that the grouping is better in geographic coordinates, suggesting that the magnetization is post tilting (Table 1). The preliminary pole position (latitude: 47 °, longitude: 174 °) is close to the Late Palaeozoic to Triassic part of the apparent polar wander path (Fig. 4). Torsvik and Sturt (1987a) also report Late Palaeozoic magnetizations in rocks in the Moine Thrust Zone. The K12 site has relatively steep inclinations that could be a Tertiary component, another component between the Tertiary and Late Palaeozoic, or a vector addition of the other two components. The lack of significant decay by alternating field demagnetization and thermal decay to above 580 °C in most specimens suggests that both the Tertiary and the Late Palaeozoic magnetizations reside in hematite. The maximum demagnetization temperatures for the magnetizations are too high for the components to have been acquired by a thermoviscous remagnetization mechanism and they are therefore interpreted to be chemical remanent magnetizations
(CP,Ms). Thermal demagnetization indicates that the specimens contain a characteristic remanent magnetization (ChRM) with southerly declinations and shallow to steep negative inclinations (Fig. 2). The site mean directions in geographic coordinates are streaked between a steep negative and shallow inclination (Fig. 3).
Some samples of Torridon Group sandstones from Bealach na Ba also contain a magnetization residing in hematite with easterly declinations and steep down inclinations at high temperatures after removal of the southerly component (Fig. 2D). This magnetization is similar to other magnetizations reported from the Torridon Group (e.g., Potts, 1990; Torsvik and Sturt,
47
Abstract
,Up
A
C
W, Up Ticks=0.05mA/M
, N Dn
N Ticks=0.1 mA/M DR
W, Up
B
V r,Up
D
300 660
660
,N Ticks=0.05mA/M Ticks=0.5mA/M
in
Fig. 2. Orthogonal projections of the demagnetization of representative specimens from (A) altered Lewisian gneiss at the Moine fault contact with the Torridonian at Loch Meodal, (B) limestone from the Durness Formation near Dumess, (C) quartzite from Conival and (D) Torridon Group sandstone from Bealach na Ba. Open symbols: vertical component and solid symbols: horizontal component. Demagnetization temperatures in °C. 1987b) and it is interpreted as a primary magnetization or an early remagnetization. Preliminary petrographic and geochemical studies indicate that hydrothermal fluids have altered the rocks in the fault zone. The limestone and quartzite (silica-cemented quartzarenite), for example, are stained red by authigenic hematite.
3. Discussion
The Late Palaeozoic-Triassic CRM is found in rocks in and near the thrust zone. We hypothesize that fluids, which moved through the fault zone, caused the hematite authigenesis/recrystalization and remag-
netization. This CRM is found in rocks that also contain kaolin mineralization (J. Parnell, unpublished data) that formed from hydrothermal fluids. Kaolin abundance increases in the vicinity of the Moine Thrust Zone and the high-temperature polytype dickite is present along the thrust plane. Preliminary petrographic studies indicate that the kaolin and authigenic hematite are intergrown at some localities suggesting they are coeval. Our preliminary interpretation is that the palaeomagnetic results date the fluid flow and kaolin mineralization. The fluid flow event could also be related to other Late Palaeozoic fluid flow events that caused dolomitization along the Highland Boundary Fault (Elmore et al., 2002) and dolomite veins in the Dalradian schist
48
Abstract
N
W
E
S Fig. 3. Equal area plot of site mean directions for the components with southerly declinations and moderate to steep inclinations. Open symbols: negative inclinations. in w e s t - c e n t r a l Scotland (Parnell et al., 2000). The fluid flow event could also be related to a dense s w a r m o f Late C a r b o n i f e r o u s - E a r l y Permian dykes that are abundant near the southern extent o f the M o i n e Thrust (Rock, 1983). There was an active hydrothermal system associated with the large Tertiary intrusions on Skye (e.g., Ferry, 1985). The C R M with steep inclinations in the M o i n e Fault Z o n e on Skye suggests that these hydrothermal fluids also migrated along the fault in the Tertiary. In summary, the results from rocks in and near the M o i n e Thrust Z o n e suggest that there were at least
150 ° Fig. 4. Apparent polar wander path for Europe (Van der Voo, 1993) with the pole positions for the Late Palaeozoic and Tertiary CRMs. Square: component with southerly declinations and steep negative inclinations, circle: component with southerly declinations and shallow to moderate negative inclinations. two post-orogenic fluid flow events. O n the Isle o f Skye, a Tertiary C R M was caused by hydrothermal fluids associated w i t h Tertiary intrusions. A Late Palaeozoic to Triassic C R M in samples o f the Durness F o r m a t i o n limestone, Torridon Group and quartzites in and near the fault zone to the north could be related to hydrothermal fluids. This magnetization and associated alteration in the M o i n e Thrust Z o n e are direct e v i d e n c e for p o s t - o r o g e n i c activity, in w h i c h the
Table 1 Preliminary palaeomagnetic data Site
N/No
In situ dec (°)
In situ inc (°)
k
~95 (°)
Tilted dec (°)
Lml Lm2 K12 DUR4 CON1 BB1 MEAN LM1/LM2
6/6 3/3 4/4 2/2 4/4 5/5 2/2 3/3
187.3 189.8 203.5 186.5 174.5 177.6 188.6 179.8
- 70.2 -60.6 -49.7 -23.2 - 40.6 - 19.1 - 65.4 - 27.7
60.8 123.0 36.3 486 50.0 13.9 . 41.1
8.7 11.2 15.5 11.4 13.1 21.3 . 19.5
. 222.2 195.3 207.2 172.2
MEAN
.
Tilted inc (°)
~95 (°) -
.
. 192.0
k
. -41.1 -40.2 - 3.4 - 27.3 . - 24.4
-
. 36.2 486 50.2 13.9
15.5 11.4 13.1 21.3
10.8
39.5
Lithology TorSS SCH LS LS QTZSS
(DUR4, Conl, BB1) N/No, number of demagnetized specimens versus number of specimens with direction; dec, declination; inc, inclination; k, precision parameter; e95, cone of 95% confidence. A tilt correction for sites LM1 and LM2 could not be determined because bedding was obscured in the fault zone. TorSS, Torridon Group sandstone; SCH, Lewisian gneiss; LS, Limestone; QTZSS, quartzite.
Abstract
thrusts v e n t e d excess heat during r e g i o n a l crustal extension.
Acknowledgements Funding was p r o v i d e d b y D e p a r t m e n t o f E n e r g y grant D E - F G 0 3 - 9 6 E R 1 4 6 4 3 to R D E and M H E .
References Dagley, E, Mussett, A.E., Skelhorn, R.R., 1990. Magnetic polarity stratigraphy of the Tertiary igneous rocks of Skye, Scotland. Geophys. J. Int. 101,395-409. Elmore, R.D., Parnell, J., Engel, M., Woods, S., Abraham, M., Davidson, M., 2002. Paleomagnetic dating of fluid-flow events in dolomitized Caledonian basement rocks, central Scotland. Geofluids 2, 299-314. Ferry, J.M., 1985. Hydrothermal alteration of Tertiary igneous rocks from the Isle of Skrye, northwest Scotland: I. Gabbros. Cont. Mineral. Petrol. 91,264-282. Fisher, R.A., 1953. Dispersion on a sphere. Proc. R. Soc. Lond., Set. A 217, 295-305.
49
Kelley, S.E, Powell, D., 1985. Relationships between marginal thrusting and movement on major internal shear zones in the Northern Highland Caledonides, Scotland. J. Sttuct. Geol. 7, 161-174. Parnell, J., Baron, M., Davidson, M., Elmore, D., Engel, M., 2000. Dolomitic breccia veins as evidence for extension and fluid flow in the Dalradian of Argyll. Geol. Mag. 137, 447-462. Ports, G.J., 1990. A palaeomagnetic study of recumbently folded and thermally metamorphosed Torridon Group sediments, Eishort anticline, Skye, Scotland. J. Geol. Soc. Lond. 147, 999-1007. Rock, N.M.S., 1983. The Permo-Carboniferous camptonite monchiquite dyke-suite of the Scottish Highlands and Islands: distribution, field and petrological aspects. Report of the Institute of Geological Sciences, No. 82/14. Torsvik, T.H., Sturt, B.A., 1987a. Multiphase magnetic overprints in the Moine Thrust Zone. Geol. Mag., 63-82. Torsvik, T.H., Sturt, B.A., 1987b. The origin and stability of remanence and the magnetic fabric of the Torridonian Red Beds, NW Scotland. Scott. J. Geol. 1, 23-28. Van der Voo, R., 1993. Paleomagnetism of the Atlantic, Tethys and Iapetus Oceans. Cambridge Univ. Press, Cambridge, 411 pp. Woods, S., Elmore, R.D., Engel, M., 2002. Paleomagnetic dating of the smectite-to-illite conversion: testing the hypothesis in Jurassic sedimentary rocks, Skye, Scotland. J. Geophys. Res. 107 (10.1029/2000JB000053), EPM 2-1-12.