GSA Data Repository 216351 Clockwise rotation of the entire Oman ophiolite occurred in a suprasubduction zone setting Antony Morris et al. 1 2 3 4 5 6 7 8 9 1 11 12 13 14 15 16 17 18 19 2 21 22 23 24 25 26 27 28 29 3 31 32 33 34 35 36 37 38 39 4 41 DATA RPOSITORY MTHODS Oriented samples were collected in the field, either as 25 mm diameter cores using a standard paleomagnetic rock drill or as oriented hand samples from which cores were prepared in the laboratory. Natural remanent magnetizations (NRMs) of samples were investigated via either alternating field demagnetization using an AGICO LDA-3A demagnetizer in 15 incremental steps from 5 to 1 mt, or via thermal demagnetization using a Magnetic Measurements Ltd MMTD8A furnace in 16 temperature increments from 1 to 58. Magnetic remanences were measured at each demagnetization step using an AGICO JR-6A spinner magnetometer. Demagnetization data were displayed on orthogonal vector plots (Zijderveld, 1967), and remanence components were isolated via principal component analysis (Kirschvink, 198) using Remasoft 3. software (Chadima and Hrouda, 26). Thermal and AF demagnetization of samples yielded the same directions at each site (Fig. DR7). Site mean directions were evaluated using Fisherian statistics (Fisher, 1953) on virtual geomagnetic poles (VGPs) corresponding to the isolated characteristic remanent magnetizations (ChRMs). The errors D and I associated with the mean declination and inclination at each site are calculated after Deenen et al. (211) from the VGPs based on the paleolatitude (λ) and the A 95 values, where: D = sin -1 (sin(a 95 )/cos(λ)) I = 2A 95 /(1+3sin 2 (λ)) The VGP scatter (i.e., A 95 ) obtained at each site was compared to the expected scatter induced by paleosecular variation (PSV) of the geomagnetic field (i.e., A 95min - A 95max ) to assess whether PSV is sufficiently represented in our datasets (Deenen et al., 211). Values of A 95 < A 95min at 3 out of 32 sites indicate that PSV is not adequately represented, most likely as a result of complete remagnetization or the influence of residual overprints after demagnetization. The remaining two sites have A 95min A 95 < A 95max indicating marginal but statistically significant averaging of PSV at site level. DATA RPOSITORY RFRNCS Chadima, M., Hrouda, F., 26, Remasoft 3. a user-friendly paleomagnetic data browser and analyzer. Travaux Géophysiques v. XXVII, p. 2 21. Deenen, M. H. L., Langereis, C. G., van Hinsbergen, D. J. J., and Biggin, A. J., 211, Geomagnetic secular variation and the statistics of palaeomagnetic directions: Geophysical Journal International, v. 186, p. 59-52. Fisher, R. A., 1953, Dispersion on a sphere: Proc. R. Soc. London, v. 217, p. 295-35.
42 43 44 45 46 47 48 49 5 51 52 53 54 55 56 57 58 59 6 61 62 63 64 65 66 67 68 69 7 71 72 73 74 75 76 77 78 79 8 81 82 83 84 85 86 87 88 89 9 Kirschvink, J. L., 198, The least-squares line and plane and the analysis of palaeomagnetic data: Geophysical Journal, Royal Astronomical Society, v. 62, p. 699-718. MacLeod, C. J. and Yaouancq, G., 2. A fossil melt lens in the Oman ophiolite: Implications for magma chamber processes at fast spreading ridges, arth and Planetary Science Letters, v. 176, p. 357-373. Petrovský,., and Kapička, A., 26, On determination of the Curie point from thermomagnetic curves: Journal of Geophysical Research, v. 111, B12S27, doi:1.129/26jb457. Tauxe, L., and Watson, G. S., 1994, The fold test: an eigen analysis approach: arth and Planetary Science Letters, v. 122, p. 331-341. Zijderveld, J. D. A., 1967, AC demagnetization of rocks: Analysis of results: Methods in Paleomagnetism, p. 254-286. DATA RPOSITORY - CAPTIONS Table DR1. Paleomagnetic results from Wadi Abyad and Wadi Khafifah, Oman ophiolite. Moho orientation is expressed as dip direction/dip. Dec = site mean declination. Inc = site mean inclination. D, I, declination and inclination error, respectively. k, α 95, precision parameter and 95% cone of confidence around the site mean characteristic remanent magnetizations (ChRMs) after Fisher (1953). K, A 95, precision parameter and 95% cone of confidence around the site mean virtual geomagnetic pole (VGP). A 95min, A 95max, minimum and maximum value of A 95 expected from paleosecular variation (PSV) of the geomagnetic field, according to Deenen et al. (211). N, number of total samples used for the statistics. Figure DR1. Typical exposure of layered in Wadi Abyad, Oman. Figure DR2. The petrological Moho exposed in Wadi Abyad, Oman. Mantle peridotites at the base of the section are overlain by modally layered. Layering is clearly visible in the upper right of the photograph, and is oriented parallel to the sharp boundary between crustal and mantle rocks (crossing the centre of the photograph). Figure DR3. Foliated exposed in Wadi Abyad, Oman. Note the steep orientation of the prominent magmatic foliation. Figure DR4. Varitextured exposed in Wadi Abyad, Oman, representing the fossil axial melt lens of the Oman spreading axis (MacLeod and Yaouancq, 2). Figure DR5. xposure of the dike rooting zone at the top of the Wadi Abyad section, Oman. Note the steeply dipping magmatic contact (to the left of the compass-clinometer), between a basaltic dike and the surrounding gabbro (right and left hand sides of the photograph, respectively). Figure DR6. Geological map of Wadi Khafifah, showing location of sampling sites. Inset: Lower hemisphere equal area projection of tilt corrected site mean magnetization directions and associated 95 cones of confidence (ellipses).
91 92 93 94 95 96 97 98 99 1 11 12 13 14 15 16 17 18 19 11 111 112 113 114 115 116 117 118 119 12 Figure DR7. Representative tilt corrected orthogonal vector plots of thermal (top) and alternating field (bottom) demagnetization data from specimens from different crustal levels in Wadi Abyad. Solid/open circles are projections of the remanence vector onto the horizontal/vertical planes respectively. Figure DR8. Representative examples of isothermal remanent magnetization acquisition curves for lower crustal rocks from Wadi Abyad (WA) and Wadi Khafifah (KF) in the Oman ophiolite, showing saturation by 3 mt consistent with remanence carried by low coercivity magnetite. Figure DR9. Respresentative examples of the variation of low field magnetic susceptibility with temperature for lower crustal rocks from Wadi Abyad (WA) and Wadi Khafifah (KF) in the Oman ophiolite. Red = heating curves, blue = cooling curves. Tc = Curie temperature, calculated using the inverse susceptibility method of Petrovsky & Kapička (26). Curie temperatures of 585-6 C indicate that magnetite is the dominant magnetic carrier in these rocks, but bumps in heating curves at lower temperatures in some samples may indicate alteration of titanomagnetite to titanomaghemite as a result of low-temperature oxidation and/or changes in susceptibility resulting from thermal annealing of stresses in magnetite. Increased susceptibility upon cooling indicates production of magnetite during heating. Figure DR1. A: qual area projection of in situ site mean directions of magnetization from layered and foliated from Wadi Abyad (circles; excluding sites WA9-11) and Wadi Khafifah (triangles). B: Data from A after restoring the Moho to horizontal at each locality. C. Positive bootstrap fold test (Tauxe and Watson, 1994) demonstrating remanence acquisition prior to tilting in these sections. Gray region contains the trends of the largest eigenvalues ( 1 s) of orientation matrices from representative pseudo-samples drawn from A during progressive untilting. Bold line is the cumulative distribution of 1 maxima of 1 and dashed lines are the bounds that enclose 95% of them.
TABL DR1. PALOMAGNTIC RSULTS FROM WADI ABYAD AND WADI KHAFIFAH, OMAN OPHIOLIT. In situ Tilt corrected Site Latitude ( N) Longitude ( ) Dec Inc Dec Inc D I k 95 K A 95 A 95min A 95max N Wadi Abyad (Moho orientation for tilt correction = 32/32) Layered : WA9 23 26' 39.4'' 57 39' 13.'' 5.3 31.3 9.4 2.1 5.9 11.8 113.9 6.3 129.8 5.9 8.3 26.5 6 WA1 23 26' 41.7'' 57 39' 27.1'' 327.2 25.3 336.1 9.1 2.2 4.4 498.8 2.5 623.4 2.2 7.4 22.1 8 WA11 23 26' 49.8'' 57 39' 41.8'' 326.6 2.9 333.4 5.5 4.3 8.6 149.2 4.5 164.4 4.3 7.4 22.1 8 WA12 23 27' 24.2'' 57 39' 48.1'' 296.7 46.1 327.4 4.2 2.1 2.7 131.2 1.9 1167.1 2. 8.3 26.5 6 WA4 23 27' 52.6'' 57 4' 37.3'' 312.6 33.4 329.2 22.7 3.1 5.3 119.9 3.5 162.5 3. 5.8 14.9 15 Foliated : WA5 23 27' 54.5'' 57 4' 38.1'' 32. 33.6 321.4 28. 1.3 2.1 1853.9 1.3 1896.3 1.3 7.4 22.1 8 WA6 23 27' 54.5'' 57 4' 37.1'' 39.9 33.8 327.4 24.3 4.8 8.2 15.2 5.4 138.5 4.7 7.4 22.1 8 WA1 23 27' 57.9'' 57 4' 38.7'' 318.4 42.2 338.6 27.4 4.5 7.3 17.9 4.6 194. 4.3 7.8 24.1 7 WA2 23 27' 57.9'' 57 4' 38.7'' 324.6 44.7 344.6 26.9 2.1 3.5 394.7 2.8 72.5 2.1 7.4 22.1 8 WA3 23 27' 57.9'' 57 4' 38.7'' 326.2 44. 345.3 25.7 3. 5.1 181.7 4.5 421.9 2.9 7.8 24.1 7 WA8 23 28' 3.6'' 57 4' 39.4'' 35.1 41.8 329.5 33. 5.2 7.7 28.2 6.4 344.8 5. 9.8 34.2 4 WA39 23 28' 1.7'' 57 4' 39.4'' 329.4 6.8 358.4 38.4 9.9 13.1 39.5 12.3 7.1 9.2 8.9 29.7 5 WA7 23 28' 16.6'' 57 4' 36.1'' 336.3 55.2 358.3 31.7 4.6 7. 115.2 5.2 159. 4.4 7.4 22.1 8 WA18-37 23 28' 35.5'' 57 4' 38.2'' 324.8 57.1 353.2 36.9 4. 5.5 31.1 4.3 4.1 3.8 4. 8.4 37 Varitextured : WA13 23 29' 2.6'' 57 4' 27.5'' 69.5 5.2 56.9 22.5 7.6 13.3 15.2 7.5 15.4 7.5 8.9 29.7 5 WA14 (discrete dike) 23 29' 2.6'' 57 4' 27.5'' 52.2 6.8 43.2 29.8 1.6 2.5 179.9 1.8 242.4 1.6 8.9 29.7 5 WA15 23 29' 1.5'' 57 4' 26.'' 56.9 56.3 47. 26. 1.1 16.8 36. 9.4 33. 9.8 7.4 22.1 8 WA16 (discrete dike) 23 29' 1.5'' 57 4' 26.'' 42.9 6.6 38.1 28.9 6.4 1.2 59.2 6. 55.1 6.2 6.5 18.1 11
Dike-rooting zone: WA17 23 28' 57.8'' 57 4' 55.4'' 75. 38.8 65.2 13.2 3.3 6.3 171.3 4.2 287. 3.3 7.4 22.1 8 Wadi Khafifah (Moho orientation for tilt correction = 173/29) Layered : KF3 22 52' 19.4'' 58 25' 45.8'' 34.9-8.3 34.2 2.1 5.6 1. 45.2 7.7 89. 5.5 7.1 2.5 9 KF4 22 53' 35.6'' 58 25' 24.4'' 358. 1.4 358.8 3.2 1.9 2.9 88.9 1.9 928. 1.8 7.4 22.1 8 KF5 22 53' 35.6'' 58 25' 24.5''. -3..9 25.7 3.6 6.1 36.8 3.8 359.5 3.5 8.3 26.5 6 KF6 22 53' 35.6'' 58 25' 24.5'' 359.7-3.6.4 25.2 2.4 4.1 498.2 3. 814.6 2.3 8.3 26.5 6 KF8 22 53' 36.3'' 58 25' 29.1'' 355.2 7.8 355.8 36.8 2.8 3.9 149.2 2.7 151.4 2.7 5.1 12.4 2 Foliated : KF2 22 51'.3'' 58 24' 57.'' 333.2 1.5 328.2 37.4 8.8 11.9 69.4 9.3 87.4 8.2 8.9 29.7 5 KF1 22 5' 16.5'' 58 25' 34.'' 334.7-11.6 334.4 15.9 2.1 3.9 911.4 2.5 1366.1 2.1 8.9 29.7 5 KF11 22 5' 16.5'' 58 25' 34.1'' 33.2-1.9 327.7 24.7 1.7 2.9 883.7 2.6 1639.9 1.7 8.3 26.5 6 KF12-27 22 51'.4'' 58 24' 57.5'' 336.9 6.9 333.5 34.6 3.5 5. 3.3 3.6 37. 3.3 3.5 6.8 52 KFS1 22 49' 51.2'' 58 25' 19.5'' 328.2-1.2 327.6 16.2 5.3 9.9 37.6 9.1 111.9 5.3 7.4 22.1 8 KFS2 22 49' 52.5'' 58 25' 19.1'' 332. -3.9 33.1 23.1 2.1 3.6 326.2 3.1 728.5 2.1 7.4 22.1 8 KFS3 22 49' 53.3'' 58 25' 18.3'' 35.3 13.1 349.4 42. 4.3 5.2 415.8 3.3 29.5 3.9 8.3 26.5 6 KFS4 22 49' 55.8'' 58 25' 16.5'' 324.7 1.9 32.8 27.1 2.8 4.5 184.5 3.4 293. 2.7 6.5 18.1 11
Figure DR1
Figure DR2
Figure DR3
Figure DR4
Figure DR5
Sediments Upper Lower & middle Mantle peridotite Fault km 2. 22 51' N 22 53' N Moho KF4-6, KF8 KF3 Wadi Khafifah KF2,12-27 N Wadi Khafifah Site mean directions: Foliated Layered KF1-11 KFS1-4 58 25' N 58 26' N Figure DR6
NRM = 1.58 Am -1 Layered WA121B 53 C NRM = 2.93 Am -1 NRM = 4. x 1-2 Am -1 NRM =.79 Am -1 Foliated WA15 Varitextured WA161 58 C 58 C 53 C 58 C 5 C 58 C Dike-rooting zone 56 C WA173C 35 C 5 C 5 C 3 C NRM = 1.9 Am -1 Layered WA121A 3 mt 1 mt NRM =.42 Am -1 Foliated WA38 3 mt Varitextured 1 mt WA163A 1 mt NRM = 4. x 1-2 Am -1 3 mt 1 mt Dike-rooting zone 3 mt NRM =.61 Am -1 WA173 Figure DR7
1. M max = 3.71 A/m 1. M max = 129. A/m.8.8 F = M/M max.6.4.2 Layered KF43A 1. ΔF/ΔF max F = M/M max.6.4.2 Foliated KF221A 1. ΔF/ΔF max 1 5 1 5 1 Applied field (mt) 1 5 1 5 1 Applied field (mt) 1. M max = 955. A/m 1. M max = 49.9 A/m.8.8 F = M/M max.6.4.2 Layered WA98 1. ΔF/ΔF max F = M/M max.6.4.2 Foliated WA292A 1. ΔF/ΔF max 1 5 1 5 1 Applied field (mt) 1 5 1 5 1 Applied field (mt) 1. M max = 295. A/m 1. M max = 12.9 A/m.8.8 F = M/M max.6.4.2 Varitextured WA154A 1. ΔF/ΔF max F = M/M max.6.4.2 Dike rooting zone WA172B 1. ΔF/ΔF max 1 5 1 5 1 Applied field (mt) 1 5 1 5 1 Applied field (mt) Figure DR8
2 6 7 Susceptibility 15 1 Susceptibility 5 4 3 2 2 5 Layered gabbro Layered gabbro Foliated gabbro WA111 1 KF53 1 WA17 T c = 585 C T c = 596 C T c = 63 C 1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7 Temperature ( C) Temperature ( C) Temperature ( C) 1 8 3 Susceptibility 6 5 4 3 Susceptibility 8 6 4 2 Foliated gabbro KF273 T c = 586 C 1 2 3 4 5 6 7 Temperature ( C) Susceptibility 7 6 5 4 3 Susceptibility 2 Varitextured gabbro Dike rooting zone 1 WA151 5 WA173D T c = 598 C T c = 595 C 1 2 3 4 5 6 7 1 2 3 4 5 6 7 Temperature ( C) Temperature ( C) 25 2 15 1 Figure DR9
1. C 94%-116% Untilting.8 N τ 1 (gray), CDF (bold line).6.4 A in situ.2 B Tilt corrected. -2 2 4 6 8 1 12 14 16 % Untilting Figure DR1