The oceanic crust in 3D: Paleomagnetic reconstruction in the Troodos ophiolite gabbro

Granot, Roi; Abelson, Meir; Ron, Hagai; Agnon, Amotz

doi:10.1016/j.epsl.2006.09.019

Cited by 14 publications

(14 citation statements)

References 47 publications

(66 reference statements)

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“…Although the gabbros studied here lack independent structural information, remanence directions together with the assumed N-S trend of rotation axis (parallels the Solea axis) are sufficient to correct for tectonic rotations. Granot et al [2006] have shown that small rotations of 21°around a rotation axis plunging 7°to the north have been accommodated within the center of the Solea axis. Progressively increasing clockwise rotations eastward indicates that the lower crust in the inside corner has undergone rotations of 44°around a rotation axis plunging 53°to the north ( Figure S1).…”

Section: Discussionmentioning

confidence: 99%

“…[11] Tectonic rotations associated with seafloor spreading are known to have affected all crustal levels of the Troodos igneous basement, and must be corrected for in order to recover the original orientation of the petrofabrics within the sampled gabbros [Granot et al, 2006]. Paleomagnetic studies of the upper crust and overlying sedimentary sequence [e.g., Morris et al, 2006] showed that the entire ophiolite had rotated by nearly 90°anti-clockwise during the emplacement (late Cretaceous to early Eocene), leading to an expected remanent magnetization direction of 273°/38°(a 95 = 6.5°).…”

Section: Discussionmentioning

confidence: 99%

“…In site we have randomly sampled five to seven oriented cores over some 5 to 15 meters of exposure to unravel the dominant trend of the silicate fabric. Paleomagnetic data from the studied sites have been published elsewhere [Granot et al, 2006[Granot et al, , 2007.…”

Section: Samplingmentioning

confidence: 99%

“…Rochette et al [1992] showed that mixing distributions of single domain to pseudo single domain titanomagnetite grain sizes can result in the Intermediate Fabric where K 2 and K 3 susceptibility axes may interchange their directions, leading to a non unique presentation of the silicate fabric by the AMS tensors. Indeed, remanence magnetization in the Troodos gabbros is carried by single to pseudo single domain titanomagnetite grain sizes [Granot et al, 2006[Granot et al, , 2007, and we therefore use only K 1 susceptibility data. We find a spatial coherence of K 1 directions for adjacent sites (Figure 1), distributed over a 10 km scale region, and hence presume that the measured K 1 directions mimic the large-scale lineation pattern of the silicate fabric.…”

Section: Magma Flow Directionmentioning

confidence: 99%

“…The location of the Solea graben was originally constrained by the orientation of normal faults, opposing tilt of sheeted dikes, and rotated blocks of lava flow [Hurst et al, 1994]. Paleomagnetic study of the gabbroic suite [Granot et al, 2006] confirmed the location of the suspected paleospreading Solea axis and showed a clockwise rotation of remanence directions in the inside corner north of the Arakapas Transform fault ( Figure S1 in the auxiliary material), similar to the rotations shown for the overlying sheeted dikes [Allerton, 1989;Bonhommet et al, 1988], pillow lavas and hydrothermal sediments (umbers) [Morris et al, 1990]. …”

Section: Tectonic Settingmentioning

confidence: 99%

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Direct evidence for dynamic magma supply fossilized in the lower oceanic crust of the Troodos ophiolite

Granot

Abelson

Ron

et al. 2011

Geophys. Res. Lett.

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Temporal and spatial variabilities of mantle upwelling and melt supply in mid‐ocean ridges (MORs) have long been documented. Such variabilities span a range of scales and have a profound effect on the structure as well as the composition of the oceanic crust. Previous seismic and gravity studies have suggested that the lower oceanic crust plays a major role in accommodating these changes in melt supply. Here we report the first direct evidence for a sharp transition from coherent sub‐horizontal to near vertical magma flows frozen in the lower oceanic crust of the Troodos ophiolite at the segment edge near a fossil ridge‐transform intersection. We constrain the preferred petrofabric lineation directions at 13 gabbroic sites using anisotropy of magnetic susceptibility (AMS) verified by electron backscatter diffraction. Pre‐emplacement accretion‐related rotations were corrected using magnetic remanence directions. We identify two provinces of nearly uniform susceptibility directions (principal axes) and attribute them to two magmatic episodes. A more focused mantle upwelling and melting episode near the segment midpoint may have resulted in lower crustal lateral magma flows along the fossil segment‐edge, whereas uniform mantle upwelling and melt supply along the entire axis may have resulted in vertical magma flows at the segment‐edge. Overall, our data verify the vital role of the lower oceanic crust in accommodating changes in mantle upwelling and melt supply beneath MORs.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Samplingmentioning

confidence: 99%

Section: Magma Flow Directionmentioning

confidence: 99%

Section: Tectonic Settingmentioning

confidence: 99%

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Direct evidence for dynamic magma supply fossilized in the lower oceanic crust of the Troodos ophiolite

Granot

Abelson

Ron

et al. 2011

Geophys. Res. Lett.

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Investigation of a marine magnetic polarity reversal boundary in cross section at the northern boundary of the Kane Megamullion, Mid‐Atlantic Ridge, 23°40′N

Tivey

2016

JGR Solid Earth

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Near‐bottom magnetic field measurements made by the submersible Nautile during the 1992 Kanaut Expedition define the cross‐sectional geometry of magnetic polarity reversal boundaries and the vertical variation of crustal magnetization in lower oceanic crust exposed along the Kane Transform Fault (TF) at the northern boundary of the Kane Megamullion (KMM). The KMM exposes lower crust and upper mantle rocks on a low‐angle normal fault that was active between 3.3 Ma and 2.1 Ma. The geometry of the polarity boundaries is estimated from an inversion of the submarine magnetic data for crustal magnetization. In general, the polarity boundaries dip away from the ridge axis along the Kane TF scarp, with a west dipping angle of ~45° in the shallow (<1 km) crust and <20° in the deeper crust. The existence of the magnetic polarity boundaries (e.g., C2r.2r/C2An.1n, ~2.581 Ma) indicates that the lower crustal gabbros and upper mantle serpentinized peridotites are able to record a coherent magnetic signal. Our results support the conclusion of Williams (2007) that the lower crust cools through the Curie temperature of magnetite to become magnetic, with the polarity boundaries representing both frozen isotherms and isochrons. We also test the effects of the rotation of this isotherm structure and/or footwall rotation and find that the magnetic polarity boundary geometry is not sensitive to these directional changes.

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Remembering Hagai (1944–2012)

Shaar

2015

Afr Archaeol Rev

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The oceanic crust in 3D: Paleomagnetic reconstruction in the Troodos ophiolite gabbro

Cited by 14 publications

References 47 publications

Direct evidence for dynamic magma supply fossilized in the lower oceanic crust of the Troodos ophiolite

Direct evidence for dynamic magma supply fossilized in the lower oceanic crust of the Troodos ophiolite

Investigation of a marine magnetic polarity reversal boundary in cross section at the northern boundary of the Kane Megamullion, Mid‐Atlantic Ridge, 23°40′N

Remembering Hagai (1944–2012)

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