Magnetic anisotropy of a sub-ophiolitic metamorphic sole (Mersin ophiolite, Türkiye)

Year 2023, Volume: 170 Issue: 170, 1 - 14, 17.04.2023

Buğra Çavdar Antony Morris Mark Anderson Luca Menegon Osman Parlak

https://doi.org/10.19111/bulletinofmre.1081170

Abstract

The Mersin ophiolite of southern Turkey is a well-exposed, Late Cretaceous, Neo-Tethyan suprasubduction zone ophiolite. It is underlain by metamorphic sole rocks inferred to have formed at the top of a down-going plate during subduction. These have a well-developed foliation and lineation observable in the field (defined by the preferred orientations of hornblende and plagioclase crystals). Here we present the first magnetic fabric data reported from the Mersin ophiolite with such settings. Anisotropy of low field magnetic susceptibility ellipsoids in sampled amphibolites have clustered, NW-plunging minimum principal axes representing poles to a SE-dipping magnetic foliation that aligns with the macroscopic metamorphic foliation plane seen in the field. Maximum AMS principal axes define a SE-plunging magnetic lineation that is parallel to the macroscopic metamorphic lineation. Oblate magnetic fabrics at specimen-level and an overall triaxial fabric at localitylevel in these rocks are consistent with the development of the
dominant metamorphic fabric by a combination of pure shear flattening and simple shearing during the formation and exhumation of the Mersin sole rocks. These observations are compatible with a recent tectonic model for the evolution of the ophiolite based on paleomagnetic data that invokes flattening and exhumation of the down-going slab in an incipient subduction zone during supra-subduction zone spreading.

Keywords

Magnetic Anisotropy, Rock Magnetism, Amphibolites, Ophiolite, Metamorphic Sole.

Supporting Institution

Directorate General for Higher and Overseas Education of the Ministry of National Education, Republic of Turkey

Thanks

We thank the Directorate General for Higher and Overseas Education of the Ministry of National Education, Republic of Turkey for the financial support provided to Buğra Çavdar during his research masters (ResM) at the University of Plymouth.

References

• Bascou, J., Raposo, M. I. B., Vauchez, A., Egydio-Silva, M. 2002. Titanohematite lattice-preferred orientation and magnetic anisotropy in high-temperature mylonites. Earth and Planetary Science Letters 198, 77-92.
• Biedermann, A. R., Koch, C. B., Pettke, T., & Hirt, A. M. (2015). Magnetic anisotropy in natural amphibole crystals. American Mineralogist, 100(8-9), 1940-1951.
• Biedermann, A.R., Kunze, K., Hirt, A.M. 2018. Interpreting magnetic fabrics in amphibole-bearing rocks. Tectonophysics 722, 566–576.
• Borradaile, G. J., Hamilton, T. (2004). Magnetic fabrics may proxy as neotectonic stress trajectories, Polis rift, Cyprus. Tectonics, 23(1).
• Borradaile, G. J., & Jackson, M. (2004). Anisotropy of magnetic susceptibility (AMS): magnetic petrofabrics of deformed rocks. Geological Society, London, Special Publications, 238(1), 299-360.
• Bouchez, J. L. (1997). Granite is never isotropic: an introduction to AMS studies of granitic rocks. In Granite: from segregation of melt to emplacement fabrics (pp. 95-112). Springer, Dordrecht.
• Cañón-Tapia, E. 2004. Anisotropy of magnetic susceptibility of lava flows and dykes: a historical account. Geological Society, London, Special Publications 238, 205-225.
• Constable, C., Tauxe, L. 1990. The bootstrap for magnetic susceptibility tensors. Journal of Geophysical Research 95, 8383– 8395.
• Di Chiara, A., Morris, A., Anderson, M. W., Menegon. L., Tremblay, T. 2020. Magnetic anisotropy reveals Acadian transpressional fabrics in an Appalachian ophiolite (Thetford Mines, Canada). Geophysical Journal International 222, 1034-1045.
• Dilek, Y., Thy, P., Hacker, B., Grundvig, S. 1999. Structure and petrology of Tauride ophiolites and mafic dike intrusions (Turkey): Implications for the Neotethyan ocean. Geological Society of America Bulletin 111, 1192.
• Escartín, J., Canales, J. P. 2011. Detachments in oceanic lithosphere: deformation, magmatism, fluid flow, and ecosystems. Eos Transactions American Geophysical Union, 92(4).
• Ferré, E. C., Teyssier, C., Jackson, M., Thill, J. W., Rainey, E.S.G. 2003. Magnetic susceptibility anisotropy: a new petrofabric tool in migmatites. Journal of Geophysical Research 108, NO. B2, 2086.
• Ferré, E., Martín-Hernández, F., Teyssier, C., Jackson, M. 2004. Paramagnetic and ferromagnetic anisotropy of magnetic susceptibility in migmatites: measurements in high and low fields and kinematic implications. Geophysical Journal International 157, 1119-1129.
• Jelínek, V. 1978. Statistical processing of magnetic susceptibility measured on groups of specimens. Studia Geophysica et Geodaetica 22, 50–62.
• Kent, J. T. 1982. The Fisher-Bingham distribution on the sphere. Journal of the Royal Statistical Society, Series B, 44, 71–80.
• Kruckenberg, S. C., Ferré, E.C., Teyssier, C., Vanderhaeghe, O., Whitney, D. L., Seaton, N. C. A., Skord, J. A. 2010. Viscoplastic flow in migmatites deduced from fabric anisotropy: an example from the Naxos dome, Greece. Journal of Geophysical Research 115, B09401.
• Martín-Hernández, F., Lüneburg, C. M., Aubourg, C., Jackson, M. 2004. Magnetic fabric: methods and applications. Geological Society, London, Special Publications 238, 551.
• Mattei, M., D’Agostino, N., Zananiri, I., Kondopoulou, D., Pavlides, S., Spatharas, V. 2004. Tectonic evolution of fault- bounded continental blocks: comparison of paleomagnetic and GPS data in the Corinth and Megara basins (Greece). Journal of Geophysical Research, 109.
• Morris, A. 2000. Magnetic fabric and palaeomagnetic analyses of the Plio-Quaternary calc-alkaline series of Aegina Island, South Aegean volcanic arc, Greece. Earth and Planetary Science Letters 176, 91-105.
• Morris, A., Anderson, M. W., Omer, A., Maffione, M., van Hinsbergen, D. J. J. 2017. Rapid fore-arc extension and detachment-mode spreading following subduction initiation. Earth and Planetary Science Letters 478, 76-88.
• Morris, A., Meyer, M., Anderson, M. W., MacLeod, C. J. 2019. What do variable magnetic fabrics in gabbros of the Oman ophiolite reveal about lower crustal magmatism at fast spreading ridges?. Geology 47, 275-278.
• Omer, A. H. (2014). Integrated geophysical, geochemical and structural analysis of the Mersin ophiolite, southern Turkey (Unpublished doctoral dissertation). University of Plymouth, Plymouth, United Kingdom.
• Parés, J. S. 2015. Sixty years of anisotropy of magnetic susceptibility in deformed sedimentary rocks. Frontiers in Earth Science 3, 1-13.
• Parlak, O., Delaloye, M., Bingöl, E. 1995. Origin of subophiolitic metamorphic rocks beneath the Mersin ophiolite, southern Turkey. Ofioliti 20, 97-110.
• Parlak, O., Delaloye, M. 1996. Geochemistry and timing of post metamorphic dyke emplacement in the Mersin Ophiolite (southern Turkey): New age constraints from 40Ar/39Ar geochronology. Terra Nova 8, 585-592.
• Parlak, O., Bozkurt, E., Delaloye, M. 1996. The obduction direction of the Mersin Ophiolite: structural evidence from subophiolitic metamorphics in the Central Tauride Belt, Southern Turkey. International Geology Review 38, 778- 786.
• Parlak, O., Delaloye, M. 1999. Precise 40Ar/39Ar ages from the metamorphic sole of the Mersin ophiolite (southern Turkey). Tectonophysics 301, 145-158.
• Parlak, O., Robertson A. H. F. 2004. The ophiolite-related Mersin Melange, southern Turkey: its role in the tectonic– sedimentary setting of Tethys in the Eastern Mediterranean region. Geological Magazine 141, 257-286.
• Parlak, O., Karaoğlan, F., Rızaoğlu, T., Klötzli, U., Koller, F., Billor, Z. 2013. U-Pb and 40Ar–39Ar geochronology of the ophiolites and granitoids from the Tauride belt: Implications for the evolution of the Inner Tauride suture. Journal of Geodynamics 65, 22– 37.
• Parlak, O., Dunkl, I., Karaoğlan, F., Kusky, T., Zhang, C., Wang, L., Koepke, J., Billor, Z., Hames, W. E., Şimşek, E., Şimşek, G., Şimşek, T., Öztürk, S. E. 2019. Rapid cooling history of a Neotethyan ophiolite: evidence for contemporaneous subduction initiation and metamorphic sole formation. Geological Society of America Bulletin 131, 2011-2038.
• Potter, D. K., Stephenson, A. 1988. Single domain particles in rocks and magnetic fabric analysis. Geophysical Research Letters 15, 1097–1100.
• Rochette, P., Jackson, M., Aubourg, C. 1992. Rock magnetism and the interpretation of anisotropy of magnetic susceptibility. Reviews of Geophysics 30, 209-226.
• Staudigel, H., Tauxe, L., Gee, J. S., Bogaard, P., Haspels, J., Kale, G., Leenders, A., Meijer, P., Swaak, B., Tuin, M., Van
• Soest, M. C., Verdurmen, E. A. Th., Zevenhuizen, A. 1999. Geochemistry and intrusive directions in sheeted dikes in the Troodos ophiolite: implications for mid-ocean ridge spreading centers. Geochemistry Geophysics Geosystems 13, 1.
• Stephenson, A. 1994. Distribution anisotropy: two simple models for magnetic lineation and foliation. Physics of the Earth and Planetary Interiors 82, 49-53.
• Tarling, D.H., Hrouda, F. 1993. The Magnetic Anisotropy of Rocks, Chapman & Hall, London, 217.
• Tauxe, L., Butler, R.F., Banerjee, S.K., Van der Voo, R. 2010. Essentials of Paleomagnetism, Berkeley, California, University of California Press, 500.
• Tekin, U.K., Bedi, Y., Okuyucu, C., Göncüoglu, M.C., Sayit, K. 2016. Radiolarian biochronology of upper Anisian to upper Ladinian (Middle Triassic) blocks and tectonic slices of volcano-sedimentary successions in the Mersin Mélange, southern Turkey: new insights for the evolution of Neotethys. Journal of African Earth Sciences 124, 409–426.
• Thompson, R., Oldfield, F. 1986. Environmental Magnetism. Allen and Unwin, London. 227.
• Van Hinsbergen, D. J., Peters, K., Maffione, M., Spakman, W., Guilmette, C., Thieulot, C., Kaymakcı, N. (2015). Dynamics of intraoceanic subduction initiation: 2. Suprasubduction zone ophiolite formation and metamorphic sole exhumation in context of absolute plate motions. Geochemistry, Geophysics, Geosystems, 16(6), 1771-1785.