Fabrics and deformational mechanisms in the high-pressure granulites of the Bacariza Formation (Cabo Ortegal Complex, NW Spain)

P. Puelles

doi:10.21701/bolgeomin.120.1.003

Autores/as

P. Puelles Universidad del País Vasco, Dpto. Geodinámica

DOI:

https://doi.org/10.21701/bolgeomin.120.1.003

Palabras clave:

Cabo Ortegal, fábrica, granulita, mecanismos deformacionales, milonita

Resumen

En las zonas de contacto entre la Formación Bacariza (Complejo de Cabo Ortegal) y las unidades adyacentes afloran granulitas milonitizadas en condiciones de alta presión formadas durante la exhumación inicial del complejo. El estudio petrográfico, microestructural y cristalográfico de los minerales constitutivos de estas rocas puede facilitar información sobre los mecanismos deformacionales operativos en profundidad. El granate acomodó parte de la deformación mediante flujo de dislocaciones y rotación rígida, la augita se deformó por flujo de dislocaciones asistido por procesos de transferencia de masa y crecimiento anisótropo mientras que la plagioclasa experimentó recristalización dinámica por rotación de subgranos y flujo de dislocaciones. La petrofábrica del cuarzo indica una temperatura de deformación que, como mínimo, fue la de las anfibolitas. Los criterios cinemáticos reconocidos apuntan a un desplazamiento relativo de los bloques de techo hacia el NNE. En su ascenso hacia la superficie tuvo lugar un proceso de retrogradación estática en condiciones de las anfibolitas seguido por un mecanismo de deformación plástica en el campo de las anfibolitas de baja temperatura o de los esquistos verdes. Durante los últimos estadios de exhumación fue operativo un proceso de microfracturación y deformación sísmica episódica en condiciones de altos esfuerzos y rápidas tasas de deformación.

Descargas

Los datos de descargas todavía no están disponibles.

Citas

Ábalos, B., Mendia, M.S. y Gil Ibarguchi, J.I. 1994. Structure of the Cabo Ortegal eclogite-facies zone (NW Iberia). Les Comptes Rendus de l'Académie des Sciences de Paris, 319, 1231-1238.

Ábalos, B., Puelles, P. y Gil Ibarguchi, J.I. 2003. Structural assemblage of high-pressure mantle and crustal rocks in a subduction channel (Cabo Ortegal, NW Spain). Tectonics, 22 (2), 1006 https://doi.org/10.1029/2002TC001405

Allison, I. y Latour, T. E. 1977. Brittle deformation of hornblende in a mylonite. Canadian Journal of Earth Sciences, 14, 1953- 1958. https://doi.org/10.1139/e77-166

Austrheim, H., Erambert, M. y Boundy, T.M. 1996. Garnets record in deep crustal earthquakes. Earth and Planetary Science Letters, 193, 223-238. https://doi.org/10.1016/0012-821X(95)00232-2

Azor, A., Simancas, J.F., Expósito, I., González Lodeiro, F. y Martínez Poyatos, D.J. 1997. Deformation of garnets in a low-grade shear zone. Journal of Structural Geology, 19, 1137-1148. https://doi.org/10.1016/S0191-8141(97)00040-0

Bass, J.D. 1995. Elasticity of minerals, glasses and melts. En: Ahrens, T.J. (eds.), Mineral Physics and Crystallography: A Handbook of Physical Constants. American Geophysical Union, Washington, 45-63. https://doi.org/10.1029/RF002p0045

Ben Jamaa, N. 1998. Les peridotites de Bay of Islands (Terre Neuve) et de Cap Ortegal (Espagne): Approche petrostructurale. Ph.D. thesis, Univ. Paris VII.

Berger, A. y Stünitz, H. 1996. Deformation mechanisms and reaction of hornblende: examples from the Bergell tonalite. Tectonophysics, 257, 149-174. https://doi.org/10.1016/0040-1951(95)00125-5

Bons, P.D, y Den Brok, S.W.J. 2000. Crystallographic preferred orientation development by dissolution-precipitation creep. Journal of Structural Geology, 22, 1713-1722. https://doi.org/10.1016/S0191-8141(00)00075-4

Brodie, K.H. y Rutter, K.H. 1985. On the relationship between deformation and metamorphism, with special reference to the behavior of basic rocks. En: A.B. Thompson y D.C. Rubie (eds.), Metamorphic reactions, Kinetics, textures, and deformation. Springer-Verlag, Nueva York, 139-179. https://doi.org/10.1007/978-1-4612-5066-1_6

Brun, J.P. y Faccenna, C. 2008. Exhumation of high-pressure rocks driven by slab rollback. Earth and Planetary Science Letters. https://doi.org/10.1016/j.epsl.2008.02.038

Bunge, H. 1982. Texture Analysis in Materials Science, Mathematical Models. Butterworths, London, 593 pp. https://doi.org/10.1016/B978-0-408-10642-9.50019-2

Díaz Aspiroz, M., Lloyd, G.E. y Fernández, C. 2007. Development of lattice preferred orientation in clinoamphiboles deformed under low-pressure metamorphic conditions. A SEM/EBSD study of metabasites from te Aracena metamorphic belt (SW Spain). Journal of Structural Geology, 29, 629-645. https://doi.org/10.1016/j.jsg.2006.10.010

Egydio-Silva, M., Vauchez, A., Bascou, J., y Hippertt, J. 2002. High-temperature deformation in the neoproterozoic transpressional Ribeira belt, Southeast Brazil. Tectonophysics, 352, 203-224. https://doi.org/10.1016/S0040-1951(02)00197-X

Etheridge, M.A., Hobbs, B.E. y Paterson, M.S. 1973. Experimental deformation of single crystals of biotite. Contributions to Mineralogy and Petrology, 38, 21-36. https://doi.org/10.1007/BF00371724

Gapais, D. y Barbarin, B. 1986. Quartz fabric transition in a cooling syntectonic granite (Hermitage massif, France). Tectonophysics, 125, 357-370. https://doi.org/10.1016/0040-1951(86)90171-X

Gil Ibarguchi, J.I., Ábalos, B., Azcárraga, J., Mendia, M. y Puelles, P. 2000. A petrological and structural excursion through the high-grade/high-pressure allochthonous units of the Cabo Ortegal Complex (NW Spain). Basement Tectonics 15, Mid-Conference Field Trip, La Coruña, 1-59.

Girardeau, J., Gil Ibarguchi, J.I. y Ben Jamaa, N. 1989. Evidence for a heterogeneous upper mantle in the Cabo Ortegal Complex, Spain. Science, 245, 1231-1233. https://doi.org/10.1126/science.245.4923.1231

Godard, G. y Van Roermund, H.L.M. 1995. Deformationinduced clinopyroxene fabrics from eclogites. Journal of Structural Geology, 17, 1425-1443. https://doi.org/10.1016/0191-8141(95)00038-F

Helmstaedt, H., Anderson, O.L. y Gavasci, A.T. 1972. Petrofabric studies of eclogite, spinel-websterite, and spinel-lherzolite xenoliths from kimberlite-bearing breccia pipes in southeastern Utah and northeastern Arizona. Journal of Geophysical Research, 77, 4350-4365. https://doi.org/10.1029/JB077i023p04350

Hirth, G. y Tullis, J. 1992. Dislocation creep regimes in quartz aggregates. Journal of Structural Geology, 14, 145-159. https://doi.org/10.1016/0191-8141(92)90053-Y

Ji, S. y Martignole, J. 1994. Ductility of garnet as an indicator of extremely high temperature deformation. Journal of Structural Geology, 16, 985-996. https://doi.org/10.1016/0191-8141(94)90080-9

Ji, S. y Martignole, J. 1996. Ductility of garnet as an indicator of extremely high temperature deformation: Reply. Journal of Structural Geology, 18, 1375-1379. https://doi.org/10.1016/S0191-8141(96)00065-X

Ji, S., Mainprice, D. y Boudier, F. 1988. Sense of shear in high-temperature movement zones from the fabric asymmetry of plagioclase feldspars. Journal of Structural Geology, 10, 73-81. https://doi.org/10.1016/0191-8141(88)90129-0

Ji, S.C., Saruwatari, K., Mainprice, D., Wirth, R., Xu, Z., y Xia, B. 2003. Microstructures, petrofabrics and seismic properties of ultra high-pressure eclogites from Sulu region, China: implications for rheology of subducted continental crust and origin of mantle reflections. Tectonophysics, 370, 49-76. https://doi.org/10.1016/S0040-1951(03)00177-X

Karato, S. y Masuda, T. 1989. Anisotropic grain growth in quartz aggregates under stress and its implication for foliation development. Geology, 17, 695-698. https://doi.org/10.1130/0091-7613(1989)017<0695:AGGIQA>2.3.CO;2

Kleinschrodt, R. y Duyster, J.P. 2002. HT-deformation of garnet, an EBSD study on granulites from Sri Lanka, India and the Ivrea Zone. Journal of Structural Geology, 24, 1829-1844. https://doi.org/10.1016/S0191-8141(01)00167-5

Kleinschrodt, R. y McGrew, A. 2000. Garnet plasticity in the lower continental crust: implications for deformation mechanisms based on microstructures and SEM-electron channeling pattern analysis. Journal of Structural Geology, 22, 795-809. https://doi.org/10.1016/S0191-8141(00)00010-9

Kruse, R., Stünitz, H. y Kunze, K. 2001. Dynamic recrystallization processes in plagioclase porphyroclasts. Journal of Structural Geology, 23, 1781-1802. https://doi.org/10.1016/S0191-8141(01)00030-X

Law, R.D. 1990. Crystallographic fabrics: a selective review of their applications to research in Structural Geology. Spec. Publ. - Geological Society, London 54, 335-352. https://doi.org/10.1144/GSL.SP.1990.054.01.30

Lawn, B.R. y Wilshaw, T.R. 1975. Fracture of brittle solids. Cambridge University Press, New York, 204 pp.

Mainprice, D., Bascou, J., Cordier P. y Tommasi, A. 2004. Crystal preferred orientations of garnet: comparison between numerical simulations and electron back-scattered diffraction (EBSD) measurements in naturally deformed eclogites. Journal of Structural Geology, 26, 2089-2102. https://doi.org/10.1016/j.jsg.2004.04.008

Martínez Catalán, J.R., Arenas, R., Díaz-García, F. y Abati, J. 1997. Variscan accretionary complex of northwest Iberia: terrane correlation and succession of tectonothermal events. Geology, 25, 1103-1106. https://doi.org/10.1130/0091-7613(1997)025<1103:VACONI>2.3.CO;2

Mauler, A., Godard, G. y Kunze, K. 2001. Crystallographic fabrics of omphacite, rutile and quartz in Vendée eclogites (Armorican Massif, France). Consequences for deformation mechanisms and regimes. Tectonophysics, 342, 81-112. https://doi.org/10.1016/S0040-1951(01)00157-3

Mehl, L. y Hirth, G. 2008. Plagioclase preferred orientation in layered mylonites: Evaluation of flow laws for the lower crust. Journal of Geophysical Research, 113, B05202. https://doi.org/10.1029/2007JB005075

Pardavi-Horváth, M. 1984. Microhardness and brittle fracture of garnet single crystals. Journal of Materials Science, 19, 1159-1170. https://doi.org/10.1007/BF01120025

Price, G.P. 1985. Preferred orientations in quartzites. In: Wenk, H.R. (ed.), Preferred Orientation in Deformed Metals and Rocks: An Introduction to Modern Texture Analysis. Academic Press, San Diego, 385-406. https://doi.org/10.1016/B978-0-12-744020-0.50023-7

Prior, D. J. 1993. Subcritical fracture and associated retrogression of garnet during mylonitic deformation. Contributions to Mineralogy and Petrology, 113, 545-556. https://doi.org/10.1007/BF00698322

Puelles, P., Ábalos, B. y Gil Ibarguchi, J.I. 2005a. Metamorphic evolution and thermobaric structure of the subduction-related Bacariza high-pressure granulite formation (Cabo Ortegal Complex, NW Spain). Lithos, 84, 125-149. https://doi.org/10.1016/j.lithos.2005.01.009

Puelles, P., Mulchrone, K., Ábalos, B. y Gil Ibarguchi, J.I. 2005b. Structural analysis of high-pressure shear zones (Bacariza Formation, Cabo Ortegal, NW Spain). Journal of Structural Geology, 27, 1046-1060. https://doi.org/10.1016/j.jsg.2005.03.002

Raimbourg, H., Toyoshima, T., Harima, Y. y Kimura, G. 2008. Grain-size reduction mechanisms and rheological cosequences in high-temperature gabbro mylonites of Hidaka, Japan. Earth and Planetary Science Letters, 267, 637-653. https://doi.org/10.1016/j.epsl.2007.12.012

Santos Zalduegui, J.F., Schärer, U., Gil Ibarguchi, J.I. y Girardeau, J. 2002. Genesis of pyroxenite-rich peridotite at Cabo Ortegal (NW Spain): geochemical and Pb-Sr-Nd isotope data. Journal of Petrology, 43, 17-43. https://doi.org/10.1093/petrology/43.1.17

Schmid, S.M. y Casey, M. 1986. Complete fabric analysis of some commonly observed quartz c-axis patterns. American Geophysical Union Geophysical Monograph, 36, 263-286. https://doi.org/10.1029/GM036p0263

Spear, F. S. 1992. Thermobarometry and P-T paths from granulite facies rocks: an introduction. Precambrian Research, 55, 201-207. https://doi.org/10.1016/0301-9268(92)90024-I

Storey, C. D. y Prior, D.J. 2005. Plastic deformation and recrystallization of garnet: a mechanism to facilitate diffusion creep. Journal of Petrology, 46, 2593-2613. https://doi.org/10.1093/petrology/egi067

Toy, V., Prior, D. y J. Norris R. 2008. Quartz fabrics in the Alpine Faultmylonites: Influence of pre-existing preferred orientations on fabric development during progressive uplift. Journal of Structural Geology, 30, 602-621. https://doi.org/10.1016/j.jsg.2008.01.001

Trepmann, C. y Stöckhert, B. 2002. Cataclastic deformation of garnet: a record of synseismic loading and postseismic creep. Journal of Structural Geology, 24, 1845-1856. https://doi.org/10.1016/S0191-8141(02)00004-4

Vance, D. y Holland, T. 1993. A detailed isotopic and petrological study of a single garnet from the Gassetts Schist, Vermont. Contributions to Mineralogy and Petrology, 114, 101-118. https://doi.org/10.1007/BF00307868

Vernooij, M.G.C., den Brok, B. y Kunze, K. 2006. Development of crystallographic preferred orientations by nucleation and growth of new grains in experimentally deformed quartz single crystals. Tectonophysics, 427 (1-4), 35-53. https://doi.org/10.1016/j.tecto.2006.06.008

Voegelé, V., Ando, J.I., Cordier, P. y Liebermann, R.C. 1998. Plastic deformation of silicate garnet I. High-pressure experiments. Physics of the Earth and Planetary Interiors, 108, 305-318. https://doi.org/10.1016/S0031-9201(98)00110-1

Vollbrecht, A., Pawlowski, J., Leiss, B., Heinrichs, T., Seidel, M. y Kronz, A. 2006. Ductile deformation of garnet in mylonitic gneisses from the Münchberg Massif (Germany). Tectonophysics, 427, 153-170. https://doi.org/10.1016/j.tecto.2006.05.024

Whitney, D., Goergen, E., Ketcham, R. y Kunze, K., 2008. Formation of garnet polycrystals during metamorphic crystallization. Journal of Metamorphic Geology, 26, 363-383. https://doi.org/10.1111/j.1525-1314.2008.00763.x