Geofísica Internacional ISSN: 0016-7169 [email protected] Universidad Nacional Autónoma de México México Urrutia-Fucugauchi, Jaime; Pérez-Cruz, Ligia; Flores-Gutiérrez, Daniel Meteorite paleomagnetism - From magnetic domains to planetary fields and core dynamos Geofísica Internacional, vol. 53, núm. 3, julio-septiembre, 2014, pp. 343-363 Universidad Nacional Autónoma de México Distrito Federal, México Available in: http://www.redalyc.org/articulo.oa?id=56831360009 How to cite Complete issue Scientific Information System More information about this article Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Journal's homepage in redalyc.org Non-profit academic project, developed under the open access initiative Geofísica Internacional (2014) 53-3: 343-363 Review Meteorite paleomagnetism - From magnetic domains to planetary fields and core dynamos Jaime Urrutia-Fucugauchi*, Ligia Pérez-Cruz and Daniel Flores-Gutiérrez Received: April 02, 2014; accepted: April 29, 2014; published on line: July 01, 2014 Resumen interacciones a escalas de dominio magnético. En este trabajo revisamos los estudios en Los meteoritos condríticos representan los cóndrulos del meteorito condrítico Allende, registros más tempranos de la evolución del que revelan relaciones entre los parámetros Sistema Solar, proveyendo información sobre magnéticos de histéresis y propiedades físicas. las condiciones, procesos y cronología de la Los parámetros y cocientes de coercitividad, formación de los primeros materiales sólidos, magnetización remanente y magnetización planetesimales y cuerpos diferenciados. La de saturación muestran correlaciones con la evidencia sobre los campos magnéticos en las densidad y tamaño de los cóndrulos, los cuales etapas tempranas de evolución del sistema están relacionados a la estructura interna, solar se ha obtenido a partir de estudios en mineralogía, composición y morfología. Los meteoritos condríticos. Estos meteoritos se cóndrulos compuestos, fragmentados y con caracterizan por la abundancia de cóndrulos, anillos de recubrimiento se caracterizan que constituyen pequeñas esferas de silicatos por propiedades de histéresis magnética de tamaño milimétrico, formadas a partir del distintas, asociadas a la composición y arreglos polvo en la nebulosa y que fueron calentadas y mineralógicos y microestructuras. Los registros enfriadas rápidamente. Los condrulos retienen de magnetización remanente y las estimacio- un registro de magnetización remanente, que nes de paleointensidades derivadas en estudios data del tiempo de calentamiento y enfriamiento del Allende y otras condrítas carbonáceas durante la formación de cóndrulos y su acreción apoyan adquisición de la magnetización bajo en planetesimales. Los estudios sobre las la influencia de campos magnéticos internos diferentes clases de meteoritos, incluyendo dentro de planetesimales. Los resultados a los meteoritos condríticos ordinarios y apoyan una rápida diferenciación, siguiendo la los meteoritos condriticos carbonáceos han formación de las inclusiones de calcio y aluminio documentado resultados contrastantes con una y cpondrulos para formar los palnetesimales. rango amplio de magnitudes de los campos Los planetesimales se caracterizarían por una magnéticos en el disco protoplanetario. Ello estructura diferenciada con núcleos metálicos ha dificultado definir la naturaleza de los con capacidad de dinamo autosustentable campos magnéticos en las etapas iniciales por periodos de varios millones de años. El de evolución. Los desarrollos recientes en meteorito condrítico Allende se formó y derivó instrumentación y técnicas de análisis de de un planetesimal parcialmente diferenciado, magnetismo de rocas y paleointensidades con un núcelo de hierro capaz de sostener un permiten una mayor precisión. Los análisis de campo magnético interno. micromagnetismo, geoquímica, petrografía y microscopía electrónica proveen de una alta Palabras clave: Paleomagnetismo, meteoritos, resolución, previamente no disponible, para campos magnéticos, dínamos, Sistema Solar. caracterizar las propiedades magnéticas e J. Urrutia-Fucugauchi* D. Flores-Gutiérrez L. Pérez-Cruz Instituto de Astronomía Programa Universitario de Perforaciones en Océanos Universidad Nacional Autónoma de México y Continentes Coyoacán 04510 Instituto de Geofísica México D.F., México Universidad Nacional Autónoma de México Coyoacán 04510 México D.F., México 343 J. Urrutia-Fucugauchi, L. Pérez-Cruz and D. Flores-Gutiérrez Abstract the Allende meteorite that reveal relationships among hysteresis parameters and physical Meteorites represent the earliest records of the properties. Coercivity, remanent and saturation evolution of the solar system, providing information remanence parameters correlate with chondrule on the conditions, processes and chronology size and density; in turn related to internal for formation of first solids, planetesimals and chondrule structure, mineralogy and morphology. differentiated bodies. Evidence on the nature Compound, fragmented and rimmed chondrules of magnetic fields in the early solar system show distinct hysteresis properties, related has been derived from chondritic meteorites. to mineral composition and microstructures. Chondrules, which are millimeter sized silicate The remanent magnetization record and spherules formed by rapid melting and paleointensity estimates derived from the cooling, have been shown to retain remanent Allende and other chondrites support remanent magnetization records dating from the time of acquisition under influence of internal magnetic chondrule formation and accretion of planetesimals. fields within parent planetesimals. Results Studies on different meteorite classes, support that rapid differentiation following including ordinary and carbonaceous chondrites, formation of calcium-aluminum inclusions have however provided contrasting results with and chondrules gave rise to differentiated wide ranges for protoplanetary disk magnetic planetesimals with iron cores, capable of fields. Developments on instrumentation and generating and sustaining dynamo action for techniques for rock magnetic and paleointensity million year periods. The Allende chondrite analyses are allowing increased precision. may have derived from a partly differentiated Micromagnetic and an array of geochemical, planetesimal which sustained an internal petrographic and electronic microscopy analyses magnetic field. provide unprecedented resolution, characterizing rock magnetic properties at magnetic domain Key words: Paleomagnetism, meteorites, scales. We review studies on chondrules from magnetic fields, dynamos, Solar System. Introduction and differentiated classes, which include ordinary and carbonaceous chondrites and Studies of meteorites provide the earliest achondrites and iron meteorites, respectively records concerning the conditions and evolution (Weisberg et al., 2006). Chondrules represent of the planetary system (Wood, 1988; Cameron, molted droplets of aggregated fine silicate dust, 1988; Lauretta and McSween, 2006). Meteorites recording transient heating events in the solar constitute the oldest rocks preserved from the nebula (Hewins, 1997; Zanda, 2004; Scott, initial stages of planetary accretion. Information 2007). They show different textures and mineral on the age of the solar system, conditions assemblages, with some containing fragments and chronology for formation of first solids, of other chondrules and rare CAIs. Preservation planetesimals and early differentiated bodies of chondrules indicates that chondrites were is based on studies of chondrites and other not melted through their subsequent history primitive meteorites (Wood, 1988; Hewins et after formation. In contrast, differentiated al., 1996; Scott, 2007; Connelly et al., 2012). meteorites, which include iron and iron-silicate Chondrites are composed by millimeter sized meteorites, were subject to various degrees of silicate spherules named chondrules and calcium- melting and metamorphism, and interpreted as aluminum rich inclusions (CAIs) embedded in derived from planetesimals later fragmented by a fine grained silicate matrix. In recent years collisions. research on the origin and evolution of the solar system has expanded, with developments from Understanding the early stages of planetary planetary missions, astronomical observations, system evolution has remained a complex discovery of exoplanets and theoretical and difficult task. Considerable effort is spent in numerical simulation models. The multi-and characterizing the distinct classes of meteorites, interdisciplinary approaches and new data which are investigated with a wide range of are providing fresh insights on the origin analytical techniques. Studies have documented of planetary systems. Major questions on new minerals and unraveled evidence on the fundamental aspects still remain open, including formation and alteration histories of meteorites conditions and chronology in the early phases. and parent planetesimals with increasing detail (Taylor et al., 1987; Nyquist et al., 2009; Weiss Many studies on meteorites focused on the and Elkins-Tanton, 2013). The conditions and petrography and geochemistry, which permitted nature of processes involved in the formation of to distinguish and characterize distinct classes of the proto-Sun, chondrules, CAIs, and early accreted meteorites. Meteorites are divided into primitive planetesimals remain poorly constrained. 344 Volume 53 Number 3 Geofísica Internacional We review micromagnetic