Studying the Thermal Metamorphism Experienced by the Parent Asteroid of Villalbeto de la Peña Ordinary Chondrite Using an Equilibrium Phase Diagram Model

Ponencia virtual expuesta en el 52nd Lunar and Planetary Science Conference (2021) celebrado online del 15 al 19 de marzoThe study of chondritic meteorites gives us the chance to recover valuable information about the thermal and collisional evolution of undifferentiated planetesimals formed early in the history of the Solar System [1]. In particular, oxygen isotopes indicate that ordinary and enstatite chondrites were probably dominant as terrestrial building blocks [2], which makes them a clear target when studying terrestrial crust and mantle. Chondrites themselves are primarily composed of the primordial protoplanetary disk materials which constituted the original building blocks of the bigger bodies in the Solar System: planets, comets and asteroids [3]. The latter bodies are the best candidates when characterizing the early stages of the Solar System aggregate

An Equilibrium Phase Diagram Model to Study the Metamorphism Experienced by the Villalbeto de la Peña Ordinary Chondrite Parent Body

51st Lunar and Planetary Science Conference (2020), March 16–20, 2020, The Woodlands, TexasThis is an implementation of the available techniques used to study metamorphic rocks to determine the formation conditions of a meteoritic sample in its parent asteroid.The authors thank the funding received from MEC through the PGC2018-097374-BI00 (JMTR) and CGL2015-66335-C2-2-R (JRE) research grants

The role of mantle and crust in the generation of calc-alkaline Variscan magmatism and its tectonic setting in the Eastern Pyrenees

The lower structural levels of the Variscan orogen exposed in the Eastern Pyrenees reveal three genetically associated magmatic suites: (i) a batholitic sized calc-alkaline granitoid (Sant Llorenç - La Jonquera, SL-LJ); (ii) minor mafic intrusions with local ultramafic cumulates (Ceret and Mas Claret mafic complexes); and (iii) peraluminous leucogranite bodies. These suites were emplaced in a syn- to post-collisional setting during the Late Carboniferous - Early Permian (ca. 315-290 Ma) in an Upper Proterozoic-Upper Ordovician metasedimentary sequence. We carried out field and petrographic work and whole-rock geochemistry (including Sr-Nd radiogenic isotopes) in order to constrain the petrogenetic relationships between them and to determine the interplay of the igneous suites with the country rock. We compare geochemical data to those from the neighbouring massifs of the Pyrenees and Catalan Coastal Ranges. The granitoids and the mafic complexes underwent variable degrees of lower crustal assimilation as demonstrated by the Sr and Nd isotopic ratios of SL-LJ granitoids and mafic rocks. Contaminated gabbro-diorites are high in Fe and Zr and contain magmatic garnet in equilibrium with an Fe-Mg amphibole. A supra-subduction metasomatized mantle source for the mafic complexes is inferred. The magma that formed the SL-LJ granitoids was of intermediate composition and may have formed by differentiation of magmas derived from partial melting of a subduction-metasomatized mantle caused by active subduction or mantle delamination or by partial melting of the lower crust triggered by underplating of mantle-derived mafic magmas. Leucogranite magmas formed later by partial melting of crustal rocks with compositions similar to the outcropping metapelites and orthogneisses. We deduce a retrograde cooling decompression path from 0.75 GPa down to 0.55 GPa from phase equilibria for a garnet-bearing diorite. This path is compatible with a local extensional context linked to a regional dextral strike-slip regime that provided space for the ascent and emplacement of the pluton. This strike-slip system is consistent with late-Variscan shear zones displacing Gondwana to the west with respect to Laurasia during the orogenic collapse

Variscan Metamorphism

Various segments of Variscan crust are currently exposed in Iberia in response to successive tectonic events during the Variscan orogeny itself and subsequent extensional and compressive events during the Alpine cycle, all accompanied by surface erosion, and collectively contributing to their exhumation. We review the main characteristics and geodynamic contexts of the metamorphic complexes developed in Iberia during the Variscan cycle, which include: (i) LP-HT complexes associated to the Cambrian-Early Ordovician rift stage; (ii) HP-LT complexes associated to subduction; and (iii) syn-to-post-collisional, MP and LP/HT complexes from the hinterland to the foreland fold-and thrust belts. All the above contexts are illustrated with case studies. Finally, a review of Variscan metamorphism in the Pyrenees and Catalan Coastal Ranges, located far away from the Rheic suture is also presented