Petrochronological studies made by our collaborators
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[TFM] Mylonitic calc-silicate from Southern Italian Alps
EN I For this week’s #TuesdayFieldMemories we would like to share a mylonitic calc-silicate from Southern Italian Alps (Forno Rosa Shear zone, in the Ossola Valley in Simonetti et al. 2023), courtesy of Dr. Stefania Corvo, which she will further discuss on our P-T- t talk session this Thursday. We see you there! Milonito calcissilicático…
[TST] Garnet porphyroclasts in ultramylonite from the Southern Italian Alps
EN I For todays #ThinSectionThursday, we present garnet porphyroclasts in an ultramylonite from the Southern Italian Alps, Premosello shear zone, Ossola Valley (courtesy of our next P-T-t talker Dr. Stefania Corvo). This feature will be part of her talk next week, on Sept 14th, in which she’ll discuss the interplay between deformation and metamorphism with…
[TFM] Eocene molasse sediments from the Southern Carpathians
EN I Eocene molasse sediments from the Southern Carpathians (here the Conglomerate, in Romania) show some typical features of subaerial mass-flow deposits as coarse- to very coarse-grained lithofacies limited by multiple discontinuities, arranged in fining-upward cycles. Molasses sequences develop during the terminal stages of orogenic events. Fluvial and alluvial fans deposits are frequently identified as…
[TFM] Pseudotachylite from the Juru shear zone (PB, Brazil)
EN I This #TuesdayFieldMemory is a pseudotachylite from the Juru shear zone (PB, Brazil) showing the main vein (centimetric) containing quartz and feldspar fractured clasts. From the main vein, injection veins oriented obliquely to its configuration are present, in which relitic grains of recrystallized quartz are observed. Contribution by Gustavo Viegas @lgviegas This rock and…
[TST] Ultraclasite from the Pernambuco shear zone (PE, Brazil)
EN I Our #ThinSectionThursday this week is an ultracataclasite from the eastern Pernambuco shear zone (PE, Brazil) containing heterogeneous fragments of ultramylonite, plagioclase and quartz. Recrystallised quartz aggregates are observed at the contact of the ultracataclasite with its host granite. (Lambda plate inserted). This rock and its geological context will be discussed on our next…
[Article] Unravelling the protracted U-Pb zircon geochronological record of high to ultrahigh temperature metamorphic rocks: Implications for provenance investigations
EN I Our article, “Unravelling the protracted U-Pb zircon geochronological record of high to ultrahigh temperature metamorphic rocks: implications for provenance investigations”, is already available on the Geoscience Frontiers website! We discuss the possible causes of bias in the analysis of U-Pb ages in rocks that underwent extreme metamorphic conditions and propose a workflow in…
[LPT] Granulite thermobarometry with Al in orthopyroxene
EN | In the world of high-grade metamorphic rocks, things can get a little tricky: from element compatibility, closure temperatures from chemical systems and migmatite field structures. One process that may occur is the late Fe-Mg exchange between minerals such as orthopyroxene, garnet and biotite. Our post shares how Pattison et al. (2003) found a…
[LPT] Thermodynamic Modeling With THERIAK-DOMINO
EN | This time, the #LearningPetroTools addresses “THERMODYNAMIC MODELING WITH THERIAK-DOMINO”. What is Theriak-Domino? What is it for and how to use it? What are the theoretical concepts behind this software and how thermodynamic modeling can help us to tell the metamorphic story of our rocks? Follow the post and find out! PT | Desta vez, o #LearningPetroTools aborda…
[LPT] Diffusion Chronometry Geospeedometry
EN | Diffusion chronometry, also known as geospeedometry, is a technique that can be used to constrain the duration of thermal pulses of a geological event, for example, by modeling the diffusion of element profiles in minerals. The technique involves measuring the diffusive loss of an element during the heating and/or cooling history of a…
[LPT] Electron Microprobe U-Th-Pb Monazite Dating
En | Monazite is widely used in petrochronological studies, as it is one of the most common radioactive minerals and one of the main hosts of U and Th in igneous and metamorphic rocks. Among the different methods used for its dating, the electron microprobe stands out for its operational cost and spot size considerably…
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