Title :

A TEM study of exsolution in Ca-rich pyroxenes from the Paris and Renazzo chondrites: Determination of type I chondrule cooling rates

Author(s) :

Cuvillier, Priscille [Auteur]
Chaumard, Noël [Auteur]
Leroux, Hugues [Auteur]
Unité Matériaux et Transformations - UMR 8207 [UMET]
Unité Matériaux et Transformations (UMET) - UMR 8207
Zanda, Brigitte [Auteur]
Hewins, Roger H. [Auteur]
Jacob, Damien [Auteur]
Unité Matériaux et Transformations (UMET) - UMR 8207
Unité Matériaux et Transformations - UMR 8207 [UMET]
Devouard, Bertrand [Auteur]

Journal title :

Meteoritics and Planetary Science

Volume number :

53

Pages :

482-492

Publication date :

2018

HAL domain(s) :

Planète et Univers [physics]/Astrophysique [astro-ph]
Physique [physics]/Matière Condensée [cond-mat]/Science des matériaux [cond-mat.mtrl-sci]
Physique [physics]/Astrophysique [astro-ph]
Planète et Univers [physics]/Sciences de la Terre
Chimie/Matériaux
Physique [physics]/Physique [physics]/Géophysique [physics.geo-ph]

English abstract : [en]

We conducted a transmission electron microscope study of the exsolution microstructures of Ca‐rich pyroxenes in type I chondrules from the Paris CM and Renazzo CR carbonaceous chondrites in order to provide better constraints ...
Show more >We conducted a transmission electron microscope study of the exsolution microstructures of Ca‐rich pyroxenes in type I chondrules from the Paris CM and Renazzo CR carbonaceous chondrites in order to provide better constraints on the cooling history of type I chondrules. Our study shows a high variability of composition in the augite grains at a submicrometer scale, reflecting nonequilibrium crystallization. The microstructure is closely related to the local composition and is thus variable inside augite grains. For compositions inside the pyroxene miscibility gap, with a wollastonite (Wo) content typically below 40 mole%, the augite grains contain abundant exsolution lamellae on (001). For grain areas with composition close to Wo40, a modulated texture on (100) and (001) is the dominant microstructure, while areas with compositions higher than Wo40 do not show any exsolution microstructure development. To estimate the cooling rate, we used the spacing of the exsolution lamellae on (001), for which the growth is diffusion controlled and thus sensitive to the cooling rate. Despite the relatively homogeneous microstructures of augite grains with Wo < 35 mole%, our study of four chondrules suggests a range of cooling rates from ~10 to ~1000 °C h−1, within the temperature interval 1200–1350 °C. These cooling rates are comparable to those of type II chondrules, i.e., 1–1000 °C h−1. We conclude that the formation of type I and II chondrules in the proto‐solar nebula was the result of a common mechanism.Show less >

Language :

Anglais

Peer reviewed article :

Oui

Audience :

Internationale

Popular science :

Non

Administrative institution(s) :

Université de Lille
ENSCL
CNRS
INRA

Collections :

• Unité Matériaux et Transformations (UMET) - UMR 8207

Research team(s) :

Matériaux Terrestres et Planétaires

Submission date :

2019-06-03T08:52:48Z
2021-02-17T15:41:44Z