Volatile Element Chemistry during Metamorphism of Ordinary Chondritic Material and Some of its Implications for the Composition of Asteroids

TL;DR

This study models the chemical changes of volatile elements during the metamorphism of ordinary chondrites, revealing insights into asteroid composition and volatile element mobilization.

Contribution

It provides the first comprehensive equilibrium calculations of trace element behavior in chondritic material during metamorphism, highlighting differences among chondrite classes.

Findings

Volatile elements show distinct mobilization patterns in H- and L-chondrites.

LL-chondrites exhibit complex abundance patterns supporting a rubble-pile parent body.

Volatility sequences differ from solar nebula predictions.

Abstract

We used chemical equilibrium calculations to model thermal metamorphism of ordinary chondritic material as a function of temperature, pressure, and trace element abundance and use our results to discuss volatile mobilization during thermal metamorphism of ordinary chondrite parent bodies. The calculations include ~1,700 solids and gases of 40 elements. We compiled trace element abundances in H-, L-, and LL-chondrites for the elements Ag, As, Au, Bi, Cd, Cs, Cu, Ga, Ge, In, Pb, Rb, Sb, Se, Sn, Te, Tl, and Zn, and identified abundance trends as a function of petrographic type within each class. We found that abundance patterns within the H- and L- chondrites are consistent with mobilization of volatile elements in an onionshell-type parent body. LL-chondrites have more complex abundance patterns that may support a rubble-pile model for the LL-chondrite parent body. We calculated volatility sequences for the trace elements in the ordinary chondritic material, which differs significantly from the solar nebula volatility sequence.