High pressure minerals in the Ch\xe2teau-Renard (L6) ordinary chondrite: implications for collisions on its parent body

Ioannis Baziotis,Chi Ma,Ana Cernok,Paul D Asimow,Dan Topa,Mahesh Anand,Jinping Hu,Ludovic Ferrière

doi:10.1038/s41598-018-28191-6

Abstract

We report the first discoveries of high-pressure minerals in the historical L6 chondrite fall Château-Renard, based on co-located Raman spectroscopy, scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy and electron backscatter diffraction, electron microprobe analysis, and transmission electron microscopy (TEM) with selected-area electron diffraction. A single polished section contains a network of melt veins from ~40 to ~200 μm wide, with no cross-cutting features requiring multiple vein generations. We find high-pressure minerals in veins greater than ~50 μm wide, including assemblages of ringwoodite + wadsleyite, ringwoodite + wadsleyite + majorite-pyropess, and ahrensite + wadsleyite. In association with ahrensite + wadsleyite at both SEM and TEM scale, we find a sodic pyroxene whose Raman spectrum is indistinguishable from that of jadeite but whose composition and structure are those of omphacite. We discuss constraints on the impact record of this meteorite and the L-chondrites in general.

Highlights

Meteorites, especially ordinary chondrites, preserve a record of impact events due to collisions among their parent asteroids[1,2,3,4]
We have analysed several of the silicate clasts in six selected regions of interest in melt veins found within a single polished thin-section of Château-Renard (NMHV-L4361; Figs 2–5 and Supplementary Figs 1–5)
We divide our observations according to the regions of interest that were studied, and in which we find the following assemblages of HP phases: (1) region MV1-a, a portion of the large vein MV1, contains ringwoodite + ahrensite (Fig. 2); (2) region MV1-b contains ringwoodite + wadsleyite + majorite (Fig. 3); (3) veins MV3 and MV5 both feature ahrensite + wadsleyite (Figs 3,4); and (4) vein MV4 contains sodic pyroxene + ahrensite + wadsleyite + clinoenstatite (Fig. 5)

Summary

Introduction

Meteorites, especially ordinary chondrites, preserve a record of impact events due to (possibly multiple) collisions among their parent asteroids[1,2,3,4]. A number of highly-shocked L6 ordinary chondrites have been previously studied, with Tenham being perhaps the most intensively investigated[3,15,16,17] In these meteorites, a variety of HP minerals have been reported including, in alphabetical order: ahrensite (Fe-analogue of ringwoodite), akimotoite (ilmenite-structured polymorph of enstatite), bridgmanite (perovskite-structured polymorph of enstatite), hemleyite (Fe-analogue of akomotoite), jadeite (monoclinic C2/c sodic pyroxene), lingunite (hollandite structured sodic plagioclase), majorite (garnet-structured polymorph of enstatite), ringwoodite (spinel-structured polymorph of olivine), stishovite (rutile-structured polymorph of quartz), tuite (a HP polymorph of merrillite), wadsleyite (modified spinel-structured polymorph of olivine), and xieite (orthorhombic HP polymorph of chromite)[6,7,9,15,17,18,19,20]. We obtain multiple compositional, spectroscopic, and structural constraints on a high-pressure pyroxene phase in Château-Renard and note the curious observation that this phase displays the Raman bands commonly associated with jadeite

Methods

Results

Discussion

Conclusion