Fe-Ni-P-S Melt Pockets in Elga IIE Iron Meteorite: Evidence for the Origin at High-Pressures Up to 20 GPa

Konstantin Litasov,Svetlana Teplyakova,Konstantin Kuper,Anton Shatskiy

doi:10.3390/min9100616

Abstract

Here we report new data on high-pressure microstructures in Elga group IIE iron meteorites, made of solidified Fe-Ni-P-S melt pockets and microcrystalline aggregates, which could be formed only at high pressures and temperatures according to the experimental data. The bulk composition of the melt pockets and crystals correspond to the Fe3P-Fe3S solid solution with the closure of an immiscibility gap at pressures near 20 GPa in static experiments. Some other melt pockets fit with the Fe2S-Fe2P compositions, which could also correspond to high pressures and temperatures. The results suggest a late shock episode during the formation of the IIE iron parent body, which may be prior or due to the final disruption that caused the meteorite arrival to Earth. It also has an important implication to the shock features in other meteorites, such as ureilite.

Highlights

The shock-melt veins and high-pressure minerals are common in chondritic and martian meteorites and rare in other types of meteorites, including lunar samples [1,2]
Rounded or irregular shape silicate inclusions caould be divided into three major types, including (1) silicate glass with abundant large Cr-diopside and minor small enstatite crystals; (2) silicate glass with tiny quenched crystals of enstatite, plagioclase, and cristobalite; (3) silicate/phosphate inclusions with liquid immiscibility
Fe3 P and Fe3 S are isostructural at high pressure and form a complete solid solution at P > 20 GPa [19]

Summary

Introduction

The shock-melt veins and high-pressure minerals are common in chondritic and martian meteorites and rare in other types of meteorites, including lunar samples [1,2]. Elga represents IIE iron meteorite group, which contains 5–20% of silicate inclusions in the metallic matrix [10,11,12,13,14,15,16,17,18]. Rounded or irregular shape silicate inclusions caould be divided into three major types, including (1) silicate glass with abundant large Cr-diopside and minor small enstatite crystals; (2) silicate glass with tiny quenched crystals of enstatite, plagioclase, and cristobalite;. Minerals 2019, 9, 616 shock melt is represented by an immiscible fine-grained mixture of silicate-phosphate and metallic parts [10,13,17]. Fe-Ni-P-S aggregates, which could be formed only at high pressures and temperatures according to the experimental phase diagrams [19,20]

Materials and Methods

Results

Discussion