Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Influences of CO2 on the Microstructure in Sheared Olivine Aggregates

Version 1 : Received: 11 April 2021 / Approved: 12 April 2021 / Online: 12 April 2021 (14:28:27 CEST)

A peer-reviewed article of this Preprint also exists.

Zhang, H.; Zhao, N.; Qi, C.; Huang, X.; Hirth, G. Influences of CO2 on the Microstructure in Sheared Olivine Aggregates. Minerals 2021, 11, 493. Zhang, H.; Zhao, N.; Qi, C.; Huang, X.; Hirth, G. Influences of CO2 on the Microstructure in Sheared Olivine Aggregates. Minerals 2021, 11, 493.

Journal reference: Minerals 2021, 11, 493
DOI: 10.3390/min11050493

Abstract

Shear deformation of a solid-fluid, two-phase material induces a fluid segregation process that produces fluid-enriched bands and fluid-depleted regions, and crystallographic preferred orientation (CPO) characterized by girdles of [100] and [001] axes sub-parallel to the shear plane and a cluster of [010] axes sub-normal to the shear plane, namely the AG-type fabric. Based on experiments of two-phase aggregates of olivine + basalt, a two-phase flow theory and a CPO-formation model were established to explain these microstructures. Here, we investigate the microstructure in a two-phase aggregate with supercritical CO2 as the fluid phase and examine the theory and model, as CO2 is different from basaltic melt in rheological properties. We conducted high‐temperature and high-pressure shear deformed experiments at 1 GPa and 1100ºC in a Griggs-type apparatus on samples made of olivine + dolomite, which decomposed into carbonate melt and CO2 at experimental conditions. After deformation, CO2 segregation and an AG-type fabric occurred in these CO2-bearing samples, inconsistency with basaltic melt-bearing samples. The SPO-induce CPO model was used to explain the formation of the fabric. Our results suggest that the influences of CO2 as a fluid phase on the microstructure of a two-phase olivine aggregate is similar to that of basaltic melt and can be explained by the CPO-formation model for the solid-fluid system.

Subject Areas

olivine aggregates; CO2; crystallographic preferred orientation; AG-type fabric

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