The aim of this study is to investigate partial melt formation and segregation in deforming environments. For this purpose we use a three phase model including baryte and two nitrates. The nitrates have an eutectic melting point at approximately 123 ° C whereas barite will resist and form a solid framework at this temperature. Thus we can control the melt proportion by the volume fraction of the nitrates. Furthermore the higher density of baryte compared to the nitrates allows simulation of gravitational processes acting between melt and restite.
Samples were prepared with a size of 35 mm in diameter and approximately 60 mm in height and were deformed while contemporary heated in the deformation rig of the tectonic lab. The samples were varied by different melt proportions and strain rate. We observed a negative correlation melt content and bulk strength up to a critical melt fraction of 17.3 %. Beyond this fraction samples start to harden which is interpreted as an effect of efficient melt segregation leading to larger melt depleted areas which control the overall strength. After deformation the samples were analyzed by polished sections on melt distribution. Hereby melt controlled structures such as melt filled shear zones and melt depleted areas have been found. Additionally specific samples were analyzed by X-ray computed tomography to visualize the interior and melt distribution in three dimensions

Further background information

Getting baryte at Grube Clara (including some nice photos)

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Structure and Tectonic Group