文章基本信息

标题：Evolution of a shear zone before, during and after melting
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作者：Amicia L. Lee ; Geoffrey E. Lloyd ; Taija Torvela 等
期刊名称：Journal of the Geological Society
印刷版ISSN：0016-7649
电子版ISSN：2041-479X
出版年度：2020
卷号：177
期号：4
页码：738-751
DOI：10.1144/jgs2019-114
语种：English
出版社：Geological Society Publishing House
摘要：Partial melt in the deforming mid- or lower continental crust causes a strength decrease and drives formation of lithological heterogeneities. However, mechanisms of formation of syn-melt deformation zones and strain partitioning in partially molten rock remain poorly understood. We use field and microstructural observations to unravel the evolution of a partial melt shear zone, Seiland Igneous Province, northern Norway. The Øksfjord shear zone (ØSZ) is one of several paragneiss shear zones present within gabbros of the Seiland Igneous Province, formed by syn-intrusive deep crustal shearing during lithospheric extension related to continental rifting. Microstructures from the ØSZ show evidence for different deformation conditions. The first phase was active pre-melt and involved deformation at high subsolidus temperatures. This was followed by syn-melt deformation of the shear zone causing a relative strength increase towards the shear zone centre upon crystallization. The third phase nucleated two parallel shear zones at the edges of the ØSZ; melt textures are absent and microstructures indicate deformation at lower temperatures and higher stresses. In effect, melt migration towards the shear zone centre ultimately led to strengthening of the shear zone core, with post-crystallization deformation focusing along shear zone margins where significant heterogeneities are present.