Ultrahigh-pressure texture inheritance during retrogression: Evidence from magnetofabrics in eclogites and ultramafic rocks (Chinese Continental Scientific Drilling project)

摘要: Abstract In order to contribute a better understanding of exhumation related retrogression processes ultrahigh-pressure (UHP) mafic and ultramafic rocks from the Chinese Continental Scientific Drilling (CCSD) in Maobei eclogite body Sulu metamorphic belt eastern China were studied for their magnetofabrics. Variably retrogressed eclogites serpentinized retrieved depth interval 100 1000 m borehole. A vein network irregular shaped veins with retrograde assemblage cuts across foliation at both low high angles. SEM imaging documents that magnetite associated pargasitic amphiboles developed around shape-preferred garnet. rims grew garnet formed within mesh texture serpentinization. Syn-serpentinization growth increased bulk susceptibilities, but reduced anisotropy. Maximum susceptibility axes garnet-peridotites trend N–S, i.e. parallel stretching lineation as defined by olivine omphacite grains. This implies magnetic fabric mimics UHP survived is inherited stage. As consequence, was not substantial ductile deformation mafic–ultramafic behaved rigid deforming quartzo-feldspathic matrix during exhumation. Internal strain restricted brittle fracturing, fluid circulation formation facilitating reactions rocks.