Abstract. Modern-style plate tectonics is characterised by the global operation of cold and deep subduction involving blueschist facies ultrahigh-pressure metamorphism. This has been a common process since Neoproterozoic, but couple studies indicate similar processes were active in Paleoproterozoic, at least on local scale. Particularly conspicuous are extreme conditions ∼ 7 GPa thermal gradien...

Introduction: In this work, we report on the results of a combined scanning electron microscopy and micro-Raman spectroscopy investigation of stishovite and coesite in shocked Hospital Hill quartzite from the Vredefort impact structure of South Africa. Sanples have investigated using optical microscopy and under the scanning electron microscope, using energy dispersive x-ray spectrometry (EDS),...

The Napier Complex in East Antarctica has a complex thermal history, including ultra-high-temperature (UHT) metamorphism. Geochronology, trace element, and isotope geochemistry of zircon, apatite, monazite three felsic gneisses collected from Harvey Nunatak were studied using sensitive high-resolution ion microprobe (SHRIMP) for the first time. Most zircons showed nebulous to fir-tree zoning, w...

This paper argues that the presence of external control of fluid composition during metamorphism of iron-formation should be indicated by the occurrence of high-grade rocks which either lack the bufering assemblages such as olivine-magnetite-quartz or by the presence of such assemblages in which the silicates show a very restricted range in composition. A review of high-grade iron-formations fr...

The Bossòst dome is an E–W-trending elongated structural and metamorphic dome developed in Cambro-Ordovician metasedimentary rocks in the Variscan Axial Zone of the central Pyrenees. A steep fault separates a northern half-dome, cored by massif granite, from an E–W-trending doubly plunging antiform with granitic sills and dykes in the core to the south. The main foliation is a flat-lying S1/2 s...

Abstract Garnet is a fundamental expression of metamorphism and one the most important minerals used to constrain thermal conditions crust. We innovative in situ laser-ablation ICP-MS/MS Lu-Hf geochronology demonstrate that garnet metapelitic rocks enclosing Cambrian eclogite southern Australia formed during Laurentian Mesoproterozoic metamorphism. porphyroblasts amphibolite-facies yielded ages...

Microdiamonds from the Akluilâk minette dykes (Nunavut, Canada) are similar to diamonds formed in subducted metamorphic rocks. High concentrations of unaggregated nitrogen and positive delta(15)N suggest that the microdiamonds formed within rocks subducted to ultrahigh pressures before being sampled by the minette magma 1.8 billion years ago. This ultrahigh pressure metamorphism in North Americ...