Quartz, mica, and amphibole exsolution from majoritic garnet reveals ultra-deep sediment subduction, Appalachian orogen

A study of various occurrences of the Al2SiO5 polymorphs in the rocks/veins of the Hamedan region, Iran: with special reference to origin of quartz-kyanite veins

The study area is a part of so-called Sanandaj-Sirjan zone or Zagros imbricate zone of the Zagros Orogen, Iran. The Hamedan region comprises a metamorphic sequence of low- to high-grade regional and contact metamorphic rocks intruded by mafic, intermediate and felsic plutonic bodies. The sequence comprises pelitic, psammitic, mafic, calc-pelitic and calc-silicate rocks.  Pelitic rocks are the m...

Elements of an orogen: regional trends in the geology of the appalachian-caledonian-hercynian-mauritanide orogen.

Recovery of an oxidized majorite inclusion from Earth’s deep asthenosphere

Minerals recovered from the deep mantle provide a rare glimpse into deep Earth processes. We report the first discovery of ferric iron-rich majoritic garnet found as inclusions in a host garnet within an eclogite xenolith originating in the deep mantle. The composition of the host garnet indicates an ultrahigh-pressure metamorphic origin, probably at a depth of ~200 km. More importantly, the fe...

Origin and tectonic evolution ofthe metamorphic sole beneath the Brooks Range ophiolite, Alaska

Structural field relations, petrologic and geochemical studies, and radiometric age aualysis of metamorphic rocks at the base of the Brooks Range ophiolite provide a record of the time, tectonic setting, and initial conditions of ophiolite emplacement during the Middle Jurassic western Brookian orogeny. The metamorphic sole of the Misheguk, Siniktanneyak, and Avan Hills ophiolite bodies is tran...

Crystal structure and Raman spectrum of a high-pressure Li-rich majoritic garnet, (Li2Mg)Si2(SiO4)3

A Li-rich majoritic garnet (LiMGt), (Li2Mg)Si2(SiO4)3, was synthesized at 15 GPa and 1500 °C and its structure studied with single-crystal X-ray diffraction and Raman spectroscopy. It is cubic with space group Ia3d and unit-cell parameters a = 11.2660(2) Å and V = 1429.91(1) Å3. The 8-, 6-, and 4-coordinated cation sites in LiMGt are occupied by (Li+ + Mg2+), Si4+, and Si4+, respectively. Where...