The conditions at which monazite and allanite were produced and destroyed during prograde metamorphism of pelitic rocks were determined in a Buchan and a Barrovian regional terrain and in a contact aureole, all from northern New England, USA. Pelites from the chlorite zone of each area contain monazite that has an inclusion-free core surrounded by a highly irregular, inclusion-rich rim. Texture...

Paragonite has been found in two chloritoid-chlorite-mica schists from the Dalradian, north of Stonehaven. The principal bulk-chemical constraints on the occurrence of this mineral within the chloritoid zone appear to be the ratios of soda to potash and the A1203 contents of the rock. The composition of paragonite coexisting with muscovite indicates a crystallization temperature of 550 ~ for ro...

The distribution coefficient KD=(Mg / Fe)garnet/(Mg/Fe)biotite has been calculated for eight garnet-biotite pairs from rocks ranging from the garnet isograd to the staurolite zone along the Stonehaven coast of NE Scotland. This distribution coefficient depends upon metamorphic temperature and is not dependent upon the Mn and Ca content of garnet. Garnet-biotite geothermometer yields temperature...

Semi-pelitic rocks ranging in grade from the prehnite–pumpellyite to the greenschist facies from southeastern Otago, New Zealand, have been investigated in order to evaluate the reactions leading to formation and breakdown of stilpnomelane. Detrital grains of mica and chlorite along with fine-grained authigenic illite and chlorite occur in lower-grade rocks with compactional fabric parallel to ...

Abstract Systematic changes in whole-rock chemistry, mineralogy, mineral textures, and chemistry are seen along a ca. 95-km traverse of late Archean granitoid orthogneisses the Shevaroy Block, Eastern Dharwar Craton, southern India. The passes from amphibolite-grade gneisses north to granulite-grade rocks (charnockite) south. Changes include depletion Rb, Cs, Th, U granulite grade as relative a...

In contrast to continent/continent collision, arc-continent collision generates very short-lived orogeny because the buoyancy-driven impedance of the subduction of continental lithosphere, accompanied by arc/suprasubduction-zone ophiolite obduction, is relieved by subduction polarity reversal (flip). This tectonic principle is illustrated by the early Ordovician Grampian Orogeny in the British ...

To assess thermal and kinetic influences on atomic mobility mineral (neo)crystallization, clumped-isotope abundances of calcite dolomite were measured alongside cation ordering U–Pb dates, across metamorphic grade within the c. 35–30 Ma Alta stock contact aureole, Utah, USA. Average Δ47 values inside aureole reflect blocking temperature (300°C–350°C) during cooling from peak temperatures. Dolom...

The north-dipping Hout River Shear Zone (HRSZ), which marks the boundary between high-grade Limpopo Complex in its hanging wall and low-grade granite-greenstone terrane of Kaapvaal Craton South Africa footwall, is a deep-crustal shear zone that controlled emplacement hot granulites over against granite-greenstones during exhumation at ~2.72–2.62 Ga. This major migration large volumes hydrous fl...