In the Himalayan region of Sikkim, well-developed inverted metamorphic sequence Main Central Thrust (MCT) zone is folded, thus exposing several transects through structure that reached similar grades at different times. In-situ LA-ICP-MS U–Th–Pb monazite ages, linked to pressure–temperature conditions via trace-element reaction fingerprints, allow key aspects evolution thrust be understood for first time. The ages show peak were earliest in structurally highest part sequence, Greater...

Granulite facies rocks frequently show a large spread in their zircon ages, the interpretation of which raises questions: Has isotopic system been disturbed? By what process(es) and conditions did alteration occur? Can dates be regarded as real reflecting several growth episodes? Furthermore, under some circumstances (ultra-)high-temperature metamorphism, decoupling U–Pb from trace element geochemistry has reported. Understanding these processes is crucial to help interpret such context P–T...

Convergent plate margins typically experience a transition from subduction to collision dynamics as massive continental blocks enter the channel. Studies of high-pressure rocks indicate that tectonic fragments are rapidly exhumed eclogite facies mid-crustal levels, but details such controversial. To understand channel we report results petrochronological study central Sesia Zone, key element internal Western Alps. This comprises two polymetamorphic basement complexes (Eclogitic Micaschist...

Quantitative constraints on the rates of tectonic processes underpin our understanding mechanisms that form mountains.In Sikkim Himalaya, late structural doming has revealed time-transgressive evidence metamorphism and thrusting permit calculation minimum rate movement a major ductile fault zone, Main Central Thrust (MCT), by novel methodology.U-Th-Pb monazite ages, compositions, metamorphic pressure-temperature determinations from rocks directly beneath MCT reveal samples ~50 km along...

The Zimithang Thrust juxtaposes two lithotectonic units of the Greater Himalayan Sequence in Arunachal Pradesh, NE India. Monazite U–Pb, muscovite 40Ar/39Ar and thermobarometric data from rocks hanging footwall constrain timing conditions their juxtaposition across structure, subsequent cooling. grains biotite–sillimanite gneiss wall yield LA-ICP-MS U–Pb ages 16 ± 0.2 to 12.7 0.4 Ma. A schistose within high strain zone yields overlapping-to-younger monazite 14.9 0.3 11.5...

Abstract The growth and dissolution behaviour of accessory phases (and especially those geochronological interest) in metamorphosed pelites depends on, among others, the bulk composition, prograde metamorphic evolution cooling path. Monazite zircon are arguably most commonly used geochronometers for dating felsic rocks, yet crystal mechanisms as a function rock pressure temperature still incompletely understood. Ages different zones monazite garnet‐bearing anatectic metapelite from Greater...

Abstract Garnet is an exceptionally useful mineral for reconstructing the evolution of metamorphic rocks that have experienced multiple tectonic or thermal events. Understanding how garnet crystallizes and its mechanical behaviour important establishing a petrological temporal record metamorphism deformation recognizing geologic stages within growth history individual crystal. Here, we integrate fine‐scale microstructural (electron backscatter diffraction [EBSD]) microchemical (Laser...

Congenital or acquired shortness of a metatarsal may cause pain in adjacent metatarsals. From 1983 to 1990, we performed nine lengthenings seven adolescent patients by metaphyseal osteotomy followed gradual distraction callus (callotasis). Two required bone grafts after the lengthening. We used rigid, unilateral external fixator designed for use hand and foot. At follow-up, from three ten years later, healing had been achieved all with an average index 50 days/cm, metatarsalgia relieved...

Uranium-lead (U-Pb) accessory mineral petrochronology has been increasingly used to constrain the timing of tectonometamorphic events. However, because mafic rocks commonly lack minerals with a high U/Pb ratio, they may be underrepresented in chronologic record. This study on polymetamorphic granulites from Archean Rae craton (northern Canada) provides striking example metamorphic cycle that entirely overlooked. We utilized Lu-Hf garnet geochronology and equilibrium phase diagram modeling...

The crystal growth history of an Au-rich sedimentary pyrite nodule from the Timmins-Porcupine Au camp, Ontario, Canada, has been investigated using Electron Backscattered Diffraction and Laser Ablation Inductively Coupled Plasma Mass Spectrometry techniques to study crystallographic processes controlling metal deportment in structure. Results show four distinct stages characterized by different microstructures, forms trace element compositions. A direct link is observed between octahedral...

Abstract Microscale dating of distinct domains in minerals that contain relics multiple metamorphic events is a key tool to characterize the polyphase evolution complex terranes. Zircon and allanite from five metasediments metaintrusive high-pressure (HP) rocks Eclogite Micaschist Complex Sesia Zone were dated by SIMS LA-ICP-MS. In metasediments, zircon systematically preserves detrital cores one or two overgrowths. An early Permian age obtained for first rim localities Malone Valley,...

Abstract Subduction zones represent one of the most critical settings for fluid recycling as a consequence dehydration subducting lithosphere. A better understanding flows within and out slab is fundamental to unravel role fluids during burial. In this study, major trace element geochemistry combined with oxygen isotopes were used investigate metasediments eclogites from Sesia Zone in order reconstruct effect internal external pulses subducted continental margin. Garnet shows variety...

Magmatic sulfide liquids are effective at concentrating a range of metals. Within magmatic systems pentlandite, an exsolution product monosulfide solid solution (MSS), is the primary host Ni, Co and significant concentrations Pd. Over last decade, LA-ICP-MS mapping has revealed non-uniform metal distributions complexity to patterns such as zonation linear alignment elements. Whereas compatibility partitioning behavior chalcophile elements during fractionation well constrained, there little...

Accessory phases are important hosts of trace elements; allanite may contain >90% the REE in a bulk rock. The mobility and redistribution several elements, notably HREE, Th, U, Y is thus controlled by reactions involving other phases, as well rock-forming minerals. As these elements commonly concentrated mature clastic sediments, suite impure quartzite was studied. Two eclogite facies samples from Monometamorphic Cover Complex Sesia Zone (Western Italian Alps) presented some detail, they...

The 40Ar/39Ar ages of metamorphic micas that crystallized at high temperatures are commonly interpreted as cooling ages, with grains considered to have lost 40Ar via thermally-driven diffusion into the grain boundary network. Recently reported laser-ablation data suggest spatial distribution Ar in does not always conform patterns predicted by theory and despite temperatures, argon was removed efficiently from local system during evolution. In Western Gneiss Region (WGR), Norway, felsic...

Abstract Canada's northern cratons record a complex poly‐metamorphic evolution in response to multiple orogenic events. The Snowbird Tectonic Zone (STZ), the principal suture between Archean Rae and Hearne cratons, is highly debated structure; it argued have accommodated modern‐style accretion either Neoarchean (2.6–2.5 Ga) or Palaeoproterozoic (ca. 1.9 Ga). To resolve this controversy, we use Lu–Hf garnet geochronology date an eclogite collected from East Athabasca mylonite triangle of STZ....