U-pb dating of titanite. 160 Ma of magmatic/hydrothermal and metamorphic activity in the Gällivare area: Re

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In situ U

u-pb dating of titanite

On zircon and titanite closure k. The younger component may be related to localized partial melting muscovite dehydration of thickened Triassic flysch-type sediments in the Songpan-Ganze terrane, and are among the youngest crustal melt granites exposed on the Tibetan Plateau. Zircon is very chemically inert and resistant to mechanical weathering—a mixed blessing for geochronologists, as zones or even whole crystals can survive melting of their parent rock with their original uranium-lead age intact. The oldest Caledonian dikes have dates that overlap with the ca. Standards of lead to constrain the in titanite from the mon lead to. Direct fabric dating by laser-ablation system and are.

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MERITS OF PB

u-pb dating of titanite

The compositions of the phases of the undeformed metaquartz diorite do not reflect the bulk rock composition, but were controlled by their position relative to reactant phases. Mineralogical changes which occurred during subsequent deformation of the metaquartz diorite are interpreted as resulting from a progressive enlargement of equilibrium domains and the partial equilibration of mineral compositions to the bulk rock composition rather than from changes in pressure and temperature. Ideal mixing on octahedral or octahedral plus tetrahedral sites and a non-ideal van Laar solution model yield the best regression results for thermodynamic fit parameters, with R-2 values of 0. Metapelites consist mainly of biotite, quartz, plagioclase, garnet, and fibrolitic to prismatic sillimanite; muscovite progressively disappears as K-feldspar appears and becomes abundant. The resulting orthogneiss consists of quartz + omphadte + garnet + phengite + paragonite + zoisite. Nearly seventy different samples of quartzofeldspathic basement and overlying metasedimentary rocks were studied.

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MERITS OF PB

u-pb dating of titanite

Hence, southeastern río de la plata craton, combined with increasing radiation damage. Zircon and monazite yielded Permian ages suggesting re crystallization during an high temperature event characterized by both metamorphism and magmatism. . Initially during high-strain deformation, fine-grained aggregates of jadeitic pyroxene + quartz + zoisite originally pseudomorphing plagioclase are inferred to have deformed by a mechanism of grain boundary sliding accommodated by diffusive mass transfer. Quartz-bearing rocks can remain undeformed even at high temperature and pressure. These ages are consistent with its reference age of about 1014 Ma.


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MERITS OF PB

u-pb dating of titanite

We propose a thermotectonic model that integrates our results with structural observations. Thus, they are interpreted to have grown from hydrous melts in the early exhumation stage. The mylonitic deformation strongly affected the lower crustal metabasic rocks of External Gabbro unit Finero Mafic Complex. Two possible explanations may account for this Triassic event: Triassic ages are possibly related to the thermal effect and fluid circulation during the emplacement of the External Gabbro unit; or alternatively, they are the response to the ductile deformation largely recognized in the whole area. In order to evaluate the best method for accurately assessing the common Pb isotopic composition of titanites in general, we analyzed samples of titanite from two Cretaceous plutons and a Grenville-age pegmatite for U-Pb and Pb-Pb systematics to investigate the relative merit of these two methods.

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Titanite u

u-pb dating of titanite

In the present study, the samples experienced peak metamorphic temperatures of 740-850 o C at 3. The data presented here indicate that ultrapotassic magmatism occurred in up to three phases at Mountain Pass ~1425, ~1405, and ~1380 Ma. The investigated rocks, both syenite and teschenite comes from a small closed quarry found in the Boguszowice Valley near Cieszyn. The closure temperature of the titanite U-Pb radiometric system is still in debate e. The aim is to shed light on the tectono-metamorphic evolution of this intermediate-lower crustal section and its bearing with the evolution of the southern and better known sectors of the Ivrea-Verbano Zone. Deposition in high-level Devonian clastic basins was active. Following this improved uncertainty propagation protocol, data can be compared at different uncertainty levels to better resolve age differences.

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Abstract: APATITE VS. TITANITE: WHICH IS BETTER FOR U

u-pb dating of titanite

In situ techniques require the characterization of naturally occurring reference materials for matrix-matched age calibration, downhole fractionation correction, and quality control Paton et al. The anchored concordia intercept apatite and titanites ages are 124. The western belt mainly consists of the southern Taihang district, as well as the Linfen and Taiyuan ore fields, whereas the eastern belt comprises the Luxi and Xu-Huai districts. The diapirs ascended adiabatically undergoing partial melting, which lowered their viscosity and increased buoyancy. In areas with a high concentration of the parent isotope, damage to the is quite extensive, and will often interconnect to form a network of radiation damaged areas. The metamorphic and microstructural evolution of the orthogneiss in the eclogite fades has been reconstructed from studies of gradational contacts between undeformed and strongly deformed rocks.

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Zircon and titanite U

u-pb dating of titanite

Alpha-recoil in U-Pb geochronology: Effective sample size matters. New data reporting standards are defined to help improve the peer review process. The upper intercept of the concordia and the discordia line will reflect the original age of formation, while the lower intercept will reflect the age of the event that led to open system behavior and therefore the lead loss; although there has been some disagreement regarding the meaning of the lower intercept ages. The Gongga Shan batholith of eastern Tibet, previously documented as a ca. There they remained for up to 30 m. The suggested closure temperature of titanite, for typical cooling rates of most geological settings, varies from 600 to 800 °C with fluid-assisted recrystallization rather than temperature-controlled thermal diffusion being also a controlling factor on the loss or exchange of radiogenic daughters Cherniak, 1993; Verts et al.

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Uranium

u-pb dating of titanite

Phase transformations in quartzofeldspathic rocks can be inhibited at the same conditions. The Xianshui-he fault is the most seismically active strike-slip fault in Tibet and is thought to record the eastward extrusion of the central part of the Tibetan Plateau. However, it is not often possible to see to what degree such factors have influenced an observed mineral assemblage from petrographic data alone. This damage is most concentrated around the parent isotope U and Th , expelling the Pb from its original position in the zircon lattice. For titanite, early empirical studies of high-grade metamorphic terranes indicated a Pb closure temperature of ~500 °C Hanson et al.

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MERITS OF PB

u-pb dating of titanite

This has three important implications. The Zr-in-titanite thermometry yields lower temperatures of 627—685 °C at 1. Many samples record Cretaceous overdispersed dates with 5-10 m. A new workflow defines the appropriate propagation of uncertainties for these data, identifying random and systematic components. The geochemical data of garnets point to high-grade metamorphic conditions. However, our results demonstrate that this is not always the case.

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U

u-pb dating of titanite

It is at present difficult to say whether characteristic disequilibrium features, observed petrographically, mean that a certain temperature was never achieved, or was only achieved for a short time. This article is protected by copyright. Buenos aires region of both apatite and 8—11 kbar and monazite and agilent 7500a q-icp-ms. E Late Scandian 390 - 375 Ma extension in a sinistral shear field bringing the ductilely deformed package into contact with brittle, highest-level rocks along detachments associated with outcrop areas of the Devonian clastic basins. In this study we present U-Pb ages of zircon and allanite dated by laser ablation—inductively coupled plasma—mass spectrometry on seven samples, to further investigate the chronology of the batholith. This caused rocks to break away from the paleosubduction channel, recrystallize in the eclogite facies, and rise as Rayleigh-Taylor instabilities. Titanite in the Fraser Zone also predominantly records a U—Pb age of 1299 ± 14 Ma, reflecting the interval of closure to radiogenic Pb mobility.

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