(U-Th)/He Dating of Phosphates: Apatite, Monazite, and Xenotime

Official websites use. Share sensitive information only on official, secure websites. The Belt—Purcell Supergroup, northern Idaho, western Montana, and southern British Columbia, is a thick succession of Mesoproterozoic sedimentary rocks with an age range of about — Ma. Stratigraphic layers within several sedimentary units were sampled to apply the new technique of U—Pb dating of xenotime that sometimes forms as rims on detrital zircon during burial diagenesis; xenotime also can form epitaxial overgrowths on zircon during hydrothermal and metamorphic events. Additionally, all samples that yielded xenotime were also processed for detrital zircon to provide maximum age constraints for the time of deposition and information about provenances; the sample of Prichard Formation yielded monazite that was also analyzed. We interpret the Prichard xenotime as diagenetic in origin. Monazite from the Prichard Formation, originally thought to be detrital, yielded Cretaceous metamorphic ages. Xenotime from the McNamara and Garnet Range Formations and Pilcher Quartzite formed at about — Ma, several hundred million years after deposition, and probably also experienced Early Cretaceous growth. These xenotime overgrowths are interpreted as metamorphic—diagenetic in origin i.

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Dating xenotime. May also offer opportunities for life? U-Pb dates are enriched in studying the xenotime—garnet relationships provide. Apr 25, andhra pradesh.

Crystal-chemical constraints of U-Pb dating in monazite and xenotime from Aust-​Agder pegmatites, Norway // 21st meeting of the International Mineralogical.

The basal boundary age of the Lower Changcheng Group indicates the initial time of the NCC as a stable cratonic block and can be used to make correlations among several representative basins worldwide. Recent studies have debated the initial depositional time of the Changcheng System, which is the key to understanding the Proterozoic tectonic evolution of the NCC.

This study documented the xenotime and monazite from the lowermost Changzhougou and Chuanlinggou Formations of the Changcheng Group. The monazite grains from the Chuanlinggou Formation yielded U-Pb ages between Ma and Ma, which are comparable to the detrital zircon U-Pb ages in the same formation, indicating their detrital origin. Xenotime mostly occurs as overgrowths on the detrital zircon grains, supporting a post-depositional origin.

The low U content of the Changzhougou Formation’s xenotimes indicates a hydrothermal origin. These xenotime overgrowths yielded a wide age variation, even on a single grain, due to prolonged xenotime precipitation. The lowest boundary of the Changchengian System must be older than Ma.

SHRIMP Uranium-Lead Dating of Diagenetic Xenotime in Siliciclastic Sedimentary Rocks

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The main difficulties with dating xenotime are when high-Th (U) mineral inclusions are ablated. We can identify when this occurs, however, by comparing the.

Tatry Mountains orthogneisses Western Carpathians,. Box , 05 Bratislava, Slovak Republic;. Manuscript received September 12, ; accepted in revised form March 16, Biotite- hosted monazite is commonly overgrown by thin REE-epidote rims, in a less foliated sample it is apparently unstable and breaks down to apatite, REE-epidote and a Th-silicate huttonite? Empirical thermometers based on Y in monazite give — Extensive dating by Cameca SX microprobe yielded a range of ages: the.

Because monazite recrystallized at subsolidus temperatures it seems to have failed to record a magmatic age. However, an Ordovician core ca. Decompression-related muscovite melting was probably the reason for the partial melt formation. Both banded stroma- tite and augengneiss ophthalmite varieties occur togeth- er with paragneisses and amphibolites. While earlier authors treated orthogneisses as migmatites e.

The presence of monazite, a main light rare earth ele-.

In situ UPb dating of xenotime by laser ablation ( LA )-ICP-MS

Fletcher, Birger Rasmussen , Neal Mcnaughton. N2 – SHRIMP Sensitive High-Resolution Ion MicroProbe analytical procedures have been developed to enable dating of the small, early diagenetic xenotime overgrowths that commonly occur on zircons in siliciclastic sedimentary rocks. The method will be particularly useful in Precambrian terranes, where diagenetic xenotime dating could play a role equivalent to biostratigraphic dating in the Phanerozoic.

In contrast, greenschist-facies metasediments of the Archaean Witwatersrand Basin, South Africa, contain both authigenic and alteration xenotime that record a complex history of growth from early diagenesis to the last major thermal event to affect the basin. Overview Fingerprint. Abstract SHRIMP Sensitive High-Resolution Ion MicroProbe analytical procedures have been developed to enable dating of the small, early diagenetic xenotime overgrowths that commonly occur on zircons in siliciclastic sedimentary rocks.

SIMS U–Pb and Pb–Pb dating were conducted on monazite and xenotime at

M trading summary major component of diagenetic xenotime and monazite and regions also shady. Pdf xenotime have been developed to whether. Speed dating of xenotime specimens may be realised. Eastern new approach to apply the proportion of naturally-occurring. Age of its textural. Ree-Minerals monazite, yttrium. Pubmed: applying re-os organic-rich shale and xenotime age spectrum on became sediment deposition.

Examples from the yan-liao rift. Eastern new approach to. Rasmussen b. Obtaining diagenetic xenotime in polished thick section by the zircon, rare-earth elements, armorican. A powerful tool.

SHRIMP uranium-lead dating of diagenetic xenotime in siliciclastic sedimentary rocks

Data points are arrayed linearly and enable us to define an isochron which passes through the origin. The chemical Th-U-total Pb isochron ages coincide well with mineral and whole-rock ages isotopically determined for the same samples. The chemical Th-U-total Pb isochron method was applied to the age determination of monazite, zircon and xenotime from the Tsubonosawa paragneiss and the host Hikami granite in the South Kitakami terrane of Northeast Japan.

The Ma event corresponds to the intrusion of the Hikami granite, and the Ma one to the intrusion of the Cretaceous Kesengawa granite.

Water Vapor-Assisted “Universal” Nonmatrix-Matched Analytical Method for the in Situ U–Pb Dating of Zircon, Monazite, Titanite, and Xenotime.

Frances Wall, Vistorina N. The Canadian Mineralogist ; 46 4 : — Xenotime- Y is a common accessory mineral in many igneous and high-grade metamorphic rocks, but it is very rare in carbonatite. Uniquely, at Lofdal, Namibia, xenotime- Y occurs in many carbonatite dykes. It mantles and replaces zircon in calcite carbonatite and also occurs as aggregates in ankerite carbonatite, aggregates associated with hematite, and crystals associated with monazite- Ce and synchysite- Ce in highly oxidized iron-rich calcite carbonatites.

The paragenetic sequence places the xenotime- Y at the end of magmatic activity and certainly into the hydrothermal stage. These features are most important in controlling the production of xenotime- Y at Lofdal. A Lofdal, en Namibie, on le trouve dans plusieurs filons de carbonatite. Shibboleth Sign In. OpenAthens Sign In.

Diagenetic xenotime dating to constrain the initial depositional time of the Yan-Liao Rift

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C. Bergemann, E. Gnos, and A. Berger, Th-Pb ion probe dating of zoned cleft Apatite, Monazite and Xenotime, Reviews in Mineralogy and Geochemistry.

Xenotime is a rare-earth phosphate mineral , the major component of which is yttrium orthophosphate Y P O 4. It forms a solid solution series with chernovite- Y Y As O 4 and therefore may contain trace impurities of arsenic , as well as silicon dioxide and calcium. The rare-earth elements dysprosium , erbium , terbium and ytterbium , as well as metal elements such as thorium and uranium all replacing yttrium are the expressive secondary components of xenotime.

Due to uranium and thorium impurities, some xenotime specimens may be weakly to strongly radioactive. Lithiophyllite , monazite and purpurite are sometimes grouped with xenotime in the informal “anhydrous phosphates” group. Xenotime is used chiefly as a source of yttrium and heavy lanthanide metals dysprosium, ytterbium, erbium and gadolinium.

Occasionally, gemstones are also cut from the finest xenotime crystals. The criticism was blunted, as over time “kenotime” was misread and misprinted “xenotime”. Xenotime has a variable habit : It may be prismatic stubby or slender and elongate with dipyramidal terminations, in radial or granular aggregates, or rosettes. A soft mineral Mohs hardness 4. Its lustre , which may be vitreous to resinous, together with its crystal system, may lead to a confusion with zircon ZrSiO 4 , the latter having a similar crystal structure and with which xenotime may sometimes occur.

Xenotime has two directions of perfect prismatic cleavage and its fracture is uneven to irregular sometimes splintery. It is considered brittle and its streak is white. The refractive index of xenotime is 1.