U-Pb Geochronology

The Lupa Goldfield, situated at the southwestern Tanzanian cratonic margin, comprises a network of auriferous quartz veins and greenschist facies mylonitic shear zones cutting a suite of Archaean—Palaeoproterozoic granitic—gabbroic intrusions. The existing geochronological database points to a protracted, but episodic 1. Molybdenite, pyrite and chalcopyrite samples from mineralized quartz veins and mylonitic shear zones yield Re—Os model ages that range from 1. The ca. New U—Pb metamorphic titanite dating of a foliated Archaean granite sample ca. Early ductile deformation is not associated with gold mineralization, but the ductile deformation fabrics and, in particular the development of rheologically weak chloritic folia, may have acted as zones of pre-existing weakness that localized strain and influenced the geometry of later auriferous mylonitic shear zones. These new age results, together with previously reported U—Pb and Re—Os ages, highlight the protracted magmatic, hydrothermal and structural evolution of the Lupa Goldfield 1. They are also consistent with other palaeo-convergent margins where orogenic gold style mineralization occurs relatively late in the orogen’s tectono-thermal history.

Uranium–lead dating

Metrics details. These sampled both oceanic brecciated material and a blackwall reaction zone in contact with a micaschist and serpentinized peridotite. Textural observations combined with new geochronological data indicate that rutile and titanite both grew below their closure temperatures during Alpine metamorphism. We present a technique to calculate the most precise and accurate ages possible using a two-dimensional U—Pb isochron on a Wetherill concordia.

Rutile from two samples gave a U—Pb isochron age of

U–Pb Titanite Dating by Single-Collector Laser Ablation, Inductively. Coupled was used to measure U/Pb and Pb isotopic ratios of titanite in samples B74 and.

Titanite CaTiSiO 5 occurs as a rare mineral in magmatic and metamorphic rocks. It is commonly found in clastic sedimentary rocks as an accessory heavy mineral — a mineral of high density. Recently, U-Pb dating of single-grains of detrital titanite has been shown to be a useful tool in sedimentary provenance studies e. Titanite U-Pb geochronologies can add important information to constrain the sediment sources of rocks and basins, and can help date precipitation of titanite.

However, there are a number of complicating factors that must be taken into consideration for reliable application of titanite U-Pb dating in provenance studies. First, titanite is less stable than zircon — the most commonly employed dating target. For example, in Palaeocene sediments in the North Sea, titanite rarely occurs as detrital grains at burial depths greater than m Morton It can also show dissolution features due to weathering and burial diagenesis e.

Second, titanite may precipitate during burial diagenesis, which would reflect the burial history of sediments and not their provenance. Precipitation of authigenic titanite is documented from deeply buried i. Moreover, titanite also occurs in shallow-buried Jurassic sandstones with no volcanic affinity Morad Thus, the formation of titanite is not necessarily linked to a volcaniclastic source, but nevertheless, the presence of volcanic material seems to promote titanite precipitation.

If authigenic titanite precipitation was incorrectly identified as detrital, this would have considerable implications for provenance investigations, as apparently titanite-rich source rocks would be wrongly inferred to be present in the sediment source area.

Common lead-corrected laser ablation ICP-MS U-Pb systematics and geochronology of titanite

U-Th-Pb systematics in zircon and titanite. U-Th-Pb isotopic analyses of zircon and titanite were made for two core samples of granite from borehole ATK-1 drilled into the Eye-Dashwa Lakes pluton. One of the samples from near the bottom of the hole The other sample from near the surface 3. The complex nature of the disturbances probably resulted from the penetration of meteoritic water into rock already modified by post-crystallization hydrothermal alteration.

This study presents new geochemical (major and trace element,. Nd–Sr isotope) and U–Pb zircon, monazite, titanite and rutile data for various rock types.

Titanite crystals commonly shows oscillatory, sector and convolute irregular zonal textures, reflecting mainly variations in Ca and Ti versus Al 1—2 wt. Fluorine content is up to 0. Consequently, the textural, geochronological and compositional data indicate relatively high-temperature, most probably early post-magmatic subsolidus precipitation of titanite.

Ackerson M. Aleinikoff J. Barboni M. Barrat J. Acta 83, 79— Bauer J. Bea F. Bernau R. In: Grecula P. Mineralia Slovaca Monographs , Bratislava, —

Titanite: The Wedge-Shaped Timepiece

Titanite is an ideal mineral for U-Pb isotopic dating because of its relatively high U, Th and Pb contents. To check the matrix effect, titanite BLR-1 and zircon standards were analyzed as the external standards. These ages are consistent with its reference age of about Ma. Our results reveal that significant matrix effect does exist between different kinds of minerals during LA-ICPMS U-Pb age determination, whereas it is insignificant between same minerals.

In addition, we determined U-Pb ages for titanites from the Early Cretaceous Fangshan pluton, which indicates a rapid cooling history of this pluton. Download to read the full article text.

Precise and accurate U-Pb LA-ICPMS dating of many U-bearing accessory minerals (e.g. apatite, allanite, titanite and rutile) is often.

Chemical Geology , , pp. View at publisher. LA-ICPMS dating of these U-bearing accessory phases typically requires a matrix-matched standard, and data reduction is often complicated by variable incorporation of common Pb not only into the unknowns but also particularly into the reference material. Common Pb correction of the age standard can be undertaken using either the Pb, Pb or Pb no Th methods, and the approach can be applied to raw data files from all widely used modern multi-collector and single-collector ICPMS instruments.

This downhole fractionation model is applied to the unknowns and sample-standard bracketing using a user-specified interpolation method is used to calculate final isotopic ratios and ages. Pb and Pb no Th corrected concordia diagrams and Pb, Pb and Pb no Th -corrected age channels can be calculated for user-specified initial Pb ratio s. All other conventional common Pb correction methods e.

The secondary Durango

U-Pb SHRIMP-II dating of titanite and pyrochlore in Lovozero and Khibiny alkaline rocks and ores.

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Here, we developed a technique for U-Pb dating of titanite using the nm ArF laser-ablation system and Agilent a Q-ICP-MS. Standards of titanite.

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Helium diffusion and (U-Th)/He thermochronometry of titanite

Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. A Nature Research Journal. Two widely held theories for the origin of Archaean lode gold deposits, the magmatic 1 and metamorphic replacement 2 models, predict that gold emplacement should have occurred near the end of late, syn-kinematic greenstone magmatism.

trace element data in titanite is particularly effective for differentiating All zircon ages for the same samples where titanite was dated have.

This paper presents new data related to the emplacement ages of the Amakinskaya and Taezhnaya kimberlites of the Mirny field, Siberia, located in the southern part of the Yakutian diamondiferous province. This study analyzed rutile and titanite grains along with zircons for U-Pb isotope composition by laser ablation LA -inductively coupled plasma-mass spectrometry ICP-MS and evaluated the applicability of rutile and titanite for the dating of kimberlite emplacements.

Both minerals contain substantial admixtures of common Pb in their Pb isotope composition. Therefore, the Pb method was applied for common Pb correction during age calculation. All age estimates correspond to the main epoch of diamondiferous kimberlite activity in the Siberian platform and suggest the formation of the Mirny kimberlite field within a single event or two separate events occurring close together in time. Results obtained from this study indicate that rutile and titanite can be useful for the dating of kimberlite emplacements.

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