Canadian Journal of Earth Sciences

Canadian Journal of Earth Sciences

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. Due to the unique location in the Ludong region, geochronological study of this area is essential for the understanding of the Cretaceous tectonic evolution of Eastern China.

U-series and U-Pb carbonate geochronology

For full functionality of this site it is necessary to enable JavaScript. Here are instructions for enabling JavaScript in your web browser. The knowledge of the timing and duration of ore-forming processes are perhaps one of the most desirable pieces of information that geologists require to draw a complete picture of the deposit and to put its genesis into a coherent regional or even global geological framework.

In many cases, it represents an essential parameter for establishing detailed genetic models, and can critically impact on exploration strategies. This necessarily requires a reliable, precise and accurate geochronometer.

This dataset accompanies the publication, ‘In situ LA-ICPMS U-Pb dating of cassiterite without a known-age matrix-matched reference material.

U—Pb ages, trace element content and oxygen isotope ratios of single zircons from five plagiogranite intrusions of the Troodos ophiolite were measured to determine their crystallization age and assess the importance of fractional crystallization versus crustal anatexis in their petrogenesis. The inferred substantial involvement of crustal component is consistent with the existence of a shallow axial magma chamber, typical of fast-spreading mid-ocean ridge settings, within the Troodos slow-spreading ridge environment.

This apparent contradiction may be reconciled by episodically intense magmatism within an otherwise slow, magmatically deprived spreading axis. Most users should sign in with their email address. If you originally registered with a username please use that to sign in. To purchase short term access, please sign in to your Oxford Academic account above.

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U-pb dating

Climate change. Geology of Britain. U-series and U-Pb capability for carbonate geochronology has been developed in the geochronology and tracers facility to support NERC climate research, benefitting from extensive knowledge transfer from our U- Th -Pb geochronology facility. Sea floor geochronology and tracers is a recently developed but rapidly growing area for the facility. This science area is focused on the chronology of sea floor deposits that can be dated by U-Th methods e.

In our efforts to U-Pb date zircons from the late Eocene Caetano caldera by SIMS (SHRIMP-RG: sensitive high resolution ion microprobe, reverse geometry).

Monazite is an underutilized mineral in U—Pb geochronological studies of crustal rocks. It occurs as an accessory mineral in a wide variety of rocks, including granite, pegmatite, felsic volcanic ash, felsic gneiss, pelitic schist and gneiss of medium to high metamorphic grade, and low-grade metasedimentary rocks, and as a detrital mineral in clastic and metaclastic sediments.

In geochronological applications, it can be used to date the crystallization of igneous rocks, determine the age of metamorphism in metamorphic rocks of variable metamorphic grade, and determine the age and neodymium isotopic characteristics of source materials of both igneous and sedimentary rocks. It is particularly useful in the dating of peraluminous granitic rocks where zircon inheritance often precludes a precise U—Pb age for magmatic zircon.

The U—Pb systematics of the mineral are not without complexity, however. Being a mineral that favors incorporation of Th relative to U, it can contain considerable amounts of excess Pb derived from initially incorporated Th, an intermediate decay product of U. Monazite is known to be capable of preserving inheritance in a manner similar to that of zircon, and it can lose Pb during episodic or prolonged heating events of uppermost amphibolite and granulite facies metamorphic grades.

Examples of U—Pb systematics from most of the above situations are presented in this paper to illustrate both the utility and complexity of monazite in geochronological studies in an attempt to encourage more widespread application of this dating method. Nadia Mohammadi , Christopher R.

Historical Geology/U-Pb, Pb-Pb, and fission track dating

Uranium—lead dating , abbreviated U—Pb dating , is one of the oldest [1] and most refined of the radiometric dating schemes. It can be used to date rocks that formed and crystallised from about 1 million years to over 4. The method is usually applied to zircon. This mineral incorporates uranium and thorium atoms into its crystal structure , but strongly rejects lead when forming. As a result, newly-formed zircon deposits will contain no lead, meaning that any lead found in the mineral is radiogenic.

Since the exact rate at which uranium decays into lead is known, the current ratio of lead to uranium in a sample of the mineral can be used to reliably determine its age.

Zircon U Pb dating shows that the Saveh igneous complex crystallized 37–40 Ma ago. •. Sr Nd isotope ratios suggest a moderately depleted mantle source for.

Geological Survey Distributor : U. Toggle navigation ScienceBase-Catalog. Your browser does not have support for cookies enabled. Some features of this application will not work. Publication Date Time Period Moscati, R. Samples in the form of mounted loose grains were prepared and analyzed for direct age dating on a laser ablation inductively coupled plasma mass spectrometer LA-ICPMS system at the U. Geological Survey in Denver, Colorado in February This data release accompanies the publication, ‘Monazite and cassiterite U-Pb dating of the Abu Dabbab rare-metal granite, Egypt: Late Cryogenian metalliferous granite magmatism in the Arabian-Nubian Shield.

The publication constrains the timing of the magmatic-hydrothermal processes of the Abu Dabbab Granite which represents the oldest, highly-evolved [

U-Pb Zircon & Apatite dating

Of all the isotopic dating methods in use today, the uranium-lead method is the oldest and, when done carefully, the most reliable. Unlike any other method, uranium-lead has a natural cross-check built into it that shows when nature has tampered with the evidence. Uranium comes in two common isotopes with atomic weights of and we’ll call them U and U.

U–Pb dating methods for all types of geological settings. At present, s imon h. Introduction in addition, its chemical structure likes uranium and zirconolite for.

Petrology Tulane University Prof. Stephen A. Nelson Radiometric Dating Prior to the best and most accepted age of the Earth was that proposed by Lord Kelvin based on the amount of time necessary for the Earth to cool to its present temperature from a completely liquid state. Although we now recognize lots of problems with that calculation, the age of 25 my was accepted by most physicists, but considered too short by most geologists. Then, in , radioactivity was discovered.

Recognition that radioactive decay of atoms occurs in the Earth was important in two respects: It provided another source of heat, not considered by Kelvin, which would mean that the cooling time would have to be much longer. It provided a means by which the age of the Earth could be determined independently. Principles of Radiometric Dating.

Radioactive decay is described in terms of the probability that a constituent particle of the nucleus of an atom will escape through the potential Energy barrier which bonds them to the nucleus. The energies involved are so large, and the nucleus is so small that physical conditions in the Earth i. T and P cannot affect the rate of decay.

U–Pb dating of mineral deposits: From age constraints to ore-forming processes

Geology ; 46 3 : — In such deposits, assessing the exact timing of reservoir property stabilization is critical to better understand the postdepositional processes favorable to the creation or preservation of porosity. However, placing reliable and accurate chronological constraints on the formation of microporosity in these reservoirs is a major challenge. In this study we performed absolute U-Pb dating of calcite cements occurring in the Urgonian microporous limestone northern Tethys margin of southeastern France.

U-Pb ages ranging between

Chemical abrasion was carried out on zircons grains of the Temora II standard for U-Pb dating prior to analyses using in situ Laser Ablation-MultiCollector Ion.

At present, Chemostrat can determine U-Pb ages for zircon and apatite crystals. Zircon is a robust mineral and so the crystals preserve the age at which they formed or underwent high grade metamorphism. Consequently, U-Pb zircon geochronology can be employed to constrain the age of the basement rocks and in turn can help to identify sediment dispersal patterns and to correlate sandstones. If the analysed zircon crystal has not suffered either Pb loss or U gain, it will plot on the concordia line from which its age can be deduced.

Sandstones frequently contain detrital zircon grains and if these grains are undisturbed and concordant, their ages provide some clue as to their provenance. Generally at least fifty grains from each sandstone sample need to be analysed in order to obtain reliable data. The age of apatite grains can be calculated by plotting their U-Pb isotopic composition to form a discordia line. Apatite has a lower closure temperature than zircon, i. Therefore, they provide different information about the source of sandstones than zircons such as low grade metamorphic rocks.

This provides further information about sediment input pathways to sedimentary basins and, when combined with detrital zircon analysis, provides a powerful tool to identify the provenance of sediments. U-Pb Dating of Apatite The age of apatite grains can be calculated by plotting their U-Pb isotopic composition to form a discordia line.

U-Pb zircon geochronology by ID-TIMS: chemical abrasion & dissolution



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