Zircon dating ppt

zircon dating ppt

How to date a zircon?

The systematics of U and Pb in zircons serve as one of the most important dating tools available in the geosciences. Until now, most zircon analyses are performed by secondary ion mass spectrometry (SIMS) or thermal ionization mass spectrometry (TIMS). SIMS offers the possibility of in-situ analysis of single crystals at high spatial resolution.

What is the importance of zircon in uranium lead dating?

Importance of zircon in uranium-lead dating. The mineral zircon adds three more fundamental advantages to uranium–lead dating. First, its crystal structure allows a small amount of tetravalent uranium to substitute for zirconium but excludes with great efficiency the incorporation of lead.

What is the best method for U-Pb analysis in zircons?

A new technique for in-situ U-Pb analysis in zircons is ICP-MS in combination with laser ablation. However, the sample volumes are small and concentrations of U and Pb can be very low, necessitating an ion detection system with very high sensitivity and low noise.

Can Sims perform in-situ zircon analysis?

Until now, most zircon analyses are performed by secondary ion mass spectrometry (SIMS) or thermal ionization mass spectrometry (TIMS). SIMS offers the possibility of in-situ analysis of single crystals at high spatial resolution.

Why is zircon used in uranium-lead dating?

The mineral zircon adds three more fundamental advantages to uranium–lead dating. First, its crystal structure allows a small amount of tetravalent uranium to substitute for zirconium but excludes with great efficiency the incorporation of lead. (It might be said that one begins with an empty box.)

What is the best way to date zircons?

Currently, zircons are typically dated by uranium-lead (U-Pb), fission-track, cathodoluminescence, and U+Th/He techniques.

Where does zircon occur in rocks?

It occurs as a common accessory mineral in igneous rocks (as primary crystallization products), in metamorphic rocks and as detrital grains in sedimentary rocks. Large zircon crystals are rare.

How rare is zircon in nature?

Zircon is rare within mafic rocks and very rare within ultramafic rocks aside from a group of ultrapotassic intrusive rocks such as kimberlites, carbonatites, and lamprophyre, where zircon can occasionally be found as a trace mineral owing to the unusual magma genesis of these rocks.

What types of Sims are used in Geosciences?

There are several different designs of SIMS currently being manufactured commercially that have applications in the geosciences (e.g., Camecas 1280, 7f, and NanoSIMS, ASIs SHRIMP and SHRIMP RG, EAGs ToF SIMS).

How does a SIMS instrument work?

Most SIMS instruments used for elemental and isotopic analyses function by accelerating ions produced in the source along a potential gradient, typically 10 KV, and then transferring these ions into the mass spectrometer.

What is the dynamic SIMS method?

In dynamic SIMS mode the primary ion beam exceeds the static limit (~1E12 ions/cm 2) producing a high yield of secondary ions. This technique is used for bulk analysis of elements and isotopes, and is particularly well-suited for analysis of isotopes and trace elements in minerals (e.g. REE in garnet).

What is Sims used for in chemistry?

This technique is used for bulk analysis of elements and isotopes, and is particularly well-suited for analysis of isotopes and trace elements in minerals (e.g. REE in garnet). Alternatively, static SIMS uses a much lower energy primary ion beam (usually Ga or Cs).

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