- D 3 1 outline the method for dating rocks
We provide examples of complex magmatic zircon from a southern Indian granulite terrane where SHRIMP II and LA-ICP-MS analyses are compared.
On the other hand, isotopically simple magmatic or metamorphic zircon can be analyzed fast and with high precision due to the large volume ablated. Size of a typical pit produced in zircon by using an ion microprobe during a 15 min analytical run (five cycles) (left) compared to the size of an ablation crater made from about 10 pulses of an excimer laser (right).
C) dating usually want to know about the radiometric dating methods that are claimed to give millions and billions of years—carbon dating can only give thousands of years.
People wonder how millions of years could be squeezed into the biblical account of history. Christians, by definition, take the statements of Jesus Christ seriously.
Magmatic zircon in high-grade metamorphic rocks is often characterized by complex textures as revealed by cathodoluminenscence (CL) that result from multiple episodes of recrystallization, overgrowth, Pb-loss and modifications through fluid-induced disturbances of the crystal structure and the original U-Th-Pb isotopic systematics.
Many of these features can be recognized in 2-dimensional CL images, and isotopic analysis of such domains using a high resolution ion-microprobe with only shallow penetration of the zircon surface may be able to reconstruct much of the magmatic and complex post-magmatic history of such grains.
In particular it is generally possible to find original magmatic domains yielding concordant ages.
In contrast, destructive techniques such as LA-ICP-MS consume a large volume, leave a deep crater in the target grain, and often sample heterogeneous domains that are not visible and thus often yield discordant results which are difficult to interpret.
The main challenge for LA-ICP-MS analysis is a reliable correction for common Pb, due to the presence of mercury in the argon gas used in many laboratories to produce the plasma that causes an isobaric interference by Pb ratios.
Different methods were developed to overcome this problem (e.g., Horn et al., 2000, Košler et al., 2002, Jackson et al., 2004, Gehrels et al., 2008 and Cottle et al., 2009), but most users simply make no correction, assuming that zircon has no or only insignificant common Pb.