Raman spectroscopy and scanning electron microscopy characterizations of fission track method datable zircon grains

Area of Science:

• Geochemistry
• Geochronology
• Materials Science

Background:

• Zircon fission track method (ZFTM) is a routine geochronological technique.
• Methodological challenges exist in ZFTM, particularly in classifying zircon grain surfaces.
• Surface features influence fission track density and age determination.

Purpose of the Study:

• To improve understanding of physicochemical phenomena during zircon crystallization.
• To address methodological difficulties in the zircon fission track method.
• To refine the classification and analysis of zircon grain surfaces.

Main Methods:

• Characterization of zircon grain surfaces using optical microscopy (OM), micro-Raman spectroscopy, and scanning electron microscopy (SEM).
• Analysis of grain surfaces before and after chemical etching.
• Application of improved methodology for zircon fission track age determination.

Main Results:

• Anomalous zircon grains exhibit subfamilies.
• Etching anisotropy in heterogeneous grains is linked to unobservable crystallographic faces.
• Age distributions for homogeneous, heterogeneous, and hybrid grains are statistically and geologically compatible.
• 60% of analyzed grains were classified as anomalous.

Conclusions:

• Advanced spectroscopic and morphological studies enhance ZFTM reliability.
• Distinguishing zircon grain surface types is crucial for accurate fission track dating.
• The refined methodology provides compatible age distributions for most zircon grain types.