Timescales of granite infancy: Advances in granite geochronology - Hoseong Lim
Channel: The Royal Society of Victoria
Date: 29/11/2022

Granite is a rock type that makes up ~70% of Earth’s continents, and is therefore an important study for understanding the history of the Earth’s crust. We can obtain the absolute age of granite by using radiometric dating techniques on a specific mineral contained in a granite rock sample, then assume that the age of the mineral is equivalent to the age of the rock. While the dating of granite is commonly derived from measuring the mineral zircon, grains of this mineral yield are found to return large age spans over tens of millions of years. Accordingly, Hoseong and colleagues have challenged the suitability of zircon for granite dating, while attempting to improve on this widely used technique. They found apatite and titanite to have great potential, as their general compositions are suitable as both age dating and environment indicators.

Most of the granite ages from Victoria reported in the literature are biotite or hornblende ages. However, zircon ages and corresponding apatite and titanite ages in this study are consistently around 20 Myrs older than the previous biotite/hornblende ages. These age differences may also occur in other granite bodies. Hoseong’s study shows fluid-mobile elements collection in addition to radiometric dating is significantly important to improve age reliability.

Zircon dating is the dominant technique in geosciences, and this fluid-mobile element quality control process may enhance reliability of the huge amount of zircon age data currently generated in geological research. The final implication of the study is the potential of apatite and titanite ages for use as alternative granite age indicators. Although more studies are required, these dating techniques can support zircon age dating and might even substitute the current zircon dating technique.

In recognition of the quality and significance of his research, Hoseong Lim is the Second Prize Winner in the Earth Sciences category for the Royal Society of Victoria's Young Scientist Research Prizes in 2022.