Japan Geoscience Union Meeting 2023

Presentation information

[J] Oral

S (Solid Earth Sciences ) » S-CG Complex & General

[S-CG51] Hybrid Geochronology beyond Zircon Geochronology

Thu. May 25, 2023 9:00 AM - 10:15 AM 202 (International Conference Hall, Makuhari Messe)

convener:Sota Niki(Geochemical Research Center, School of Science, The University of Tokyo), Hideki Iwano(Kyoto Fission-Track Co., Ltd.), Chairperson:Sota Niki(Geochemical Research Center, School of Science, The University of Tokyo), Hideki Iwano(Kyoto Fission-Track Co., Ltd.)

9:45 AM - 10:00 AM

[SCG51-04] Multi-mineral geochronology of Na–Al-rich metasomatic rocks in serpentinites

*Tatsuki Tsujimori1, Yasuhito Osanai2 (1.Tohoku University, 2.Kyushu University)

Keywords:U-Pb dating, metasomatism, serpentinite

The development of modern U–Pb geochronology has involved technological innovation in conjunction with new ideas that have emerged from the field of geological sciences. During last three decades, in-situ zircon U–Pb dating becomes a robust and widely used method for geochronology, providing valuable insights into the timing and nature of geological processes, including magmatic or metamorphic events recorded in orogenic belts. However, the interpretation of data from U–Pb dating of zircon and other common datable minerals, such as monazite, apatite, rutile, and titanite, requires careful consideration of several issues and limitations. Although reconnaissance U–Pb dating for other minerals has just begun, it has the potential to expand our understanding of geological processes.

The Na–Al-rich metasomatic rocks, including jadeitite and albitite, found within a forearc serpentinite complex, are ideal research targets for deciphering the chemical compositions and geodynamic behaviors of slab fluids. We have been exploring the use of U–Pb dating method to determine the timing of slab-fluid activities. In this contribution, we present our new geochronological dataset from albitite, a Na–Al-rich metasomatic rock, formed by slab-fluid activities in a forearc serpentinite complex. One of the authors has previously reported that Sr-rich accessory minerals in albitite, known as "riebeckite-bearing albitite," in the Omi serpentinite mélange of the Hida Mountains, Japan, can be datable using U–Pb method (See Tsujimori et al.'s JPGU2019 abstract at https://confit.atlas.jp/guide/event/jpgu2019/subject/SMP32-14/detail ). However, our new zircon U–Pb dating data from the same rocks reveal a more complex history, challenging the previous interpretation of the simple reactivation of metasomatic mineralization in the Paleozoic serpentinite mélange in Cretaceous time. Our case study highlights the advantages of multi-mineral U–Pb age dating for fluid-induced metasomatic mineralization within a forearc wedge mantle serpentinite. We also discuss how the hybrid geochronology is important for understanding complex geological processes.