[B-CG06] Decoding the history of Earth: From Hadean to the present

[BCG06-07] Hydrogen isotope analysis of apatite inclusions in the Hadean to early Archean zircon

Daiki Tanaka¹, *Shinji Yamamoto¹, Shoichi Itoh², Shuhei Sakata³ (1.Graduate School of Environment and Information Sciences, Yokohama National University, 2.Graduate School of Faculty of Science, Kyoto Uiversity, 3.Earthquake Research Institute)

Keywords:Hadean-early Archean, zircon, apatite, hydrogen isotope analysis

We measured hydrogen isotopic composition of apatite inclusions trapped in Hadean to early Archean igneous zircons from sedimentary rocks in Jack hills greenstone belt and tonalitic rocks in Acasta gneiss, Labrador gneiss, and Tanzawa tonalite in order to compare the isotopic ratio of ancient ocean with that of modern oceanic water.

Hydrogen isotope analysis with SIMS show the data sets with the range about δD=-50 to -340 from Jack Hills zircons (3.3 to 4.3 Ga), -15 to -265‰ from Acasta (3.5 to 4.0 Ga) and Labrador (3.8 to 3.9 Ga), and -57±19‰ from Tanzawa tonalite (4.5 Ma) samples. In addition, we evaluated the micro-cracks in zircon to exclude the negative possibility of secondary hydrogen interaction of apatite inclusions. Assuming the magma type the apatite crystalized, Arc-type apatite have the composition δD= -106 to -170‰, and Mantle-type have δD= -232±27‰ and -338±22‰, respectively. The data set above-mentioned result in the Archaean ocean δD= -84±19‰ and mantle water δD= -232±27‰ and -338±22‰.