Deciphering the evolution history of volatile elements toward the formation of the water-planet, recorded in lunar potassium feldspar

2020 Fiscal Year Final Research Report

• Project/Area Number: 17H02992
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Geochemistry/Cosmochemistry
• Research Institution: Ibaraki University
• Principal Investigator: Hashizume Ko 茨城大学, 理工学研究科(理学野), 教授 (90252577)
• Co-Investigator(Kenkyū-buntansha): 山中 千博 大阪大学, 理学研究科, 准教授 (10230509) ; 藤谷 渉 茨城大学, 理工学研究科(理学野), 准教授 (20755615) ; 掛川 武 東北大学, 理学研究科, 教授 (60250669)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 月岩石 / 揮発性元素 / アンモニア / イオン照射 / SIMS分析

Outline of Final Research Achievements

This project aims at deciphering the origin of nitrogen trapped in Moon rocks. A novel ion-microprobe analytical technique that enables detection of ammonium-form nitrogen concentrated in potassium-bearing minerals was developed. To enhance the detection sensitivity of nitrogen, carbon ions were implanted to the rock minerals. A high gain of cyanide ions was confirmed from terrestrial potassium-feldspars with known nitrogen concentrations. Compatible nitrogen ion intensities were confirmed in potassium-feldspar from lunar meteorites. We estimate nitrogen concentration of approximately 100 ppm in this specific mineral, which is much higher than the bulk concentration of nitrogen, generally of the order of 1 ppm.

Free Research Field

地球宇宙化学

Academic Significance and Societal Importance of the Research Achievements

月岩石中に含まれる窒素を始めとした揮発性元素の起源と進化の理解は、月だけではなく地球の揮発性元素の様子、ひいては、地球が水惑星となった過程を正しく把握するための鍵だと目されている。今回、微小な造岩鉱物に濃集した窒素の起源を紐解くための基礎技術の開発に成功し、月岩石中の揮発性元素の起源を紐解く新たな突破口が確立された。