@article{oai:nagoya.repo.nii.ac.jp:00014598,
 author = {今山, 武志 and 鈴木, 和博 and Imayama, Takeshi and Suzuki, Kazuhiro},
 journal = {名古屋大学加速器質量分析計業績報告書},
 month = {Mar},
 note = {Monazites, approximately [(LREE,Th,U,Ca)(p,Si)O4], from two leucogranite samples in far-eastern Nepal Himalaya were dated by the chemical U-Th-total Pb isochron method (CHIME). Monazites in foliated biotite leucogranite exhibit significant chemical characteristics by different grains or within individual grains. Some monazite grains have strongly undergone the chemical alteration through the monazite-huttonite substitution (p^5+ +REE^3+ ↔Si^4+ + Th^4+). Other grains, especially surrounding feldspars, have slightly occurred the monazite-cheralite substitution (2REE3+ ↔ Ca^2+ +Th^4+), and have the relatively higher concentrations of ThO2, compared to the huttonite-rich monazite. Furthermore, a significant intra-crystal chemical zoning is observed in individual monazite grains, indicating that Y content decreases from core and to rim. Monazites selected using chemical criteria (0.95 < (Ca + Si)/ (Th + U +Pb +S) < 1.05), which could be discriminate the metamict monazite due to the destruction of the crystalline structure from the original monazites, construct together a pseudo-isochron of 16.4 ± 1.7 Ma in PbO-ThO2* diagram. Also, monazites from quartz-rich leucogranite have homogenous compositions of Y, Th and U contents, and yields the weight mean chemical ages of 16.6 ± 2.6 Ma, in agreement with the age of the foliated biotite leucogranite. Our data suggest that the CHIME ages combined with the chemical zoning patterns such as Y, Th, U, Ca, and Pb of monazites can provide a powerful tool to elucidate the complex zoning patterns of monazite and to know the precise timing of granite crystallization from magmatic monazite., 第23回名古屋大学年代測定総合研究センターシンポジウム平成22(2010)年度報告},
 pages = {55--64},
 title = {極東ネパールヒマラヤ優白質花崗岩の高精度CHIMEモナザイト年代(予報)},
 volume = {22},
 year = {2011}
}