Provenance analysis of psammitic gneisses in the Hida, Maizuru, Ryoke and Kurosegawa terranes, viewed from detrital heavy minerals

(1)对独居石和锆石颗粒的精确电子探针分析已经成功地发展了一种新的测年方法：CHIME(化学Th-U-全铅等时线方法)。(2)米诺地体和平田地体侏罗纪砂岩中碎屑独居石颗粒的CHIME年龄集中在1750-1400 Ma左右，少量集中在1250 Ma、850 Ma和250 Ma左右。(3)来自日本中部水津鲁地体上三叠统纳贝群的碎屑独居石的CHIME年龄主要在400-500 Ma之间，比米诺和Hida地体的碎屑独居石和锆石要年轻得多。(4)侵入日本中部Hgneida的花岗岩中的独居石和锆石颗粒。屈服编钟年龄约为250 Ma；这个年龄与以前报道的灰色花岗岩的前寒武纪Rb-Sr全岩年龄有很大的不同。(5)南北上地体Hikami花岗岩中的Tsubonosawa副片麻岩获得了350-2000 Ma的钟状锆石年龄；很少有一些圆润的锆石颗粒显示太古宙时代，年龄可达3000 Ma。这是日本群岛太古宙碎屑锆石的首次记录。

(1) Precise electron microprobe analysis of monazite and zircon grains has been successful to develop a new dating method: CHIME (Chemical Th-U-total Pb Isochron Method).(2) CHIME ages of detrital monazite grains in Jurassic sandstones of the Mino and Hida terranes concentrate around 1750-1400 Ma, with minor concentrations around 1250, 850 and 250 Ma.(3) CHIME ages of detrital monazites from the Upper Triassic Nabae Group in the Maizuru terrane range largely from ca. 400 to 500 Ma, being much younger than those from the Mino and Hida terranes.(4) Monazite and zircon grains from the Gray Granite, intruding the Hida gneiss in central Japan, yield CHIME ages of ca. 250 Ma; this age is much different from the previously-reported Precambrian Rb-Sr whole-rock age for the Gray Granite.(5) The Tsubonosawa paragneiss included in the Hikami Granite in the South Kitakami terrane yield CHIME zircon ages of 350-2000Ma; rarely some well-rounded zircon grains show an Archean age as old as 3000Ma.This is the first record of Archean detrital zircons from the Japanese Islands.