PRIMARY FORMATION AGES AND CIRCUMUSTANCES OF PRECRETACEOUS ROCKS MAKING UP THE RYOKE BELT IN HONSHU ARC

本州岛弧Ryoke带的原生岩形成时代和环境

• 批准号: 10440139
• 负责人: KAGAMI Hiroo
• 金额: $ 8.32万
• 依托单位: NIIGATA UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B).
• 财政年份: 1998
• 资助国家: 日本
• 起止时间: 1998 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-10440139/
• 关键词: Ryoke Belt; Continental Lithosphere; Sedimentary-origin metamorphic rock; Nd Model Age; U-Pb Zircon Age; Sr and Nd Isotopic Ratios; Proterozoic; Mafic to Felsic Igneous Rocks; 苦鉄質岩類; 花崗岩類; 大陸性リソスフェアマントル; 苦鉄質火成岩類; 花崗岩; 原生代初期〜中期; 起源物質; 三畳記〜ジュ

Crustal evolution of the Ryoke Belt is as follows ; (1) 2000-1800Ma.Granitic upper crust was formed from depleted mantle-origin lower crust, which is a primitive basement of the Ryoke Belt. These age data were obtained from Nd model ages of sedimentary-origin metamorphic rocks and granites, which were calculated using depleted mantle parameters, and U-Pb zircons contained in Cretaceous Ryoke granites and Jurassic mafic rocks. (2) 1750-1600Ma. Ceologic events of this age range are not clear. These age data were obtained from Nd model calculations of sedimentary-origin metamorphic rocks and granites. (3)220-190Ma. Mafic volcanism and plutonism took place under continental circumustances. These magmas were derived from continental lithospheric mantle. Age data of this range were measured using Sm-Nd whole rock isochron and whole rock-mineral isochron of gabbros and metadiabases. (4) 170-160Ma. Some mafic to intermediate rocks were formed during this age range. Age data of this range were obtained from Sm-Nd and Rb-Sr whole rock isochrons and Sm-Nd whole rock-mineral isochron. (5) 125-70Ma. Voluminous felsic igneous activity took place during this age ranges under island arc and continental margin circumustances. These age data were obtained from Rb-Sr whole rock isochron. Sm-Nd and Rb-Sr whole rock-mineral isochronos. As initial Sr and Nd isotopic compositions of these rocks are the same as the 220-190Ma mafic rocks, the felsic magmas are considered to have derived from the continental lithosphere lower crust and upper mantle.The Cretaceous to Paleogene igneous rocks showing the same isotopic features with Ryoke felsic igneous rocks are widely distributed in the Honshu Arc, which means that the Ryoke-type continental lithosphere basically made up the Honshu Arc.

陆屋带的地壳演化如下：（1）2000- 1800 Ma，花岗岩类上地壳是由亏损的幔源下地壳形成的，它是陆屋带的原始基底。这些年龄数据来自于沉积成因的变质岩和花岗岩的Nd模式年龄，这是使用亏损地幔参数计算的，以及白垩纪Ryoke花岗岩和侏罗纪基性岩石中所含的U-Pb锆石。(2)1750-1600Ma。该年龄段的脑血管事件尚不清楚。这些年龄数据是由沉积成因的变质岩和花岗岩的Nd模型计算得到的。（3）220-190Ma。镁铁质火山作用和深成岩作用发生在大陆环境下。岩浆来源于大陆岩石圈地幔。用辉长岩和变辉长岩的Sm-Nd全岩等时线和全岩-矿物等时线测定了该范围的年龄。(4)170-160Ma。一些镁铁质到中性岩石形成于这个年龄段。根据Sm-Nd、Rb-Sr全岩等时线和Sm-Nd全岩-矿物等时线获得了该范围的年龄数据。(5)125-70Ma。在岛弧和大陆边缘环境下，该年龄段发生了大量的长英质岩浆活动。这些年龄数据来自Rb-Sr全岩等时线。Sm-Nd和Rb-Sr全岩矿物等时线。由于这些岩石的初始Sr、Nd同位素组成与220- 190 Ma基性岩相同，认为长英质岩浆来源于大陆岩石圈下地壳和上地幔，与Ryoke长英质岩浆具有相同同位素特征的白垩纪-早第三纪岩浆岩在本州岛弧广泛分布，这意味着Ryoke型大陆岩石圈基本上构成了本州弧。

项目成果

田結庄良昭: "高Sr同位体比初生値を有する近畿地方白亜紀〜古第三紀花崗岩類"地質学論集. 53. 309-321 (1999)

Yoshiaki Tayusho：“近畿地区具有高 Sr 同位素比主要值的白垩纪至古近纪花岗岩”地质评论 53. 309-321 (1999)。

Tainosho, Y.: "High initial Sr isotopic ratios of Cretaceous to Early Paleogene granitic rocks in Kinki district, Southwest Japan."Mem.Geol.Soc.Japan. no.53. 309-321 (1999)

Tainosho, Y.：“日本西南部近畿地区白垩纪至早古近纪花岗岩的初始 Sr 同位素比率较高。”Mem.Geol.Soc.Japan。

Fujii, H.: "Sr-Nd isotopic systematics and geochenistry of intermediate plutonic rocks from Ikoma Mountains, Southwest Japan : evidence for a sequence of Mesozoic magmatic activity in the Ryoke Belt."The Island Arc. Vol.9. 37-45 (2000)

Fujii, H.：“日本西南部生驹山脉中间深成岩的 Sr-Nd 同位素系统学和地球化学：Ryoke 带中生代岩浆活动序列的证据。”岛弧。

Yuhara, M.: "Rb-Sr whole rock isochron ages and source materials of granitic rocks in Awaji Island, Southwest Japan Arc."Bull.Geol.Surv.Japan. Vol.49. 477-491 (1998)

Yuhara, M.：“日本西南弧淡路岛花岗岩的 Rb-Sr 全岩等时线年龄和来源材料。”Bull.Geol.Surv.Japan。

Yuhara, M.: "Geochronology characterization and petrogenesis of granitoids in the Ryoke Belt, Southwest Japan Arc : constraints from K-Ar, Rb-Sr and Sm-Nd systematics."The Island Arc. Vol.9. 64-80 (2000)

Yuhara, M.：“日本西南弧 Ryoke 带花岗岩类的年代学特征和岩石成因：来自 K-Ar、Rb-Sr 和 Sm-Nd 系统学的约束。”岛弧。