Metamorphism and granite genesis in the Hidaka Metamorphic Belt, Hokkaido, Japan
Metamorphism and granite genesis in the Hidaka Metamorphic Belt, Hokkaido, Japan
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日本北海道日高变质带的变质作用和花岗岩成因
DOI：
10.1111/j.1525-1314.1991.tb00508.x
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发表时间：
1991
影响因子：
3.4
通讯作者：
M. Owada
中科院分区：
文献类型：
--
作者：
Y. Osanai;M. Komatsu;M. Owada
日高变质带主体带为岛弧型隆起地壳剖面。地壳形成于第三纪早期，是白垩纪两个弧沟系统碰撞的结果。地壳变质序列可划分为四个变质带（Ⅰ-Ⅳ带），其中Ⅳ带为麻粒岩相变质带。
对日高带的演化进行了详细的研究，根据对变质岩，特别是新发现的含十字石麻粒岩的修正P-T-t分析，证实了在增生沉积岩和洋壳岩的构造增厚事件之后，存在一个恒压加热路径。在峰期变质事件（c。53 Ma），区域地温梯度达到33-40° C km−1，麻粒岩单元最低部分的最高P-T条件为830° C，7 kbar。在这一部分，Gt-Opx-Cd片麻岩的XH 2 O约为0.15，Gt-Cd-Bt片麻岩的XH 2 O约为0.4。麻粒岩单元的P-T-XH 2 O条件完全处于泥质和杂砂岩变质岩发生流体部分熔融的区域内。这与麻粒岩单元最低部分的Gt-Opx-Cd片麻岩的残余岩性质相一致。
主带部分熔融的可能性对主带中的过铝质（S型）花岗岩的成因具有重要意义，主带中的S型花岗岩为麻粒岩带中的Opx-Gt-Bt英云闪长岩、角闪岩带中的Gt-Cd-Bt英云闪长岩和Bt-Mus片麻岩带中的Cd-Bt-Mus英云闪长岩。这些强过铝质英云闪长质岩石的矿物学和化学性质允许它们被认为是来自S型花岗质岩浆的地壳深熔作用的泥质变质岩在地壳深部。
The Main Zone of the Hidaka Metamorphic Belt is an uplifted crustal section of island-arc type. The crust was formed during early Tertiary time, as a result of collision between two arc–trench systems of Cretaceous age. The crustal metamorphic sequence is divided into four metamorphic zones (I–IV), in which zone IV is in the granulite facies.
A detailed study of the evolution of the Hidaka Belt, based on a revised P–T–t analysis of the metamorphic rocks, notably a newly found staurolite-bearing granulite, confirms a prograde isobaric heating path, after a supposed event of tectonic thickening of accretionary sedimentary and oceanic crustal rocks. During the peak metamorphic event (c. 53 Ma), the regional geothermal gradient attained 33–40° C km−1, and the highest P–T condition obtained from the lowest part of the granulite unit is 830° C, 7 kbar. In this part, XH2O of Gt–Opx–Cd gneiss is about 0.15 and that of Gt–Cd–Bt gneiss is 0.4. The P–T–XH2O condition of the granulite unit is well within a field where fluid-present partial melting of pelitic and greywacke metamorphic rocks takes place. This is in harmony with the restitic nature of the Gt–Opx–Cd gneiss in the lowest part of the granulite unit.
The possibility that partial melting took place in the Main Zone is significant for the genesis of the peraluminous (S-type) granitic rocks within it. The S-type granitic rocks in this zone are Opx–Gt–Bt tonalite in the granulite zone, Gt–Cd–Bt tonalite in the amphibolite zone, and Cd–Bt–Mus tonalite in the Bt–Mus gneiss zone. The mineralogical and chemical nature of these strongly peraluminous tonalitic rocks permit them to be regarded as having been derived from S-type granitic magma generated by crustal anatexis of pelitic metamorphic rocks in deeper crust.