Crustal differentiation due to partial melting of granitic rocks in an active continental margin, the Ryoke Belt, Southwest Japan
Crustal differentiation due to partial melting of granitic rocks in an active continental margin, the Ryoke Belt, Southwest Japan
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日本西南部 Ryoke 带活动大陆边缘花岗岩部分熔融导致的地壳分异
DOI：
10.1016/j.lithos.2015.04.021
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发表时间：
2015
期刊：
影响因子：
3.5
通讯作者：
KAMEI Atsushi
中科院分区：
文献类型：
--
作者：
AKASAKI Eri;OWADA Masaaki;KAMEI Atsushi
亚洲太平洋大陆边缘主要由白垩纪至古近纪的大量花岗质岩石组成。产于西南日本弧的良屋带的良屋花岗岩类可分为较老和较年轻的花岗岩类。高钾纪部花岗岩代表了较年轻的花岗岩侵入体，出露于Ryoke带西部的柳井地区。纪部花岗岩与同时代的冰室岳石英闪长岩共生，其侵入年龄为91 Ma。然而，Gamano-Obatake花岗闪长岩，较老的花岗岩，侵入主机Ryoke片麻岩在95 Ma。Gamano-Obatake花岗闪长岩的特征是混合岩结构的局部发育，这归因于冰室岳石英闪长岩侵入花岗闪长岩。在石英闪长岩附近的花岗闪长岩中，有浅色的矿池和斑片。在纪部花岗岩的Sr和Nd同位素组成范围内绘制了校正到91 Ma的釜野小岳花岗闪长岩的Sr和Nd同位素组成。地球化学模拟表明，部分熔融发生在Gamano-Obatake花岗闪长岩，并导致了纪部花岗岩岩浆的形成。冰室岳石英层被认为是这一事件的热源。这可能是形成演化较年轻的陆块花岗岩和活动大陆边缘地壳分异的一个重要过程。
The continental margin of Pacific Asia is dominated by the voluminous Cretaceous to Paleogene granitic rocks. The Ryoke granitoids that occur in the Ryoke Belt in the Southwest Japan Arc are divided into the older and younger granites. The high-K Kibe Granite represents the younger granitic intrusion and is exposed in the Yanai area in the western part of Ryoke Belt. The Kibe Granite is associated with the coeval Himurodake Quartz Diorite and their intrusive age is 91 Ma. However, the Gamano-Obatake Granodiorite, the older granite, intruded the host Ryoke gneisses at 95 Ma. The Gamano-Obatake Granodiorite is characterized by the localized development of migmatitic structure attributed to the intrusion of the Himurodake Quartz Diorite into the granodiorite. Leucocratic pools and patches occur in the granodiorite in the vicinity of the quartz diorite. The Sr and Nd isotopic compositions of the Gamano-Obatake Granodiorite corrected to 91 Ma are plotted within those of the Kibe Granite. Geochemical modeling suggests that partial melting took place in the Gamano-Obatake Granodiorite and resulted in the formation of the Kibe Granite magma. The Himurodake Quartz Diorite is believed to be a heat source for this event. This can be considered as an essential process for the formation of the evolved younger Ryoke granite and for the crustal differentiation in the active continental margin.