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Greenstone and terrigeous clastics in the Hidaka Supergroup, northern Hokkaido

北海道北部日高超群的绿岩和陆源碎屑岩

基本信息

批准号：
02640600
负责人：
KIMINAMI Kazuo
金额：
$ 1.22万
依托单位：
Yamaguchi University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-02640600/
关键词：
accretionary prism greenstone melange collision of active ridge Hidaka Supergroup Rurochi Formation

项目摘要

I have gained the following results through the research.1). The Rurochi Formation. which occurs in the northern part of Hokkaido. consists mainly of black shale, alternating beds of sandstone and snale, and greenstones. Black shale and exotic blocks of green siliceous shale withi in the formation yield Eocene radiolarian assemblages. The greenstones are composed of massive basalt, pillow basalt and basic tuff. Basalts have been intruded frequently into black shale. Glassy chilled margins of basalt and baked parts of black shale confirm the primary nature of these igneous contacts. Argillaceous xenoliths in the basaltic rock, and pillow lavas with inter-pillow black shale are also common.2). The Makimine Formation is made mainly up argillite and greenstones. The greenstones comprise dolerite, massive basalt, pillow basalt and basic tuff. Some dolerite sills with double chilled margins less than a few centimeters in thickness are interlayered with black shale. In most cases the black shale shows gradational alteration to light-colored baked rock over a range of a few centimeters from dolerite contacts, due to the thermal effect of dolerite emplacement. - Dolerites commonly contain xenoliths of black shale. These facts indicate that the basaltic rocks were intruded into and extruded upon unconsolidated fine-grained clastic sediments.3). The Mugi Formation is represented by argillite and greenstones. Some of the basalt lavas with chilled margins are in immediate contact with black shale, which has locally suffered thermal effects along its contact. Xenoliths of black shale occur locally in the basalts.4). The basaltic rocks in the formations were generated at a spreading ridge on the basis of their chemical features. In this context, we therefore conclude that the greenstones were emplaced in connection with a ridge-forearc collision.

通过研究，我得到了以下结论：1）。流池组。发生在北海道的北方。主要由黑色页岩、砂岩与砂岩相间层和绿岩组成。地层中的黑色页岩和外来的绿色硅质页岩块产生始新世放射虫组合。绿岩由块状玄武岩、枕状玄武岩和基性凝灰岩组成。玄武岩经常侵入黑色页岩中。玄武岩的玻璃状冷却边缘和黑色页岩的烘烤部分证实了这些火成岩接触的主要性质。玄武质岩石中的泥质捕虏体和枕状熔岩与枕间黑色页岩也很常见。Makimine组主要由泥质岩和绿岩组成。绿岩包括粗玄岩、块状玄武岩、枕状玄武岩和基性凝灰岩。一些粗玄岩岩床的双冷边厚度小于几厘米，与黑色页岩互层。在大多数情况下，由于粗玄岩侵位的热效应，黑色页岩在距离粗玄岩接触面几厘米的范围内表现出对浅色烘烤岩石的渐变蚀变。- 白云岩通常含有黑色页岩捕虏体。这些事实表明，玄武质岩石侵入和挤压在松散的细粒碎屑沉积物。Mugi组以泥质岩和绿岩为代表。一些具有冷却边缘的玄武岩熔岩与黑色页岩直接接触，黑色页岩沿其接触沿着局部遭受热效应。黑色页岩捕虏体局部产于玄武岩中。根据玄武质岩石的化学特征，这些岩石形成于扩张脊。在这种情况下，我们因此得出结论，绿岩侵位与一个脊弧前碰撞。