权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Analysis of the Relationship Between the Gosaisyo and Takanuki Metamorphic Rocks in the Abukuma Metamorphic Terrane, Japan

日本阿武隈变质地体御斋庄与高贯变质岩关系分析

基本信息

批准号：
01460061
负责人：
HIROI Yoshikuni
金额：
$ 4.1万
依托单位：
Chiba University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1990
项目状态：
已结题

项目摘要

The Abukuma metamorphic rocks are lithologically and structurally divided into the Gosaisyo and Takanuki Series.1. It has revealed that these two units are in structurally discordant relation. Moreover, decollement blocks of the Takanuki Series occur in the Gosaisyo Series.2. The Rb-Sr whole-rock isochron are of the Jumonji plutonic mass, which is intruded along the boundary between the Gosaisyo and Takanuki Series, is 122+20 Ma. The age may be close to the time when the Gosaisyo Series thrust up onto the Takanuki Series.3. Sector-zoned garnet, which was considered to be peculiar to the Takanuki Series, has been revealed to occur in the pelitic-psammitic rocks of the Gosaisyo Series close to the Takanuki Series. This clearly shows that the high-temperature rapid loading and subsequent unloading are in common to these two geological units and that the loading was due to the overthrusting of the Gosaisyo Series onto the Takanuki Series.4. The homogenization of growth-zoned garnet porphyroblasts by the intracrystalline diffusion of elements suggests about 4 m. Y. As the duration of high-temperature conditions. This suggests 5 mm/year as the rate of subduction and subsequent uplift, because at least 3 kb loading and unloading took place over that time span.5. The mica K-Ar dating yields ages of 90-105 Ma. The lowerーgrade rocks tend to have older ages.6. The ion microprobe dating of zircon from meta-quartz porphyry, which is intruded into the Gosaisyo Series, yields about 120 Ma as the time of crystallization from magma and a few m. y. Younger age as the metamorphic time.Thus the two distinct metamorphic units in the Abukuma terrane are well-documented, and now we may be able to construct a new tectonic model in the arc-trench system.

阿武隈变质岩从岩性和构造上分为五西庄和高贯系列。 1．事实表明，这两个单位在结构上是不协调的关系。此外，Takanuki 系列的 decollement 块出现在 Gosaisyo 系列中。2。沿着Gosaisyo和Takanuki系列之间的边界侵入的Jumonji深成体的Rb-Sr全岩等时线为122+20 Ma。年代可能接近御斋庄系列推上高贯系列的年代。3。扇形分区石榴石被认为是 Takanuki 系列特有的，现已被发现出现在靠近 Takanuki 系列的 Gosaisyo 系列的泥质-砂质岩中。这清楚地表明，高温快速加载和随后的卸载对于这两个地质单元来说是共同的，并且加载是由于Gosaisyo系列对Takanuki系列的推覆所致。4。通过元素的晶内扩散，生长区石榴石原卟啉细胞的均质化表明约为 4 m。 Y.随着高温条件的持续时间。这表明俯冲和随后的抬升速率为 5 毫米/年，因为在这段时间内至少发生了 3 kb 的加载和卸载。5。云母 K-Ar 测年得出的年龄为 90-105 Ma。较低品位的岩石往往有较古老的年龄。6．对侵入Gosaisyo系列的变石英斑岩中的锆石进行离子探针测年，得出岩浆结晶时间约为120Ma，还有几m。 y。变质时间更早。因此，阿武隈地体中两个不同的变质单元得到了充分的记录，现在我们也许能够在弧海沟系统中构建一个新的构造模型。