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Application of gravimetry to field geological survey -Clarification of the Kurosegawa Terrane in the eastern half of the Chichibu Terrane

重力测量在野外地质调查中的应用-秩父地体东半部黑濑川地体的澄清

基本信息

批准号：
13640465
负责人：
SAKA Yukiyasu
金额：
$ 0.38万
依托单位：
Waseda University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

项目摘要

2001: The Gokasho-Arashima Tectonic Line (G-A), which runs through the medial zone of the Chichibu Terrane of the Shima Peninsula, has been regarded as the eastern extension of the Kurosegawa Terrane of Shikoku. Geological survey and gravimetry at its western terminal clarified following two evidence; 1. G-A characterized by the serpentinite zone does not overlie the Chichibu Terrane as a tectonic nappe, but represents a longitudinal fault disecting the Chichibu Terrane. 2. Due to poor road network, gravimetry as a preliminary research of the field geological survey did not bring about any contribution. 3. In another area (Kanto Mountains), various rocks exotic to the sedimentary rocks composing the Chichibu Terrane were newly found along a narrow fault zone (Naguri Fault Zone) and this fault zone was ascertained as the eastern extremity of the Kurosegawa Terrane. Along this fault zone, a marked negative anomaly of gravity was traced and testified the usefulness of gravimetry for detecting a fault zone.2002 : 1. Along the boundary zone of the North and Kurosegawa Terrane of the Chichibu Terrane of the Shima Peninsula, serpentinite blocks were newly discovered. These serpentinite blocks were concluded to be overlain by the rock mass of the North Terrane with a low-angled fault plane. The character of this fault was inferred by gravimetry. 2. Gravimetry was extended to the northwestern extension of the Naguri Fault Zone of the Kanto Mountains. A marked negative anomaly of gravity was traced and it strongly suggests the northwestern extension of the Naguri Fault Zone, although any rocks characteristic of the Kurosegawa Terrane have not been found in spite of detailed field survey.

2001年，横贯岛岛半岛秩父地体中部地带的高笠山-荒岛构造线（G-A）被认为是四国黑川地体的东部延伸。其西终点站的地质调查和重力测量澄清了以下两点证据；1. 以蛇纹岩带为特征的G-A并不是构造推覆体，而是纵向断裂，分隔了秩父地体。由于道路网络较差，重力测量作为野外地质调查的初步研究并没有带来任何贡献。3. 在另一个地区（关东山脉），沿一条狭窄的断裂带（Naguri断裂带）新发现了构成Chichibu地体的沉积岩的各种外来岩石，该断裂带被确定为黑家川地体的东端。在该断裂带沿线，追踪到明显的重力负异常，证明了重力法探测断裂带的有效性。2002: 1；在岛马半岛秩部地体的北地体与黑家川地体的交界地带，新发现了蛇纹岩块体。这些蛇纹岩块体被北地体的低角度断裂面岩体所覆盖。这个断层的性质是用重力法推断出来的。2. 将重力测量扩展到关东山脉Naguri断裂带的西北延伸部分。尽管经过详细的野外调查，仍未发现任何具有黑川地系特征的岩石，但发现了一个明显的重力负异常，这强烈表明Naguri断裂带向西北延伸。