Alteration of Rokko Granites
Alteration of Rokko Granites
复制标题
六甲花岗岩的蚀变
DOI：
10.5026/jgeography.112.3_360
复制
发表时间：
2003
影响因子：
3.1
通讯作者：
M. Utada
中科院分区：
文献类型：
--
作者：
M. Utada
六甲山脉主要由三种岩石单元组成：布引花岗闪长岩、六甲花岗岩和土桥石英闪长岩。通过 XRD 分析和磁化率计检查这些岩石的蚀变。所有花岗岩都分为四类蚀变：未蚀变（A）、未蚀变（B）、风化和热液蚀变。未蚀变 (A) 岩石不包含任何次生矿物，并显示出高磁化率 (MS)，可能接近原始磁化率（n × 10-3 SI 单位）。未蚀变的 (B) 岩石也不含有次生矿物，但其 MS 明显较低。这些岩石通常分布在围绕并切割六甲山脉的主要断层沿线的破碎带中。风化岩石是由高岭土的存在来定义的。它们的 MS 非常低（n × 10-5 SI 单位）。山脊北部保留了高度风化的岩石，而南部则遭受严重侵蚀。六组热液蚀变岩根据特征矿物的存在而定义，例如丝光沸石、钙沸石、绢云母、绿泥石-蒙脱石系列、高岭石和方解石。热液蚀变岩石表明 MS 相对较低（n × 10-4-10-5 SI 单位）。大多数热液蚀变发生在沿着或平行于主要断裂带，尤其是北部的沙场山、汤谷和有马断裂带以及南部的布引和诹访山断裂带。
The Rokko Mountains are mainly composed of three rock units : Nunobiki granodiorite, Rokko granite, and Dobashi quartz diorite. Alteration of these rocks is examined by XRD analysis and magnetic susceptibility meter. All granite rocks are divided into four categories of alteration : unaltered (A), unaltered (B), weathered, and hydrothermally altered. Unaltered (A) rocks do not contain any secondary minerals and indicate high magnetic susceptibilities (MS), which are probably near the original ones (n × 10-3 SI unit). Unaltered (B) rocks also do not contain secondary minerals, but their MS is clearly low. These rocks are typically distributed in crushed zones along the main faults that enclose and cut the Rokko Mountains. Weathered rocks are defined by the presence of kaolin. Their MS are very low (n × 10-5 SI unit). Highly weathered rocks are preserved at the northern part of the backbone of mountains, while they are heavily eroded at the southern part. Six groups of hydrothermally altered rock are defined by the presence of characteristic minerals such as mordenite, calcium zeolites, sericite, chlorite-smectite series, kaolinite, and calcite. Hydrothermally altered rocks indicate comparatively low MS (n × 10-4-10-5 SI unit). Most hydrothermal alteration occurred along or parallel to main faults, especially Shabayama, Yusodani, and Arima faults at northern part and Nunobiki and Suwayama faults at southern part.