Unravelling multiple thermotectonic events accommodated by the Highland Boundary Fault: Insights from K-Ar dating
Unravelling multiple thermotectonic events accommodated by the Highland Boundary Fault: Insights from K-Ar dating
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解开高地边界断层所容纳的多个热构造事件：来自 K-Ar 测年的见解
DOI：
10.1016/j.jsg.2023.105030
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发表时间：
2024
影响因子：
3.1
通讯作者：
McKay L
中科院分区：
文献类型：
--
作者：
McKay L
多个再活化事件和长的滑动历史导致复杂的断层结构，在没有绝对时间限制的情况下，其解开仍然具有挑战性。我们应用伊利石断层岩的K-Ar同位素测年，再加上X射线衍射和显微结构分析，以约束，第一次，伊利石生产脆性断层运动的苏格兰高地边界断层（HBF）容纳的时间。伊利石年龄分析（IAA）图表明，多个故障上的HBF活化事件。IAA图的红色叶状混乱的断层角砾岩符合一个“正常”的IAA模式与年轻的年龄记录的“自生”1 Millite（306-276和300-272马）和旧的日期为“碎屑”2 M1 illite（554-502和471-427马）。相反，叠加蓝色断层泥的IAA图扭转了“正常”趋势，具有较老的“自生”1 M伊利石（348-314和276-25 Ma）和较年轻的“碎屑”2 M伊利石（258-234和250-226 Ma）年龄。我们提出这一结果从非均匀剪切和应变局部化。在蓝色断层泥的本地化豆荚，应变加速粘土矿物的生长，增加微晶的大小，并通过缺陷迁移促进从1 M到2 M1伊利石的多型转化。在其他地方的蓝色断层泥，并在红色的叶状混乱断层泥，低应变制度允许1 M多型体保持不变。
Multiple reactivation episodes and long slip histories lead to complex fault structures, whose unravelling remains challenging in the absence of absolute time constraints. We apply K–Ar isotopic dating of illitic fault rocks, coupled with X-ray diffraction and microstructural analyses to constrain, for the first time, timing of illite-producing brittle fault movements accommodated by the Highland Boundary Fault (HBF), Scotland. Illite Age Analysis (IAA) plots indicate multiple fault reactivation events on the HBF. IAA plots for the red foliated chaotic fault-breccia conform to a ‘normal’ IAA pattern with younger ages recorded for ‘authigenic’ 1 M illite (306-276 and 300-272 Ma) and older dates for ‘detrital’ 2M1illite (554-502 and 471-427 Ma). Conversely, IAA plots for the superimposed blue fault-gouge reverse the ‘normal’ trend, with older ‘authigenic’ 1 M illite (348-314 and 276-25 Ma) and younger ‘detrital’ 2M1illite (258-234 and 250-226 Ma) ages. We propose this results from heterogeneous shearing and strain localisation. In localised pods of the blue fault-gouge, strain accelerated clay mineral growth, increased crystallite-size, and facilitated polytypic transformation from 1 M to 2M1illite via defect migration. Elsewhere in the blue fault-gouge, and in the red foliated chaotic fault-gouge, low strain regimes allowed the 1 M polytype to remain unaltered.