Granite rock towers shaped by mesh‐like joint sets, which formed in the shallower portion of a granite body during cooling at depth
Granite rock towers shaped by mesh‐like joint sets, which formed in the shallower portion of a granite body during cooling at depth
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由网状节理组形成的花岗岩岩塔，这些节理组在深度冷却过程中在花岗岩体的较浅部分形成
DOI：
10.1111/iar.12484
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发表时间：
2023
期刊：
影响因子：
1.5
通讯作者：
Kato Hironori
中科院分区：
文献类型：
--
作者：
Chigira Masahiro;Kato Hironori
花岗岩在冷却阶段的应力状态下发生断裂，为后期的地形演化提供了条件。这项研究阐明了在花岗岩冷却过程中可以形成三角形网状节理，它们可以成为地面上形成岩石塔和岩心的结构原因。使用无人驾驶飞行器对广岛的天狗岩进行了调查，天狗岩由石塔和花岗岩芯岩组成。岩石塔由高角度网状接缝形成，这些接缝可能是在花岗岩冷却期间形成的，并由三个接缝组主导。所有节理组都具有尖锐的平面，表明它们是脆性断裂。一个节理组被其他两个节理组切割，经常伴随细晶岩和石英脉，并在整个暴露的花岗岩中发育;这一组可能首先在冷却过程中形成，然后被细晶岩从深处穿透。另外两个节理组是高角度共轭节理组，仅限于花岗岩岩体的较浅部分，并没有延伸到更深处，这强烈表明它们形成于岩体的快速冷却的较浅部分，可能靠近其顶部。这三个节理组形成了具有不同横截面的岩柱，其中形成了初期的岩芯。地下风化沿着节理和随后的风化产物的折返形成了现在的岩石塔和岩芯，仅在花岗岩的较浅部分。
Granite is fractured according to the stress state during the cooling stage, providing predispositions for later topographic evolution. This study clarified that triangular mesh‐like joints can be made during granite cooling and that they can become the structural causes for the formation of rock towers and corestones on the ground. Tengu rock, which consists of rock towers and granite corestones in Hiroshima, was investigated using an unmanned air vehicle. The rock towers were shaped by high‐angle mesh‐like joints, which were likely made during the cooling of the granite and are dominated by three joint sets. All the joint sets have sharp planar surfaces, which suggests that they are brittle fractures. One joint set is cut by the other two joint sets, frequently accompanies aplite and quartz veins and is developed in the whole exposed granite; this set likely formed first during cooling and then was penetrated by aplite from depth. The other two joint sets are high‐angle conjugate joint sets, are limited to the shallower portion of the granite pluton and do not extend deeper, which strongly suggests that they formed in a rapidly cooled shallower portion of the pluton, probably near its roof. These three joint sets form rock columns with parallelogram cross‐sections, in which incipient corestones were made. Subsurface weathering along the joints and subsequent exhumation of the weathering products formed the present rock towers and corestones only in the shallower portion of the granite.