Field, hand specimen, and microscopic investigations alongside X-ray diffraction analyses revealed four types of hydrothermal alteration (Type-A, -B, -C, and -D) based on the mode of occurrence of altered rocks and alteration mineral assemblage at Hakusui-kyo and Horai-kyo along the Arima-Takatsuki Tectonic Line (ATTL) in western Japan. Type-A alteration locally occurred as gray alteration halos with sulfide minerals. Type-B and -C alterations were confined to fault gouge veins and occurred as greenish-gray veins and brown veins, respectively. Type-C alteration crosscut Type-B alteration. These alterations were associated with a number of granitic fragments including cohesive breccia and micrographic facies. Type-D alteration occurred locally in brown sediments. Different mineralogical features in the four alterations are summarized as (Type-A) illite; (Type-B) chlorite; (Type-C) limonite (Fe³⁺ hydroxides and goethite) and calcite; and (Type-D) limonite. We propose that the alterations can be broadly divided into Paleocene hydrothermal alteration (Type-A) and post-Late Miocene hydrothermal alteration (Type-B, -C, and -D): Type-A alteration occurred at approximately 200 °C during hydrothermal activity after a granitic intrusion in Late Cretaceous; Type-B, -C and -D alterations occurred under hydrothermal activity accompanying deep fluids with repeated ascents invoked by the seismicity of the ATTL after the Late Miocene. The fluids may have been the “Arima-type thermal waters” (i.e., mixtures of convective groundwater and Na-Ca-Cl-HCO₃-type fluids). Type-B alteration occurred in fractures at depths where the temperature was ≥150 °C. Type-C alteration overprinted Type-B alteration as a result of mixing of new deep fluids and descending oxidized meteoric water near the surface. Fe³⁺ hydroxides and calcite precipitated from the fluids due to the oxidation of Fe²⁺ and the degassing of CO₂, respectively, at ambient to near-boiling temperatures. When the ascending fluids gushed out from the fractures, they generated Type-D alteration at the surface under similar temperature conditions due to the oxidation of Fe²⁺.

中文翻译：

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日本西部有马-高月构造线白水峡和宝来峡六甲花岗岩热液蚀变的岩石学和矿物学研究

根据白水蚀变岩和蚀变矿物组合的发生模式，野外、手部标本和显微镜研究以及 X 射线衍射分析揭示了四种类型的热液蚀变（类型-A、-B、-C 和-D）沿日本西部有马-高月构造线 (ATTL) 的 -kyo 和 Horai-kyo。A 型蚀变局部发生为带有硫化物矿物的灰色蚀变晕。B 型和 C 型蚀变仅限于断层泥脉，分别以绿灰色脉和棕色脉出现。C 型改造横切面 B 型改造。这些改变与许多花岗岩碎片有关，包括粘性角砾岩和显微相。D 型蚀变发生在棕色沉积物中。四个蚀变的不同矿物学特征概括为（A型）伊利石；(B型)亚氯酸盐；(Type-C) 褐铁矿 (Fe³⁺氢氧化物和针铁矿）和方解石；和（D 型）褐铁矿。我们认为这些蚀变可以大致分为古新世热液蚀变（A 型）和中新世晚期热液蚀变（B、-C 和 -D 型）：A 型蚀变发生在大约 200 °C 的热液过程中晚白垩世花岗岩侵入后的活动；B、-C 和-D 型蚀变发生在热液活动下，伴随着深部流体，在晚中新世之后 ATTL 的地震活动引起了重复上升。流体可能是“Arima 型热水”（即对流地下水和 Na-Ca-Cl-HCO _{3 的}混合物型流体）。B型蚀变发生在温度≥150°C的深度裂缝中。由于新的深层流体和下降的氧化大气水在地表附近混合，C 型蚀变覆盖了 B 型蚀变。由于 Fe ²⁺的氧化和 CO ₂的脱气，Fe ³⁺氢氧化物和方解石分别在环境温度至接近沸点的温度下从流体中沉淀出来。当上升流体从裂缝中喷出时，由于Fe ²⁺的氧化，在相似温度条件下在地表产生了D型蚀变。