The Santa Catalina‐Tortolita‐Rincon Mountains of Southeast Arizona are a classic metamorphic core complex (MCC) and represent footwall exposures of crustal rocks exhumed by a detachment system. This study presents new evidence for the formation of the majority of ductile deformation during the Eocene (~46 Ma), synchronous with the emplacement of the regionally significant Wilderness Sills Suite (57–45 Ma). The evidence is provided by Eocene U‐Pb ages of syn‐ to late kinematic dikes emplaced in the principal ductile mylonitic fabric of the Catalina forerange, earlier than the brittle normal fault system and the formation of Tucson basin beginning with the latest Oligocene. Well‐documented shear sense indicators may not reflect extension at that time (Eocene), but more likely the direction of crustal flow now rotated during later extension. Muscovite‐plagioclase Rb‐Sr isochron ages of three mylonitic rocks are all clustered around 34 Ma, which is inferred to be the last age when these rocks were being deformed under ductile conditions following the emplacement of the Wilderness Sills Suite and various related dikes. Biotite‐plagioclase Rb‐Sr ages on the same rocks demonstrate that the section cooled below ~300°C at 25–26 Ma during the development of normal faulting. Normal faulting was synchronous with the emplacement of the Catalina Intrusive Suite. New U‐Pb age results for Catalina Intrusive Suite indicate a combined mean age of 24.9 Ma. Chemical compositions of hornblende‐plagioclase pairs were obtained on six Catalina Intrusive Suite samples; depth estimates for the emplacement of the Catalina Intrusive Suite average of about 6 km. These results suggest that the exposed Catalina ductile detachment system was at about 5 km beneath the surface at 25 Ma. These new data bring new light into the development of this core complex and suggest that the similarity in orientations of principal ductile and brittle fabrics at the Catalina MCC locality are coincidental. Neither was the principal ductile fabric developed during the low‐angle normal faulting of the latest Oligocene nor was this exposed section a midcrustal one at that time. Transient, pluton emplacement‐enhanced, and extension‐related ductile deformation at shallow crustal levels operated locally at ~25 Ma but that does not account for the development of the majority of the Catalina MCC mylonites.

中文翻译：

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亚利桑那州东南部 Catalina Metamorphic Core 综合体的新时间和深度限制

亚利桑那州东南部的 Santa Catalina-Tortolita-Rincon 山脉是典型的变质岩核复合体 (MCC)，代表了拆离系统挖掘出的地壳岩石的下盘暴露。这项研究为始新世 (~46 Ma) 期间大部分韧性变形的形成提供了新证据，与具有区域意义的 Wilderness Sills Suite (57-45 Ma) 的就位同步。证据是由位于 Catalina 前序带的主要延展性糜棱岩结构中的同至晚期运动脉岩的始新世 U-Pb 年龄提供的，早于脆性正断层系统和从最新渐新世开始的图森盆地的形成。有据可查的剪切感指标可能无法反映当时的扩张（始新世），但更有可能是在后期扩张期间地壳流动方向发生了旋转。三种糜棱岩的白云母-斜长石 Rb-Sr 等时线年龄都聚集在 34 Ma 附近，推测这是这些岩石在 Wilderness Sills Suite 和各种相关岩脉就位后在韧性条件下变形的最后一个时代。同一岩石上的黑云母-斜长石 Rb-Sr 年龄表明，在正断层的发展过程中，该剖面在 25-26 Ma 时冷却到~300°C 以下。正常断层与 Catalina Intrusive Suite 的部署同步。Catalina Intrusive Suite 的新 U-Pb 年龄结果表明综合平均年龄为 24.9 Ma。在六个 Catalina Intrusive Suite 样品上获得了角闪石-斜长石对的化学成分；Catalina Intrusive Suite 的平均深度估计约为 6 公里。这些结果表明，暴露的 Catalina 韧性脱离系统在 25 Ma 时位于地表下约 5 公里处。这些新数据为这个核心复合体的发展带来了新的线索，并表明 Catalina MCC 地区的主要韧性和脆性织物方向的相似性是巧合的。在最近渐新世的低角度正断层期间发育的主要韧性织物既不是当时的中地壳，也不是中地壳。浅层地壳的瞬态、岩体侵位增强和与伸展相关的延性变形在~25 Ma 局部运行，但这并不能解释大多数 Catalina MCC 糜棱岩的发育。这些新数据为这个核心复合体的发展带来了新的线索，并表明 Catalina MCC 地区的主要韧性和脆性织物方向的相似性是巧合的。在最近渐新世的低角度正断层期间发育的主要韧性织物既不是当时的中地壳，也不是中地壳。浅层地壳的瞬态、岩体侵位增强和与伸展相关的延性变形在~25 Ma 局部运行，但这并不能解释大多数 Catalina MCC 糜棱岩的发育。这些新数据为这个核心复合体的发展带来了新的线索，并表明 Catalina MCC 地区的主要韧性和脆性织物方向的相似性是巧合的。在最近渐新世的低角度正断层期间发育的主要韧性织物既不是当时的中地壳，也不是中地壳。浅层地壳的瞬态、岩体侵位增强和与伸展相关的延性变形在~25 Ma 局部运行，但这并不能解释大多数 Catalina MCC 糜棱岩的发育。在最近渐新世的低角度正断层期间发育的主要韧性织物既不是当时的中地壳，也不是中地壳。浅层地壳的瞬态、岩体侵位增强和与伸展相关的延性变形在~25 Ma 局部运行，但这并不能解释大多数 Catalina MCC 糜棱岩的发育。在最近渐新世的低角度正断层期间发育的主要韧性织物既不是当时的中地壳，也不是中地壳。浅层地壳的瞬态、岩体侵位增强和与伸展相关的延性变形在~25 Ma 局部运行，但这并不能解释大多数 Catalina MCC 糜棱岩的发育。