The Klamath Mountains in northern California and southern Oregon are thought to record 200+ m.y. of subduction and terrane accretion, whereas the outboard Franciscan Complex records ocean-continent subduction along the North American margin. Unraveling the Klamath Mountains' Late Jurassic history could help constrain this transition in subduction style. Key is the Mesozoic Condrey Mountain Schist (CMS), comprising, in part, a subduction complex that occupies a structural window through older, overlying central Klamath thrust sheets but with otherwise uncertain relationships to more outboard Klamath or Franciscan terranes. The CMS consists of two units (upper and lower), which could be correlated with (a) other Klamath terranes, (b) the Franciscan, or (c) neither based on regional structures and limited extant age data. Upper CMS protolith and metamorphic dates overlap with other Klamath terranes, but the lower CMS remains enigmatic. We used multiple geochronometers to constrain the timing of lower CMS deposition and metamorphism. Maximum depositional ages (MDAs) derived from detrital zircon geochronology of metasedimentary rocks are 153–135 Ma. Metamorphic ages from white mica K-Ar and Rb-Sr multi-mineral isochrons from intercalated and coherently deformed metamafic lenses are 133–116 Ma. Lower CMS MDAs (<153 Ma) predominantly postdate other Klamath terrane ages, but subduction metamorphism appears to start before the earliest coherent Franciscan underplating (ca. 123 Ma). The lower CMS thus occupies a spatial and temporal position between the Klamath Mountains and Franciscan and preserves a non-retrogressed record of the Franciscan Complex's early history (>123 Ma), otherwise only partially preserved in retrogressed Franciscan high grade blocks.

中文翻译：

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康德雷山片岩的构造演化：晚侏罗世至早白垩世方济会俯冲和底侵的完整记录

加利福尼亚州北部和俄勒冈州南部的克拉马斯山脉被认为记录了 200 多米的俯冲和地体增生，而舷外的方济会综合体则记录了沿北美边缘的海洋-大陆俯冲。解开克拉马斯山脉晚侏罗世的历史可能有助于限制俯冲类型的转变。关键是中生代康德雷山片岩（CMS），部分由俯冲复合体组成，该俯冲复合体占据了穿过更古老的、上覆中央克拉马斯冲断层的结构窗口，但与更外侧的克拉马斯或方济会地体的关系不确定。CMS 由两个单元（上单元和下单元）组成，根据区域结构和有限的现存年龄数据，它们可能与 (a) 其他克拉马斯地体、(b) 方济会地体、或 (c) 均不相关。上部 CMS 原岩和变质日期与其他克拉马斯地体重叠，但下部 CMS 仍然是个谜。我们使用多个地质计时仪来限制较低的 CMS 沉积和变质作用的时间。根据变沉积岩碎屑锆石年代学得出的最大沉积年龄 (MDA) 为 153–135 Ma。来自插层和相干变形变质铁透镜体的白云母 K-Ar 和 Rb-Sr 多矿物等时线的变质年龄为 133-116 Ma。较低的 CMS MDA（<153 Ma）主要晚于其他克拉马斯地体年龄，但俯冲变质作用似乎开始于最早的相干方济各底侵（约 123 Ma）之前。因此，较低的 CMS 占据了克拉马斯山脉和方济各会之间的空间和时间位置，并保留了方济会复合体早期历史（> 123 Ma）的非退行记录，否则仅部分保存在退行的方济会高品位地块中。