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首页> 外文期刊>Journal of geophysical research. Solid earth: JGR >The ~(40)Ar/~(39)Ar thermochronology of core complexes and other basement rocks in Sonora, Mexico: Implications for Cenozoic tectonic evolution of northwestern Mexico
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The ~(40)Ar/~(39)Ar thermochronology of core complexes and other basement rocks in Sonora, Mexico: Implications for Cenozoic tectonic evolution of northwestern Mexico

机译：墨西哥索诺拉的〜（40）Ar /〜（39）Ar热年代学：对墨西哥西北部新生代构造演化的启示

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摘要

Northwestern Mexico remains an important region for understanding the tectonic evolution of the North American Cordillera. Ilowever, many fundamental aspects of the geologic history of the region remain poorly known. We present new ~(40)Ar/~(30)Ar thermochronology of exposed basement rock from throughout Sonora, Mexico, including from metamorphic core complexes. These results provide new constraints on the Late Cretaceous to Cenozoic tectonic evolution of northwestern Mexico. Following Laramide (ca. 80-50 Ma) emplacement, most Sonoran plutons experienced rapid post-magmatic cooling to ～400- 200℃, which we attribute to shallow level emplacement. Following this rapid cooling, plutons cooled slowly (<10℃/m.y.) from the Paleocene to the Oligocene, suggesting that the early Tertiary was a period of tectonic quiescence within Sonora during which exhumation was minor. Core complexes are the only exposed Sonoran basement that remained > 300℃ until the late Oligocene. Rapid footwall cooling documents that extension at Sonoran core complexes began synchronously at ca. 25 Ma, despite the fact that these regions are separated by > 200 km. Extension at most Sonoran core complexes continued until ca. 15 Ma, although extension at the Magdalena core complex ceased earlier (ca. 21-20 Ma). Slip at each core complex was 10-30 km and occurred at average rates of 1-9 mm/yr. This major period of extension primarily occurred during subduction, indicating that relative plate motions between the Pacific and North American plates cannot be invoked as a driving force for this phase of extension.
机译：墨西哥西北地区仍然是了解北美山脉构造演化的重要地区。但是，该地区地质历史的许多基本方面仍然鲜为人知。我们提出了墨西哥整个索诺拉地区（包括变质岩心复合体）裸露的地下岩石的新〜（40）Ar /〜（30）Ar热年代学。这些结果为墨西哥西北部晚白垩世至新生代构造演化提供了新的约束。在拉拉米（约80-50 Ma）的位置之后，大多数Sonoran岩体经历了后岩浆快速冷却至〜400-200℃，这归因于浅水平的位置。在这种快速冷却之后，小行星从古新世到渐新世缓慢地冷却（<10℃/ m.y。），这表明第三纪早期是索诺拉（Sonora）的一个构造静止期，在此期间发掘很少。核心络合物是唯一的暴露的Sonoran地下室，直到渐新世晚期才保持> 300℃。快速的底盘冷却文件表明，Sonoran核心复合体的扩建始于大约30℃。 25 Ma，尽管这些区域相距> 200 km。大多数Sonoran核心复合体的扩展一直持续到大约10年。尽管玛格达莱纳核心地带的扩建工作较早就停止了（约21-20 Ma），但时间为15 Ma。每个核心复合体的滑移量为10-30 km，平均滑移速率为1-9 mm /年。这个主要的扩展期主要发生在俯冲期间，这表明太平洋板块和北美板块之间的相对板块运动不能作为该扩展阶段的驱动力。

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