Cenozoic tectono-thermal history of the southern Talkeetna Mountains, Alaska: Insights into a potentially alternating convergent and transform plate margin
Cenozoic tectono-thermal history of the southern Talkeetna Mountains, Alaska: Insights into a potentially alternating convergent and transform plate margin
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DOI：
10.1130/ges02008.1
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发表时间：
2019-07
期刊：
影响因子：
2.5
通讯作者：
Patrick Terhune;J. Benowitz;J. Trop;P. O’Sullivan;R. Gillis;J. Freymueller
中科院分区：
文献类型：
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作者：
Patrick Terhune;J. Benowitz;J. Trop;P. O’Sullivan;R. Gillis;J. Freymueller
阿拉斯加南部的中新生代会聚边缘历史主要是弧岩浆作用、岩浆增生、走滑断层系统和可能的扩张脊俯冲。我们应用40 Ar/39 Ar，磷灰石裂变径迹（AFT），磷灰石（U-Th）/He（AHe）地质年代学和热年代学的深成岩和火山岩在阿拉斯加南部的塔尔凯特纳山记录区域岩浆作用，岩石冷却，并推断折返模式作为该地区的变形历史的代理，更好地描绘了整个构造历史的阿拉斯加南部。来自侏罗纪花岗岩类的白云母、黑云母和钾长石的高温40Ar/39Ar热年代学表明，158 - 125 Ma）冷却和古新世（约。61 Ma）热重置。塔尔凯特纳山脉南部的40 Ar/39 Ar全岩火山年龄和45个AFT冷却年龄主要为古新世-始新世，表明该山脉具有形成于较早构造环境的古地形成分。中新世AHe冷却年龄在城堡山断层的10公里内，表明垂直位移为12 - 3公里，城堡山断层也有助于塔尔凯特纳山脉的地形发展，可能是对雅库塔特微板块的平板俯冲的响应。阿拉斯加南部边界山脉断层系统以北的古新世-始新世火山和折返相关的冷却年龄是相似的，没有显示出S-N或W-E的进展，这表明一个广泛同步和广泛的火山和折返事件，与阿拉斯加中南部活跃的东西向扩张脊的穿时俯冲相冲突。为了调和这一点，我们提出了一个新的模式，阿拉斯加南部的新生代构造演化。我们推断，近平行于沟板断裂开始于约。60 Ma，并导致折返，岩石冷却同步横跨阿拉斯加中南部，在南部塔尔凯特纳山脉的发展中发挥了主要作用，并可能是一个时期的阿拉斯加南部转换边缘构造。
The Mesozoic–Cenozoic convergent margin history of southern Alaska has been dominated by arc magmatism, terrane accretion, strike-slip fault systems, and possible spreading-ridge subduction. We apply 40Ar/39Ar, apatite fission-track (AFT), and apatite (U-Th)/He (AHe) geochronology and thermochronology to plutonic and volcanic rocks in the southern Talkeetna Mountains of Alaska to document regional magmatism, rock cooling, and inferred exhumation patterns as proxies for the region’s deformation history and to better delineate the overall tectonic history of southern Alaska. High-temperature 40Ar/39Ar thermochronology on muscovite, biotite, and K-feldspar from Jurassic granitoids indicates postemplacement (ca. 158–125 Ma) cooling and Paleocene (ca. 61 Ma) thermal resetting. 40Ar/39Ar whole-rock volcanic ages and 45 AFT cooling ages in the southern Talkeetna Mountains are predominantly Paleocene–Eocene, suggesting that the mountain range has a component of paleotopography that formed during an earlier tectonic setting. Miocene AHe cooling ages within ∼10 km of the Castle Mountain fault suggest ∼2–3 km of vertical displacement and that the Castle Mountain fault also contributed to topographic development in the Talkeetna Mountains, likely in response to the flat-slab subduction of the Yakutat microplate. Paleocene–Eocene volcanic and exhumation-related cooling ages across southern Alaska north of the Border Ranges fault system are similar and show no S-N or W-E progressions, suggesting a broadly synchronous and widespread volcanic and exhumation event that conflicts with the proposed diachronous subduction of an active west-east–sweeping spreading ridge beneath south-central Alaska. To reconcile this, we propose a new model for the Cenozoic tectonic evolution of southern Alaska. We infer that subparallel to the trench slab breakoff initiated at ca. 60 Ma and led to exhumation, and rock cooling synchronously across south-central Alaska, played a primary role in the development of the southern Talkeetna Mountains, and was potentially followed by a period of southern Alaska transform margin tectonics.