Large-scale, short-lived metamorphism, deformation, and magmatism in the Chugach metamorphic complex, southern Alaska: A SHRIMP U-Pb study of zircons
Large-scale, short-lived metamorphism, deformation, and magmatism in the Chugach metamorphic complex, southern Alaska: A SHRIMP U-Pb study of zircons
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阿拉斯加南部楚加奇变质杂岩中大规模、短暂的变质作用、变形和岩浆作用：SHRIMP U-Pb 锆石研究
DOI：
10.1130/b30507.1
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发表时间：
2012
影响因子：
4.9
通讯作者：
K. Stüwe
中科院分区：
文献类型：
--
作者：
D. Gasser;D. Rubatto;E. Bruand;K. Stüwe
我们提出了灵敏的高分辨率离子微探针 (SHRIMP) U-Pb 地质年代学和来自阿拉斯加南部楚加奇变质杂岩的锆石的微量元素化学，这使我们能够精确地限制峰值变质作用的年龄和持续时间。从混合岩变沉积片麻岩中分离出来的锆石显示出薄（5-30 μm）的过度生长，其中含有微量元素成分，表明生长处于或接近变质峰。此类增生体的 5 个 U-Pb 年龄和来自杂岩体西部和中部侵入变沉积岩的岩浆锆石的 2 个 U-Pb 年龄范围在 54.0 ± 0.9 Ma 和 52.6 ± 1.0 Ma 之间，并且彼此在误差范围内。来自该杂岩体东南部的一个样本得出的锆石过度生长年龄为 51.3 ± 0.7 Ma，与来自西部和中部的七个样本中的两个样本的误差范围内。结合之前的萨纳克-巴拉诺夫带岩浆岩的 U-Pb 锆石年龄，我们的数据将变质作用和岩浆作用的年龄和持续时间限制在最大~3 m.y的时间跨度内。大约之间杂岩体西部和中部约 200 公里长的路段上的温度分别为 55 和 52 Ma。时间跨度约 2 m.y.大约之间52 和 50 Ma 被限制在从该综合体的东南部到巴拉诺夫岛的范围内。杂岩体发育的沉积物的最大沉积年龄（约 60 Ma）将进行变质作用的时间限制在 ∼5 m.y 的狭窄时间窗口内。这种短暂的前变质作用，以及随后沿边缘约 800 公里的近同步峰值变质作用和岩浆作用可能是山脊俯冲的结果，并讨论了该地区演化的构造模型。
We present sensitive high-resolution ion microprobe (SHRIMP) U-Pb geochronology and trace-element chemistry of zircons from the Chugach metamorphic complex, southern Alaska, which allow us to precisely constrain the age and duration of peak metamorphism. Zircons separated from migmatitic metasedimentary gneisses show thin (5–30 μm) overgrowths with trace-element compositions indicating growth at or close to the metamorphic peak. Five U-Pb ages of such overgrowths and two U-Pb ages from magmatic zircons from plutons intruding the metasediments from the western and central parts of the complex range between 54.0 ± 0.9 Ma and 52.6 ± 1.0 Ma and are within error of each other. One sample from the southeastern part of the complex yields a zircon overgrowth age of 51.3 ± 0.7 Ma, which is within error of two of the seven samples from the western and central parts. Combined with previous U-Pb zircon ages of magmatic rocks of the Sanak-Baranof belt, our data constrain the age and duration of metamorphism and magmatism to a time span of maximum ∼3 m.y. between ca. 55 and 52 Ma on an ∼200-km-long section in the western and central part of the complex. A time span of ∼2 m.y. between ca. 52 and 50 Ma is constrained from the southeastern part of the complex to Baranof Island. Maximum depositional ages of the sediments in which the complex developed (ca. 60 Ma) limit the time available for prograde metamorphism to a narrow time window of ∼5 m.y. This short time span for prograde metamorphism, followed by near-synchronous peak metamorphism and magmatism for ∼800 km along the margin could be the result of ridge subduction, and tectonic models for the evolution of this region are discussed.
影响因子：
5
作者：
N. Tailby;A. Walker;A. Berry;J. Hermann;K. Evans;J. Mavrogenes;H. O’Neill;I. S. Rodina;A. Soldatov;D. Rubatto;S. Sutton
通讯作者：
N. Tailby;A. Walker;A. Berry;J. Hermann;K. Evans;J. Mavrogenes;H. O’Neill;I. S. Rodina;A. Soldatov;D. Rubatto;S. Sutton