Late Proterozoic–Paleozoic evolution of the Arctic Alaska–Chukotka terrane based on U-Pb igneous and detrital zircon ages: Implications for Neoproterozoic paleogeographic reconstructions
Late Proterozoic–Paleozoic evolution of the Arctic Alaska–Chukotka terrane based on U-Pb igneous and detrital zircon ages: Implications for Neoproterozoic paleogeographic reconstructions
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DOI：
10.1130/b26510.1
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发表时间：
2009-09
影响因子：
4.9
通讯作者：
J. Amato;J. Toro;E. Miller;G. Gehrels;G. L. Farmer;E. S. Gottlieb;A. B. Till
中科院分区：
文献类型：
--
作者：
J. Amato;J. Toro;E. Miller;G. Gehrels;G. L. Farmer;E. S. Gottlieb;A. B. Till
阿拉斯加西北部的苏厄德半岛是北极阿拉斯加-楚科奇海的一部分，这是一个来自劳伦西亚西部的地壳碎片，其起源和前中生代的演化不确定。变形火成岩的U-Pb锆石年代学揭示了一个以前未知的中长英质火山事件在870马，与裂谷有关的岩浆活动与早期解体的Rodinia东部同时代。苏厄德半岛的片麻岩体获得了大量680 Ma的U-Pb年龄。根据870 Ma和680 Ma火成岩的中元古界Nd模式年龄，以及上覆盖层岩石中2.0和1.0 Ga之间的碎屑锆石年龄，北极阿拉斯加-楚科奇海具有前新元古代基底。花岗质岩石U-Pb测年结果表明，泥盆纪岩浆活动量较小。12个变质古生代硅质岩盖层样品的碎屑锆石U-Pb定年结果表明，在934个锆石中，锆石年龄主要集中在700-540 Ma，峰值分别为720-660 Ma、620-590 Ma、560-510 Ma、485 Ma和440-400 Ma。泥盆纪和宾夕法尼亚州的年龄高峰是目前在最年轻的碎屑锆石的样品。这些数据表明，苏厄德半岛是外来的西劳伦，因为丰富的新元古代碎屑锆石，这是罕见的或缺乏下古生代科迪勒支大陆架岩石。根据最年轻的碎屑岩年龄峰推断的最大沉积年龄包括最晚元古代-早寒武世、寒武纪、奥陶纪、志留纪、泥盆纪和宾夕法尼亚纪。这些最大沉积年龄与苏厄德半岛含碳酸盐岩的牙形石年龄重叠。北极阿拉斯加-楚科奇海的显著特征包括新元古代长英质岩浆岩侵入2.0-1.1 Ga地壳，其上覆有古生代碳酸盐岩和古生代硅质岩，其中含有新元古代碎屑锆石。新元古代的年龄与冈瓦纳周边的阿瓦隆-卡多米亚弧系、波罗的海的Timanide造山带以及早白垩世美亚盆地开放之前邻近北极阿拉斯加的其他环北极地区的年龄相似。我们的新元古代重建将北极阿拉斯加-楚科奇海置于波罗的海附近的位置，劳伦特东北部，与阿瓦隆-卡多米亚弧岩沿着走向的弧系中。以前发表的动物群数据表明，苏厄德半岛的西伯利亚和劳伦的联系早奥陶纪的时间。从古元古代到古生代，北极阿拉斯加-楚科奇海与东劳伦西亚、波罗的海、冈瓦纳弧缘和西伯利亚之间的地质联系有助于约束从新元古代Rodinia历史到中生代北极盆地开口的古地理模型。
The Seward Peninsula of northwestern Alaska is part of the Arctic Alaska–Chukotka terrane, a crustal fragment exotic to western Laurentia with an uncertain origin and pre-Mesozoic evolution. U-Pb zircon geochronology on deformed igneous rocks reveals a previously unknown intermediate-felsic volcanic event at 870 Ma, coeval with rift-related magmatism associated with early breakup of eastern Rodinia. Orthogneiss bodies on Seward Peninsula yielded numerous 680 Ma U-Pb ages. The Arctic Alaska–Chukotka terrane has pre-Neoproterozoic basement based on Mesoproterozoic Nd model ages from both 870 Ma and 680 Ma igneous rocks, and detrital zircon ages between 2.0 and 1.0 Ga in overlying cover rocks. Small-volume magmatism occurred in Devonian time, based on U-Pb dating of granitic rocks. U-Pb dating of detrital zircons in 12 samples of metamorphosed Paleozoic siliciclastic cover rocks to this basement indicates that the dominant zircon age populations in the 934 zircons analyzed are found in the range 700–540 Ma, with prominent peaks at 720–660 Ma, 620–590 Ma, 560–510 Ma, 485 Ma, and 440–400 Ma. Devonian- and Pennsylvanian-age peaks are present in the samples with the youngest detrital zircons. These data show that the Seward Peninsula is exotic to western Laurentia because of the abundance of Neoproterozoic detrital zircons, which are rare or absent in Lower Paleozoic Cordilleran continental shelf rocks. Maximum depositional ages inferred from the youngest detrital age peaks include latest Proterozoic–Early Cambrian, Cambrian, Ordovician, Silurian, Devonian, and Pennsylvanian. These maximum depositional ages overlap with conodont ages reported from fossiliferous carbonate rocks on Seward Peninsula. The distinctive features of the Arctic Alaska–Chukotka terrane include Neoproterozoic felsic magmatic rocks intruding 2.0–1.1 Ga crust overlain by Paleozoic carbonate rocks and Paleozoic siliciclastic rocks with Neoproterozoic detrital zircons. The Neoproterozoic ages are similar to those in the peri-Gondwanan Avalonian-Cadomian arc system, the Timanide orogen of Baltica, and other circum-Arctic terranes that were proximal to Arctic Alaska prior to the opening of the Amerasian basin in the Early Cretaceous. Our Neoproterozoic reconstruction places the Arctic Alaska–Chukotka terrane in a position near Baltica, northeast of Laurentia, in an arc system along strike with the Avalonian-Cadomian arc terranes. Previously published faunal data indicate that Seward Peninsula had Siberian and Laurentian links by Early Ordovician time. The geologic links between the Arctic Alaska–Chukotka terrane and eastern Laurentia, Baltica, peri-Gondwanan arc terranes, and Siberia from the Paleoproterozoic to the Paleozoic help to constrain paleogeographic models from the Neoproterozoic history of Rodinia to the Mesozoic opening of the Arctic basin.