Prolonged metamorphism during long-lived terrane accretion: Sm-Nd garnet and U-Pb zircon geochronology and pressure-temperature paths from the Salmon River suture zone, west-central Idaho, USA
Prolonged metamorphism during long-lived terrane accretion: Sm-Nd garnet and U-Pb zircon geochronology and pressure-temperature paths from the Salmon River suture zone, west-central Idaho, USA
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长寿地体增生过程中的长期变质作用：美国爱达荷州中西部鲑鱼河缝合带的 Sm-Nd 石榴石和 U-Pb 锆石地质年代学和压力-温度路径
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发表时间：
2017
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通讯作者：
J. Schwartz
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作者：
M. McKay;E. Bollen;K. Gray;H. Stowell;J. Schwartz
美国爱达荷州西部的萨蒙河缝合带记录了中生代火山弧岩增生到劳伦西亚西部期间与造山作用有关的中地壳变质和变形。我们目前的岩相学和显微结构观察，石榴石地球化学，压力-温度等化学相图，和Sm-Nd石榴石和U-Pb锆石年龄调查的时间和条件的变质鲑鱼河缝合带。Salmon River缝合带由三个逆冲岩片组成：从东到西，角闪岩相的Pollock Mountain板块、上绿片岩-角闪岩相的Rapid River板块和绿片岩相的Heavens Gate板块。波洛克山板块在141 ~ 124 Ma的西北-东南向地壳缩短过程中，在~700 °C温度下承受了6 ~>8 kbar的等温载荷。下面的Rapid River板在约600-650 °C下从7至约10 kbar等温加载。124-112 Ma变质作用，与峰后晚期变质作用和约124 - 112 Ma变质作用同时发生。118 Ma上覆波洛克山板块的折返。在快速河板块，逆冲岩席侵位引起高应变韧性变形，并导致线性-平面组构的区域发展。同变形-后变形岩浆活动的206 Pb/238 U锆石年龄记录约为1.25 μ m。117 Ma或更年轻的两个板块并置在东南倾斜的波洛克山逆冲断层上。同生124-112 Ma快速河板块的变质作用，约。118 Ma的波洛克山板块的折返，以及约。117 Ma或更年轻的运动沿着波洛克山断层表明，快速河板块的变质作用可能部分是由逆冲并列和加载沿着波洛克山断层。在这种情况下，我们解释说，变质记录穿时逆冲推覆在长期（>30万年）。爱达荷州西部的增生造山作用。LITHOSPHERE; v. 9; no. 5; p. 683-701; GSA数据储存库项目2017234|在线发布于2017年6月30日doi：10.1130/L642.1
The Salmon River suture zone of western Idaho (USA) records mid-crustal metamorphism and deformation associated with orogenesis during Mesozoic accretion of volcanic arc terranes to western Laurentia. We present petrographic and microstructural observations, garnet geochemistry, pressure-temperature isochemical phase diagrams, and Sm-Nd garnet and U-Pb zircon ages to investigate the timing and conditions of metamorphism in the Salmon River suture zone. The Salmon River suture zone is comprised of three thrust sheets: from east to west, the amphibolite facies Pollock Mountain plate, upper greenschist to amphibolite facies Rapid River plate, and greenschist facies Heavens Gate plate. The Pollock Mountain plate was isothermally loaded from 6 to >8 kbar at ~700 °C between 141 and 124 Ma during northwest-southeast crustal shortening. The underlying Rapid River plate was isothermally loaded from 7 to ~10 kbar at 600–650 °C during ca. 124–112 Ma metamorphism, which is contemporaneous with lateto post-peak metamorphism and ca. 118 Ma exhumation of the overlying Pollock Mountain plate. In the Rapid River plate, thrust sheet emplacement induced high-strain ductile deformation and led to regional development of linear-planar fabrics. The 206Pb/238U zircon ages for syndeformational to postdeformational magmatism record ca. 117 Ma or younger juxtaposition of the two plates on the southeast-dipping Pollock Mountain thrust fault. Coeval 124–112 Ma metamorphism of the Rapid River plate, ca. 118 Ma exhumation of the Pollock Mountain plate, and ca. 117 Ma or younger movement along the Pollock Mountain fault suggest that metamorphism of the Rapid River plate was possibly driven in part by thrust juxtaposition and loading along the Pollock Mountain fault. In this context, we interpret that metamorphism records diachronous thrust stacking during prolonged (>30 m.y.) accretionary orogenesis in western Idaho. LITHOSPHERE; v. 9; no. 5; p. 683–701; GSA Data Repository Item 2017234 | Published online 30 June 2017 doi:10.1130/L642.1