Structural and rheological evolution of the Laramide subduction channel in southern California
Structural and rheological evolution of the Laramide subduction channel in southern California
复制标题
南加州拉拉米德俯冲通道的结构和流变演化
DOI：
10.5194/se-8-379-2017
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发表时间：
2016
期刊：
影响因子：
3.4
通讯作者：
J. Platt
中科院分区：
文献类型：
--
作者：
Haoran Xia;J. Platt
抽象的。位于加州南部圣盖博山脉的Pelona片岩形成于Laramide俯冲通道，具有多期变形/变质作用，为研究俯冲通道的流变学性质提供了有价值的信息。岩石学和显微构造分析表明，Pelona片岩经历了三次主要的变形/变质事件。俯冲的火山和沉积原岩在D1记录对齐的矿物包裹体在钠长石和绿帘石变斑晶。由碳质物质的拉曼光谱和多硅白云母气压计得出的俯冲结束时的变质温度和压力分别为519 ± 20 °C和10.5 ± 0.4 kbar。D1期主要变形机制为石英压溶，D1期末剪切应力小于10 MPa。D2，第一阶段折返的Pelona片岩沿着上部分的俯冲通道在回流期间，记录的退变质，等倾褶皱，和一个普遍的包裹在较早的斑晶。D2期变粗砂岩主要以石英压溶变形为主，变黑岩主要以位错蠕变变形为主。变粗砂岩中的剪切应力小于10 MPa，而变黑岩中的剪切应力介于8.3 + 2.7/− 1.5和12.9 + .9/− 2.3 MPa之间，导致应变速率为1.4 × 10−13至5.5 × 10−13 s−1。地形驱动模式被认为是D2折返的主要驱动力。D3记录了文森特断层上的正常运动，该断层将片岩与上覆弧和大陆基底分开。这导致了第二阶段的折返，在Pelona片岩的上部形成了一个主要的向斜和相关的糜棱岩组构。D3开始时的条件为390 ± 13 °C和5.8 ± 0.8千巴，由TitaniQ温度计和多硅白云母地质压力计给出。变形以石英位错蠕变为主，应变速率为4.5 ± 1.2 × 10−13 s−1，剪切应力为20.1 + 7.3/− 4.0 MPa。
Abstract. The Pelona Schist in the San Gabriel Mountains, southern California, formed in the Laramide subduction channel, exhibits multiple phases of deformation/metamorphism and provides valuable insights into the rheological properties of the subduction channel. Petrological and microstructural analysis indicates that the Pelona Schist has undergone three major deformational/metamorphic events. Subduction of volcanic and sedimentary protoliths during D1 was recorded by aligned mineral inclusions in albite and epidote porphyroblasts. Metamorphic temperature and pressure at the end of subduction yielded by Raman spectroscopy of carbonaceous material and phengite barometry were 519 ± 20 °C and 10.5 ± 0.4 kbar, respectively. During D1 the dominant deformation mechanism was quartz pressure solution, and the estimated shear stress at the end of D1 was less than 10 MPa. D2, the first stage exhumation of the Pelona Schist along the upper section of the subduction channel during return flow, was recorded by retrogressive metamorphism, isoclinal folding, and a pervasive schistosity that wraps around earlier porphyroblasts. Metagreywacke was deformed mainly by quartz pressure solution and metachert was deformed dominantly by dislocation creep during D2. The shear stress in metagreywacke was less than 10 MPa and that in metachert was between 8.3 + 2.7/− 1.5 and 12.9 + .9/− 2.3 MPa, resulting in a strain rate of 1.4 × 10−13 to 5.5 × 10−13 s−1. A topography driven model is proposed as the main driving force of D2 exhumation. D3 records normal-sense movement on the Vincent Fault, which separates the schist from overlying arc and continental basement. This resulted in the second stage of exhumation, creating a major synform and associated mylonitic fabric in the upper section of the Pelona Schist. Conditions at the beginning of D3 were 390 ± 13 °C and 5.8 ± 0.8 kbar given by the TitaniQ thermometer and phengite geobarometer. The deformation was dominated by quartz dislocation creep with a strain rate of 4.5 ± 1.2 × 10−13 s−1 at a shear stress of 20.1 + 7.3/− 4.0 MPa.
影响因子：
5.3
作者：
Beaumont, C.;Jamieson, R. A.;Warren, C. J.
通讯作者：
Warren, C. J.