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首页> 外文期刊>Geological Society of America Bulletin >Magmatic evolution of the eastern Coast Plutonic Complex, Bella Coola region, west-central British Columbia
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Magmatic evolution of the eastern Coast Plutonic Complex, Bella Coola region, west-central British Columbia

机译：不列颠哥伦比亚省中西部贝拉库拉地区东部海岸多岩体综合体的岩浆演化

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The eastern Coast Plutonic Complex in west-central British Columbia (51-54°N) consists of a broad belt of Jurassic to Eocene granitic to dioritic intrusive rocks that collectively represent more than 140 m.y. of nearly continuous, subduction-related mag-matism. Seven distinct intrusive suites have been identified in the Bella Coola region, including, from oldest to youngest, the Howe Lake, Stick Pass, Firvale, Desire, Fougner, Big Snow, and Four Mile suites. Pre-Late Cretaceous rocks were produced by episodic subduction-related magmatism characterized by partial melting of preexisting lower-arc crust, with minimal incorporation of evolved continental material. The eastern Coast Plutonic Complex experienced a magmatic lull between ca. 110 and 95 Ma, coincident with sinistral transpression potentially linked to translational displacement of the Wrangellia-Alexander composite terranes. Crustal thickening in Late Cretaceous time (ca. 100-90 Ma), possibly due to underplat-ing of the Wrangellia-Alexander terrane, produced a deep crustal root (>40 km) that likely extended into the eclogite transition zone. Adakitic magmas (ca. 95-67 Ma) were produced by partial melting of an amphibo-litic protolith in this thickened lower-arc crust. Adakitic plutons are pre-, syn-, and postkinematic with respect to Late Cretaceous high-angle shear zones, and they are coeval and spatially associated with postkinematic two-mica granites (ca. 70-75 Ma) having a hybrid A-type geochemistry. We suggest that delamination of this dense crustal root led to voluminous magmatism, extension, and crustal exhumation in Paleocene-Eocene time. The successive intrusive events in the eastern Coast Plutonic Complex may reflect a predictable evolutionary progression common to all continental arc systems.
机译：不列颠哥伦比亚省中西部（51-54°N）的东部海岸深部复合体由侏罗纪至始新世的花岗岩至闪长侵入岩的宽阔带组成，共同代表了140m.y。与俯冲有关的岩浆几乎是连续的。在贝拉库拉地区已经确定了七个不同的侵入式套房，包括从最老到最小的豪​​湖，棍子通行证，Firvale，欲望，富纳，大雪和四英里套房。晚白垩纪岩石是通过与俯冲有关的岩浆作用而产生的，其特征是早已存在的下弧地壳部分融化，而对演化的大陆物质的掺入却很少。东部海岸的Plutonic Complex在大约2年之间经历了岩浆平静。 110和95 Ma，与可能与Wrangellia-Alexander复合地层的平移位移有关的窦性压迫相吻合。在白垩纪晚期（约100-90 Ma），地壳增厚，可能是由于Wrangellia-Alexander地层的下盘作用所产生的地壳深部（> 40 km），可能延伸到了榴辉岩过渡带。通过在该增厚的下弧地壳中部分两栖类原生质岩融化，产生了岩浆岩浆（约95-67 Ma）。相对于白垩纪晚期高角度剪切带来说，阿达克特岩体是运动前，同运动和后运动的，它们与运动学上具有混合A型地球化学特征的两云母花岗岩（约70-75 Ma）同生并在空间上相关。我们认为，在古新世-始新世时期，该致密地壳根的分层导致大量岩浆作用，伸展和地壳发掘。东海岸的Plutonic Complex中的相继侵入性事件可能反映了所有大陆弧系统共有的可预测的演化进程。

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