Subduction initiation recorded in the Dadeville Complex of Alabama and Georgia, southeastern United States
Subduction initiation recorded in the Dadeville Complex of Alabama and Georgia, southeastern United States
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DOI：
10.1130/ges02643.1
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发表时间：
2023-10
期刊：
影响因子：
2.5
通讯作者：
N. Becker;Freya R. George;George L. Guice;James L Crowley;W. R. Nelson;Joseph F. Browning-Hanson;Supratik Roy;D. Viete
中科院分区：
文献类型：
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作者：
N. Becker;Freya R. George;George L. Guice;James L Crowley;W. R. Nelson;Joseph F. Browning-Hanson;Supratik Roy;D. Viete
阿拉巴马州和乔治亚州（美国东南部）的Dadeville复合体代表了阿巴拉契亚山脉南部最大的暴露基性-超基性岩组。由于保存不良、化学蚀变和构造改造，达德维尔杂岩的具体构造起源一直难以推断。结合锆石U-Pb年代学，研究了达德维尔杂岩记录的岩浆和变质作用及其时间。我们的数据揭示了火山岩地球化学的上地层演化，从弧前玄武岩到博宁岩。我们从三个角闪岩样品中获得的新的U-Pb锆石结晶数据表明，弧前/原弧火山作用的时间不迟于约467 Ma。新的热气压测量表明，Dadeville杂岩随后经历了深度、高变质作用，压力-温度条件为770kbar，温度为760°C。本文提供的数据支持一个模型，即在俯冲起始和原弧发育期间，Dadeville杂岩在俯冲带的弧前区域形成，然后在造山过程中进行深埋/逆冲。
The Dadeville Complex of Alabama and Georgia (southeastern United States) represents the largest suite of exposed mafic-ultramafic rocks in the southern Appalachians. Due to poor preservation, chemical alteration, and tectonic reworking, a specific tectonic origin for the Dadeville Complex has been difficult to deduce. We obtained new whole-rock and mineral geochemistry coupled with zircon U-Pb geochronology to investigate the magmatic and metamorphic processes recorded by the Dadeville Complex, as well as the timing of these processes. Our data reveal an up-stratigraphic evolution in the geochemistry of the volcanic rocks, from forearc basalts to boninites. Our new U-Pb zircon crystallization data—obtained from three amphibolite samples—place the timing of forearc/protoarc volcanism no later than ca. 467 Ma. New thermobarometry suggests that the Dadeville Complex rocks subsequently experienced deep, high-grade metamorphism, at pressure-temperature conditions of >7 kbar and >760 °C. The data presented here support a model for formation of the Dadeville Complex in the forearc region of a subduction zone during subduction initiation and protoarc development, followed by deep burial/underthrusting of the complex during orogenesis.