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Inferences on late-stage evolution of the Russell Lake Allochthon and the Soapstone Ridge Complex in Georgia, Southern Appalachians, based on chlorite geothermometry
International Journal of Earth Sciences ( IF 2.3 ) Pub Date : 2020-04-09 , DOI: 10.1007/s00531-020-01861-5
Jeff B. Chaumba

Chlorite is a common mineral in most metamorphosed mafic and ultramafic rocks and the use of chlorite as a geothermometer was applied to rocks from the southern Appalachian Piedmont for this study. In particular, chlorite-bearing rocks from the Russell Lake Allochthon (RLA) and the Soapstone Ridge Complex (SSR) are the focus of this investigation. The RLA is composed of numerous metamorphosed mafic and ultramafic bodies exposed within rocks of the Carolina superterrane which forms part of the peri-Gondwana realm of the Southern Appalachians. The SSR is one of the largest metamorphosed mafic and ultramafic bodies in the southern Appalachians; it is in thrust contact with underlying rocks of the Piedmont domain, which forms part of the Iapetan realm of the Southern Appalachians. The metamorphosed bodies that comprise the RLA are generally small, with outcrop areas generally not exceeding a few square kilometers. In the RLA and SSR, chlorite occurs together with zoned amphiboles. In the RLA, chlorite exhibits low total iron atoms per formula unit and dominantly plots in the ripidolite field. In contrast, SSR chlorites are poorer in total iron and almost all are clinochlores. Results of chlorite geothermometry from rocks of the RLA yield temperatures which range from ~ 280 to ~ 320 °C, whereas chlorites from the SSR yield temperatures which range from ~ 201 to ~ 250 °C. These calculated temperatures indicate that chlorites in the RLA were formed at slightly higher temperatures in comparison to those from the SSR, which may suggest that these bodies were subjected to different late-stage metamorphic conditions and may also have originated under different tectonic settings. The RLA and SSR are approximately 100 km apart and a terrane boundary occurs between them; these bodies were each metamorphosed, and likely evolved, in different regions and each was later thrusted onto its country rocks during the final stages of the assembly of Pangea.



中文翻译:

基于绿泥石地热法的南阿巴拉契亚格鲁吉亚罗素湖Allochthon湖和Soapstone Ridge复杂体后期演化的推论

在大多数变质的镁铁质和超镁铁质岩石中,亚氯酸盐是一种常见的矿物,本次研究将亚氯酸盐用作地热仪应用于来自阿巴拉契亚山脉南部的岩石。特别是,来自罗素湖Allochthon(RLA)和Soapstone Ridge Complex(SSR)的含绿泥石的岩石是这项研究的重点。RLA由暴露在卡罗莱纳州超地层岩石中的许多变质的镁铁质和超镁铁质体组成,构成南阿巴拉契亚山脉的冈瓦纳河外围。SSR是阿巴拉契亚南部最大的变质镁铁质和超镁铁质体之一。它与皮埃蒙特(Piedmont)域的下伏岩石成推力接触,该岩石构成了南部阿巴拉契亚人伊阿佩坦(Iapetan)领域的一部分。包含RLA的变体通常很小,露头面积一般不超过几平方公里。在RLA和SSR中,亚氯酸盐与分区的两性闪石一起出现。在RLA中,亚氯酸盐在每个分子式单位中显示出较低的总铁原子,并且在水滑石场中占优势。相比之下,SSR亚氯酸盐的总铁含量较差,几乎全部都是斜绿石。RLA岩石中亚氯酸盐的地热测量结果表明,温度范围为〜280至〜320°C,而SSR的绿泥石过程的温度范围为〜201至〜250°C。这些计算出的温度表明,与SSR相比,RLA中的亚氯酸盐形成温度略高,这可能表明这些物体经历了不同的后期变质条件,也可能起源于不同的构造环境。RLA和SSR相距约100公里,它们之间形成了地界。这些天体在不同的区域变质并可能演化,然后在Pangea组装的最后阶段被推入其乡村岩石中。

更新日期:2020-04-21
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