...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Journal of Volcanology and Geothermal Research >Origin of rhyolite by crustal melting and the nature of parental magmas in the Oligocene Conejos Formation, San Juan Mountains, Colorado, USA
【24h】

Origin of rhyolite by crustal melting and the nature of parental magmas in the Oligocene Conejos Formation, San Juan Mountains, Colorado, USA

机译：美国科罗拉多州圣胡安山渐新世Conejos组中地壳熔融流纹岩的起源和母岩浆的性质

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Four closely spaced volcanoes (Summer Coon; Twin Mountains; Del Norte; Carnero Creek) form the east-central cluster of Conejos volcanic centers. These Conejos rocks range from high-K basaltic andesite to rhyolite, with andesite volumetrically the most abundant. Summer Coon and Twin Mountains are composite volcanoes. The Del Norte and Carnero Creek volcanoes are deeply eroded dacite shields. Rhyolite (10% of our Conejos analyses but a much smaller percentage by volume) is only known from Summer Coon and Twin Mountains volcanoes, although high-SiO_2 dacite occurs in the Del Norte volcano. The younger Hinsdale Formation contains a related series ranging from transitional basalt to high-K andesite; we use Hinsdale Formation analyses to represent Conejos parental magmas. Conejos and Hinsdale magmas evolved through AFC processes: Basalt, after interacting with lower crust, assimilated low K/Rb crust, similar in some ways to Taylor and McLennan (Taylor, S.R., and McLennan, S.M., 1985, The continental crust: its composition and evolution. Oxford, Blackwell Scientific.) model upper crust; main series basaltic andesite fractionated to high-K andesite; rhyolite was produced by melting of high K/Ba upper crustal rocks similar to granite gneiss known from inclusions and basement outcrops. Some rhyolite may have been back-mixed into fractionating andesite and dacite. Field evidence for assimilation includes sanidinite-facies, partially melted, gneiss blocks up to 1 m in diameter. Temperature estimates (1100-900℃) from two-pyroxene equilibria are consistent with this interpretation, as are the sparsely porphyritic nature of the most-evolved rhyolites and the absence of phenocrystic alkali feldspar. Our study supports the conclusions of previous workers on AFC processes in similar, but generally more mafic, Conejos magmas of the southeastern San Juan Mountains. Our results, however, emphasize the importance of crustal melting in the generation of Conejos rhyolite. We further speculate that Conejos magmatism, and the San Juan Volcanic Field (SJVF) in general, may represent an early phase of Rio Grande rift magmatism, the erogenic geochemical signature of the series having been generated through multi-level and extensive assimilation of varied Precambrian orogenic and anorogenic rocks.
机译：四个紧密间隔的火山（萨姆库恩；双子山；德尔诺特；卡内罗克里克）形成了科内霍斯火山中心的中东部集群。这些Conejos岩石范围从高K玄武质安山岩到流纹岩，其中安山岩的体积最多。夏季浣熊和双子山是复合火山。 Del Norte和Carnero Creek火山是深受侵蚀的达西特盾构。流纹岩（占我们Conejos分析的10％，但体积百分比要小得多）仅在夏季北部和双子山火山中才知道，尽管Del-Norte火山中出现了高SiO_2的镁铝榴石。较年轻的欣斯代尔组包含相关的系列，从过渡玄武岩到高钾安山岩。我们使用Hinsdale地层分析来代表Conejos父母的岩浆。 Conejos和Hinsdale岩浆是通过AFC过程演化而成的：玄武岩在与下地壳相互作用之后，吸收了低K / Rb地壳，在某些方面类似于Taylor和McLennan（Taylor，SR和McLennan，SM，1985，大陆壳：其组成牛津，布莱克韦尔科学公司（Blackwell Scientific）。主系列玄武质安山岩分馏成高钾安山岩；流纹岩是通过熔化高K / Ba上地壳岩石产生的，类似于包裹体和基底露头中已知的花岗岩片麻岩。一些流纹岩可能已经被回混成分馏的安山岩和榴辉岩。同化的现场证据包括直径达1 m的部分熔化的片麻岩块。由二吡rox平衡得出的温度估计值（1100-900℃）与这种解释是一致的，演化最多的流纹岩的稀疏斑状性质和不含表象长石的长石也是如此。我们的研究支持先前工人在东南圣胡安山类似但普遍为黑镁质岩浆岩中进行AFC过程的结论。然而，我们的结果强调了地壳融化在Conejos流纹岩生成中的重要性。我们进一步推测，Conejos岩浆作用和一般的圣胡安火山场（SJVF）可能代表了里奥格兰德裂谷岩浆作用的早期阶段，该系列的人为地球化学特征是通过对不同的前寒武纪进行多层次和广泛的同化而产生的。造山和造山岩石。

著录项

相似文献

  • 外文文献
  • 中文文献
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号