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首页> 外文期刊>GSA Bulletin >40Ar/39Ar age spectra for biotite and hornblende from plutonic rocks in the Victorville region, California
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40Ar/39Ar age spectra for biotite and hornblende from plutonic rocks in the Victorville region, California

机译：加利福尼亚州维克多维尔地区深成岩中黑云母和角闪石的40Ar / 39Ar年龄谱

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摘要

40Ar/39Ar data from plutonic rocks in the Mojave Desert near Victorville, California, provide preliminary insight into the complex thermal history of this region and suggest that some plutons here may be significantly older than any plutons in the Sierra Nevada to the north. Near Victorville, multiple deformation and metamorphism of platform-miogeoclinal strata is inferred to postdate deposition of Permian rocks and predate intrusion of monzonite plutons. Monzonite that intrudes multiply deformed Paleozoic marble and that is unconformably overlain by the Mesozoic (Triassic or Jurassic) Fairview Valley Formation has hornblende with an age spectrum typical of severe 40Ar loss. We interpret the age of the highest temperature increment (fusion), 233 ± 14 m.y., as a minimum age for this pluton. The total gas age for the hornblende is only 169.9 m.y. Biotite from the same rock exhibits a plateau age of 76.59 ± 1.24 m.y. The Fairview Valley Formation is overlain by volcanic rocks of the Sidewinder sequence. These rocks were folded and intruded by quartz monzonite that postdates all penetrative deformation in the region. Biotite-hornblende tonalite at Quartzite Mountain is part of one of these younger quartz monzonite plutons, and its biotite yields a plateau age of 73.16 ± 1.11 m.y. This age is the same at the 95% confidence level as the age of biotite from the older monzonite; thus, this younger thermal event was at least the partial cause for the argon loss pattern displayed by the monzonite hornblende. Hornblende gabbro that intrudes Paleozoic marble at Sidewinder Mountain and is in turn contact metamorphosed by later plutonic rocks has hornblende with a disturbed 40Ar/39Ar age spectrum. The 1025, 1050, and 1075 °C steps contain 44.64% of the total argon and yield a common age of 119.2 ± 3.4 m.y., which we interpret as the best estimate for the age of the hornblende.
机译：来自加利福尼亚维克多维尔附近的莫哈韦沙漠中的深部岩石的 40 Ar / 39 Ar数据为对 该区域的复杂热史，表明这里的某些 胶子可能比北方内华达山脉 的任何胶子都显着老。在维克多维尔附近，可以推断 和台盆-微斜斜坡地层的变质作用，以推迟二叠纪岩石的沉积和蒙脱石岩体的侵入[sup> 。侵入多变形的 古生代大理石的Monzonite，不均匀地被中生代 （三叠纪或侏罗纪）费尔维尤谷地层覆盖，其角闪石 具有年龄谱典型的严重的 40 Ar丢失。我们将 最高温度增量（融合）的年龄233± 14 m.y.解释为该子体的最小年龄。角闪石的总瓦斯年龄 仅为169.9m.y.y。来自同一 岩石的黑云母的高原年龄为76.59±1.24m.y。 费尔维尤谷地层被 Sidewinder序列的火山岩覆盖。这些岩石被 石英蒙脱石折叠并侵入，该石英蒙脱石推迟了该区域中所有渗透变形 的发生。石英岩山中的黑云母-角闪石斜长石是这些年轻的石英蒙脱石岩体之一的一部分，其黑云母产生的高原年龄为73.16±1.11 my 这个年龄在95％的置信度水平上与年龄较大的蒙脱石中黑云母的年龄 相同；因此，这种年轻的热事件至少是造成独居石角闪石显示氩气损失模式的部分原因。 侵入Sidewinder山的古生代大理石并依次变质的 接触角，后来被深成岩岩石变质的Hornblende gabbro的hornblende 受到干扰 40 < / sup> Ar / 39 Ar年龄谱。 1025、1050和 1075°C步骤包含的总氩气含量为44.64％，产率 的常见年龄为119.2±3.4 my，我们将其解释为 作为角闪石年龄的最佳估计。

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  • 来源
    《GSA Bulletin》 |1981年第4期|164-169|共6页
  • 作者

    ELIZABETH L. MILLER; JOHN F. SUTTER;

  • 作者单位

    Department of Geology, Stanford University, Stanford, California 94305;

    Department of Geology and Mineralogy, The Ohio State University, Columbus, Ohio 43210;

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