Rb–Sr dating of sphalerites from Tennessee and the genesis of Mississippi Valley type ore deposits
Rb–Sr dating of sphalerites from Tennessee and the genesis of Mississippi Valley type ore deposits
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DOI：
10.1038/346354a0
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发表时间：
1990-07
期刊：
影响因子：
64.8
通讯作者：
S. Nakai;A. Halliday;S. Kesler;H. D. Jones
中科院分区：
文献类型：
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作者：
S. Nakai;A. Halliday;S. Kesler;H. D. Jones
密西西比山谷型（MVT）矿床通常由铅、锌和铁硫化物的某种组合以及重晶石、萤石、白云石和方解石组成。它们被认为是由沉积序列中的流体排出形成的1 -3，但由于缺乏可靠的地质年代学数据，它们的确切起源仍然存在争议。在最近一个被广泛引用的模型中，美国中部和东部的MVT矿床是在晚古生代阿勒格尼造山带（3.3亿-2.5亿年）4期间，由沉积序列的构造挤压驱动的大规模横向流体流动的结果。在这里，我们报告的第一个直接Rb-Sr年龄的闪锌矿从MVT存款，并提出这是一个有用的地质年代学技术的硫化物矿化与不良的年龄控制。东田纳西州科伊矿闪锌矿的Rb-Sr数据确定的等时线年龄为3.77亿± 2.9亿年，排除了与阿勒格尼造山带的任何成因联系。相反，美国东部的MVT矿化作用显然是由与较老的奥陶系造山带（3.8 - 3.5亿年）有关的逆冲过程中排出的流体产生的。
MISSISSIPPI Valley type (MVT) ore deposits commonly consist of some combination of lead, zinc and iron sulphides accompanied by barite, fluorite, dolomite and calcite. They are thought to form by fluid expulsion from sedimentary successions1–3,but their exact origin has remained controversial because of the scarcity of reliable geochronological data. In a recent and widely quoted model the MVT deposits of the central and eastern United States formed as a result of large-scale lateral fluid flow driven by the tectonic squeezing of sedimentary successions during the late Palaeozoic Alleghenian orogeny (330–250 Myr)4. Here we report the first direct Rb–Sr dating of sphalerites from an MVT deposit and propose this as a useful geochronological technique for sulphide mineralization with poor age control. Rb–Sr data for sphalerites from Coy mine, East Tennessee, define an isochron age of 377 ± 29 Myr, ruling out any genetic connection with the Alleghenian orogeny. Instead, MVT mineralization in the eastern United States was apparently generated from fluids expelled during thrusting associated with the older Acadian orogeny (380–350 Myr).