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首页> 外文期刊>Economic geology and the bulletin of the Society of Economic Geologists >Ion Microprobe U-Pb Age and Zr-in-Rutile Thermometry of Rutiles from the Daixian Rutile Deposit in the Hengshan Mountains, Shanxi Province, China
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Ion Microprobe U-Pb Age and Zr-in-Rutile Thermometry of Rutiles from the Daixian Rutile Deposit in the Hengshan Mountains, Shanxi Province, China

机译：山西横山岱县金红石矿床金红石的离子微探针U-Pb年龄和Zr-金红石温度法

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The Daixian rutile deposit is located in the Hengshan Mountains in the Trans-North China Orogen; it is considered to be one of the largest rutile deposits in China, with 6 million metric tons (Mt) of contained titanium. Most of the rutile ores are hosted in garnet-free anthophyllite gneiss with minor Mg hornblende, feldspar, quartz, phlogopite, rutile, zircon, and titanite. Rutile grains are euhedral, 0.02 to 0.50 mm in size, contain 98.649 to 99.784 wt % TiO_2, and form chains, thin layers along the foliation, and dense aggregates. Rutiles are compositionally homogeneous and contain no detectable mineral inclusions except local ilmenite lamellae and zircon. Crystallization temperatures of the rutile are estimated at ～640℃ at 0.7 GPa, and ～647℃ without pressure calibration according to the Zr-in-rutile thermometer, recording amphibolite facies metamorphism of an intermediate P/T ratio series. Variations in Nb versus Cr in rutiles indicate a connection of the ores to mafic protolith; not a pelitic rock derived from aluminous sedimentary rocks. SIMS U-Pb analyses of rutiles from the deposit yield a mean ~（207）Pb/~（207）Pb age of 1780.2 ± 9.6 Ma. Considering the closure temperature (up to ～650℃), grain sizes and recrystallization of the rutile, this age is more likely to represent closure and/or recrystallization time rather than peak metamorphism period, so the rutile deposit formed not younger than ～1780 Ma. This unique garnet-free rutile deposit was metamorphosed from mafic rocks in amphibolite facies during the Paleoproterozoic or Archean, being distinct from any other metamorphic rutile deposits, such as the known eclogite-related types.
机译：代县金红石矿床位于中国北部华北造山带横山山脉。它被认为是中国最大的金红石矿床之一，其中含有600万吨的钛。大多数的金红石矿石都存放在不含石榴石的直闪石片麻岩中，并伴有少量的镁角闪石，长石，石英，金云母，金红石，锆石和钛铁矿。金红石晶粒为正反面，尺寸为0.02至0.50 mm，包含98.649至99.784 wt％的TiO_2，并形成链状，沿叶状的薄层和密集的聚集体。金红石在成分上是均质的，除了局部的钛铁矿薄片和锆石之外，没有可检测到的矿物包裹体。在0.7 GPa下，金红石的结晶温度估计为〜640℃，根据金红石型Zr温度计未进行压力校准，测得的结晶温度为〜647℃，记录了中间P / T比系列的闪石相变质作用。金红石中Nb与Cr的变化表明矿石与镁铁质原石之间存在联系。不是源自铝质沉积岩的珍珠岩。用SIMS U-Pb分析金红石矿床得到的平均〜（207）Pb /〜（207）Pb年龄为1780.2±9.6 Ma。考虑到关闭温度（最高〜650℃），金红石的晶粒尺寸和重结晶，这个年龄更可能代表关闭和/或重结晶时间，而不是峰值变质期，因此形成的金红石沉积层不小于〜1780 Ma 。这种独特的不含石榴石的金红石矿床是在古元古代或太古宙时期从角闪石相中的镁铁质岩中变质的，不同于任何其他变质金红石矿床，例如已知的榴辉岩相关类型。

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