Well-Constrained Mineralization Ages by Integrated 40Ar/39Ar and U-Pb Dating Techniques for the Xitian W-Sn Polymetallic Deposit, South China
Well-Constrained Mineralization Ages by Integrated 40Ar/39Ar and U-Pb Dating Techniques for the Xitian W-Sn Polymetallic Deposit, South China
复制标题
华南西田钨锡多金属矿床40Ar/39Ar和U-Pb综合测年技术精确确定成矿年龄
DOI：
10.5382/econgeo.4889
复制
发表时间：
2022-06-01
期刊：
影响因子：
5.8
通讯作者：
Qiu, Hua-Ning
中科院分区：
文献类型：
--
作者：
Bai, Xiu-Juan;Liu, Man;Qiu, Hua-Ning
许多存款类型（如造山型Au、层控型Cu矿床和密西西比河谷型铅锌矿床）由于缺乏合适的矿物，用传统的同位素测年方法仍难以确定成矿年龄。本文采用高精度的~（40）Ar/~（39）Ar法对热液矿床中石英、闪锌矿等非钾矿物中普遍存在的流体包裹体进行了定年研究。西田钨锡多金属存款矿床中含有几种适合同位素测年的矿物。40 Ar/39 Ar激光分步加热的16云母从矿脉，云英岩，成矿花岗岩产生平坦的年龄谱，从而明确的成矿年龄范围为152.4 +/- 1.5（2 σ）至148.1 +/- 1.4 Ma，平均为150.2 +/- 0.6 Ma。对9个石英样品进行了40 Ar/39 Ar递进破碎，获得了清晰的原生流体包裹体等时线，其等时线年龄为153.7- 149.9Ma，平均为151.6 ± 0.6Ma。三个手标本中锡石的Pb-206/U-238加权平均年龄分别为151.5 +/- 1.7（2 σ）、149.7 +/- 2.1和151.7 +/- 2.1 Ma。这些新的年代学数据和前人的辉橄榄岩Re-Os年龄，得到锡田钨锡多金属存款的成矿年龄为153-148 Ma，也证实了石英40 Ar/39 Ar递进破碎法是一种可行、有效的定年方法。此外，该技术还可同时获得次生流体包裹体的重要年龄信息。我们期望这种新的测年技术将被广泛应用于确定在热液成矿、油气聚集、变质作用、构造活动和其他地质过程中捕获在矿物中的地质流体。
Mineralization ages of many mineral deposit types (such as orogenic Au, stratabound Cu, and Mississippi Val-ley-type Pb-Zn deposits) are still difficult to date by the traditional isotopic chronometry because of the lack of suitable minerals. We have made efforts to establish a widely suitable dating technique to determine ore forma-tion ages using a high-precision 40Ar/39Ar method on ubiquitously present fluid inclusions in quartz, sphalerite, and other nonpotassium minerals from hydrothermal deposits. The Xitian W-Sn polymetallic deposit in central South China contains several minerals suitable for isotopic dating for interchronometer comparison. 40Ar/39Ar laser step heating of 16 micas from ore veins, greisen, and metallogenic granites yields flat age spectra and thus well-defined ore formation ages ranging from 152.4 +/- 1.5 (2 sigma) to 148.1 +/- 1.4 Ma with an average of 150.2 +/- 0.6 Ma. 40Ar/39Ar progressive crushing of nine quartz samples produces well-defined isochron lines for their primary fluid inclusions corresponding to isochron ages of 153.7-149.9 Ma with an average of 151.6 +/- 0.6 Ma. Cassiterites from three hand specimens have weighted mean Pb-206/U-238 ages of 151.5 +/- 1.7 (2 sigma), 149.7 +/- 2.1, and 151.7 +/- 2.1 Ma. All these new geochronological dates and previous molybdenite Re-Os ages yield well-constrained mineralization ages of 153-148 Ma for the Xitian W-Sn polymetallic deposit, which also confirms conclusively that the quartz 40Ar/39Ar progressive crushing technique is a feasible, valid dating technique. Fur-thermore, significant age information on the secondary fluid inclusions is potentially obtained simultaneously by this technique. We expect that this novel dating technique will be widely applied to determine the geologic fluids trapped in minerals during hydrothermal mineralization, hydrocarbon accumulation, metamorphism, tectonic activities, and other geologic processes.