Using in situ SHRIMP U-Pb monazite and xenotime geochronology to determine the age of orogenic gold mineralization: An example from the Paulsens Mine, Southern Pilbara Craton
Using in situ SHRIMP U-Pb monazite and xenotime geochronology to determine the age of orogenic gold mineralization: An example from the Paulsens Mine, Southern Pilbara Craton
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DOI：
10.5382/econgeo.2017.4507
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发表时间：
2017-08
期刊：
影响因子：
5.8
通讯作者：
I. Fielding;S. Johnson;Jian-Wei Zi;B. Rasmussen;J. Muhling;D. Dunkley;S. Sheppard;M. Wingate
中科院分区：
文献类型：
--
作者：
I. Fielding;S. Johnson;Jian-Wei Zi;B. Rasmussen;J. Muhling;D. Dunkley;S. Sheppard;M. Wingate
Paulsens是位于西澳大利亚皮尔巴拉克拉通南缘Wyloo Inlier的中造山型金存款矿床。金赋存于褶皱和断裂辉长岩脉中的石英硫化物脉中，斜锆石的U-Pb结晶年龄为2701 ± 11 Ma。脉中和热液蚀变围岩中的独居石和磷钇矿产生了三个不同的约1000年的U-Pb年龄。2400、1730和1680 Ma。自形磷钇矿与石英-硫化物脉中含圆形自然金包裹体的黄铁矿之间的结构关系表明，原生金矿化与磷钇矿结晶同步，时间为2403 ± 5 Ma，与寄主岩石的普遍蚀变同时发生，独居石年龄分别为2398 ± 37和2403 ± 38 Ma。区域尺度的热液事件。1730 ± 28和1721 ± 32 Ma时，千枚岩中独居石生长; 1655 ± 37 Ma时，碳酸盐脉形成; 1680 ± 9 Ma时，金再活化或新金的引入。CA。矿化和热液蚀变的2400 Ma年龄不符合该地区任何已知的变形事件，表明皮尔巴拉南部地区的低温构造演化与以前认识的明显不同，也更复杂。独居石和磷钇矿的原位二次离子质谱定年技术将有助于更好地定位南摩羯座北方造山带的造山型金矿，这些技术可用于全球范围内的造山型金矿勘探。
Paulsens is a mesothermal orogenic gold deposit located in the Wyloo Inlier on the southern margin of the Pilbara craton of Western Australia. Gold occurs in quartz-sulfide veins hosted within a folded and faulted gabbro dike, from which baddeleyite yields a U-Pb crystallization age of 2701 ± 11 Ma. Monazite and xenotime in the veins and from hydrothermally altered country rocks yield three distinct U-Pb dates of ca. 2400, 1730, and 1680 Ma. Textural relationships between euhedral xenotime and pyrite with rounded native gold inclusions from within the quartz-sulfide veins show that the primary gold mineralization was synchronous with xenotime crystallization at 2403 ± 5 Ma, and coeval with pervasive alteration of the host rocks, which yield monazite ages of 2398 ± 37 and 2403 ± 38 Ma. Regional-scale hydrothermal events at ca. 1730 and 1680 Ma are linked to the growth of monazite within phyllitic rocks at 1730 ± 28 and 1721 ± 32 Ma, carbonate veining at 1655 ± 37 Ma, and gold remobilization or introduction of new gold at 1680 ± 9 Ma. The ca. 2400 Ma age for mineralization and hydrothermal alteration does not correspond with any known deformation event in the region, indicating a significantly different and more complicated low-temperature tectonothermal evolution for the southern Pilbara region than previously recognized. The in situ secondary ion mass spectrometry dating of monazite and xenotime employed here will lead to better targeting of orogenic gold deposits in the northern Capricorn Orogen, and these techniques can be utilized for orogenic gold exploration worldwide.