Two age populations of zircons from the Timber Creek kimberlites, Northern Territory, as determined by laser ablation ICP MS analysis
Two age populations of zircons from the Timber Creek kimberlites, Northern Territory, as determined by laser ablation ICP MS analysis
复制标题
DOI：
10.1046/j.1440-0952.2001.485894.x
复制
发表时间：
2001-10
影响因子：
1.2
通讯作者：
E. Belousova;W. Griffin;S. Shee;S. Jackson;S. O’Reilly
中科院分区：
文献类型：
--
作者：
E. Belousova;W. Griffin;S. Shee;S. Jackson;S. O’Reilly
北领地的木材溪金伯利岩中存在两个金伯利岩锆石群。激光烧蚀ICP MS U-Pb测年，主群年龄为1483 ± 15（2σ）Ma，另一群年龄为179 ± 2 Ma。这两个年龄组的区别强烈支持Hf同位素数据相同的锆石。虽然微量元素模式的两个人口是典型的幔源锆石，“年轻”的人口有稍高的浓度，但具有较低的Hf，Nb，Ta和Pb的含量。微量元素含量和Hf同位素组成的明显差异表明，两个锆石群体的岩浆来源不同。测年结果表明，Timber Creek金伯利岩的侵位年龄不可能大于“年轻”锆石群的年龄（179 ± 2 Ma）。这澄清了之前报道的Timber Creek锆石SHRIMP年龄（1462 ± 53 Ma）与这些金伯利岩侵入的维多利亚河流域沉积物年龄（1200 Ma）之间的不一致。Timber Creek金伯利岩是西澳大利亚和南澳广泛分布的侏罗纪金伯利岩活动的新延伸（Wanderlites、Orroroo、Cleve和Eurelia金伯利岩）。
Two populations of kimberlitic zircon are present in the Timber Creek kimberlites, Northern Territory. Laser ablation ICP MS U—Pb dating yields an age of 1483 ± 15 (2σ) Ma for the main group and an age of 179 ± 2 Ma for the other group. This distinction of two age groups is strongly supported by Hf isotope data on the same zircons. Although the trace element patterns of both populations are typical of mantle derived zircons, the ‘young’ population has slightly higher concentrations of most trace elements, but has lower Hf, Nb, Ta and Pb contents. The distinct differences in trace element contents and Hf isotopic composition of the two zircon populations indicate that they were derived from different magma sources. The dating results indicate that the emplacement age of the Timber Creek kimberlites cannot be older than the age of the ‘young’ zircon population (i.e. 179 ± 2 Ma). This clarifies the inconsistency between the previously reported SHRIMP age of the Timber Creek zircons (1462 ± 53 Ma) and the much younger age (1200 Ma) of the sediments of the Victoria River Basin into which these kimberlites have intruded. The Timber Creek kimberlites are a newly recognised extension of the widespread Jurassic kimberlite activity known in Western Australia and South Australia (Wandagee, Orroroo, Cleve and Eurelia kimberlites).