Determination of the age of the Australian continent by single-grain zircon analysis of Mt Narryer metaquartzite
Determination of the age of the Australian continent by single-grain zircon analysis of Mt Narryer metaquartzite
复制标题
通过纳里尔山变石英岩的单晶锆石分析确定澳大利亚大陆的年龄
DOI：
10.1038/315052a0
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发表时间：
1985
期刊：
影响因子：
64.8
通讯作者：
Claude J. Alègre
中科院分区：
文献类型：
--
作者：
U. Schärer;Claude J. Alègre
地球演化的一个根本制约因素是大陆地壳首次出现的时间。因此，最近发表的澳大利亚锆石年龄为 4,200–4,100 密尔的报告具有相当重要的意义。这一年代测定是通过澳大利亚国立大学的 SHRIMP 离子微探针的单晶分析实现的。为了通过替代方法证实这些古老锆石的存在，我们通过传统的固源质谱法和单晶粒和单晶粒的各个碎片的同位素稀释分析研究了相同的锆石群。我们的结果既没有证实 4,200–4,100 Myr 的年龄，也没有证实离子探针上获得的特定不一致模式。我们获得的年龄模式可以通过 3,800–3,300 Myr 前的锆石结晶来解释。可能的原生年龄约为 3,750–3,600 Myr，与邻近片麻岩的模型 Sm/Nd 年龄（纳里尔山石英岩的可能源岩）一致，较年轻的年龄被解释为与区域变质叠印的 Rb/Sr 年龄相一致的锆石过度生长年龄。
A fundamental constraint on the evolution of the Earth is the time of the first occurrence of continental crust. The recent publication1of ages of 4,200–4,100 Myr for zircons from Australia is therefore of considerable importance. This dating was achieved by single-grain analysis on the SHRIMP ion microprobe at the Australian National University. To substantiate the existence of these old zircons by an alternative method, we studied the same zircon population by conventional solid-source mass spectrometry and isotope dilution analysis of single grains and individual fragments of single grains. Our results confirm neither the 4,200–4,100-Myr ages nor the particular discordancy patterns obtained on the ion probe. The age pattern we obtained can be explained by zircon crystallization 3,800–3,300 Myr ago. Probable primary ages of ∼3,750–3,600 Myr coincide with model Sm/Nd ages for the adjacent gneisses2, the possible source rocks of the Mt Narryer quartzite, and the younger ages are interpreted as those of zircon overgrowth compatible with a Rb/Sr age for the regional metamorphic overprint2.