Abstract

Zircon from spatially and temporally distinct igneous rock units across the Gawler Craton, Australia, show subtle differences in trace and rare earth element ratios. These igneous suites range in composition from granite, rhyolite to gabbro and originate from the ca 2450 Ma Sleaford Complex, the ca 1850 Ma Donington Suite, the ca 1633–1608 Ma St Peter Suite, the ca 1595–1587 Ma Gawler Range Volcanics and the ca 1595–1575 Ma Hiltaba Suite granites. The geochemical characterisation of zircon is carried out on relatively unaltered samples in order to establish primary signatures and to understand the processes controlling the geochemical signatures of the igneous suites. A range of zircon morphologies and internal textures that are preserved in these igneous suites infer the geological history of the host rock, including metamorphism and multiple episodes of zircon saturation suggesting a complex magma evolution. Despite differences in whole-rock geochemistry between igneous suites, zircon largely overlaps geochemically. However, subtle differences in Th/U, U/Hf and (Nb + Ta)/P ratios are evident between the Donington Suite, Gawler Range Volcanics and Hiltaba Suite. This is likely due to the tectonic setting, composition of the crystallising magma and timing of zircon crystallisation in the magma evolution. The subtle geochemical differences in zircon show the potential of using these ratios to aid in provenance studies with large populations of zircon that are of similar age. However, as the dataset is limited and focused only on unaltered samples, further work needs to be undertaken to look at the altered counterparts of these igneous suites.

1. KEY POINTS

2. Zircon recovered from unaltered samples of spatially and temporally distinct igneous suites in the Gawler Craton is used here.

3. Th/U, U/Hf and (Nb + Ta)/P ratios of zircon can discriminate the Donington Suite, Gawler Range Volcanics and Hiltaba Suite.

4. Zircon morphologies, internal textures and geochemical characteristics are a value aid to provenance studies.

摘要

横跨澳大利亚Gawler Craton的时空不同火成岩单元中的锆石在痕量和稀土元素比率上显示出细微的差异。这些火成岩套件的组成范围从花岗岩，流纹岩到辉长岩，起源于ca 2450 Ma Sleaford建筑群，ca 1850 Ma Donington套件，ca 1633-1608 Ma St Peter套件，ca 1595-1587 Ma Ma Gawler山脉火山和钙1595–1575 Ma Hiltaba套房花岗岩。锆石的地球化学特征是在相对不变的样品上进行的，以建立原始特征并了解控制火成岩组地球化学特征的过程。这些火成岩套件中保留的一系列锆石形态和内部纹理可以推断出宿主岩的地质历史，包括变质作用和锆石饱和度的多次发作，暗示着复杂的岩浆演化。尽管火成岩组之间的全岩石地球化学存在差异，但锆石在地球化学上有很大的重叠。但是，Donington Suite，Gawler Range Volcanics和Hiltaba Suite之间的Th / U，U / Hf和（Nb + Ta）/ P比的细微差别是显而易见的。这可能是由于构造背景造成的，岩浆演化过程中结晶岩浆的组成和锆石结晶的时间。锆石中细微的地球化学差异显示了使用这些比率来协助年龄相似的大量锆石种群物源研究的潜力。但是，由于数据集是有限的，并且只关注未更改的样本，因此需要进一步研究这些火成岩组的对应副本。

1. 关键点

2. 这里使用的是从Gawler Craton的时空上不同的火成岩样品的未改变样品中回收的锆石。

3. 锆石的Th / U，U / Hf和（Nb + Ta）/ P比可以区分Donington Suite，Gawler Range Volcanics和Hiltaba Suite。

4. 锆石的形态，内部结构和地球化学特征对物源研究具有重要的价值。