The Sargur Group has been considered to be the oldest group (>3.0 Ga) in the Archaean sequence of the Dharwar Craton in south India, whereas the rocks of the Dharwar Supergroup are younger (between 3.0 and 2.55 Ga). The supracrustal units of the Sargur Group were deposited during the Archaean period. The Banavara quartzite forms part of the supracrustal Sargur Group and contains significant amounts of chromian spinel (Cr-spinel). Here, U–Pb and Hf isotopes of detrital zircons are integrated with compositional data and X-ray refinement parameters for Cr-spinels to decipher the provenance of the metasediments. Zircons show an age spectrum from 3.15 to 2.50 Ga, and juvenile Hf isotopic compositions (ϵHf = +0.8 to +6.4) with model ages between 3.3 and 3.0 Ga. Major- and trace-element contents of the Cr-spinels do not resemble those in the Sargur ultramafic rocks, but resemble well-characterized Archaean anorthosite-hosted chromites. Cr-spinel trace-element signatures indicate that they have undergone secondary alteration or metamorphism. X-ray refinement parameters for the Cr-spinels also resemble the anorthosite-hosted chromites. We conclude that the detrital minerals were probably derived from gneissic and anorthositic rocks of the Western Dharwar Craton, and that the Sargur Group sequences have experienced a younger (2.5 Ga) metamorphic overprint.

中文翻译：

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巴纳瓦拉石英岩中碎屑锆石和铬尖晶石的 U-Pb 和 Hf 同位素研究及其对印度南部达瓦尔克拉通演化的意义

Sargur 群被认为是印度南部达瓦尔克拉通太古宙序列中最古老的群（>3.0 Ga），而达瓦尔超群的岩石更年轻（介于 3.0 和 2.55 Ga 之间）。Sargur 群的地壳上单元沉积于太古代时期。Banavara 石英岩是地壳上 Sargur 群的一部分，含有大量铬尖晶石 (Cr-spinel)。在这里，碎屑锆石的 U-Pb 和 Hf 同位素与 Cr 尖晶石的成分数据和 X 射线细化参数相结合，以破译变质沉积物的来源。锆石的年龄范围为 3.15 至 2.50 Ga，而模型年龄为 3.3 至 3.0 Ga 的幼年 Hf 同位素组成 (εHf = +0.8 至 +6.4)。Cr-尖晶石的主量元素和微量元素含量与 Sargur 超镁铁质岩石中的含量不同，但类似于特征明确的太古代斜长岩为载体的铬铁矿。Cr-尖晶石微量元素特征表明它们经历了次生蚀变或变质作用。Cr-尖晶石的 X 射线细化参数也类似于以斜长石为主体的铬铁矿。我们得出结论，碎屑矿物可能来自西达瓦尔克拉通的片麻岩和斜长岩，并且 Sargur 群层序经历了较年轻的（2.5 Ga）变质叠印。Cr-尖晶石的 X 射线细化参数也类似于以斜长石为主体的铬铁矿。我们得出结论，碎屑矿物可能来自西达瓦尔克拉通的片麻岩和斜长岩，并且 Sargur 群层序经历了较年轻的（2.5 Ga）变质叠印。Cr-尖晶石的 X 射线细化参数也类似于以斜长石为主体的铬铁矿。我们得出结论，碎屑矿物可能来自西达瓦尔克拉通的片麻岩和斜长岩，并且 Sargur 群层序经历了较年轻的（2.5 Ga）变质叠印。