This study demonstrates that dykes that are coeval and cogenetic with plutons can provide an important tool for recognizing discrete batches of magma with similar overall chemical compositions and physical attributes, but different isotopic characteristics, and which contributed to pluton formation. The Qianlishan granitic pluton, located in the Qin–Hang fault zone separating the Yangtze block from the Cathaysia block in South China, was emplaced at 155–152 Ma in the Late Jurassic. It consists of a central zone of strongly differentiated zinnwaldite-bearing equigranular granite surrounded by a less differentiated porphyritic granite. The pluton is spatially associated with an extensive granitic dyke swarm dated here at 153–152 Ma, demonstrating a coeval relationship. Amongst the dykes, two discrete end-member sources can be identified from the bimodal nature of their zircon hafnium and oxygen systematics, with one group showing a range in ε_Hf(t) of -11·9 to -8·0 and in δ¹⁸O of 9·0–10·4‰, whereas in the other group the ranges are from -7·3 to -4·1 and 8·4–9·4‰, respectively. This contrasts with the two phases of the Qianlishan pluton, which record wide ranges in ε_Hf(t) of -11·1 to -5·1 and in δ¹⁸O of 8·3–10.4‰, but without bimodality. Hence, the overlapping Hf–O isotopic profiling shows the dykes and pluton to be cogenetic. Small-volume magma batches, with their rapid transport through the crust and quick cooling, are all typical features of dyke generation, thus preserving the original heterogeneous Hf–O isotopic signatures that are characteristic of two distinct crustal sources. However, although the pluton was formed from similar sources to the dykes, the bimodal source identity was lost during its assembly through mixing of the magma batches. These findings also provide a potential explanation for the wide range of zircon hafnium isotopic systematics typical of granitic plutons, as shown by sampling at all scales.

中文翻译：

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共生堤坝是识别花岗岩岩体组装中不同岩浆批次的关键

这项研究表明，与p同生并与之共生的堤坝可以提供重要的工具，以识别具有相似的整体化学组成和物理属性，但同位素特征不同，并导致p形成的岩浆离散批次。前秦山花岗岩岩体位于秦汉断层带，该岩体将扬子和华夏地块分隔开来，在侏罗纪末期位于155-152 Ma。它由高分化的含锌锰铁矿的等粒花岗岩的中心带和低分化的斑状花岗岩包围。岩体在空间上与这里日期为153-152 Ma的广泛的花岗岩堤群相关联，表明其具有同时代的关系。在堤坝中ε_的Hf（t）的-11·9至-8·0和δ ¹⁸ 9 O·0-10·4‰，而另一组中的范围是从-7·3 -4·1和8 ·4–9·4‰。与此相反，千里山岩体，它记录在宽范围中的两个阶段ε_的Hf的-11（T）·1至-5·1和δ ¹⁸O为8·3-10.4‰，但无双峰。因此，重叠的Hf-O同位素分析表明，堤和岩体是共生的。小体积的岩浆批次，它们通过地壳的快速运输和快速冷却，都是堤坝生成的典型特征，因此保留了原始的非均质Hf–O同位素特征，这是两个不同地壳源的特征。但是，尽管岩浆是由与堤坝相似的来源形成的，但在双峰源的组装过程中，由于混合了岩浆批次而失去了双峰来源。这些发现还为花岗岩类岩溶体中典型的锆ha同位素系统的广泛应用提供了可能的解释，如通过各种规模的采样所显示的。