The study of enclaves in granitic plutons provides fundamental information on the petrogenesis of their host rocks. Here we combine U–Pb zircon ages, petrography, geochemistry and Nd–Hf isotope composition to investigate the origin of dioritic–granodioritic enclaves and their host granodiorites and biotite granites in the Xuehuading–Panshanchong area, which is a pivotal site to study the Palaeozoic intracontinental orogenic processes of the South China Block. Obtained ages indicate that the host rocks were formed in early Silurian time (c. 432 Ma). The enclaves are fine grained, but with mineral assemblages similar to their hosts and contain amphibole, biotite and plagioclase. All rocks have fractionated rare earth element patterns ((La/Yb)N = 2.86–8.16), except for one biotite granite that has a concave rare earth element pattern ((La/Yb)N = 1.50). Most rocks are depleted in Ta–Nb–Ti, and have negative Eu anomalies and ϵNd(t) (–8.86 to –5.75) and zircon ϵHf(t) (–13.30 to –4.11, except for one, –39.08). We interpret that the enclaves were formed at the borders of magma-ascending conduits, where the mafic mineral crystallization was enhanced by rapid cooling. Conversely, the biotite granites were produced by fractional crystallization from a related granodiorite magma. The sample with a concave rare earth element pattern may have been influenced by hydrothermal fluid–melt interaction. Geochemical modelling suggests that the granodiorites were likely generated by disequilibrium melting of heterogeneous amphibolites in the middle–lower crust. Considering the geological data for the Palaeozoic magmatic rocks in the South China Block, we propose that the Xuehuading–Panshanchong magmatism was likely triggered by piecemeal removal of the thickened lithospheric root and subsequent thermal upwelling of mantle, without a mantle-derived magma contribution to the granites.

中文翻译：

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早志留世花岗质岩石和伴生的飞地作为同源岩浆系统快速冷却的证据：以华南地块雪花顶-盘山冲岩体为例

花岗岩岩体中的飞地研究提供了有关其主岩成因的基本信息。在这里，我们结合U-Pb锆石年龄、岩石学、地球化学和Nd-Hf同位素组成，研究了雪花顶-盘山冲地区闪长岩-花岗闪长岩飞地及其宿主花岗闪长岩和黑云母花岗岩的成因，这是研究古生界的关键地点。华南陆块的陆内造山过程。获得的年龄表明主岩形成于志留纪早期（C。432 毫安）。这些飞地是细粒状的，但具有与其宿主相似的矿物组合，并含有闪石、黑云母和斜长石。所有岩石都有分馏的稀土元素模式 ((La/Yb)ñ= 2.86–8.16)，除了一种具有凹入稀土元素图案的黑云母花岗岩 ((La/Yb)ñ= 1.50)。大多数岩石贫化 Ta-Nb-Ti，具有负 Eu 异常和 εNd(t)（–8.86 到 –5.75）和锆石 εHf(t)（–13.30 到 –4.11，除了一个，–39.08）。我们解释说，飞地是在岩浆上升管道的边界形成的，快速冷却增强了镁铁质矿物的结晶。相反，黑云母花岗岩是通过相关花岗闪长岩岩浆的分级结晶产生的。具有凹入稀土元素图案的样品可能受到热液 - 熔体相互作用的影响。地球化学模型表明，花岗闪长岩可能是由中下地壳非均质角闪岩的不平衡熔融产生的。结合华南地块古生代岩浆岩地质资料，