Abstract Whether the formation of early Paleozoic granites in the South China Block was related to intracontinental orogenic processes or oceanic subduction continues to be debated. Here, we present whole-rock major element, trace element, and Sr Nd isotopic data, as well as secondary ion mass spectrometry and laser ablation–inductively coupled plasma–mass spectrometry zircon U Pb geochronological and Hf O isotopic data, from biotite, two-mica, and muscovite granites in the Baiyunshan and Maofengshan areas of Guangzhou City, South China. Zircon U Pb ages reveal that these rocks were formed during the early Paleozoic (446–438 Ma). These muscovite- and biotite-bearing granites have high SiO2 (69.0–80.4 wt%) and K2O (3.19–5.32 wt%) contents, and low MgO (0.46–1.17 wt%) contents. The granites are enriched in Rb, Th, U, and Pb, and depleted in Ba, Sr, Nb, and Ti. The Baiyunshan muscovite granites and Maofengshan biotite granites are slightly to moderately enriched in light rare-earth elements [LREEs; (La/Yb)CN = 2.27–15.1] with slight to pronounced negative Eu anomalies (Eu/Eu* = 0.27–0.72), whereas the Baiyunshan two-mica granites are significantly enriched in LREEs [(La/Yb)CN = 19.6–32.1] with moderate negative Eu anomalies (Eu/Eu* = 0.42–0.58). These muscovite- and biotite-bearing granites have enriched whole-rock Nd and zircon Hf isotopic compositions (eNd(t) = −12.1 to −7.6; eHf(t) = −11.4 to −0.8), and high zircon δ18O values (8.5‰–10.0‰). We suggest that the Baiyunshan granites were formed by partial melting of metasedimentary rocks, as they contain primary muscovite and have high zircon δ18O values. The Maofengshan granites were formed by partial melting of a hybridized crustal source containing metasedimentary rocks with subordinate amphibolites, as they have high zircon δ18O values, variable whole-rock SiO2 contents, and biotite compositions similar to those crystallized in I- and S-type magmas. These granites, along with the widespread early Paleozoic S-type granites in the Wuyi–Yunkai orogen, are distributed across a broad area rather than in a narrow belt. In addition, early Paleozoic S-type granites in the South China Block generally do not show younging trends from east to west or south to north. Moreover, the Baiyunshan–Maofengshan granites show geochemical characteristics similar to syn- or post-collisional granites and different from volcanic arc granites. We therefore propose that these muscovite- and biotite-bearing granites were formed in an intracontinental orogenic setting.

中文翻译：

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华南广州地区早古生代陆内花岗岩：变质沉积为主的地壳源的部分熔融

摘要 华南地块早古生代花岗岩的形成是否与陆内造山过程或大洋俯冲有关仍存在争议。在这里，我们展示了全岩主要元素、微量元素和 Sr Nd 同位素数据，以及二次离子质谱和激光烧蚀-电感耦合等离子体-质谱锆石 U Pb 年代学和 Hf O 同位素数据，来自黑云母、两个-华南广州市白云山和帽峰山地区的云母和白云母花岗岩。锆石 U Pb 年龄表明这些岩石形成于早古生代（446-438 Ma）。这些含白云母和黑云母的花岗岩具有高 SiO2 (69.0–80.4 wt%) 和 K2O (3.19–5.32 wt%) 含量，以及低 MgO (0.46–1.17 wt%) 含量。花岗岩富含铷、钍、铀和铅，而贫钡、锶、铌和钛。白云山白云母花岗岩和帽峰山黑云母花岗岩中轻稀土元素[LREEs; (La/Yb)CN = 2.27–15.1] 有轻微到明显的负 Eu 异常 (Eu/Eu* = 0.27–0.72)，而白云山二云母花岗岩中轻稀土元素显着富集 [(La/Yb)CN = 19.6 –32.1] 具有中等的负 Eu 异常（Eu/Eu* = 0.42–0.58）。这些含白云母和黑云母的花岗岩富含全岩 Nd 和锆石 Hf 同位素组成（eNd(t) = -12.1 至 -7.6；eHf(t) = -11.4 至 -0.8）和高锆石 δ18O 值（8.5 ‰–10.0‰）。我们认为白云山花岗岩是由变沉积岩部分熔融形成的，因为它们含有原生白云母，锆石 δ18O 值很高。帽峰山花岗岩是由含有变质沉积岩和次生角闪岩的混合地壳源部分熔融形成的，因为它们具有较高的锆石δ18O值、可变的全岩SiO2含量以及与在I型和S型岩浆中结晶的黑云母相似. 这些花岗岩与武夷-云开造山带中广泛分布的早古生代S型花岗岩一起分布在广阔的区域而不是狭窄的带中。此外，华南地块早古生代S型花岗岩总体上不表现出由东向西或由南向北的年轻化趋势。此外，白云山-毛峰山花岗岩的地球化学特征类似于同碰撞或碰撞后花岗岩，不同于火山弧花岗岩。