Six acidic dykes were discovered surrounding the Laiziling pluton, Xianghualing area, in the western Cathaysia Block, South China. A number of captured zircons are found in two of these acidic dykes. By detailed U–Pb dating, Lu–Hf isotopes and trace-element analysis, we find that these zircons have ages clustered at c. 2.5 Ga. Two acidic dyke samples yielded upper intersection point 206U/238Pb ages of 2505 ± 42 Ma and 2533 ± 22 Ma, and weighted mean 207Pb/206Pb ages of 2500 ± 30 Ma and 2535 ± 16 Ma. The majority of these zircons have high (Sm/La)N, Th/U and low Ce/Ce* ratios, indicating a magmatic origin, but some grains were altered by later hydrothermal fluid. Additionally, the magmatic zircons have high Y, U, heavy rare earth element, Nb and Ta contents, indicating that their host rocks were mainly mafic rocks or trondhjemite–tonalite–granodiorite rock series. Equally, their moderate Y, Yb, Th, Gd and Er contents also indicate that a mafic source formed in a continental volcanic-arc environment. These zircons have positive ϵHf(t) values (2.5–6.9) close to zircons from the depleted mantle, with TDM (2565–2741 Ma) and TDM2 (2608–2864 Ma) ages close to their formation ages, indicating that these zircons originated directly from depleted mantle magma, or juvenile crust derived from the depleted mantle in a very short period. We therefore infer that the Cathaysia Block experienced a crustal growth event at c. 2.5 Ga.

中文翻译：

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华夏地块 2.5 Ga 地壳生长事件：侏罗纪酸性岩脉中捕获锆石的年代学和地球化学证据

华南华夏地块西部香花岭地区来子岭岩体周围发现6条酸性岩脉。在其中两个酸性岩脉中发现了许多捕获的锆石。通过详细的 U-Pb 测年、Lu-Hf 同位素和微量元素分析，我们发现这些锆石的年龄集中在C。2.5 Ga. 两个酸性堤坝样品产生上交点206你/238铅年龄 2505 ± 42 Ma 和 2533 ± 22 Ma，加权平均207铅/206Pb 年龄为 2500 ± 30 Ma 和 2535 ± 16 Ma。这些锆石中的大多数具有高 (Sm/La)ñ、Th/U 和低 Ce/Ce* 比值，表明岩浆起源，但一些颗粒被后来的热液改变。此外，岩浆锆石具有较高的Y、U、重稀土元素、Nb和Ta含量，表明其母岩主要为镁铁质岩或长长花岗岩-闪长岩-花岗闪长岩系列。同样，它们适度的 Y、Yb、Th、Gd 和 Er 含量也表明镁铁质源是在大陆火山弧环境中形成的。这些锆石具有正 ϵ氢氟酸(吨) 值 (2.5–6.9) 接近贫化地幔的锆石，其中吨DM(2565–2741 Ma) 和吨DM2（2608-2864 Ma）年龄接近其形成年龄，表明这些锆石直接起源于贫化地幔岩浆，或在很短的时间内从贫化地幔中衍生出幼壳。因此，我们推断华夏地块在C。2.5 嘎。