The Xinxing granitic pluton is a large batholith cropping out in southern South China with its long axis parallel to the regional NE–trending faults. We conduct the first comprehensive study of zircon laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) U–Pb chronology and trace element chemistry, rock-forming mineral chemistry and whole-rock element and Sr–Nd isotope geochemistry for this pluton. Our new data indicate that the pluton was emplaced during the interval 234–232 Ma, i.e. early Indosinian rather than late Mesozoic as previously considered. The southern pluton consists of syenogranite and monzogranite, which are composed of K-feldspar, oligoclase, quartz and ferri-biotite. The northern pluton consists of monzogranite and granodiorite, which are composed of andesine, K-feldspar, quartz and magnesio-biotite. The southern granites have high SiO 2 contents (72.5–79.2 wt%) and high FeO T /(FeO T + MgO) (T refers to total) ratios with low Mg# [atomic Mg/(Mg + Fe T )]. They are enriched in rare earth elements and depleted in Sr and Ba with Zr + Y + Ce + Nb >350 ppm and 10,000 × Ga/Al >2.6. Their initial magma temperatures are unusually high (>886 °C). All those features strongly suggest an affinity with A-type granites. The northern granites have lower SiO 2 contents (63.4–72.5 wt%) and lower FeO T /(FeO T + MgO) ratios as well as higher Mg# than the southern granites. They are also enriched in rare earth elements and depleted in Sr and Ba, with high Ga/Al ratios and high Zr + Y + Ce + Nb contents. Geochemical data and major element modeling confirm that the southern A-type granites were generated by the moderate degree (~49%) shallow (ca. 15–20 km depth) dehydration melting of the early Paleozoic granitoids triggered by intraplating of basaltic magmas. Subsequent moderate degree (~57%) fractionation of such crustal melts produced the more felsic granites in the southern pluton, whereas subsequent mixing of such crustal melts with about 8 to 48% intraplated mafic magmas generated the less felsic granites in the northern pluton. Interaction of mafic magmas with A-type crustal melts causes the northern granites to lose some diagnostic geochemical features of A-type granites such as high FeO T /(FeO T + MgO) ratios and to be transitional towards I-type granites. We further suggest their origin to have been related to the transtension of the regional NE–trending strike-slip faults coupled with the early Indosinian continental collisions.

中文翻译：

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华南南部新兴岩体早印支期A型花岗岩的成因及构造意义

新兴花岗质岩体是华南南部出露的大型基岩，其长轴平行于区域NE向断裂。我们对锆石激光烧蚀-电感耦合等离子体-质谱 (LA-ICP-MS) U-Pb 年代学和微量元素化学、造岩矿物化学和全岩元素以及 Sr-Nd 同位素地球化学进行了首次综合研究这个冥王星。我们的新数据表明，岩体是在 234-232 Ma 之间就位的，即印支早期而不是之前考虑的中生代晚期。南部岩体由正长花岗岩和二长花岗岩组成，由钾长石、寡长石、石英和铁黑云母组成。北部岩体由二长花岗岩和花岗闪长岩组成，由中长石、钾长石、石英和镁黑云母组成。南部花岗岩具有高 SiO 2 含量 (72.5-79.2 wt%) 和高 FeO T / (FeO T + MgO)（T 指总）比率和低 Mg # [原子 Mg / (Mg + Fe T)]。它们富含稀土元素，贫 Sr 和 Ba，Zr + Y + Ce + Nb> 350 ppm 和 10,000 × Ga / Al> 2.6。它们的初始岩浆温度异常高（> 886°C）。所有这些特征强烈表明与 A 型花岗岩的亲和力。与南部花岗岩相比，北部花岗岩具有较低的 SiO 2 含量 (63.4-72.5 wt%) 和较低的 FeO T / (FeO T + MgO) 比率以及较高的 Mg #。它们还富含稀土元素并贫 Sr 和 Ba，具有高 Ga / Al 比率和高 Zr + Y + Ce + Nb 含量。地球化学数据和主要元素模型证实，南部 A 型花岗岩是由中等程度（~ 49%）浅层（约 49%）形成的。15-20 公里深度）由玄武质岩浆内侵引发的早古生代花岗岩的脱水熔融。随后这种地壳熔体的中等程度（~57%）分馏在南部岩体中产生了更多的长英质花岗岩，而随后这种地壳熔体与约 8% 至 48% 的板内基性岩浆混合，在北部岩体中产生了较少的长英质花岗岩。基性岩浆与 A 型地壳熔体的相互作用导致北部花岗岩失去了 A 型花岗岩的一些诊断地球化学特征，如高 FeO T / (FeO T + MgO) 比值，并向 I 型花岗岩过渡。我们进一步认为它们的起源与区域 NE 走向的走滑断层的传播以及早期印支大陆碰撞有关。