Abstract The Kadavur massif-type anorthosite, which intruded the basement of the Madurai Block in southern India, comprises anorthosite, leucogabbro, and (noritic) gabbro with minor Fe-Ti oxide ores. The U-Pb zircon SIMS dating indicates that the magmatism occurred during the Neoproterozoic period (Tonian), i.e., noritic gabbro (790.4 ± 5.1 Ma), gabbro (793.0 ± 4.1 Ma), leucogabbro (784.9 ± 4.1 Ma), and anorthosite (790.7 ± 4.3 Ma). Combined with the published age data from the coeval charnockite and A-type granite, we conclude that the anorthosite-charnockite-rapakivi granite suite was emplaced during ca. 785–805 Ma. In-situ zircon Hf-O isotopic data of the Kadavur gabbros and anorthosite provide insights on the source and evolution of the parental magmas of the massif-type anorthosites. Zircons from the anorthosite are characterized by ancient crustal eHf(T) values (−11.4 to −6.5) and higher δ18O values (5.92 to 6.4‰). In contrast, zircons from the coarse-grained gabbro have relatively primitive eHf(T) values (−6.3 to −2.3) and mantle-like δ18O values (4.86–5.73‰). Moreover, zircons from the noritic gabbro and leucogabbro have eHf(T) values (−11.1 to −3.7) and δ18O values (5.35 to 6.77‰) distributed between those of the anorthosite and coarse-grained gabbro. The new zircon Hf-O data demonstrate that the parental melt of the anorthosite was subjected to crustal contamination during the early evolution stages, producing an evolved magma with crustal isotope and trace element signatures. In contrast, the gabbros show less crustal influence and like to represent original magma source of the Kadavur Complex. The zircon Hf-O isotope compositional array from the primitive gabbros to the more-evolved anorthosite demonstrates that the parental magmas were derived from partial melting of the upper mantle with varying crustal input, which can be up to 30–40% for the anorthosite formation. Contamination of the ponded basaltic magmas by the felsic crust can effectively increase the SiO2, Al2O3, Na2O, and Sr contents in the magmas, which was likely essential for enormous plagioclase fractionation in the massif-type anorthosites.

中文翻译：

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地块型斜长岩地层下地壳-地幔相互作用：来自印度南部新元古代Kadavur复合体锆石U-Pb-Hf-O同位素的新证据

摘要 侵入印度南部马杜赖地块基底的卡达武尔地块型斜长岩由斜长岩、白辉长岩和（蓝长岩）辉长岩和少量铁钛氧化物矿石组成。U-Pb锆石SIMS定年表明岩浆活动发生在新元古代（托尼阶），即紫长岩辉长岩（790.4±5.1 Ma）、辉长岩（793.0±4.1 Ma）、白辉长岩（784.9±4.1 Ma）和斜长岩（ 790.7 ± 4.3 毫安）。结合已发表的来自同时期的 charnockite 和 A 型花岗岩的年龄数据，我们得出结论，斜长岩-charnockite-rapakivi 花岗岩套件在约 785–805 马。Kadavur 辉长岩和斜长岩的原位锆石 Hf-O 同位素数据提供了关于地块型斜长岩母岩浆来源和演化的见解。来自斜长岩的锆石的特征是古代地壳 eHf(T) 值（-11.4 至 -6.5）和更高的 δ18O 值（5.92 至 6.4‰）。相比之下，粗粒辉长岩中的锆石具有相对原始的 eHf(T) 值（-6.3 至 -2.3）和类似地幔的 δ18O 值（4.86-5.73‰）。此外，紫辉长岩和白辉长岩的锆石的 eHf(T) 值（-11.1 至 -3.7）和 δ18O 值（5.35 至 6.77‰）分布在斜长岩和粗粒辉长岩之间。新的锆石 Hf-O 数据表明，斜长岩的母熔体在早期演化阶段受到地壳污染，产生了具有地壳同位素和微量元素特征的演化岩浆。相比之下，辉长岩表现出较少的地壳影响，喜欢代表卡达武尔杂岩体的原始岩浆来源。从原始辉长岩到演化程度更高的斜长岩的锆石 Hf-O 同位素组成排列表明，母岩浆来源于具有不同地壳输入的上地幔部分熔融，斜长岩形成的比例可达 30-40% . 长英质地壳对堆积玄武质岩浆的污染可以有效地增加岩浆中 SiO2、Al2O3、Na2O 和 Sr 的含量，这可能是地块型斜长岩中大量斜长石分馏所必需的。