The Nagercoil block is the southernmost crustal segment of the Southern Granulite Terrane (SGT) in India and is mainly composed of charnockitic rocks and felsic gneisses (charnockite suite). In this study, we present petrologic, geochemical, zircon U–Pb, REE, and Hf isotopic studies on the charnockites and leucogneiss from the Nagercoil block. Based on field investigations and petrologic studies, the charnockites can be divided into garnet-bearing and garnet-absent anhydrous granulite facies rocks with orthopyroxene. The charnockites and leucogneiss show transition from adakites to non-adakitic magmatic rocks, with enrichment in LREEs (light rare earth elements) and LILEs (large ion lithophile elements), and depletion in HREEs (heavy rare earth elements) and HFSEs (high field strength elements). Some of the charnockites and the leucogneiss show typical HSA (high silica adakite) characters, (high SiO₂, Al₂O₃, Ba–Sr, La/Yb, and Sr/Y). The HSA is considered to have formed from the interaction of slab derived melts and peridotitic mantle wedge. The high Ba–Sr features were possibly inherited from subducted oceanic crust melting under the high thermal gradient condition during Precambrian. The magmas were underplated and subjected to fractional crystallization. Zircon grains from the charnockite and leucogneiss show zoned magmatic cores surrounded by structureless metamorphic rims. Magmatic zircon grains from the charnockites show ages ranging from 1983 ± 8.8 Ma to 2046 ± 14 Ma, and the metamorphic domains show an age range of 502 ± 14 Ma to 547 ± 8.7 Ma. Zircon from the leucogneiss yielded magmatic and metamorphic ages of 1860 ± 20 Ma and 575.6 ± 8.8 Ma. Both charnockites and leucogneiss show two prominent age peaks at 1987 Ma and 568 Ma. The REE data of the zircon grains show LREE depletion and HREE enrichment, with the metamorphic grains showing more depletion in HREE. Zircon Hf isotopic data of the magmatic cores of zircon grains from the charnockite yielded ε_Hf(t) values from −1.17 to 0.46 with T_DM and TC DM and age peaks at 2392 and 2638 Ma, suggesting Neoarchean to Paleoproterozoic juvenile sources. We suggest that the high Ba–Sr adakitic charnockite suite from the Nagercoil block formed in a Paleoproterozoic magmatic arc setting during the assembly of the Columbia supercontinent, and underwent high-grade metamorphism associated with the amalgamation of the Gondwana supercontinent during the late Neoproterozoic–Cambrian. Our study provides new insights into the vestiges of Columbia fragments within the Gondwana assembly with two distinct cycles of crustal evolution.

Nagercoil区块是印度南部Granulite Terrane（SGT）的最南端地壳部分，主要由菱镁矿岩和长英质片麻岩（菱镁矿组）组成。在这项研究中，我们介绍了对Nagercoil块体中的霞长石和白垩纪的岩石学，地球化学，锆石U-Pb，REE和Hf同位素研究。根据野外调查和岩石学研究，将菱锰矿分为含邻石榴石的石榴石和不含石榴石的无水粒状岩相岩。菱锰矿和白垩纪岩体从Adakite向非Adakitic岩浆岩过渡，富集了LREEs（轻稀土元素）和LILEs（大离子锂亲石元素），而HREEs（重稀土元素）和HFSEs（高场强）耗尽元素）。₂，铝₂ O ₃，Ba–Sr，La / Yb和Sr / Y）。HSA被认为是由板坯衍生的熔体和橄榄岩地幔楔的相互作用形成的。在前寒武纪期间，在高热梯度条件下，高Ba-Sr特征可能是由俯冲洋壳融化所继承的。对岩浆进行底层电镀，并进行分步结晶。菱镁矿和白垩纪的锆石颗粒显示出带状的岩浆岩心，周围环绕着无结构的变质边缘。菱镁矿中的岩浆锆石晶粒年龄范围为1983±8.8 Ma至2046±14 Ma，变质域的年龄范围为502±14 Ma至547±8.7 Ma。来自白垩纪的锆石的岩浆和变质年龄为1860±20 Ma和575.6±8.8 Ma。夏诺克岩和白带片岩均在1987 Ma和568 Ma出现两个突出的年龄高峰。锆石颗粒的稀土元素数据显示LREE耗尽和HREE富集，而变质颗粒的HREE消耗更多。夏洛特锆石岩浆岩心的锆石con同位素数据。ε_的Hf（吨）值从-1.17至0.46与Ť _DM和Ť ÇDM和年龄峰在2392和2638马，提示新太古代至古元少年源。我们建议，在哥伦比亚超大陆的组装过程中，在古元古代岩浆弧环境中形成的Nagercoil块中的高Ba-Sr砂质辉长岩组，并在新元古代-寒武纪晚期经历了与冈瓦纳超大陆合并相关的高级变质作用。 。我们的研究提供了两个不同地壳演化周期的冈瓦纳地块内哥伦比亚碎片遗迹的新见解。