南印度麻粒岩地體(SGT)富含斜方輝石(orthopyroxene)的高級變質岩地體，其構造複雜由多個剪切帶構成和區分，可細分為3塊(Nilgiri–Namakkal Block、Madurai Block、Trivandrum Block)，本研究區位於Nilgiri–Namakkal Block。根據鋯石鈾鉛定年結果，得到了3個樣本的變質年齡分別為825±110為百萬年、717±77百萬年、545.8±6.8百萬年，而磷灰石鈾鉛定年測得的樣本變質年齡為509.7±9.9 百萬年，顯示在新元古代有變質作用。透過結合分析εHf(t) vs 鈾鉛年齡和TDM1模型年齡得出在約28~25億年前有新生岩漿來源的地殼增生，而約5億年前有古老大陸地殼的參與。大離子親石元素(LILE，Ba、K、Pb)為富集，高場強元素(HFSE，Nb、Ta、Ti)虧損為隱沒帶的特徵，地球化學數據圖證實為具大陸弧構造環境特徵。球粒隕石標準化的稀土元素（REE）分布圖中重稀土元素的走勢平坦。本文將鈾鉛定年、鋯石鎦鉿同位素、陰極發光影像、主微量元素地球化學分析之結果來進行綜合性討論。

The Southern Granulite Terrane (SGT) in South India is a high-grade metamorphic region rich in orthopyroxene. Its structure is complex, with many shear zones that divide it into different crustal blocks. It could be divided into three main blocks: the Nilgiri–Namakkal Block, the Madurai Block, and the Trivandrum Block. This study focuses on the Nilgiri–Namakkal Block. Zircon U–Pb dating shows that three samples have metamorphic ages of 825 ± 110 Ma, 717 ± 77 Ma, and 545.8 ± 6.8 Ma. Apatite U–Pb dating gives a meta-morphic age of 509.7 ± 9.9 Ma, showing that metamorphism happened during the Neo-proterozoic(about 1000–541Ma). Analysis of εHf(t) values together with U–Pb ages and TDM1 model ages suggests that new magmatic crust from the mantle was added between about 2.8 and 2.5 Ga, and that old continental crust was involved around 500 Ma. Geo-chemical data show enrichment in large ion lithophile elements (LILE: Ba, K, Pb) and depletion in high field strength elements (HFSE: Nb, Ta, Ti), which are typical signs of subduction zones. Tectonic discrimination diagrams confirm that the setting was a conti-nental arc. The chondrite-normalized rare earth element (REE) patterns show a flat trend in heavy rare earth elements (HREE). This study combines the results of U–Pb dating, zircon Lu–Hf isotope analysis, CL image, and major and trace element geochemistry for a comprehensive discussion.

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