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首页> 外文期刊>Journal of Asian earth sciences >Arc magmatism in the Delhi Fold Belt: SHRIMP U-Pb zircon ages of granitoids and implications for Neoproterozoic convergent margin tectonics in NW India
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Arc magmatism in the Delhi Fold Belt: SHRIMP U-Pb zircon ages of granitoids and implications for Neoproterozoic convergent margin tectonics in NW India

机译：德里褶皱带的弧岩浆作用：花岗岩类的SHRIMP U-Pb锆石年龄及其对印度西北部新元古代的收敛边缘构造的影响

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摘要

The northwestern region of Peninsular India preserves important records of Precambrian plate tectonics and the role of Indian continent within Proterozoic supercontinents. In this study, we report precise SHRIMP zircon U-Pb ages from granitoids from the Sirohi terrane located along the western fringe of the Delhi Fold Belt in Rajasthan, NW India. The data reveal a range of Neoproterozoic ages from plagiog-ranite of Peshua, foliated granite of Devala, and porphyritic granite of Sai with zircon crystallization from magmas at 1015 ±4.4 Ma, 966.5 + 3.5 and 808 ±3.1 respectively. The plagiogranite shows high SiO_2, Na_2O and extremely low K_2O, Rb, Ba, comparable with typical oceanic plagiogranites. These rocks possess low LREE and HREE concentrations and a relatively flat LREE-HREE slope, a well-developed negative Eu-anomaly and conspicuous Nb and Ti anomalies. Compared to the plagiogranite, the foliated Devala granite shows higher SiO_2 and moderate Na_2O, together with high K_2O and comparatively higher Rb, Ba, Sr and REE, with steep REE profiles and a weak positive Eu anomaly. In contrast to the plagiogranite and foliated granite, the porphrytic Sai granite has comparatively lower SiO_2 moderately higher Na_2O, extremely high Y, Zr, Nb and elevated REE. The geochemical features of the granitoids [HFSE depletion and LILE enrichment, Nb- and Ta-negative anomalies], and their plots in the fields of Volcanic Arc Granites and those from active continental margins in tectonic discrimination diagrams suggest widespread Neoproterozoic arc magmatism with changing magma chemistry in a protracted subduction realm. Our results offer important insights into a long-lived active continental margin in NW India during early and mid Neoproterozoic, consistent with recent similar observations on Cryogenian magmatic arcs widely distributed along the margins of the East African Orogen, and challenge some of the alternate models which link the magmatism to extensional tectonics associated with Rodinia supercontinent breakup.
机译：印度半岛西北部地区保留着前寒武纪板块构造的重要记录，以及印度大陆在元古代超大陆内部的作用。在这项研究中，我们报告了印度西北部拉贾斯坦邦德里折褶带西缘的Sirohi地层的类花岗岩中的类固醇的精确SHRIMP锆石U-Pb年龄。数据揭示了一定范围的新元古代年龄，分别是佩舒亚的斜长花岗岩，德瓦拉的叶状花岗岩和塞伊的斑岩花岗岩，并分别从岩浆中析出了锆石，分别为1015±4.4 Ma，966.5 + 3.5和808±3.1。斜长花岗岩具有较高的SiO_2，Na_2O和极低的K_2O，Rb，Ba，与典型的海洋斜长花岗岩相当。这些岩石的LREE和HREE浓度低，LREE-HREE斜率相对平坦，负Eu异常发育良好，Nb和Ti异常明显。与斜长花岗岩相比，叶面德瓦拉花岗岩具有较高的SiO_2和适度的Na_2O，以及较高的K_2O和相对较高的Rb，Ba，Sr和REE，具有陡峭的REE剖面和弱的Eu正异常。与斜长花岗岩和片状花岗岩相比，杂色赛义花岗岩具有相对较低的SiO_2，适度较高的Na_2O，极高的Y，Zr，Nb和较高的REE。花岗岩的地球化学特征[HFSE耗竭和LILE富集，Nb和Ta负异常]，以及它们在火山弧花岗岩和活动大陆边缘的田块在构造判别图中的分布表明，新元古代弧岩浆活动随岩浆的变化而变化持久俯冲领域的化学反应。我们的结果提供了重要的见解，使人们对新元古代早期和中期印度西北地区一个长期活跃的大陆边缘提供了重要的见解，这与最近关于在东非造山带边缘广泛分布的低温岩浆弧的类似观察结果相符，并对一些替代模式提出了挑战。将岩浆作用与与罗迪尼亚超大陆破裂有关的伸展构造联系起来。

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  • 来源
    《Journal of Asian earth sciences》 |2013年第15期|83-99|共17页
  • 作者

    C.V. Dharma Rao; M. Santosh; Sung Won Kim; Shengrong Li;

  • 作者单位

    National Disaster Management Authority, A-1, Safdarjung Enclave, New Delhi, India;

    Department of Interdisciplinary Science, Faculty of Science, Kochi University, Akebono-cho, Kochi 780-8520, fapan,School of Earth Sciences and Mineral Resources, China University of Geosciences Beijing, 29 Xueyuan Road, Beijing 100083, China;

    Geological Research Division, Korea Institute of Geoscience and Mineral Resources, Daejeon 305-350, South Korea;

    School of Earth Sciences and Mineral Resources, China University of Geosciences Beijing, 29 Xueyuan Road, Beijing 100083, China;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    Sirohi terrane; Aravalli Mobile Belt; South Delhi Terrane; Granites; Zircon U-Pb SHRIMP geochronology; Neoproterozoic;

    机译：Sirohi terrane;Aravalli移动腰带;南德里Terrane;花岗岩Zircon U-Pb SHRIMP年代学;新元古代;

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