Felsic dykes in the Neoproterozoic Nagar Parkar Igneous Complex,SE Sindh,Pakistan: geochemistry and tectonic settings |
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| Authors: | Tahseenullah Khan Mamoru Murata M Qasim Jan Hafiz Ur Rehman Muhammad Zafar Hiroaki Ozawa Anwar Qadir Saqib Mehmood |
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| Institution: | 1.Department of Earth and Environmental Sciences,Bahria University,Islamabad,Pakistan;2.Department of Geosciences, Faculty of Science, Naruto University of Education,National University Corporation,Naruto,Japan;3.National Centre of Excellence in Geology,University of Peshawar and COMSTECH Islamabad,Peshawar,Pakistan;4.Department of Earth and Environmental Science, Faculty of Science,Kagoshima University,Kagoshima,Japan;5.International Cooperation Center for the Teacher Education and Training,Naruto University of Education,Naruto,Japan;6.Department of Geology,Haripur University,Haripur,Pakistan |
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| Abstract: | The Nagar Parkar Igneous Complex consists of Neoproterozoic igneous and metamorphic rocks dissected by mafic, felsic, and rhyolitic dykes. The latter can be classified broadly into porphyritic felsic dykes intruding gray and pink granites at Nagar Parkar and the surrounding areas, and the orthophyric felsic dykes intruding amphibolites, deformed pink granites, and the alkaline mafic dykes in the Dhedvero area, north of Nagar Parkar. The porphyritic felsic dykes are composed of perthites, quartz, and albitic plagioclase whereas the orthopheric felsic dykes contain K-feldspar (dominant), plagioclase, and minor quartz. Geochemically, the porphyritic and orthophyric felsic dykes are subalkaline and alkaline demonstrating post-orogenic A2- and OIB-A1-type characteristic on Nb–Y–Ce and Nb–Y–3Ga ternary plots, respectively. One orthophyric felsic dyke contains normative acmite and sodium metasilicate. This study suggests two distinct tectonic regimes for the origin of the felsic dykes of the area. The porphyritic felsic dykes show similarities with the ~800–700 Ma granites of the area, the rhyolite dykes of the Mount Abu, western Rajasthan in India, and the granites of the Seychelles microcontinent. The orthophyric felsic dykes show chemical resemblance with the Tavidar volcanic suite of western Rajasthan and the Silhouette and North islands of the Seychelles microcontinent. This study confirms spatial and temporal links among the Rodinian fragments exposed in the Nagar Parkar area of Pakistan, western Rajasthan of India, and the Seychelles microcontinent. |
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