Geochemistry and geochronology of the mafic dikes in the Taipusi area, northern margin of North China Craton: Implications for Silurian tectonic evolution of the Central Asian Orogen
Autor: | Jingya Cao, Huan Li, Jing-Hua Wu, Hua Kong, Jillian Aira S. Gabo-Ratio, Xi-Ming Wu, Xiao-Shuang Xi, Qian-Hong Wu, Neng-Li Peng |
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Rok vydání: | 2017 |
Předmět: |
geography
geography.geographical_feature_category Fractional crystallization (geology) 010504 meteorology & atmospheric sciences Volcanic arc Geochemistry 010502 geochemistry & geophysics 01 natural sciences Continental arc Craton Geochronology General Earth and Planetary Sciences Mafic Petrology Geology 0105 earth and related environmental sciences Zircon Petrogenesis |
Zdroj: | Journal of Earth System Science. 126 |
ISSN: | 0973-774X 0253-4126 |
Popis: | The Taipusi area in the Bainaimiao Arc Belt is located in the northern margin of the North China Craton, at the southern margin of the middle Central Asian Orogenic Belt. It is characterized by large exposures of mafic dikes. In this contribution, we present first-hand whole-rock major and trace elements, zircon U–Pb geochronology and in situ trace element geochemistry data for these mafic rocks, which reveal their petrogenesis and tectonic evolution. These mafic dikes display varied compositions of $$\hbox {SiO}_{2}$$ (49.42–54.29%), $$\hbox {TiO}_{2}$$ (0.63–1.08%), $$\hbox {Al}_{2}\hbox {O}_{3}$$ (13.94–17.60%), MgO (4.66–10.51%), $$\hbox {Fe}_{2}\hbox {O}_{3}$$ (1.59–3.07%), FeO (4.60–6.90%), CaO (4.57–8.91%), $$\hbox {Na}_{2}\hbox {O}$$ (1.61–4.26%), $$\hbox {K}_{2}\hbox {O}$$ (0.92–2.54%) and $$\hbox {P}_{2}\hbox {O}_{5}$$ (0.11–0.29%). They are mainly of high-K calc-alkaline series with indistinct Eu anomalies, enriched in large ion lithophile elements (e.g., Rb, Ba, K and Sr) but depleted in high field strength elements (e.g., Nb, P and Ti). These suggest that the crystallizing magma was derived from enriched mantle altered by metasomatic fluids in a subduction setting with imprints of active continental margin features. The high concentrations of Hf, U, Th, Pb and Y, pronounced positive Ce but slightly negative Eu anomalies in zircons indicating that the magma underwent a fractional crystallization and crustal contamination process, with medium to high $$f\hbox {O}_{2}$$ . Zircon LA–ICP–MS U–Pb dating yielded concordant ages of 437–442 Ma for these mafic dikes, which is consistent with the early Paleozoic volcanic arc magmatic activity in the Bainaimiao area. Hence, we conclude that the Bainaimiao Arc Belt is a continental arc formed by the southward subduction of the Paleo-Asian ocean during early Paleozoic. |
Databáze: | OpenAIRE |
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