| Autor: |
Yu Zhang, Kefu Yu, Handong Qian |
| Jazyk: |
angličtina |
| Rok vydání: |
2018 |
| Předmět: |
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| Zdroj: |
Minerals, Vol 8, Iss 12, p 575 (2018) |
| Druh dokumentu: |
article |
| ISSN: |
2075-163X |
| DOI: |
10.3390/min8120575 |
| Popis: |
Cenozoic volcanic rocks were recently discovered during full-coring kilometer-scale major scientific drilling in the Xisha Islands, northwestern South China Sea. A systematic mineralogical study of these samples was performed for this paper. The results show that the volcanic rock samples are basaltic pyroclastic. The major elements demonstrate that the clinopyroxenes are diopside and fassaite, which contain high Al2O3 (5.33⁻11.2 wt. %), TiO2 (2.13⁻4.78 wt. %) and CaO (22.5⁻23.7 wt. %). Clinopyroxenes have high REE abundances (104⁻215 ppm) and are strongly enriched in LREE (LREE/HREE = 3.56⁻5.14, La/YbN = 2.61⁻5.1). Large-ion lithophile elements show depleted characteristics. Nb/Ta shows obvious fractionation features: Nb is lightly enriched, relative to primitive mantle, but Ta is heavily depleted, relative to primitive mantle. The parental magma of the basaltic pyroclastic rocks belongs to a silica-undersaturated alkaline series, characterized by a high temperature, low pressure, and low oxygen fugacity. The AlIV content increases with decreasing Si concentration. The Si-unsaturated state causes Si-Al isomorphic replacement during the formation of clinopyroxene. The electric charge imbalance caused by the replacement of Si by Al is mainly compensated by Fe3+. The clinopyroxene discrimination diagrams show that the parental magma formed in an intraplate tectonic setting environment. |
| Databáze: |
Directory of Open Access Journals |
| Externí odkaz: |
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