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The 825 Ma Yiyang high-MgO basalts of central South China: Insights from Os-Hf-Nd data
Wu, Tao1,3; Wang, Xuan-Ce2,3; Li, Wu-Xian4; Wilde, Simon A.2; Tian, Liyan5,6; Pang, Chong-Jin7; Li, Jie4
Source PublicationCHEMICAL GEOLOGY

High-MgO basaltic lavas, including komatiites and picrites, have long been used as probes of both the chemical and thermal evolution of the mantle through time. The ca. 825 Ma Yiyang high-MgO basalts in the central South China Block (SCB) were considered to be the first evidence for > 1500 degrees C mantle melts by a Rodinian mantle plume. However, later studies proposed that they may have been generated within an arc setting and can be classified as boninites. Here we present a comprehensive Os-Hf-Nd isotopic study of the Yiyang basalts. The Yiyang basalts have high MgO ( > 10%), Ni ( > 182 ppm), Cr ( > 667 ppm) and Os contents (mostly > 0.3 ppb) with radiogenic Os isotopes ((Os-187/Os-188)(i) = 0.134 to 0.282). They have relatively uniform whole-rock Nd and Hf isotopes with epsilon(Nd)(t) and epsilon(Hf)(t) values ranging from -3.7 to -1.3 and from + 2.9 to + 4.3, respectively. Our new data indicate that although crustal assimilation and fractional crystallization (AFC) may have played a role in the geochemical diversity of the Yiyang basalts, the enrichment in light rare earth elements (LREE) and large-ion lithophile elements (LILE) relative to high field strength elements (HSFE) most likely are features of the primary magma. The Yiyang high-MgO basalts, along with contemporary high-MgO basalts in the central SCB, have lower SiO2 contents, and Al2O3/TiO2 ratios, but higher TiO2, Zr, Nb, and Nd contents and Th/U ratios than typical boninites. The presence of negative Ba anomalies and depletion in middle REE (MREE) to heavy REE (HREE) in these high-MgO basaltic rocks are also distinct from what is observed in typical boninites. Therefore, the primary magma of the Yiyang basalts had similar whole-rock geochemical compositions to that of komatiites and plume-derived basalts. Their decoupled Hf-Nd isotopes indicate that recycled oceanic sediments may have been incorporated into their source. They have primitive mantle-like Al2O3/TiO2 ratios (21 - 23) and flat HREE patterns. However, unlike other Al-undepleted or Munro-type komatiites, their mantle source did not undergo earlier melting events. Our new results support the view that the Yiyang basalts are komatiitic and not boninitic, and that they were likely derived from a Rodinian mantle plume.

KeywordNeoproterozoic Komatiitic Basalts Plume-derived Magma Recycled Sediments South China Block Rodinia
Indexed BySCI
Funding OrganizationAustralian Research Council (ARC) ; National Natural Science Foundation of China (NNSFC)
Funding ProjectAustralian Research Council (ARC)[FT140100826] ; National Natural Science Foundation of China (NNSFC)[41373020] ; National Natural Science Foundation of China (NNSFC)[41702047]
WOS KeywordMid-atlantic Ridge ; Large Igneous Province ; Carius Tube Digestion ; Re-os ; Volcanic-rocks ; Yangtze Block ; Isotope Systematics ; Lu-hf ; Trace-element ; Mantle Plume
WOS Research AreaGeochemistry & Geophysics
WOS SubjectGeochemistry & Geophysics
WOS IDWOS:000450330000009
Citation statistics
Cited Times:4[WOS]   [WOS Record]     [Related Records in WOS]
Document Type期刊论文
Corresponding AuthorWang, Xuan-Ce
Affiliation1.Zhejiang Univ, Ocean Coll, 1 Zheda Rd, Zhoushan 316021, Peoples R China
2.Changan Univ, Sch Earth Sci & Resources, Xian 710054, Shaanxi, Peoples R China
3.Curtin Univ, Dept Appl Geol, Inst Geosci Res, GPO Box U1987, Perth, WA 6845, Australia
4.Chinese Acad Sci, Guangzhou Inst Geochem, State Key Lab Isotope Geochem, Guangzhou 510640, Guangdong, Peoples R China
5.Chinese Acad Sci, Inst Deep Sea Sci & Engn, Sanya 572000, Peoples R China
6.Qingdao Natl Lab Marine Sci & Technol, Lab Marine Geol, Qingdao 266061, Peoples R China
7.Guilin Univ Technol, Coll Earth Sci, Collaborat Innovat Ctr Explorat Hidden Nonferrous, Guilin 541004, Peoples R China
Recommended Citation
GB/T 7714
Wu, Tao,Wang, Xuan-Ce,Li, Wu-Xian,et al. The 825 Ma Yiyang high-MgO basalts of central South China: Insights from Os-Hf-Nd data[J]. CHEMICAL GEOLOGY,2018,502(1):107-121.
APA Wu, Tao.,Wang, Xuan-Ce.,Li, Wu-Xian.,Wilde, Simon A..,Tian, Liyan.,...&Li, Jie.(2018).The 825 Ma Yiyang high-MgO basalts of central South China: Insights from Os-Hf-Nd data.CHEMICAL GEOLOGY,502(1),107-121.
MLA Wu, Tao,et al."The 825 Ma Yiyang high-MgO basalts of central South China: Insights from Os-Hf-Nd data".CHEMICAL GEOLOGY 502.1(2018):107-121.
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