Petrogenesis of the Late-Triassic alkaline magmatism in the Jiaodong area: Evidence from U-Pb age, Hf-O isotopes of zircons

	Petrogenesis of the Late-Triassic alkaline magmatism in the Jiaodong area: Evidence from U-Pb age, Hf-O isotopes of zircons
	Chen JingZhi; Jiang Neng
刊名	ACTA PETROLOGICA SINICA
	2011-12-01
卷号	27 期号:12 页码:3557-3574
关键词	Oxygen isotopes of zircons Neoproterozoic Late Triassic Alkaline rocks Jiaodong Yangtze crust
ISSN号	1000-0569
文献子类	Article
英文摘要	Post-collisional magmatism contains important information and is a way to understand the nature of sources, background of the Earth' s deep dynamics, tectonic evolution of orogens and mantle-crust interaction during the subduction/collision process. The Late Triassic alkaline magmatism in Weihai, East Shandong (Jiaodong), northern part of the Su-Lu UHP belt, is remarkable because its forming time was close to closure time of the Dabie-Sulu Orogen (240 similar to 225 Ma). The episode of alkaline igneous rocks includes Xingjia alkaline gabbros, Jiazishan syenites, intermediate-mafic dikes and Chashan syeno-granites. Overall, the Late Triassic alkaline rocks are enriched in potassium, LILE and LREE, depleted in HFSE, mafic rocks are mostly enriched in MgO concentrations. Whole-rock Sr-Nd isotope compositions are relatively homogeneous, ((87)Sr/(86)Sr), (212Ma) = 0. 7059 similar to 0. 7074, epsilon(Nd) (212Ma) = - 14. 5 similar to - 16. 5. These chemical and isotopic characteristics indicate that the rocks were originated front an enriched mantle source. Zircon UPb dating results of two intermediate dikes, a syenitic dike and a syeno-granite are obtained, ranging from 210 similar to 216Ma and consistent with previous age data. This indicates that these alkaline rocks formed within a short period. Besides these Triassic ages, there are a group of Neoproterozoic ages (750 similar to 600Ma) in one of the intermediate dikes and a syenitic dike. Hf isotopic compositions of Triassic zircons from one of the intermediate dikes show large variations, (epsilon(Hf)(t) = - 8. 2 similar to - 21. 2); whereas those from other samples exhibit relative similar values (epsilon(Hf)(t) = - 16. 8 similar to - 22. 2). In-situ oxygen isotopes of zircons from samples with Neoproterozoic ages show inhomogeneous characteristics, delta(18)O values of zircons vary from 4. 76 parts per thousand similar to 6. 46 parts per thousand and 1. 12 parts per thousand similar to 6. 74 parts per thousand, respectively, including spots lower than mantle values. Other two samples without Neoproterozoic ages exhibit different oxygen isotopes, which are uniform and have no (18)O depletion, with the two weighted mean delta(18)O values at 6. 88 +/- 0. 18 parts per thousand and 5. 86 +/- 0. 36 parts per thousand for an intermediate dike and a syenitic dike, respectively. Based on the information of Neoproterozoic ages and (18)O depletion of zircons from one of the intermediate dikes and one syenitic dike, We suggest that the subducted Yangtze crust could have been contributed to the Late Triassic magmatism, and the Late Triassic alkaline rocks in this area were derived from partial melting of the subducted Yangtze lithospheric mantle and crust, coupled with subsequent fractionation. This magmatism would have driven by heat brought from asthenosphere upwelling due to the subduction of the South China Block beneath the North China Block during Triassic.
WOS关键词	SULU OROGENIC BELT ; NORTH CHINA CRATON ; ULTRAHIGH-PRESSURE METAMORPHISM ; COESITE-BEARING ZIRCON ; IN-SITU ANALYSIS ; EASTERN CHINA ; DABIE OROGEN ; SOUTH CHINA ; LU-HF ; TECTONIC AFFINITY
WOS研究方向	Geology
语种	英语
出版者	SCIENCE PRESS
WOS记录号	WOS:000299019000005
内容类型	期刊论文
源URL	[http://ir.iggcas.ac.cn/handle/132A11/74708]
专题	中国科学院地质与地球物理研究所
通讯作者	Chen JingZhi
作者单位	Chinese Acad Sci, Inst Geol & Geophys, State Key Lab Lithospher Evolut, Beijing 100029, Peoples R China
推荐引用方式 GB/T 7714	Chen JingZhi,Jiang Neng. Petrogenesis of the Late-Triassic alkaline magmatism in the Jiaodong area: Evidence from U-Pb age, Hf-O isotopes of zircons[J]. ACTA PETROLOGICA SINICA,2011,27(12):3557-3574.
APA	Chen JingZhi,&Jiang Neng.(2011).Petrogenesis of the Late-Triassic alkaline magmatism in the Jiaodong area: Evidence from U-Pb age, Hf-O isotopes of zircons.ACTA PETROLOGICA SINICA,27(12),3557-3574.
MLA	Chen JingZhi,et al."Petrogenesis of the Late-Triassic alkaline magmatism in the Jiaodong area: Evidence from U-Pb age, Hf-O isotopes of zircons".ACTA PETROLOGICA SINICA 27.12(2011):3557-3574.