地质科学Issue(3)：653-678,26.
七宝山早白垩世火山岩地球化学特征及其构造意义
Geochemistry of Early Cretaceous volcanic rocks from the Qibaoshan area and their tectonic implications
摘要
Abstract
Late Mesozoic volcanic rocks from the Qibaoshan area,called the Bamudi Formations,occur along the eastern margin of the Cuanshuai Basin in the Shandong segment of the Tan-Lu fault zone. Two volcanic-rock samples yielded LA-ICP MS 206Pb/238U zircon weighted mean ages were 120. 1±0. 6 Ma and 118. 5 ±1. 1 Ma respectively, belonging to the Early Cretaceous. These rocks are rich in alkali and Na2O concentrations with variable SiO2 contents (56. 02% -66.45%). They are to calc-alkaline to alkaline series with an average cr of 4. 01 and most of them plot in the trachyte field with minor trachyandesite. Compared with adakites in studied area, these volcanic rocks have lower MgO contents (0. 52% ~ 2. 02% ) and Mg# (16 ~ 42) except TYS49 samples. The Qibaoshan volcanic rocks are enriched in LILEs(e. G. Rb,Ba,Sr)and LREEs and depleted in HFSEs(Nb,Ta,Ti)and HREEs.with weak negative Eu anomalies(average = 0. 85). They have enriched Sr-Nd-Pb compositions (Isr = 0. 708 4 ~ 0. 709 8, εNd (t) = -20.4 ~ -16. 2, 206Pb/204Pb(t) = 16.44 ~ 17.19, 207Pb/204Pb (t) = 15. 39 ~ 15.47, 208Pb/204Pb (t) = 36. 82 ~ 37. 65). The geochemical characteristics of these rocks indicate that the primitive magma was dominantly derived from the lower crust of the North China Craton ( NCC ) with an involvement of materials from the lithospheric mantle and asthenosphere. The Qibaoshan volcanic rocks framed in a crust extensional setting. The asthenosphere upwelling heated lithosphere and induced partial melting of lower crust, produced lithospheric mantle-derived and crustal-derived magmas. They mixed and solidified to form the Qibaoshan volcanic rocks. This paper further suggest that the Tan-Lu fault zone is an intensive thinning zone,its occurrence and activities provides an inducing and promoting role during the lithosphere thinning and plays an important role in the destruction of the North China Craton.关键词
七宝山/早白垩世/火山岩/地球化学/构造意义Key words
Qibaoshan/ Early Cretaceous/ Volcanic rocks/ Geochemistry/ Tectonic implications分类
天文与地球科学引用本文复制引用
牛漫兰,吴齐,朱光,谢成龙,刘国生,傅朋远,姜伦..七宝山早白垩世火山岩地球化学特征及其构造意义[J].地质科学,2011,(3):653-678,26.基金项目
国家自然科学基金项目(编号:40603010,41072162,90714004)资助. （编号:40603010,41072162,90714004）
