The Lithospheric Thinning Mechanism of North China Craton: Re-Os Isotopic Geochemistry Constraint from the Cretaceous Basic to Intermediate Basic Igneous Rocks in Shandong Province
详细信息
- 责任者：Yang Hongmei (Isotope Geochemistry Lab. ; Wuhan Institute of Geology and Mineral Resources ; Ministry of Land and Resources ; Wuhan 430223 ; China) ; Ling Wenli
- 刊名：Earth Science
- 出版年：2013
- 卷期：38(3)
- 关键词：火成岩 ; igneous rocks ; 地壳减薄 ; crustal thinning ; 山东 ; Shandong Province
- 页码：p.529-540
- 图表：illus., 1 table, 62 refs.
- 分类号：0801
- issnNo：ISSN1000-2383
- isbnNo：CN42-1233/P
摘要
A Re-Os isotopic study of Mesozoic igneous basic to intermediate basic rocks from the western-,eastern-and Yishu fault belt tectonic units in Shandong province,North China Craton(NCC),is carried out.The samples consists of 13 intrusive rocks from the Jinan,Yinan plutons and Guanshui dykes,and 13 volcanic rocks from the Anqiu,Mengyin,Feixian and Fangcheng volcanic successions.Most samples have relatively low Re(0.076×10-9-0.711×10-9)and Os(0.006×10-9-1.030×10-9)contents and high radiogenic 187Os/188Os ratios,with corresponding initial 187Os/188Os ratio of 0.131 6-0.529 1 and γOs(t)of 4.30-319.00,except for rock MAQ0609 of the Anqiu trachyandesite with initial 187Os/188Os ratio of 1.463 and γOs(t)of 1 060.000.The igneous rocks show a wide range of 0.125 to 2.090 Ga in Os isotope modal age(TMA).On the γOs(t)vs.εNd(t)and(87Sr/86Sr)i vs.γOs(t)diagrams,these rocks are positioned between the lithospheric mantle and crust fields,indicative of a crust-mantle interaction-related origin.All but one Guanshui gabbro(MGS0610)and Feixian basalts of the samples display no clear positive correlation between γOs(t)and(La/Ta)N or(Th/Nb)N,which suggests that the role of crustal assimilation or contamination during the magma ascending was insignificant.Compared with the Paleozoic mantle xenoliths,these mantle-derived rocks have evidently younger Os modal ages,higher Re/Os and 187Os/188Os ratios.These crustal signs are likely to have been resulted from interactions of partial melts derived from delaminated lower crust rocks with ambient mantle under an upper mantle depth.Besides,on the Re/Yb vs.Yb diagram,samples of the Mengyin andesites and Yinan diorites are plotted between the Mesozoic pyroxene xenoliths and crust components,which may be best explained by mantle source rocks metasomatized by partial melts of delaminated eclogitic lower crust.Furthermore,a Mengyin andesite MMY-12(SiO2=56.4%)has a modal age as old as 2.090 Ga,and high Mg#(64.6)and Os content(0.089×10-9),which provides an additional evidence for lithospheric thinning-related interaction between the delaminated lower crust and the convecting upper mantle.
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