Early Cretaceous granitic rocks from the southern Jiaodong Peninsula, eastern China: implications for lithospheric extension
Early Cretaceous granitic rocks from the southern Jiaodong Peninsula, eastern China: implications for lithospheric extension
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DOI：
10.1080/00206814.2018.1474388
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发表时间：
2019-05
影响因子：
2.6
通讯作者：
Q. Yan;I. Metcalfe;Xuefa Shi;Pingyang Zhang;Fengchun Li
中科院分区：
文献类型：
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作者：
Q. Yan;I. Metcalfe;Xuefa Shi;Pingyang Zhang;Fengchun Li
摘要测定了胶东半岛南部晚中生代花岗岩的锆石U-Pb年龄、主量元素和微量元素组成以及Sr、Nd、Pb同位素组成。五连山、小竹山和大竹山岩体年龄分别为119.1 ~ 122.3 Ma、114.2 Ma和108.9 Ma。主要元素和微量元素特征表明，这些花岗岩属于伸展环境下形成的碱性a型花岗岩。微量元素组成Ba、K、P、Ti呈强烈的可变负异常，Rb、Th、U、Pb、Ce、Zr、Hf呈正异常，为a型花岗岩的典型特征。Sr和Nd同位素组成变化，87Sr/86Sr(i) = 0.70540 ~ 0.7071, εNd(t) = - 14.5 ~ - 20.9。全岩Pb同位素组成范围为（206Pb/204Pb）t = 15.707 ~ 16.561, (207Pb/204Pb)t = 15.376 ~ 16.462, (208Pb/204Pb)t = 36.324 ~ 37.064。同位素模拟表明其成因介于郯庐大断裂周围新生代玄武岩挖出的地幔与下陆壳之间，可以解释为11-18%的地幔与82-89%的陆壳混合。根据最新整理的资料，我们认为胶东半岛南部及崂山地区在106 ~ 126 Ma期间处于造山带的区域伸展环境。花岗岩可能是晚中生代岩石圈减薄和去克拉通化（即晚中生代克拉通破坏事件）的结果。图形抽象
ABSTRACT Zircon U–Pb ages, major element and trace element compositions, and Sr, Nd, and Pb isotopic compositions for late Mesozoic granites from the southern Jiaodong Peninsula (eastern China) were determined. Ages for the Wulianshan, Xiaozhushan, and Dazhushan plutons are 119.1–122.3, 114.2, and 108.9 Ma, respectively. Major and trace element characteristics show that these granitic rocks belong to alkaline, A-type granites formed in an extensional setting. Trace element compositions show strong, variable negative anomalies in Ba, K, P and Ti, and positive anomalies in Rb, Th, U, Pb, Ce, Zr, and Hf, which are typical characteristics of A-type granites. Variable Sr and Nd isotopic compositions, 87Sr/86Sr(i) = 0.70540–0.7071 and εNd(t) = −14.5 to −20.9. Whole-rock Pb isotopic compositions have the following ranges, (206Pb/204Pb)t = 15.707–16.561, (207Pb/204Pb)t = 15.376–16.462, and (208Pb/204Pb)t = 36.324 to 37.064. Isotopic modelling indicates an origin that lies between mantle tapped by Cenozoic basalts around the Tan-Lu megafault and lower continental crust (LCC), and which can be explained by mixing of 11–18% mantle and 82–89% LCC. Based on new and compiled data, we suggest that the southern Jiaodong Peninsula, as well as the Laoshan area, was in a regional extensional setting of an orogenic belt during 106–126 Ma. The granitic rocks may be the result of late Mesozoic lithospheric thinning and decratonization (i.e. late Mesozoic craton destruction event occurring throughout eastern China). GRAPHICAL ABSTRACT