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Early Cretaceous granitic rocks from the southern Jiaodong Peninsula, eastern China: implications for lithospheric extension

Version 2 2018-06-22, 06:51
Version 1 2018-05-21, 10:28
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posted on 2018-06-22, 06:51 authored by Quanshu Yan, Ian Metcalfe, Xuefa Shi, Pingyang Zhang, Fengchun Li

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).

Funding

This work was supported by the National Programme on Global Change and Air-Sea Interaction (GASI-GEOGE-02), Basic Scientific Fund for National Public Research Institutes of China (2016S01), the NSFC-Shandong Joint Fund for Marine Science Research Centers (U1606401), National Natural Science Foundations of China (Grant Numbers 41776070, 41230960, 41322036), AoShan Talents Program Supported by Qingdao National Laboratory for Marine Science and Technology (Grant Number 2015ASTP-ES16), and Taishan Scholarship from Shandong Province. IM acknowledges support from the Australian Research Council.

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