The geochemical variations of mid-Cretaceous lavas across western Shandong Province, China and their tectonic implications |
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| Authors: | Jifeng Ying Xinhua Zhou Hongfu Zhang |
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| Institution: | (1) State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, Beijing, 100029, China |
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| Abstract: | Major and trace element as well as Sr–Nd isotopic compositions of mid-Cretaceous lavas across western Shandong Province, China
have been studied. These lavas can be generally divided into southern Shandong group (including Pingyi and Mengyin) and northern
Shandong group (including Laiwu and Zouping) based on their geochemistry. The southern group lavas are characterized by extreme
enrichment in LREE, large ion lithophile elements (LILE), and depletion in HFSE along with EMII-like Sr–Nd isotopic compositions,
suggesting that the crustal involvements play a significant role in their petrogenesis. Comparing studies with Fangcheng basalts
reveal that the Triassic continent–continent collision between the Yangtze craton (YC) and the North China craton (NCC), and
subsequent extensive modification of the sub-continental lithospheric mantle (SCLM) beneath the south part of the NCC by silicic
melts released from the subducted Yangtze lower crust, formed an enriched lithospheric mantle which was the source of the
southern Shandong group lavas. In contrast, the northern Shandong group lavas are mildly enriched in LREE and LILE relative
to those of the southern group lavas. The isotope compositions are also distinctive in that the Sr isotopic ratios are very
low. Available geochemical evidence and comparing studies with spatially closed related mafic intrusions suggest that the
SCLM feeding the northern group lavas seems to be linked to carbonatitic metasomatism and changed modal proportion of phlogopite
and clinopyroxene in the mantle rather than subduction-related modifications. The contrasting geochemical characters of the
mid-Cretaceous lavas across western Shangdong suggest that the SCLM of the NCC is spatially heterogeneous in Mesozoic. |
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| Keywords: | China Shandong Province Geochemistry Mid-Cretaceous Lavas |
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