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Geochemistry of the Cenozoic Potassic Volcanic Rocks in the West Kunlun Mountains and Constraints on Their Sources

Acta Geologica Sinica(English Edition) 2004年第4期78卷 912-920页

作者： ZHANGZhaochong XIAOXuchang WANGJun WANGYong LUOZhaohua InstituteofGeology ChineseAcademyofGeologicalSciencesBeijing100037 InstituteofGeology ChineseAcademyofGeologicalSciencesBeijing100037／／ChinaUniversityofGeosciencesBeijing100087 ChinaUniversityofGeosciences Beijing100087

The geochemical characteristics of the Cenozoic volcanic rocks from the north Pulu, east Pulu and Dahongliutan regions in the west Kunlun Mountains are somewhat similar as a whole. However, the volcanic rocks from the Dahongliutan region in the south belt are geochemically distinguished from those in the Pulu region (including the north and east Pulu) of the north belt. The volcanic rocks of the Dahongliutan region are characterized by relatively low TiO2 abundance, but more enrichment in alkali, much more enrichment in light rare earth elements and large ion lithosphile elements than those from the Pulu region. Compared with the Pulu region, volcanic rocks from the Dahongliutan region have relatively low 87Sr/86Sr ratios, and high εNd, 207Pb/204Pb and 208Pb/204Pb. Their trace elements and isotopic data suggest that they were derived from lithospheric mantle, consisting of biotite- and hornblende-bearing garnet lherzolite, which had undertaken metasomatism and enrichment. On the primitive mantle-normalized patterns, they display remarkably negative Nb and Ta anomalies, indicating the presence of early-stage subducted oceanic crust. The metasomatism and enrichment resulted from the fluid released from the crustal materials enclosed in the source region in response to the uplift of asthenospheric mantle. Based on the previous experiments it can be inferred that the thickness of the lithosphere ranges from 75 to 100 km prior to the generation of the magmas. However, the south belt differs from the north one by its thicker lithosphere and lower degree of partial melting. The different thickness of the lithosphere gives rise to corresponding variation of the degree of crustal contamination. The volcanic rocks in the south belt are much more influenced by crustal contamination. In view of the tectonic setting, the generation of potassic magmas is linked with the uplift of asthenosphere resulted from large-scale thinning of the lithosphere after the collision of Indian and

关键词： potassic magma lithospheric mantle asthenospheric mantle metasomatism west Kunlun Mountains

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Sources and Petrogenesis of Late Triassic Dolerite Dikes in the Liaodong Peninsula:Implications for Post-collisional Lithosphere Thinning of the Eastern North China Craton

Sources and Petrogenesis of Late Triassic Dolerite Dikes in ...

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中国科学院地质与地球物理研究所2007学术年会

作者： SIMON A.WILDE DEPARTMENT OF APPLIED GEOLOGY CURTIN UNIVERSITY OF TECHNOLOGY.PO BOX U1987 PERTHWA 6845.AUSTRALIA

A combination of major and trace element,whole-rock Sr,Nd and Hf isotope,and zircon U-Pb isotopic data are reported for a suite of dolerite dikes from the Liaodong Peninsula in the northeastern North China *** study aimed to investigate the source,petrogenesis and tectonic setting of the *** high-resolution ion microprobe U-Pb zircon analyses yield a Late Triassic emplacement age of～213 Ma for these dikes,post-dating the collision between the North China and Yangtze cratons and consequent ultrahigh-pressure *** geochemical groups of dikes have been identified in the Liaodong Peninsula based on their geochemical and Sr-Nd-Hf isotope ***Ⅰdikes are tholeiitic,with high TiO and total FeO and low MgO contents, absent to weak negative Nb and Ta anomalies,variable (Sr/Sr)(0.7060-0.7153),ε(t)(-0.8 to -6.5) andε

关键词： mafic dike asthenospheric mantle lithosphenc mantle delamination North China Craton

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