Geochemical Characteristics and Petrogenesis of Mesozoic Lamprophyres from Zhangjiahe, South Qinling, China
详细信息
- 责任者：Yang Chaogui (State Key Laboratory of Ore Deposit Geochemistry ; Institute of Geochemistry ; Chinese Academy of Scinces ; Guiyang 550002 ; China) ; Liu Shen
- 刊名：Acta Mineralogica Sinica
- 出版年：2013
- 卷期：33(1)
- 页码：p.119-128
- issnNo：ISSN1000-4734
- isbnNo：CN52-1045/P
摘要
Zircon LA-ICP-MS U-Pb analysis yields an age of 225 ±1.5 Ma for lamprophyres from Zhangjiahe,South Qinling,China,indicating that these rocks were formed during late Indochina stage.The contents of SiO2range from 49.31% to 52.87%,with K2O(0.86 %-1.34%) and Na2O(1.87%-2.84%) contents,and Na2O>K2O,indicating calc-alkaline series.High MgO contents range from 13.11% to 15.88% and with Mg# value(77.74-80.44),enrichment in large ion lithosphile elements(LILEs,Rb,Ba,Th,U and Sr),LREE and Pb,depletion in the high field strength elements(HFSEs),such as Nb,Ta,Zr and Hf.The isotopic compositions of the rocks are characterized by high initial87Sr/86Sr ratios(0.714697-0.716534) and negative εNd(t) value(-8.55--9.09),showing that the mantle source of the search area could be the EM2 type mantle.In addition,the lamprophyres have high contents of Cr(1161×10-6- 1597×10-6),Co(60.3×10-6-77.2×10-6) and Ni(220×10-6-366×10-6).Based on above discussions,we proposed that the studied lamprophyres are from an enrichment lithospheric mantle source which is metasomatized by the fluid from the dehydration of the subducted oceanic(Paleo-Mianlue Ocean) sediments.There is fractionation of olivine and clinopyroxene with the primary magma ascent,but without much influence.Tectonic and geodynamic investigation indicates that the studied lamprophyres are formed in a post-orogenic extensional setting after the collision between the Yangtze and South Qinling micro-plate.