The Petrogeochemistry And Petrogenesis Of Mafic Dikes In Qingdao And Its Adjacent Areas

Qingdao lies in the joint of eastern Jiaonan lift and Jiaolai basin.It is of importantgeological significance for its particular tectonic settings,to discussing the petrologicalgeochemistry of Mafic dikes (lamprophyres) in this area and rebuilding regionalgeological evolution.This paper reports the result of geochemistry data of typical samples from thearea and adjacent districts using the technology of thin section and polarizationmicro-image analysis,bulk rocks chemistry analysis,ICP-AES,ICP-MS and EPMA.The results show that the area is divided into two basic dykes that named Spessartiteand Kersantite,and the Spessartite majority. The rocks are varying degrees ofweathering and alteration.Hornblende and biotite are the basic dark phenocrysts of these Mafic dikes(lamprophyres),which occurred the different degrees of alteration and the alterationproducts are chlorite and magnetite.There is culour zone in some phenocrysts ofbiotite,which shows that there is fast crystallization in the magma.Spessartite andKersantite are alkaline series in this area, and their REE distribution generally showeda rightist mode,heavy obvious fractionation,light REE but LREE enrichment, andHREE relative loss, and LREE distribution changes, and HREE is relatively flat.Andthere is noδCe andδEu.This paper shows that, the Mafic dikes (lamprophyres) are the products of thelower degrees of partial melting of mantle magma.And diagenetic process dominatedfractional crystallization of hornblende, biotite and plagioclase.These rocks areFormed after the emplacement of granitic rocks of Laoshan stage in the the lateYanshan and the role of the massive volcanic eruptions and magma emplacement withtension to upper mantle,which makes partial melt of upper mantle and rise along thetectonic fracture, widely formed the lamprophyre.