Petrogenesis Of Diabase-dykes From Zhongba In Southern Tibet And It's Tectonic Environment Significance

Mafic dikes from Zhongba region in southern Tibet provide important information for the study of Tethys Himalaya and its surrounding area tectonic evolution.In this paper,through field survey of the dyke intrusion horizon,Combining the major and trace elements characteristics of diabase and LA-ICP-MS zircon U-Pb dating analyzed petrogenesis of diabase-dykes and it's tectonic environment significance.Results show,major element is characterized by high TiO₂?2.81³.27%?and Fe₂O₃?10.79¹2.14?,higher P₂O₅?0.32%⁰.38%?and lower MgO?5.11%⁶.71%?.The amount of rare earth elements and fractionation of light and heavey rare earth are very high,enrichment of light rare earth and large ion lithophile elements?LILE??Rb,Ba?,loss of high field strength elements?HFSE??Nb,Ta?,no obvious Eu anomaly.Incompatible elements(?La/Nb?_PM??Th/Nb?_PM?La/Ta?Nb/U?Ce/Pb)indicating Zhongba diabasic-dike suffered some degree of lower crustal contamination.The magma originated from enriched mantle source region composed mainly of garnet and spinel?spinel<garnet?with low degree partial melting?4%10%?.Main elements Characteristics and curves of trace and rare earth from Zhong ba diabasic dike are similar to earliest Early Cretaceous mafic dikes from Gyangze,Kangma,and Cona,which are under the background of stretching tension.LA-ICP-MS zircon U-Pb dating results of diabasic-dike is 129.8±1.3Ma?MSWD=6.7?.From above regional correlation and geochemical discrimination diagram,the article tend to believe earliest Early Cretaceous there are hot spots in the Neo-Tethys ocean basin in Zhong ba.The interaction between hot spots or mantle plume and lithospheric caused mantle-derived magma upwelling and extensive invasion to the Jurassic strata.