Geochemical Characteristics Of Adakitic Porphyries From The Mujicun Deposit Of The Laiyuan Area

Since Mesozoic，North China Craton (NCC) had been re-activated，which resulted inlarge-scale Mesozoic magmatism and development of extensional basins. During theMesozoic re-activation，large-scale Mesozoic granitic intrusions and volcanic rocks withassociated metal deposits，were generated in northern Taihang Mountains，NCC. NNEZijinguan and wulongou deep faults are main structures controlling the Mesozoic magmatismand associated mineralization in the north Taihang Mountains.On the bases of available published data，I studied in detail geological and petrologiccharacteristics of ore-bearing dioritic porphyrites in the Mujicun area. In this paper，we reportresults of major-trace and rare earth elements for the Mujicun porphyrites，and discuss thenature of their magma source and its geodynamic setting. This study gets followingconclusions:(1)Mujicun dioritic porphyrites are sub-volcanic rocks of the Tiaojishan volcanism， andimportant components of the Mujicun volcanic edifice;(2)Comparing with typical adakites, the Mujicun porphyrites display adakiticgeochemical affinities;(3)The Mujicun porphyrites have high K and Mg#values. Considering their cratonsetting，we define the porphyrites as C-adakite;(4)On the base of their geological setting and geochemical data， the adakitic magmawas generated by partial melting of thickened lower crust with garnet amphibolite and/oreclogite. The interaction between hot mantle and adakitic melt from partial melting of thedetached lower crust resulted in elevated contents of Mg#and some compatible traceelements in the porphyrites. On the other hand， high U and Pb contents of the porphyritesindicates contamination of upper crust materials in the rising process of the adakitic magma.