Assemblages of shoshonitic series,adakites and porphyry Cu-Au deposits in the Luzong volcanic basin:A clue to ridge subduction in Eastern China
We studied on two types of Mesozoic magmatic rocks in Luzong volcanic basin,Nb-enriched shoshonites and adakites in Shaxi.The formation age of Shaxi adakites is 127.6-128.8Ma,later than that of Luzong shonshonites.They have similar characteristics of major elements (SiO2,Al2O3,Fe2O3 contents) and show similar distribution pattern of trace elements (enriched in LILEs and depleted in HFSEs) and REEs (enriched in LREEs and depleted in HREEs,no Eu negative anomaly,flat HREEs pattern).Sr-Nd-Pb and Lu-Hf isotopic compositions of the two types of rocks show a few differences,exhibit MORB and subducting sediments in their source,distinct from adakites/granites derived from LCC of Yangtze craton.The shoshonites have high K2O+Na2O contents and K2O/Na2O ratios,high Nb contents and Nb/Ta ratio (14.99 av.) close to the value of subducting sediments(~14.2),varied Mg#,low Ce/Pb and Sr/La,low Ba/La and varied Th/Yb,suggesting an origin of subducting sediments with oceanic crust compositions.The adakites have high MgO contents,Mg#,Sr contents and S/Y ratios,low (La/Yb)N,decoupling Sr/Y and (La/Yb)N,exhibit of characteristics of slab melting derived adakites.The feature of low Sr/La,Th/Yb ratios and varied Ce/Pb,Ba/La ratios further supports that they are derived from partial melting of oceanic crust with subducting crust added,either.The combination of adakites and Nb-enriched shoshonites support a ridge subduction of paleo-pacific in the LYRB in Mesozoic,and it is probably the cause of large scale of Cu-Au mineralization in LYRB in Mesozoic.
Jiang-Hong Deng Xiao-Yong Yang Shuang Li Wei-Dong Sun
CAS Key Laboratory of Crust-Mantle Materials and Environments,University of Science and Technology o CAS Key Laboratory of Isotope Geochronology and Geochemistry,Guangzhou Institute of Geochemistry,Chi
国际会议
贵阳
英文
273-273
2012-06-16（万方平台首次上网日期，不代表论文的发表时间）