Dehydration melting of amphibolite at 1.5 GPa and 800–950C:Implications for the Mesozoic potassium-rich adakite in the eastern North China Craton  

作　　者：Zhilin Ye Fang Wan Neng Jiang Jingui Xu Yuanyun Wen Dawei Fan Wenge Zhou 

机构地区：[1]Key Laboratory of High-Temperature and High-Pressure Study of the Earth’s Interior,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang,550081,China [2]University of Chinese Academy of Sciences,Beijing,100049,China [3]Minco International Mining Consulting Ltd.,Beijing,100012,China [4]Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing,100029,China [5]Center for Lunar and Planetary Sciences,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang,550081,China

出　　处：《Geoscience Frontiers》2021年第2期896-906,共11页地学前缘（英文版）

基　　金：the National Natural Science Foundation of China(Grant Nos.41772043 and 41802043);the Chinese Academy of Sciences“Light of West China”Program(Dawei Fan,2017 and Jingui Xu,2019);the Youth Innovation Promotion Association CAS(Dawei Fan,2018434);the Innovation and Entrepreneurship Funding of High-Level Overseas Talents of Guizhou Province(Dawei Fan,[2019]10).

摘　　要：Mesozoic intermediate-felsic magmatic rocks in the eastern North China Craton commonly show geochemical similarity to adakites.However,the lack of direct constraints from partial melting experiments at high pressures and temperatures fuels a debate over the origin of these rocks.In this work,we performed partial melting experiments at 1.5 GPa and 800–950℃on amphibolite samples collected from the vicinity of the Mesozoic potassium-rich adakitic rocks in the Zhangjiakou area,northern margin of the North China Craton.The experimental melts range from granitic to granodioritic compositions,with SiO_(2)=56.4–72.6 wt.%,Al_(2)O_(3)=16.1–19.3 wt.%,FeO^(*)=2.4–9.6 wt.%,MgO=0.3–2.0 wt.%,CaO=0.6–3.8 wt.%,Na_(2)O=4.7–5.3 wt.%,and K_(2)O=2.6–3.9 wt.%,which are in the ranges of the surrounding Mesozoic potassium-rich adakitic rocks,except for the higher Al_(2)O_(3)contents and the data point at 1.5 GPa and 800℃.Trace element compositions of the melts measured by LA-ICP-MS are rich in Sr(849–1067 ppm)and light rare earth elements(LREEs)and poor in Y(<10.4 ppm)and Yb(<0.88 ppm),and have high Sr/Y(102–221)and(La/Yb)n(27–41)ratios and strongly fractionated rare earth element(REE)patterns,whereas no obvious negative Eu anomalies are observed.The geochemical characteristics show overall similarity to the Mesozoic potassium-rich adakitic rocks in the area,especially adakites with low Mg#,again except for the data point at 1.5 GPa and 800℃.The results suggest that partial melting of amphibolite can produce potassium-rich adakitic rocks with low Mg#in the eastern North China Craton under the experimental conditions of 1.5 GPa and 850–950℃.The experimental restites consist of hornblende(Hbl)+plagioclase(Pl)+garnet(Grt)±clinopyroxene(Cpx),a mineral assemblage significantly different from that of the nearby Hannuoba mafic granulite xenoliths which consist of Cpx+orthopyroxene(Opx)+Pl±Grt.Chemically,the experimental restites contain higher Al_(2)O_(3)but lower MgO and CaO than the Hannuoba mafic granulite

关 键 词：AMPHIBOLITE Partial melting Eastern North China Craton Potassium-rich adakitic rocks Hannuoba granulite xenoliths 

分 类 号：P619.211[天文地球—矿床学] P588.3[天文地球—地质学]