高校地质学报2012，Vol.18Issue(1)：41-51,11.
含水大陆下地壳的部分熔融:大别山C型埃达克岩成因探讨
Partial Melting of Hydrous Lower Continental Crust: Discussion on the Petrogenesis of C-Type Adakites From the Dabie Orogen
摘要
Abstract
On the basis of continental composition, principles of partial melting of hydrous mafic rocks, and the published experimental data, we discuss the partial melting mechanism of lower continental crust. By comparing the Dabie C-rype adakites with experimental melts, we provide constraints on the magma source, melting conditions (temperature and pressure), and the melting degree. Overall, the lower continental crust of East China, including the Dabie orogen, is basic to intermediate (50～60 % SiO2) and slightly hydrous. Thus, fluid-absent dehydration melting of hydrous minerals is a major mechanism for the lower continental crust generating hydrous felsic melts and anhydrous residues. More than ～20% garnet in the residues could be formed by partial melting of amphibolite at a medium pressure (1.0～1.2 Gpa, equivalent to 35～40 km), which is essential to makethe coexisting melt to possess adakitic signatures (especially low Y, high Sr/Y and La/Yb). Based on a H2O activity model and solidus of metamafic rocks, dehydration partial melting, which occurs at ～950 ℃, could lead to a maximum melting proportion of 15-20%, meeting the requirement for efficient melt segregation. The Dabie C-type adakitic rocks, are of high-K calc-alkaline series (3.5～5% K2O), and it is very clear, when compared with experimental melts, that they cannot be derived from low-K protoliths with reasonable melting degrees. In the light of the highly incompatible behavior of K in the course of partial melting, our calculation based on the partition coefficients between melt and possible residues indicates that high-K calc-alkaline melts similar to the Dabie C-type adakitic rocks can be generated by 15～20% (mass basis) partial melting of amphibolites with～l wt% K2O.关键词
C型埃达克岩/大陆下地壳/角闪岩/部分熔融/大别山Key words
C-type adakite/ lower continental crust/ amphibolite/ partial melting/ Dabie orogen分类
天文与地球科学引用本文复制引用
张超,马昌前,Francois HOLTZ..含水大陆下地壳的部分熔融:大别山C型埃达克岩成因探讨[J].高校地质学报,2012,18(1):41-51,11.基金项目
国家建设高水平大学公派研究生项目 （）
德意志学术交流中心(DAAD)国际博士生项目 （DAAD）
中国地质大学(武汉)优秀博士学位论文创新基金 （武汉）
国家自然科学基金重点项目(90814004,40334037) （90814004,40334037）
中国地质调查局工作项目(1212011121270)联合资助 （1212011121270）
