摘要
来自大别-苏鲁地区晚中生代镁铁质岩石表现出类似于岛弧火山岩的富集大离子亲石元素(LILE)、轻稀土元素(LREE)和相对亏损高场强元素(HFSE)的微量元素地球化学特征,和高度富集的放射成因 Sr(I_(Sr)=0.7065～0.7090)和低放射成因 Nd(ε_(Nd)(t)=-19～-10)的同位素组成;同时它们显示出一定程度的 Nb/Ta 和 Zr/Hf 内部分馏特征,反映其地幔源区曾受到了相对富金红石和 CO_2的熔体交代作用。我们倾向认为深俯冲陆壳在俯冲或折返过程中发生部分熔融作用形成的熔体与地幔反应是形成大别-苏鲁地区造山带富集岩石圈地幔的重要机制。
Late Mesozoic mafic rocks （including mafic dikes/lamprophyres, volcanic rocks and ultramafic to mafic intrusions） from the Dabie-Sulu region show arc-like trace element features （high LILE/HFSE and LREE/HFSE ratios） and have highly radiogenic Sr （Isr = 0.7065 ～ 0.7090） and non-radiogenic Nd （ENd （t） = -19 ～-10） isotopic compositions. Most of the mafic rocks have superchondritic Nb/Ta and Zr/Hf ratios, probably as a consequence of relatively CO2- and rutile- rich melt metasomatism in response to the detachment/breakoff of the Yangtze subducted continental slab. The enriched Sr-Nd isotopic signatures in these mafic rocks suggest that the metasomatic melts were probably derived from the subducted continental crust as evidenced by the high-pressure to uhrahigh-pressure metamorphic assemblage in the orogen. The geochemical and isotopic features of the mafic rocks from the Dabie-Sulu region indicate that interaction between melts derived from the subducted continental slab and the overlying mantle is an important mechanism for LILE and LREE enrichment of the lithospheric mantle beneath the orogen.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2005年第4期1265-1270,共6页
Acta Petrologica Sinica
基金
国家科技部重点基础研究规划项目(G1999075504)
中国科学院知识创新工程项目(GIGCX-04-04)
关键词
俯冲陆壳
镁铁质岩浆作用
岩石圈地慢
晚中生代:北大别
Subducted continental crust, Mafic magmatism, Lithospheric mantle, Late Mesozoic, Northern Dabie terrane
