大别山北部条带状片麻岩及其伴生的斜长角闪岩的裂谷成因:岩石地球化学论据  

RIFL GENESIS OF BANDED GNEISSES AND ASSOCIATED AMPHIBOLITESFROM MORTHERN DABIE MOUNTAINS: EVIDENCE FROM PETROLOGIC GEOCHEMISTRY

作　　者：刘贻灿[1] 徐树桐[2] 李曙光[1] 陈冠宝[2] 

机构地区：[1]中国科学技术大学地球和空间科学学院,安徽合肥230026 [2]安徽省地质调查院,安徽合肥230001

出　　处：《矿物岩石》2004年第1期1-4,共4页Mineralogy and Petrology

基　　金：国家973专项(大陆板块会聚边界的地幔动力学与现代地壳作用);国家自然科学基金项目(编号40172079)

摘　　要：　岩石地球化学特征表明:大别山北部条带状片麻岩及其伴生的斜长角闪岩的原岩分别是碱性的I型花岗岩类和碱性的玄武岩,属于一套双峰式火山岩。Hf Rb/10 Ta×10和Hf Rb/10 Ta×30判别图解指示条带状片麻岩原岩属于板内花岗岩;斜长角闪岩的87Sr/86Sr=0.722345,143Nd/144Nd=0.511919,εNd(0)=-14.0,fSm/Nd=-0.15和εNd(800Ma)=-11.0,具有大陆玄武岩特征;同时,206Pb/204Pb=18.10,207Pb/204Pb=15.41和208Pb/204Pb=38.16,也接近于陆壳成分而且更接近下地壳成分,它的原岩有可能来源于古老的陆壳,推测其原岩形成时,其所在地区已经发育了比较成熟的大陆地壳。因此,它们应形成于新元古代(大约700Ma～800Ma左右)由扬子大陆发生裂解而形成的裂谷环境中。Petrologic geochemistry of the banded gneisses and associated amphibolites from northern Dabie Mountains suggests that their protoliths were alkaline I-type granitoid and basalt respectively. Hf-Rb/10-Ta×10 and Hf-Rb/10-Ta×30 discrimination of the banded gneisses imply that they were originated from intracontinental granites,^(87)Sr/^(86)Sr=0.722 345,^(143)Nd/^(144)Nd=0.511 919,ε_(Nd)(0)=-14.0,f_(Sm/Nd)=-0.15 and ε_(Nd)(800 Ma)=-11.0 from the amphibolites indicate that they are characteristic of the continental basalt.The Pb isotope data of ^(206)Pb/^(204)Pb=(18.10),^(207)Pb/^(204)Pb=15.41 and ^(208)Pb/^(204)Pb=38.16 also show that their compositions are close to that of continental crust and even to that of the lower crust.Therefore, the banded gneisses and associated amphibolites from northern Dabie Mountains under the rift setting on the Yangtze continent plate during the Proterozoic (or 700 Ma～800 Ma).

关 键 词：斜长角闪岩 条带状片麻岩 岩石地球化学 裂谷 大别山 

分 类 号：P588.345[天文地球—岩石学]