| Crust-Mantle Interaction in Dabie Orogenic Belt, Central China： Geochemical Evidence from Late Cretaceous Basalts |
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| 引用本文： | 匡少平,张本仁.Crust-Mantle Interaction in Dabie Orogenic Belt, Central China： Geochemical Evidence from Late Cretaceous Basalts[J].中国地球化学学报,2003,22(3):231-243. |
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| 作者姓名： | 匡少平 张本仁 |
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| 作者单位： | [1]CollegeofChemistryandMoleculeEngineering,QingdaoUniversityofScienceandTechnology,Qingdao266042,China [2]InstituteofGeochemistry,ChinaUniversityofGeosciences,Wuhan430074,China |
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| 基金项目： | theNationalNaturalScienceFoundationofChina(No.49794043)，theOpenLaboratoryofConstitutionInteractionandDynamicsoftheCrust MantleSystemofChina |
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| 摘 要： | It has been suggested that eclogites in the Dabie orogenic belt are exhumation prod-ucts, which had subducted into the deep-seated mantle and undergone ultra-high pressure meta-morphism during the Triassic. But no direct evidence supports this process except the calculated p-T conditions from mineral thermobarometem. The Late Cretaceous basalts studied in the pres-ent paper, however, have provided some geochemical evidence for crust-mantle interaction in the area. These basalts are distributed in Mesozoic faulted basins in central and southern Dabieorogenic belt. Since little obvious contamination from continental crust and differentiation-crys-tallization were observed, it is suggested, based on a study of trace elements, that the basaltsare alkaline and resultant from batch partial melting of the regional mantle rocks, and share thesame or similar geochemical features with respect to their magma source. In the spider diagram normalized by the primitive mantle, trace element geochemistry data show that their mantle sources are enriched in certain elements concentrated in the continental crust, such as Pb, K,Rb and Ba, and slightly depleted in some HFSE such as Hf, P and Nb. Pb-Sr-Nd isotopic com-positions further suggest the mantle is the mixture of depleted mantle (DM) and enriched one(EMI EMII). This interaction can .explain the trace element characteristics of basaltic mag-mas, i.e.,the enrichment of Pb and the depletion of Hf, P and Nb in basalts can be interpre-ted by the blending of the eclogites in DOB (enriched in Pb and depleted in Hf, P and Nd)with the East China depleted mantle (As compared to the primitive mantle, it is neither en-riched in Pb nor depleted in Hf, P and Nb). It is also indicated that the eclogites in the Dahieorogenic belt were surely derived from the exhumation materials, which had delaminated into thedeep-seated mantle. Moreover, the process subsequently resulted in compositional variation of the mantle (especially in trace elements and isotopes) , as revealed by the late mantle-derivedbasalts in the Dabie orogenic belt.
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| 关 键 词： | 微量元素 晚白垩纪 玄武岩 中国 造山运动 地球化学 大别山 铅-钕-锶同位素 |
Crust-mantle interaction in Dabie orogenic belt,central China: Geochemical evidence from Late Cretaceous basalts |
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| Shaoping,Kuang,Benren,Zhang.Crust-mantle interaction in Dabie orogenic belt,central China: Geochemical evidence from Late Cretaceous basalts[J].Chinese Journal of Geochemistry,2003,22(3):231-243. |
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| Authors: | Shaoping Kuang Benren Zhang |
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| Institution: | (1) College of Chemistry and Molecule Engineering, Qingdao University of Science and Technology, 266042 Qingdao, China;(2) Institute of Geochemistry, China University of Geosciences, 430074 Wuhan, China |
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| Abstract: | It has been suggested that eclogites in the Dabie orogenic be lt are exhumation products, which had subducted into the deep-seated mantle and undergone ultra-high pressure metamorphism during the Triassic. But no direct evidence supports this process except the calculated p-T conditions from mineral thermobarometers. The Late Cretaceous basalts studied in the prese nt paper, however, have provided some geochemical evidence for crust-mantle int eraction in the area. These basalts are distributed in Mesozoic faulted basins i n central and southern Dabie orogenic belt. Since little obvious contamination f rom continental crust and differentiation-crystallization were observed, it is suggested, based on a study of trace elements, that the basalts are alkaline and resultant from batch partial melting of the regional mantle rocks, and share th e same or similar geochemical features with respect to their magma source. In th e spider diagram normalized by the primitive mantle, trace element geochemistry data show that their mantle sources are enriched in certain elements concentrate d in the continental crust, such as Pb, K, Rb and Ba, and slightly depleted in s ome HFSE such as Hf, P and Nb. Pb-Sr-Nd isotopic compositions further suggest the mantle is the mixture of depleted mantle and enriched one . T his interaction can explain the trace element characteristics of basaltic magmas , i.e., the enrichment of Pb and the depletion of Hf, P and Nb in basalts can be interpreted by the blending of the eclogites in DOB (enriched in Pb and deplete d in Hf, P and Nd) with the East China depleted mantle (As compared to the primi tive mantle, it is neither enriched in Pb nor depleted in Hf, P and Nb). It is a lso indicated that the eclogites in the Dabie orogenic belt were surely derived from the exhumation materials, which had delaminated into the deep-seated mantl e. Moreover, the process subsequently resulted in compositional variation of the mantle (especially in trace elements and isotopes), as revealed by the late man tle-derived basalts in the Dabie orogenic belt. |
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| Keywords: | trace element Pb-Nd-Sr isotopes enriched mantle eclogite Late C retaceous basalt continental crust Dabie orogenic belt eastern China |
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