太行山地区中、新生代玄武质岩浆的源区特征与时空演化  

Source characteristics and temporal-spatial evolution of Mesozoic and Cenozoic basaltic magmatism in the Taihang Mountains.

作　　者：汤艳杰[1] 张宏福[1] 英基丰[1] 张瑾[1] 

机构地区：[1]中国科学院地质与地球物理研究所岩石圈演化国家重点实验室,北京100029

出　　处：《岩石学报》2006年第6期1657-1664,共8页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(40225009;40503004);中国科学院知识创新工程项目(KZCX3-SW-135)联合资助成果。

摘　　要：本文总结了太行山地区中生代辉长岩和新生代玄武岩的元素和同位素组成,其组成显示它们的地幔源区存在着明显的差别。新生代玄武岩以碱性玄武岩为主,含有少量橄榄拉斑玄武岩,它们来自软流圈的部分熔融,并伴有少量古老岩石圈地幔组分的加入。相比之下,中生代辉长岩具有明显不同的地球化学特征:SiO_2含量高,LREE和LILE(Ba,Th,U)富集以及HFSE(Nb,Ta,Zr和Ti)亏损,Sr-Nd同位素富集(大多数^(87)Sr/^(86)Sr_i＞0．705,^(143)Nd/^(144)Nd_i＜0．512)、Pb同位素亏损(^(206)Pb/^(204)Pb_i＜17．5,^(207)Pb/^(204)Pb_i＜15．5,^(208)Pb/^(204)Pb_i＜38．0)。这些特征表明中生代辉长岩来源于经过富硅熔体强烈改造的古老岩石圈地幔,这种富集改造过程很可能与华北克拉通内部元古代的俯冲/碰撞事件有关。古老且同位素富集的岩石圈地幔残存至新生代,并被新生代玄武岩携带的地幔橄榄岩捕虏体所记录。A summary of elemental and isotopic compositions of the Mesozoic gabbros and Cenozoic basalts from the Taihang Mountains shows a remarkable difference in their mantle sources. Cenozoic basalts are mainly alkaline basalts with minor olivine tholeiites and originated from partial melting of asthenosphere with some involvements of old subcontinental lithospheric mantle. In contrast, the Mesozoic gabbros are high in SiO2 content, enriched in LREE and LILE （Ba, Th, U） and depleted in HFSE （Nb, Ta, Zr and Ti ）. They are also enriched in Sr-Nd isotopes （most ^87Sr/^86Sri 〉 0. 705, ^143Nd,/^144Ndi 〈 0. 512 ） and depletion in Pb isotopes （^206Pb/^204pbi 〈 17.5, ^207Pb/^204Pbi 〈 15.5, ^208Pb/^204Pbi〈 38.0）. These geochemical features indicate that these Mesozoic gabbros were generated from enriched old lithospheric mantle, which was greatly modified by silicate melt. Such a modification might be related to the Proterozoic subduction/collision during the formation of the Trans-North China Orogen. The old and isotopically enriched lithospheric mantle is existent till the Cenozoic, as recorded in mantle peridotitic xenoliths from Cenozoic basalts of the region.

关 键 词：中生代辉长岩 新生代玄武岩 地幔源区 岩石圈演化 太行山 

分 类 号：P588.124[天文地球—岩石学] P588.145[天文地球—地质学]