【作者】 张贵山；

【导师】 胡瑞忠； 温汉捷；

【作者基本信息】 中国科学院研究生院（地球化学研究所） ， 地球化学， 2006， 博士

【摘要】 中国东南部位于亚洲东部大陆边缘的南段，处于扬子地块、印度板块和太平洋板块的中间地区，是中生代太平洋板块与欧亚板块相互作用的活跃区域，一直是地质学家关注的地区。晚中生代古太平洋板块对欧亚大陆的俯冲作用，以及大规模的钙碱性岩浆作用，是中国东南部晚中生代重要的构造-岩浆热事件。有关构造属性转换时间及大陆动力学演化过程、岩石圈伸展与地壳拉张期次和深部地质过程等问题，已成为当前重点研究的课题。基于此，本文以福建晚中生代以来的基性脉岩、基性岩、碱性超基性岩为研究对象，运用岩石学、矿物学、元素地球化学、同位素地球化学及K-Ar同位素测年等研究方法，较为系统地研究了闽西碱性超基性岩、闽北角闪辉长岩、闽西及闽东南基性脉岩的地质地球化学特征，对岩石成因、源区性质、成岩时代等进行了详细的分析，并据此反演福建及中国东南部中生代以来岩石圈伸展和地壳拉张期次、岩石圈地幔属性及演化性质，探讨了中国东南部中生代以来的大陆动力学背景。本次研究中获得以下几点初步认识： 1、闽西柳城新生代玻基辉橄岩呈岩筒侵入的，岩石化学研究表明，玻基辉橄岩属于钠质硅不饱和碱性超基性岩；系统的微量元素研究显示，岩浆在上升侵位过程中未发生明显的地壳混染作用，微量元素、稀土元素的地球化学特征是地幔源区性质的继承，地幔源区来自HIMU型地幔端元，HIMU型地幔端元的形成与大洋俯冲脱水板片及携带的沉积物再循环相关；柳城玻基辉橄岩由低程度部分熔融形成（约2.9％），全岩K-Ar测年为12.6±1.3Ma，为中新世，岩石产出构造背景为陆内裂谷。 2、系统的地质地球化学研究表明，闽北赤门角闪辉长岩为低钾（拉斑）系列，有高Al₂O₃，Na₂O＞K₂O特征，微量元素具有富集LILE、LREE，亏损HFSE特征，岩浆的地幔源区为富集型，具有EMⅡ性质；与沿海地区辉长岩对比研究，认为赤门辉长岩株可能是中国东南部由拉张向裂谷转换的标志，全岩K-Ar测年为67.6±5.4Ma，晚白垩世末期，岩体的形成动力学背景为拉张带-初始裂谷。 3、闽西基性岩脉主要呈NW向展布；对闽西基性脉岩的岩石学、矿物学和地球化学特征进行了研究，基性脉岩为亚碱性岩石系列，稀土元素、不相容元素和Sr、Nd同位素表现出两种不同的地球化学特征，闽西存在两个不同地幔源区，即弱亏损地幔源区和富集地幔源区（类似EMⅡ型地幔端元），源自弱亏损地幔源区形成的基性脉岩以LILE弱富集、不出现Nb、Ta、Ti负异常和同位素Nd弱亏损及Sr弱富集为特征，源于富集地幔源区的基性脉岩，以不同程度富集LILE、LREE、有Ta、Nb、Ti负异常和Nd、Sr更多还原

【Abstract】 The SE China is located at the southern section of eastern Asia continental margin, and lies among the Yangtze Plate, Indian Plate and Pacific Plate. It is an active region due to the interaction between Pacific Plate and Eurasian Plate in Mesozoic, so for a long time it attracts geologists’ attention worldwide. In Late Mesozoic, the subduction of paleo-Pacific Plate to Eurasian Plate and large scale calc-alkaline magmatism are important tectono-magmatic events in SE China. The tectonic transformation time, the continental dynamic evolution processes, the lithospheric extension stages and the deep geological processes all become the key topics of current researches. This paper focuses on petrology, mineralogy, element geochemistry, isotope geochemistry and K-Ar ages of the mafic dikes and alkaline mafic-ultramafic rocks in Fujian province. By systematical geologic-geochemical studies on the western mafic-ultramafic rocks, northern bojite stocks, western and southeastern mafic dikes in Fujian province, we analyzed in detail of the petrogenesis, source region characteristics and intrusion ages, preliminarily discussed the geodynamic setting of SE China since Mesozoic, and retrieved the crustal extension stages, mantle source and evolution characteristics underneath Fujian province in Mesozoic. The following conclusions have been obtained:1. The Liucheng limburgites of western Fujian province formed in Cenozoic are intrusive pipes. The petrochemical study indicates that they belong to Si-unsaturated agpaitic alkaline ultramafic rocks and systematical trace element geochemical studies show that crustal assimilation was infrequent during the ascend and emplacement processes of magma. The limburgites had successive trace element geochemical characteristics of HIMU mantle source region, and the HIMU mantle was resulted from the subduction of dehydrated oceanic slab and the recycle of sediments. The Liucheng limburgites originated by means of 2.9% partial melting of mantle. The whole rock K-Ar age of limburgites is 12.6±1.3Ma （Miocene）, and the geotectonic setting for these rocks is continental rift.2. Systematical geologic-geochemical studies indicate that the Chimen bojite stocks in northern Fujian belong to low-K（tholeiite） rock series which characterized by high Al₂O₃ and Na₂O>K₂O. These stocks are enriched in LILE and LREE, and deficited in HFSE. The source of stocks is enriched mantle with the features of EM Ⅱ. Compared to the coastal gabbro, the Chimen bojite stocks can be used as an indicator for the transference from the crustal extension into continental rift. The whole rock K-Ar age is 67.6±5.4Ma, being in Late Cretaceous, and the geodynamic setting for these rocks is extension belt - primary rift.3. The wastern Fujian mafic dikes mainly distributed in NW direction. Studies on petrology, mineralogy and geologic-geochemistry show that they belong to subalkaline rock series. They can be divided into two types in geochemical characteristics of REE, incompatible elements and Sr-Nd isotopes, which indicate that there are two type mantle source regions in western Fujian, namely sub-depleted mantle source region and enriched mantle source region. The mafic dikes originated from the sub-depleted mantle are characterized by LILE sub-enrichment, no Nb、 Ta、Ti negative anomalies, Nd isotopic sub-deficiency and Sr isotopic sub-enrichment; while the mafic dikes originated from the enriched mantle are characterized by varying degree enrichment of LILE and LREE, Nb、 Ta、 Ti negative anomalies and Nd, Sr isotopic enrichment, the mixing of the crust and the mantle更多还原