鄂东南地区晚中生代侵入岩的地球化学和成因及对岩石圈减薄时限的制约  

Geochemistry and petrogenesis of Late Mesozoic granitoids in southeastern Hubei Province and constrains on the timing of lithospheric thinning,Middle-Lower Reaches of the Yangtze River,eastern China

作　　者：谢桂青[1,2,3] 李瑞玲[4] 蒋国豪[3] 赵财胜[4] 侯可军[1] 

机构地区：[1]中国地质科学院矿产资源研究所国土资源部成矿作用与资源评价重点实验室,北京100037 [2]中国地质大学地质过程与矿产资源国家重点实验室,北京100083 [3]中国科学院地球化学研究所矿床地球化学国家重点实验室,贵阳550002 [4]中国地质调查局发展研究中心,北京100037

出　　处：《岩石学报》2008年第8期1703-1714,共12页Acta Petrologica Sinica

基　　金：国家自然科学重点基金(40434011和40402011);国家重点基础研究课题(2007CB411407和2007CB411405);中国科学院地球化学研究所开放室基金(200402);中国博博士后项目联合资助

摘　　要：鄂东南地区侵入岩是长江中下游地区晚中生代岩浆岩带的重要组成部分,但其成因和构造背景的研究显得薄弱。本文在前期工作的基础上,开展鄂东南地区侵入岩的主量、微量和稀土元素地球化学特征的研究,探讨地球化学特征所蕴含的成因和岩石圈减薄的时限。鄂东南地区侵入岩具有高碱富钾特征,微量元素以富集大离子亲石元素和轻稀土元素,而亏损高场强元素(Nb、Ta 和 Ti)为特征。研究认为鄂东南地区中生代侵入岩不能完全归为埃达克岩,早期中(酸)性岩具有埃达克岩的地球化学特征,晚期酸性岩明显不同于埃达克岩。鄂东南地区侵入岩的地球特征表明它们是富集地幔部分熔融形成的岩浆同化混染了下地壳物质并发生分离结晶作用的产物。结合年代学和地球化学特征,初步认为早白垩世(132～128Ma) 可能是长江中下游地区岩石圈减薄高峰时间。The granitoids in southeastern Hubei Province are an important component of the Middle-Lower Yangtze River igneous rock belt, but the genesis and tectonic setting are poorly constrained. Geochemical study was carried out for these granitoids in southeastern Hubei Province, eastern China, in order to constrain their petrogenesis and timing of lithospheric thinning. These granitoids dominantly exhibit high alkali and high K20 contents, and are characterized by enrichment in light rare earth elements （LREE） and large ion lithophile elements （LILE）, and relative depletion in Nb, Ta and Ti. Geochemical evidence indicated that intermediate-acid rocks during the earlier stage are similar to high-SiO2 adakite, but acid-rocks during the later stage such as granite and granite porphyry are different from adakite, and these granitoids originated as partial melts of an enriched mantle source that experienced significant contamination of lower crust materials and fractional crystallization during magma ascent. Integration of geochronology with the changing compositional trends for these granitoids indicates that lithospheric thinning probably commenced in the Early Cretaceous（ 132 - 128 Ma） in the Middle-Lower Yangtze River, eastern China.

关 键 词：地球化学特征 成因 部分熔融和地壳混染 岩石圈减薄时限 鄂东南地区 

分 类 号：P588.122[天文地球—岩石学] P594.1[天文地球—地质学]