福建明溪麻粒岩包体的年代学和矿物学特征:地温曲线及其华南中生代壳-幔相互作用意义  

Geochronology and Mineralogy of the Mingxi Granulite Xenoliths from Fujian,South China:Geotherm and Implications for the Mesozoic Crustal-mantle Interaction

作　　者：黄小龙[1] 钟军伟[1,2] 于洋[1,3] 李洁[1,3] 

机构地区：[1]中国科学院广州地球化学研究所,同位素地球化学国家重点实验室,广州510640 [2]昆明理工大学国土资源工程学院,昆明650093 [3]中国科学院大学,北京100049

出　　处：《矿物岩石地球化学通报》2013年第2期212-221,共10页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：中国科学院知识创新工程项目(KZCX1-YW-15-2;KZCX2-YW-QN106);国家自然科学基金创新研究群体项目(41121002)

摘　　要：明溪新生代玄武岩中的麻粒岩包体将为探讨华南地区中生代壳-幔相互作用过程提供线索。锆石U-Pb定年表明麻粒岩包体的原岩曾经历多期次岩浆活动,并以最后的晚侏罗世-早白垩世岩浆活动最强,其锆石εHf(t)值普遍较低(-16.1～-6.3),应以再循环地壳物质为主。根据矿物成分估算麻粒岩包体的平衡温度(756～826℃)、压力(0.55～0.78GPa),结合橄榄岩包体的平衡温压资料,重建了明溪地区地温曲线,由此推得的岩石学壳幔边界深度(～25km)明显浅于地震莫霍面深度(～31km),表明该区存在明显的壳幔过渡带。华南内陆地区曾经历中生代岩浆底侵作用过程,可能是华南中生代广泛岩浆活动的重要原因。The granulite xenoliths in the Mingxi Cenozoic basalts provide a clue to understand the Mesozoic crustal- mantle interaction in South China. Zircon U-Pb dating of the Mingxi granulite xenolith reveals that the protolith were formed by multi-episodes of magmatisms. The dominant and the last magmatisms, which have negative zircon εHf（t） values （--16.1^--6.3）, occurred in the Late Jurassic and the Early Cretaceous, respectively. These all suggest that the protolith of the Mingxi granulite xenolith was dominantly derived from the recycled crustal materi- als. In combination with P-T data of the Mingxi peridotite xenoliths, the lower crust-upper mantle geotherm be- neath the Mingxi area are reconstructed according to the equilibrium t-p of the granulite xenoliths （756--826℃ and 0.55~0.78 GPa） calculated by the mineral compositions. The depth of petrologic crust-mantle boundary （~ 25 km） calculated from the Mingxi new geotherm is much lower than the seismic Moho depth （~ 31 km） ,suggesting a distinct crust-mantle transition zone in the area. Thus, the Mesozoic underplating may have occurred in the lower crust beneath the inland of South China, which may be an important mechanism of generating the Mesozoic felsic magmatism in South China.

关 键 词：下地壳 麻粒岩包体 地温曲线 底侵作用 中生代 华南 

分 类 号：P588.3[天文地球—岩石学]