【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。更多还原

【Abstract】 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 materials.In combination with P-T data of the Mingxi peridotite xenoliths,the lower crust-upper mantle geotherm beneath 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.更多还原