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幔源玄武质岩浆底侵并与下部地壳的相互作用,是地壳增生和改造的一种重要方式,也是形成钙碱性花岗岩类杂岩的重要机制,因此,在钙碱性花岗岩中往往保存着壳幔作用的信息,本文以福建平潭钙碱性火成杂岩为例,据其单粒锆石U-Pb法定年和全岩Sm-Nd同位素研究,结合闽东南的地球物理资料,讨论这一地区的壳-幔相互作用问题1 平潭火成杂岩地质概况福建平潭县是我国第五大岛,岛上出露角闪辉长岩、花岗闪长岩和花岗岩,它们的出露面积比约为6:12:82,构成以花岗岩为主体的钙碱性杂岩,这一面积比说明,不可能由一种基性岩浆演化出面积比之大约20倍的花岗岩类,野外观察表明,角闪辉长岩呈岩株、岩墙穿插在花岗岩中,岩墙边界弯曲呈细褶状,在岩墙附近的花岗质岩石中常集结着大量定向分布的浑圆状、鱼群状辉长质岩石包状,构成层流状(Stromatitic-like)构造,其中一些较大的岩石包体具冷凝边,有的又具反向脉(Back-vein),这些包体是同深成岩墙边缘的两种岩浆混合过程中的条带状辉长质岩浆碎块,以上地质学证据表明,平潭火成杂岩是由两种独立的岩浆,即辉长质岩浆和花岗质岩浆,近于同时结晶形成的,
The mantle-basaltic basaltic magma underplating and its interaction with the lower crust is an important way of crustal proliferation and transformation as well as an important mechanism for the formation of calc-alkaline granitoids. Therefore, it is often preserved in calc-alkaline granites Based on the U-Pb dating of single granulite and the Sm-Nd isotopic study of whole rock and the geophysical data of the southeastern part of Fujian Province, this paper discusses the study on the role of crust and mantle in the study. The crust-mantle interaction problem in this area 1 Geological Survey of Pingtan Hematite Complex Pingtan County, Fujian Province, is the fifth largest island in China with hornblende, granodiorite and granite on the island Exposed area ratio of about 6:12:82, constitute granite-based calc-alkaline complex, the area ratio shows that it is impossible to evolve from a basic magmatic area ratio of about 20 times the granite class, Field observations show that the hornblende gabbro is a rock strain and the dyke wall is interspersed in the granite. The boundary of the dyke wall is narrowly pleated. Granite rocks near the dyke wall often gather a large number of directional distribution of rounded, fish The gabbro-like petrological rocks form a Stromatitic-like structure, one of them Some of the larger rock inclusions have condensation edges and some have backward-veins. These inclusions are banded gabbro magma fragments during mixing with the two magmas at the edge of the deep dike, The above geological evidence shows that the Pingtan volcanic complex is composed of two independent magmas, ie, palaeo-protolith magmatism and granitic magma, which are formed almost simultaneously,