闽西北加里东期混合岩及花岗岩的成因：同变形地壳深熔作用

Petrogenesis of the Caledonian migmatites and related granites in northwestern Fujian province,south China:syn-deformational crustal anatexis.

本文选取闽西北前寒武纪变质基底中的混合岩和花岗岩为研究对象,以探讨两者之间的成因联系。详细的岩石学和主量、微量元素地球化学以及锆石 U-Pb 年代学研究表明,闽西北混合岩是同变形地壳深熔作用的产物,基底变质岩中的黑云母在较低温(约800℃)、H_2O 不饱和的条件下发生脱水熔融反应产生熔体,构造变形作用在熔体的分离和迁移过程中起到了重要作用。闽西北基底变质岩可能为形成混合岩和花岗岩的源岩,其深熔产生的初始熔体发生结晶分异作用,堆晶产物形成了混合岩的浅色体,而残余熔体继续演化形成花岗岩。混合岩和相关花岗岩形成基本同时,其成岩年龄为437～441Ma,它们均为华南加里东期构造热事件的产物。

A suite of migmatites and related granites from northwestern Fujian Province （South China） were studied in order to explore their linkage in formation. Detailed studies of lithology and geochemistry including zircon U-Pb geochronology suggest that the migmatites were derived from the syn-deformational crustal anatexis. The original granitic melts were likely produced by dehydrationmelting of the biotite from metasedimentary rocks in basement under relatively low temperature （ ca. 800℃ ） and H2O-undersaturated conditions; structural deformation played a key role in melt segregation and migration. Basement metasedimentary rocks are the likely source for the migmatites and related granites. The leucosomes were probably formed by the fractional crystallization and crystal accumulation of the initial granitic melts, and the remaining melts continued to evolve and ultimately crystallized as granites. The migmatites and related granites, coeval with the zircon U-Pb age from 437Ma to 441Ma, were formed by the Caledonian tectonothcrmal event in South China.