中文摘要:西坑花岗伟晶岩型稀有金属矿田中，伟晶岩出露有数百条，按造岩矿物等特征可分为四个类型。从近海西期混合花岗岩接触带的第1类型到远离接触带的第Ⅳ类型，脉体的产状、规模、矿物和化学成分，以及流体包裹体和稳定同位素等方面，均呈现规律性的变化。第Ⅳ类型伟晶岩脉体复杂，规模大，分异和交代作用发育，围岩蚀变强烈，矿物成分最复杂，稀有元素 矿产的工业意义最大，伟晶岩的形成与海西构造旋回晚期深熔混合岩化作用密切相关，混合岩化作用使基底变质岩系中的稀有元素活化，并随同富碱质和挥发组分的熔体一溶液迁移，在混合花岗岩外围的裂隙中富集形成各类伟晶岩。
Abstract:The Xikeng pegmatite field lies in the eastern margin of South China Fold System; in Fujian Province, it is located at the connection of three major tectonic cycles. Although folds and faults are both well developed in the area, the distribution of pegmatites is obviously controlled by the former which, according to the axial trend, can be assigned to NEE group and NNE group, with the former group having most intimate affinity with the pegmatites. There exists apparent injection relationship between the pegmatites and the surrounding Smian schist and granulitite. The granitoids extensively distributed in the field belong either to Variscan or to Yenshuiian cycle, and it is evident that the pegmatites are genetically related to Variscan migmatitic granites. The pegmatites can be grouped into form- types: muscovite-orthoclase-early albite pegmatite (I), muscovite-albite-orthoclase pegmatite (II), muscovite-or-thoclase-ajbite pegmatite (III), and muscovite-albite-spodumene pegmatite (W) . From the contact zone of Variscan migmatitic granites outwards, pegmatites of Type I to Type IV appear in turn, with their form, size and interior zoning gradually becoming larger and more complex. Owing to strong metasomatism and multi-step emplacement of pegmatitic melt-solution, the sequence of interior assemblage zones in the pegmatites does not always represent the sequence of original crystallization. Mineral composition of the pegruatites is extremely complicated. 81 sorts of minerals have so far been found, including 5 species of Li-minerals, 6 species of Be-minerals, 3 species of Cs-minerals, 6 families of Nb, Ta-minerals and 18 species of phosphates. From Type I to Type IV, the mineral assemblages tend to grow complex, together with the synchronous intensification of rare metal and Sn mineralizations. Most of Type IV pegmatites have economic value. Diffusion halos of Li, Rb and Cs are distinct in the altered wall rocks. The features of fluid inclusions in the minerals are significantly different either in different types of pegmatites or in different parts of a single pegmatite vein. Oxygen isotope ratios of migmatitic granites and pegmatites are comparatively low (δ18O=9.3-10.4‰), and also than 9.5‰. Isotope ages of pegmatites are 235-328 Ma with their initial 87Sr/86Sr values of rock-forming fluids are higher ratio being 0.715-0.746. According to the temporal and spatial relationship between the pegmatites and the migmatitic granites, combined with the features of pegmatites themselves, it can be thought that the Xikeng granitic pegmatites are products of differentiation related closely to migmatitic granites.
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杨岳清，倪云祥，郭永泉，仇年铭，陈成湖，蔡朝发，张亚萍，刘加斌，陈月仙.1987.福建西坑花岗伟晶岩成岩成矿特征[J].矿床地质,6(3):10~21.1987.Rock-Forming And Ore-Forming Characteristics Of The Xikeng Granitic Pegmatites In Fujian Province[J].Mineral Deposits6(3):10~21
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