扬子地台西缘富碱花岗斑岩特征及成因探讨

After studying systematically petology, mineralogy, perochmistry. REE geocheminstry and strontium, sulphur, lead isotope of the alkali-rich granite prophyry distributed extensively in the Yangtze platfrom western margin's alkali-rich granite porphyry, we point out that the alkallurich granite porphyry have the properties of new intrusive era. Range of the isotope age is from 36 Ma to 51 Ma. They belong to the Himalaya date. Main mineral componets of the alkali-rich granite porhyry consist of K-feldspar (35% - 45% ), quartz (36%±), plagloclase (15%±) and biotite (10%±). Accessary minerals of the rock belong to type of xenotime-zircon-monayite. Chemical composition of the alkali-rich granite porphyry are SiO2-poor Al2O3-rich and alkalisirich, sufficeient patassiunl, (K2O+Na2O) range of the alkali-rich granite porphyry is 8. 59%～11. 27%. Average is 9. 85%. The REE total of the alkali-rich granite porphyry is less. Average coefficient is 0. 52. The REE distribution Pattern is a smooth curve steeply sloping to right (87Sr/86Sr)i＝0. 7073. The lead is from the upper mantle. Range of the sulphur isotope δ34S%, is harrow and is close to aerolite--sUlphurcomposition. The petrogenic substances possibly come from the upper mantle. Petrogentictype belongs to "A" type of granite.