摘要
产于陕西岚皋地区碱质基性－超基性潜火山杂岩中的金云角闪辉石岩类捕虏体，主要由透辉石、富钛韭闪石、金云母、磷灰石、榍石、及钛铁矿组成。捕虏体发育三联晶、碎裂边、肯克变形等固相线下变形变质结构，矿物学特征表明，透辉石、富钛韭闪石、金云母为地幔来源，是地幔交代作用的产物；与正常地幔尖晶石二辉橄榄岩相比，捕虏体富ＴｉＯ２、Ｆｅ２Ｏ３、ＣａＯ、Ｎａ２Ｏ、Ｋ２Ｏ，贫ＭｇＯ，其稀土元素具富集特征，尤其富集ＬＲＥＥ；微量元素分配型式显示了富亲石不相容元素的特征。岩相学、矿物学及岩石化学特征表明：该类捕虏体为交代地幔捕虏体，它代表了北大巴山早古生代裂谷作用时期的异常地幔，是地幔交代作用的产物。交代营力可能源于地幔热缕的上升，交代过程推测为深处小范围的流体交代及随后硅酸岩熔体的“弥散”
Phlogopite amphibole pyroxenite xenoliths included in alkali basic ultrabasic subvolcanic complex in Langao, Shaanxi Province are composed of diopside, Ti rich pargasite, phlogopite, apatite, sphene and ilmenite, which have triple points, cataclastic, kink banded textures. Mineral chemistry shows that clinopyr oxene, amphibole, phlogopite are fromed by mantle metasomatism. Compared with original spinel lherzolite from Eastern China, the xenoliths are enriched in TiO 2, Fe 2O 3, CaO, Na 2O, K 2O, with an apparent depletion in MgO. Chondrite normalized REE patterns and primordial mantle normalized trace elements data show that they are enriched in REE (especially LREE) and incompatible trace elements. The petrographic, mineralogical and geochemcial characteristics indicate that the xenoliths are metasomatized mantle xenoliths, which offer the evidences for mantle metasomatism and represent the anomalous mantle of early Palaeozic rift in North Daba Mts. The processes of metasomatism varied from liquid metasomatism in the deep mantle (>90km) to siliceous melt metasomatism.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
1997年第1期1-13,共13页
Acta Petrologica Sinica
基金
国家自然科学基金
关键词
金云角闪辉岩
辉石岩
捕虏体
地幔交代作用
Phlogopite amphibole pyroxenite
Xenolith
Mantle metasomatism
Langao, Shaanxi Province
