摘要
贵州省镇远地区的钾镁煌斑岩(Lamproite)的分布在大地构造上受地台和地台内隆起与坳陷间的深断裂控制,为浅成侵入脉岩,呈岩墙或岩床产出,规模不大,厚几厘米至数米,长数十米至千米,已见于深冲、白坟、思南塘等岩群。岩石具煌斑结构,块状构造,斑晶为钛金云母、透辉石、假像橄榄石,基质除上述矿物外,还有透长石、白榴石、角闪石、磷灰石、锆石、金红石等,还见到微量镁铝榴石和铬铁矿。其中钛金云母、铬铁矿、镁铝榴石的矿物化学成分与西澳同类岩石十分接近,投入米切尔,J·格尼有关图件中,均落入钾镁煌斑岩趋势区。岩石化学成分属钾质超基性岩,K_2O>Na_2O,K_2O/Na_2O为20.85～66.51,富含TiO_2,但MgO较西澳同类岩石略低。富含Sr、Ba、Zr、Nb、P等痕量元素。稀土总量高,富集轻稀土。稀土分配模式与西澳同类岩石一致。D_5岩体中经1987年再次选矿证实含微量金刚石。
The lamproites in Zhenyuan area, Guizhou, are structurally confined to the deep faults in the platform or the platformal fold belts. They are the hypabysal intrusions and occured as a dike or a sheet ranging from several centimetres to several metres thick and tens to thousand metres long in the Shenchong, Baifen and Sinantang complexes. The rocks, as a whole, display distinct lamprophyric textures and massive structures with porphyritic crystals of Ti-phlogopite, diopside and pseudo-olivine. The matrix minerals, except that mentioned above, are consisted of sanidine, leucite, amphibole, apatite, zircon, rutile as well as a few pyrope and chromite. The compositions of phlogopite, chromite and pyrope are similar to that of lamproites from West Australia, which in Mycher, J. Geny diagram are plotted to the area of lamproite. These rocks petrochemically belong to the potash-ultramafic and characterized by K_2O>Na_2O, K_2O/Na_2O=20.85—66.51. They have a higher content of REE and the REE patterns display an enrichment of LREE, which are similar to that of West Australia. The experiment of mineral separation indicated that there is a small amount of diamond in the D_5 body.
出处
《岩石矿物学杂志》
CAS
CSCD
1989年第2期97-109,共13页
Acta Petrologica et Mineralogica
关键词
钾镁煌斑岩
岩石特征
lamproite
phlogopite
pyrope
chromite
rutile
