摘要
本文百次研究了山东金伯利岩中橄榄石的产状、含量、大小、世代、形态、颜色、环带、矿物包体、折光率、2V、化学成分、端员组分特征及红外光谱和穆斯堡尔谱特征,并分析研究了橄榄石的成因。指出了无色—浅绿色的、含MgO、Cr2O3、NiO高的橄榄石是找金刚石矿的指示性矿物。
Olivine in kimberlites of Shandong Province is known to have six main modes of occurrence: (1) megacrysts (>10mm); (2) coarse-grained olivine (5-10mm); (3) medium-grained olivine (2-5 mm); (4) microgranular or groundmass olivine (<0.2mm); (5) olivine as inclusions in diamond; and (6) olivine in deep-seated xenoliths of kimberlite.Megacrystalline and macrocrystalline olivine occurs as rounded crystals, whereas groundmass olivine as subhedral and euhedral erystals. Olivine in Shandong kimberlites ranges from colorless through light green to green in color, and the relationship between the color and the size is like this: large crystals (macrocrysts)are colorless and light green, while small crystals (groundmass olivine)are green, suggesting that the former contain higher Fo than the latter. Three compositional variation trends have been observed from core to rim of the olivine: (1) iron-increasing trend; (2) magnesium-increasing trend; (3) coexistence of the above two trends in the same olivine. However, the zonal variation is very limited, e.g., Fo varies in the range of 0.2-1.6% from core to rim. Usually with Fo decreasing NiO contents decrease and CaO contents increase.With the increase in diamondcontent of kimberlites, Fo values of olivine increase, e. g., olivine of diamond-rich kimberlite from Shengli-1 of Shandong contains higher Fo (90.2-92.5%) than that of diamond-poor kimberlites from Hongq1-6 of of Shandong (88-89.5%).There are 10 strong absorption bands(982,948,880,837,606,510,465,420,380 and 363cm^(-1)) within the range of 350-1200 cm^(-1) in infrared spectra of olivine from Shengli-1 kimberlite pipe. The presence of 420 cm(-1) and 606 cm^(-1) shows that the olivine in question belongs to forsterite.
出处
《岩石矿物学杂志》
CAS
CSCD
1991年第4期354-362,共9页
Acta Petrologica et Mineralogica
