摘要
本文研究了金伯利岩中,作为巨晶和粗晶,基质相矿物,与金云母、镁铝榴石、铬尖晶石等矿物的连生体,金刚石中包裹体矿物及金伯利岩地幔岩包裹体矿物产出的钛铁矿的大小,形态、皮壳及化学成分、端元组分、环带及成分变异趋势。并与其他岩类中的钛铁矿作了对比。探讨了不同产状、共生组合类型的钛铁矿的成因。指出了与金刚石紧密伴生的钛铁矿的标型特征及找矿意义。
Megacrysts and macrocrysts of ilmenite generally occur as rounded-ellipsoidal nodules in Kimberlites, and their surfaces are commonly coated with alteration products of perovskite, serpentine and carbonite.Groundmass ilmenite occurs as euhedral crystals up to 0.5mm but typically less than 0.05 mm across. Megacrysts and macrocrysts of ilmenite in kimberlites from China are higher in MgO, Cr_2O_3 and MgTiO_3, and lower in MnO,MnTiO_3 and FeTiO_3 than those of ilmenite in the groundmass.A negative correlation exists between MgTiO_3 and FeTiO_3 in ilmenite macrocrysts in kimberlites, and FeTiO_3 and MnTiO_3 in ilmenite in the groundmass, With increasing MgO, MgTiO_3 and Cr_2O_3 contents of megacrysts and macrocrysts of ilmenite within and between kimberlite provinces, the diamond content of kimberlites tends to increase. Ilmenite macrocrysts in kimberlites are higher in Cr_2O_3,MgO and MgTiO_3, and lower in FeTiO_3 than those of other rocks, reflecting some differences between pressure conditions with respect to their formation. The higher the MgTiO_3 content of ilmenite is, the greater the depth of ilmenite formation will be. Most of the ilmenites are homogeneous. However, some ilmenites show a zonal pattern, with two distinctive zones:(a) Mg-enriched zone and(b) Mn-enriched zone.
出处
《矿物学报》
CAS
CSCD
北大核心
1991年第2期141-147,共7页
Acta Mineralogica Sinica
关键词
钛矿
铁矿
金伯利岩
ilmenite
kimberlite
diamond
