摘要
本文根据南海深海沉积物36个站位发现的微球粒,应用显微镜、电镜、电子探针等仪器的测试分析和对比研究,将微球粒划分为铁质、石质和玻璃质三种类型和六种成分.阐述了球粒的形貌、微结构构造和地球化学特征,并进一步探讨了球粒的地外起源.
The spherules in the sediments on the middle region of South China Sea (12 °-20 ° N, 111° -118 ° E) found in identification of the heavey mineral are described in this paper. Their diameters vary form 50 to 250 micrometers. Nearly one hundred spherules were observed under the microscope, and the study of microscopic texture and structure for fourty of them was made. Ten spherules were subjected to chemical composition investigations using an electron-probe micro-analyzer.
The spherules in region of investigation may be classified into three groups, and each group can be further subdivided into two types on the basis of the content of the major elements, as follows:
1. Iron spherules: The spherules are spherical to ellipsoidal and raindrop in shape, opaque, black colored, metallic luster, strong magnetism, smooth to simple microlitic texture on surface.
(1) Iron-rich magnetic spherules with nickel: Such spherules have two-layer structure with a core riching in Ni and Fe. The outer layer is composed mostly of Fe.
(2) Iron-rich magnetic spherules without nickel: The spherules are composed mostly of Fe but with traces of Ti (0.05%), Mn (0.14%), Al, Si and so on.
2. Stoney spherules: The spherules are spherical to elliposidal, like-steel colored to dark colored, sem-metallic luster, also with magnetism , a complex microlitic texture on surface.
(1) . Fe-Mg-rich silicate spherules: The chemical components contain mostly Si (SiO232-40%) , Fe (FcO 23-42% ), with minor Al, Ca, Mn and so on. These stoney spheres are composed of olivine and magnetite often with the olivine crystals being organized in alignment across major portions of the spherules.
(2) Ca-Al-rich silicate spherules: The chemical components contain mostly Si (SiO232.5%), Al (A12O325.3%), Ca (CaO22%) with minor Fe, Mg, Ti and so on.
3. Glassy spherules: The spherules are uncrystalline, spherical, transparent, vitreous luster, yellow to brown colored. The feature of surface shows gasification marks and melting marks. The chemical composition is similar to that of the stoney spherules. They can be also further subdivided into: (1) . Fe-Mg-rich glassy spherules: (2) .Ca-Al-rich glassy spherules.
The possible sources of the three groups habve been assigned on the basis of the chemical composition and microscopic texture. A high Ni content is generally considered as a good indication of extraterrestrial origin. The absence of Ni dose not necessarily rule out an extraterrestrial origin, however, because the Ni content may be depleted during the ablation process as the meteorites pass through the atmosphere. Origin of terrestrial contamination is rich in Mn and Ti. Therefore, the iron spherules mentioned in this paper may belong to origin of meteorite.
Both the stoney and glassy spherules are similar in chemical composition. The element abundance of the Fe-Mg-rich spherules is analoqous to that of spherulitic meteorite. They may be formed as ablation products of stoney meteorites. Sources of the Ca-Al-rich spherules are more difficult to identify. In proportion to the terrestrial volcanic origin, The difference in the morphologies and chemical components. Volcanic particles often contain large amounts of Si and are often irregular in shape. It was found that of the element abundance of the Ca-Al-rich spherules is similar to that of the material at the high elevation of the moon and these spherules have gasification marks. Hence, these spherules are possible from the moon.
出处
《沉积学报》
CAS
CSCD
北大核心
1989年第3期31-38,共8页
Acta Sedimentologica Sinica
