大吉山花岗岩中宇宙尘的初步研究

大吉山花岗岩人工重砂中的宇宙尘呈黑色,具强磁性,平均粒径为0.206mm,按形态可分为球状、椭球状和不规则状,按成分可分为铁质和硅酸质两种类型。主要矿物有方铁矿、α-Fe、自然铜、钠长石和钾长石。主要组构类型有瘤状突起构造、喷气孔构造、“毛刺”构造、壳层构造、空腔构造、花边构造和脑纹状构造。通过研究得出如下结论:(1)大吉山宇宙尘是低氧逸度条件下高温淬火形成的非平衡结晶产物;(2)宇宙尘的来源与大吉山花岗岩的成因有密切联系,是花岗岩岩源层的残留物;(3)宇宙尘可以作为花岗岩成因指示物。

Primary Study of Cosmic Dust from Dajishan Graniite

Cosmic dusts with black colour, strong magnetism and average grade of0.206mm (from 0.1 to 0.4 mm) has been first found in the artificial pla-cers from Dajishan granite, The shapes can be divided into three groups;sphere, ellipse sphere and irregular, According to the compositions, two types,iron and silicate spherules, are distinguished, The main minerals are as follows;wustite, magnetite, a-Fe, Cu, albite and K-feldspar. The fabrics are skeletoncrystal, brain-pattern, lace-Iike, pearl-string etc, Chromite, SiC and whitneyitealso exist in the artificial placers, All these imply that the particles are of cosmic genesis derived from exterrestrial space, We suggest that; (1) the cosmic dustis products of nonequilibrium crystallization under the condition of low oxy-gen fugacity, high temperature and rapid drop in temperature; ( 2 ) the sourceof cosmic dust has a strong relation to the genesis of Dajishan granite, the co-smic dust may be the residules of strata from which granitic magma is origi-nated; (3} cosmic dust in granite can be used as an indicator of genesis studyof granitic rocks.