Abstract: In order to obtain the size of representative samples and its constraints, the relationships of the representative samples with crystal contents and crystal size are preliminarily discussed by statistical simulations of the holocrystalline rocks’texture and the idealized granitic compositions. The maximum possible difference between the original and measured crystal contents of samples, and the size of representative samples are determined under the variations of crystal contents and size. The greatest difference between the original and measured crystal contents of samples can be obtained by counting the number of phenocrysts across the sections of samples. The size of representative samples can be acquired by using the average crystal size. The deviation between the measured and original crystal contents are much more higher for coarse-grained samples with the same sample size. The largest representative samples are needed when the crystal content reach 20% for phenocrysts or coarse-grained minerals in equigranular texture. Finally, two examples including the Mapeng and Fangshan intrusions are used to examine the validity and practicability.

Key words: rock textures, representative samples, crystal contents, crystal size, granitic rocks, phenocryst

摘要： 为了获得代表性样品的大小和其约束条件, 基于全晶质岩石结构的特征, 以理想的花岗岩成分为基础, 利用模拟统计的方法, 初步探讨了代表性样品与矿物含量和矿物粒径之间的关系, 获得了矿物含量和粒径变化时, 样品大小对矿物实际含量和真实含量间最大可能差值的影响。统计样品截面视域中斑晶数目的多少, 可以获取样品中矿物实际含量与真实含量的最大差距。利用斑晶的平均粒度可以近似获得代表性样品的大小。相同大小样品下, 粒径大的样品偏离真实含量的程度更高, 斑晶或等粒结构中的粗粒矿物含量是20% 时, 所需代表性样品最大。最后以麻棚岩体和房山岩体为实例进行了验证和应用说明。

关键词: 岩石结构, 代表性样品, 矿物含量, 矿物粒径, 花岗质岩石, 斑晶