千里山花岗岩体中钾长石成分和结构态研究  

A STUDY ON THE COMPOSITION AND STRUCTURAL STATE OF K-FELDSPARS FROM QIANLISHAN GRANITES, HUNAN PROVINCE

作　　者：徐红[1] 赵明[1] 季寿元[1] 

机构地区：[1]南京交通高等专科学校,南京大学地球科学系

出　　处：《南京大学学报（自然科学版）》1995年第1期121-127,共7页Journal of Nanjing University（Natural Science）

摘　　要：对湖南郴县千里山花岗岩体的钾长石进行了研究．钾长石的成分在Ｏｒ９７Ａｂ２到Ｏｒ７８Ａｂ２１范围内变化，Ａｎ的含量通常小于３％，钾质相中的Ｏｒ含量在Ｏｒ９３和Ｏｒ８８之间．钾长石是在４００～６００℃的较低温度下结晶而成的，它们的结构态较接近于最大微斜长石，三斜度变化范围为０．７２～０．８５；Ａｌ、Ｓｉ有序度也较高，约为０．６２～０．９６；Ａｌ占位率ｔ；为０．８８～０．９７左右，而且它们的微量元素含量与其三斜度呈反消长的关系．钾长石的成分和结构态可作为判别稀有元素矿化花岗岩的一种参考标志．The k-feldspars from Qianlishan biotite granites, Chen county.of Hunan province, have been investigated in this paper. These biotite granites are amajor source of the economic metals W, Sn, Be, Nb and Ta. The textural variatios in these rocks are considered together with the composition and structural state of the k-feldspars. The structural states of the k--feldspar were determined from X-ray powder diffractograms by two methods: the three-peak method of Wright (1968) and the Goldsmith and Laves (1954) method. The bulk chemical compositions and trace element contents of k-feldspar were determined by EMA, ICP and chemical analytical methods respectively. The compositions of the k-feldspar separate ranges between Or97Ab2 and Or78Ab21, An content is usually less than 3%, Or content of the potassic phase is between Or98 and Or88, and these k-feldspars may have crystallized at lower temperatures, around 400～600℃ Stractural states of the k-feldspars are close to those of the maximum microcline. Triclinicity values vary between 0.72-0.85, and degrees of Al, Si order vary from 0.62 to 0.96. The Al occupancies in tetrahedral site ti are 0.88-0.97 or so. The Sr, Ba and Ph contents of k-feldspar are higher and Cr content is lower ill the central part than that in the marginal part of Qianlishan granites, but negative correlations between these trace element contents in the k-feldspars and their triclinicity are observed. Data on structural states of k-feldspar from Qianlishan biotite granites. indicate that the barren granites are characterized by k-feldspars of intermediate micrbcline structure while those from mineralization granites are usually of m axim urn m icrocline structure. The variable factors which govern the Al, Si order of k-feldspars are the temperature, the omposition of the aqueous fluid and the duration of rock fluid interaction. The differences in degree of Al, Si order of the k-feldspars may be attributed to the variations in the above parameters. The most-ordered k-feldspars must have crystallized

关 键 词：结构态 钾长石 花岗岩 化学成分 

分 类 号：P588.121[天文地球—岩石学]