川西义敦措莫隆含锡花岗岩铁叶云母矿物学研究

Mineralogy of siderophyllite from the Sn-bearing granites in Comolong, Yidun, western Sichuan

关键词:  铁叶云母  穆斯堡尔谱  含锡花岗岩

Key words:  siderophyllite  Mossbauer spectrum  Sn-bearing granite

摘要:

通过对措莫隆花岗岩中铁叶云母的矿物学研究,可得出如下结论:①可利用铁叶云母中的化学成分及H₂O⁺,F^-,Cl^-来表征岩浆期后热液的性质和成岩成矿条件;②穆斯堡尔谱证实有33.45%的Fe³⁺进入四面体,并据此修正铁叶云母的晶体化学经验式;③Fe²⁺的I.S,Q.S值与Fe/(Fe+Mg)呈正相关,可定性反映其形成时温度和fo₂;④Fe²⁺在M₁,M₂晶位上的有序度能反映岩浆结晶温度高低和冷却速度快慢;⑤铁叶云母b₀值大小主要与Fe³⁺多少有关;⑥根据铁叶云母的化学成分判断措莫隆花岗岩属于含锡花岗岩;⑦根据铁叶云母的红外光谱及差热分析特征判断措莫隆花岗岩属于壳源型岩浆成因。

Abstract:

The Comolong Sn polymetallic deposit located in the Yidun island-arc zone, western Sichuan are believed to have a genetic affiliation to the late Yanshanian Comolong granites. Biotite is identified as an only silicate mineral with volatile components in the granites. The most important observations are that:(1) the chemical compositions and H₂O⁺, F^- and Cl^- in siderophyllite may be used to characterize the rock and ore forming conditions and the nature of magmas; (2) the crystallochemical formula should be revised in that 33.45% of Fe³⁺ turned out by Mossbauer spectra to be aligned in the siderophyllite tetrahedrons; (3) there is a positive correlation between I.S and Q.S volumes of Fe²⁺ and Fe/(Fe+Mg) ratios for siderophyllite, which may indicate the temperatures and oxygen fugacity during the formation of granite masses; (4) Fe²⁺ ordering at M₁ and M₂ sites may reflect the crystallization temperatures and cooling speeds of magmas; (5) the b 0 values for siderophyllite are always changeable as a function of Fe³⁺ contents; (6) the Comolong granites can be assigned, deduced from the chemical compositions of siderophyllite, to the Sn-bearing granites, and (7) the Comolong granites may be postulated to be of crustal derived magmatic origin in the light of infrared absorption spectroscopy and differential thermal analysis.