矽卡岩矿床中共生单斜辉石—石榴子石特征及其地质意义  

CHARACTERISTICS OF PARAGENETIC CLINOPYROXENE-GARNET PAIRS IN SKARN DEPOSITS AND THEIR GEOLOGICAL SIGNIFICANCE

作　　者：林文蔚[1] 赵一鸣[1] 蒋崇俊 

机构地区：[1]中国地质科学院矿床地质研究所

出　　处：《矿床地质》1990年第3期195-207,共13页Mineral Deposits

摘　　要：通过对我国与Fe,Cu,Mo,W,Sn等主要矿化类型有关的矽卡岩的研究,揭示出不同矿化类型的矽卡岩有其特定的共生单斜辉石-石榴子石矿物对的成分特征、含铁率比值及其变化规律。依据Fe、Al等组分在共生单斜辉石-石榴子石间的分配,估算各种矿化类型矽卡岩形成的氧逸度和酸度条件,从而划分出我国含矿矽卡岩的氧逸度—酸度相。不同矿化类型的矽卡岩共生单斜辉石-石榴子石的成分特征、形成环境及其变化规律密切联系于其成矿母岩特征、成因类型和成岩条件。Studies of skarns related to Fe, Cu, Mo, W and Sn mineralizations show that the paragenetic clinopyroxene-garnet pairs in skarns of different mineralization types each have their specific composition and ferriferous ratios. In the direction of Fe-Cu-Mo-W-Sn, the diopside-andradite pair in skarn grades progressively into hedenbergite-grossular pair, accompanied by the increase in K_p value. According to mineral assemblages in skarn and composition of paragenetic pyroxene-garnet pair, oxygen fugacities for the formation of various mineralized skarns have been calculated; the formulae for estimating formation acidities of skarns are given on the basis of the composition of paragenetic clinopyroxene-garnet pair(see formulae 19, 20 in the paper proper). In this way, several oxygen fugacity-acidity phases have been distinguished: high oxygen fugacity-low acidity phase, characterized by log fo_2≥-20 and pH≥5 or 5.5; intermediate oxygen fugacity-normal aoidity phase, with log fo_2=-20- -23 and pH=4.5-5.9; low oxygen fugacity-high acidity phase, with log fo_2≤-23 and pH=3.5-5.5. Various mineralized skarns were formed under the condition of log fo_2=-26- -17 and pH=3.5-7.5.The variation trend of oxygen fugacity-acidity during the formation of various types of skarns is discussed; it is also pointed out that deep internal relations in rock-forming and ore-forming geologic-geochemical characteristics and metallogenic physicochemical conditions do exist among magmatism, skarnization, acidic leaching metasomatism and metallization in the process of the formation of skarn deposits.

关 键 词：矽卡岩 矿床 单斜辉石 石榴子石 

分 类 号：P618.204[天文地球—矿床学]