吉林省金城洞——0夹皮沟花岗岩——绿岩带中金矿床同位素地球化学及地质意义

ISOTOPE GEOCHEMISTY AND ITS GEOLOGICAL SIGNIFICANCE OF GOLD DEPOSITS IN THE JINCHENGDONG—JIAPIGOU GRANITE—GREENSTONE BFLT IN JILIN PROVINCE

通过金城洞一夹皮沟绿岩带硫、铅、氢、氧、铷-锶同位素地球化学研究,认为硫同位素演化经历两次分馏作用、铅同位素具三阶段演化特点,它们的演化与2700～2200Ma和1800～1500Ma两次强变形变质-岩浆热事件有关。绿岩是矿源层,流体具变质热液性质。求得成矿的fO_2=3.16×10^(23)～1.0×10^(-3)Pa.pH=6.5～7.7,T=200～350℃。成矿过程经历:矿源形成期(>2700Ma);矿化发生期(2700～2200Ma);主成矿期(1800～1500Ma);迭加改造、再生矿化期(250～150Ma)。

The author has studied in detail the geochemical characteristics of S, Pb, Rb, Sr, H, O and their geological significance of the gold deposits in the area. A brief presentation is given as follows: 1. The evolution of isotope S experienced at least two times of fracturation; isotope Pb displays a feature of three—staged evolution. Their evolution is related chiefly to the heat event of strongly plastic metamorphic deformation occurred in 2700—2200Ma and the heat event of strongly brittle—plastic metamorphic deformation occurred in 1800—1500Ma. As the diseguilibrium of development of metamorpbic deformation occurred in different sections of the ore fields or in the same one results in dissimilarity and regularity of characteristics of the isotope S, so the two are the important indicators for predicting and evaluating the gold mineralization. 2. The ore—forming fluid pocesses chiefly the nature,of metamorpbic thermal solution, but contains a certain amount of meteoric water, and mixes with a Small amount of remelted magmatic thermal solution. In ore—forming process, fO_2=1.0×10^(-36)～3.16×10^(-33)bar, pH=6.5～7.0, T=200～350℃. 3. The granite—greenstone terrain is the source of S, Pb and ore—forming material as well as ore—forming fluid of mineralization of gold deposits. 4. Mineralization of gold experienced chiefly four epoches: (1) befoire 2700Ma—formation of greenstone—formation of ore source; (2) 2700—2200Ma, strongly plastic metamorphic deformation—occurring of mineralization; (3) 1800—1500Ma, strongly brittle—plastic metamorphic deformation—conversion of mineralization to ore formafion (the chief epoch of mineralization); (4) 250—150Ma, weaker Phanerozoic magmatie activity—transformation, superpo sifion and rejuvenation of gold mineralization.