小兴安岭地区与加里东期花岗岩类有关的矿床成矿系列

METALLOGENIC SERIES OF ORE DEPOSITS RELATED TO CALEDONIAN GRANITOIDS IN XIAOHINGGANLING REGION

加里东期花岗岩类岩浆活动及与其有关的成矿作用，在小兴安的地区形成了一批铁、铜、锌、铅、锡、钼和钨等矽卡岩型和热液型的矿床。这些成因上紧密相关的矿床形成时间相近。不过，在不同的岩浆活动阶段和不同的地质环境中形成的矿床，其矿化特征又有明显的差别，而且，矿种和矿化类型在空间的分布上，呈现有规律的分带现象。本文着眼于研究上述的矿床所处的地质背景、成矿条件和成矿作用，用成矿系列的观点，对矿床进行成矿亚系列和矿床式的划分。并研究了区域矿化分带和重要矿区的矿化分带及其成因问题。

This paper has studied ore deposits related to Middle Caledonian granitoids in Xiaohinggan-ling region in such aspects as their geological settings,metallogenic conditions,metallogenicmechanism,and evolutionary regularity of magma and mineralization. With the theory of metal-logenic series,the authors have made classificatiori for metallogenic subseries and types of ore de-posits,and probed into regularity of regional mineralization zoning as well as mineralization zon-ing of important ore districts. Xiaohigganling region lies in the northern part of the well-known Xiaohingganling-Zhang-guangcailing iron and polymetallic ore-forming belt.The study region approximately correspondsto the second-order tectonic units(Maolin-Milan geosynclinal folded belt and Wuxing-Guan-siogzhen intermediate upwarped belt)of Yichun-Yanshou geosynclinal folded system,being theactive conjunction zone between Xiaohingganling-Songnen old land and Laoyeling old land.In thisregion,geological structures are very complex and noted for multicyclic development;neverthe-less,the principal cycle remains the geosynclinal fold ed system forined in Middle Caledonian,which is characterized by multiphase and inherited activities,Caledonian geosyncline evolved onthe basis of an active and nonuniform sialic crust;when it changed from an expansion environ-ment to a contraction environment,the increase in intrageosynclinal pressure and tectonic stressled to the formation of remelted hybrid granite in the sialic basement.With the deepening of thedownwarping action of Caledonian geosyncline,the intensification of folding and the formation ofdeep faults,there occurred syntectic granodiorite;in addition,through complete deep differentia-tion and assimilation of wall rocks,the syntectic magma formed highly-acid and alkali-richadamellite and K-feldspar granite,whicli were both products of Middle Caledonian tectonism.Their related ore-forming processes formed a series of iron,copper,lead,zinc,tin,tungsten andmolybdenum skarn and hydrothermal deposits in favorable tectonic positions of the region.Though different in characteristics,these cre deposits were formed quite close to each other intime and restricted by the same major geological action,had intimate genetic connection and iden-tical magmatic-hydrothermal origin,and occurred exclusively in Yichun-Yanshou geosynclinalfolded svstem. Mineralization had much to do with evolution of magma and was closely related tointrusive rocks in time,space and genesis. Corresponding to three Middle Caledonian subcycles,the ore-forming processes might be divided into three main metallogenic subseries related toremelting type hybrid granite and granite porphyry,iron-lead zinc metallogenic subseries relatedto syntectic granodiorite,and tungsten-molybdenum-lead-zinc-iron metallogenic subseries relatedto highly-acid and alkali-rich granite.Wall rocks of ore deposits of different subseries are all mainly carbonate rocks of CambrianQianshan Formation. Regionally,these deposits are distributed almost equidistantly in columnsin nearly north-south direction and in zones northwestward.Ore deposits related to different evo-lutionary stages of magma had their respective distribution space and formed distinct mineraliza-tion zoning under the influence of regional geochemical field and tectonic activity,From south tonorth,the major ore species vary gradually in order of iron→iron,lead,zinc→lead,zinc→tung-sten,molybdenum,lead,zinc→tungstem,This must have resulted from such factors as long in-tense inherited tectonic activity,temporal-spatial differences,source of magma,and uneven dis-tribution of crustal and even upper mantle materials.