大兴安岭北段富林矽卡岩铜矿床成因:印支期含矿岩浆源区特征、蚀变矿物学及勘查意义

发布时间：2018-03-25 17:31

本文选题：晚古生代　切入点：富林铜矿床　出处：《岩石学报》2017年02期

【摘要】：新近发现的印支期富林矽卡岩铜矿床位于大兴安岭北段新林区新林镇东约90km。矿区发育与成矿直接相关的花岗岩和侵入花岗岩中的花岗斑岩,矿体主要赋存于花岗岩与古元古代兴安桥组大理岩和早奥陶世黄斑脊山组钙质粉砂岩接触带内。富林矿床矿化与矽卡岩密切相关,整个矿化过程可分为两期:矽卡岩期和石英-硫化物期,5个阶段:早期矽卡岩阶段、退化蚀变阶段、氧化物阶段、早期硫化物阶段和晚期硫化物阶段,其中铜矿化主要发生在早期硫化物阶段。硫化物主要包括黄铜矿和黄铁矿,并含少量闪锌矿、方铅矿、斑铜矿等。蚀变类型包括石榴子石-透辉石矽卡岩化、阳起石-透闪石矽卡岩化、绿帘石矽卡岩化、绿泥石化、绢云母-粘土化、钾长石化和局部角岩化。电子探针分析(EMPA)结果表明:矿区内的石榴子石属钙铝-钙铁榴石系列,主要为钙铁榴石,辉石为透辉石-钙铁辉石系列,以透辉石为主,闪石主要为透闪石、阳起石以及少量镁绿钙闪石和铁浅闪石,帘石为黝帘石-绿帘石系列。黑云母以镁铁黑云母和铁叶云母为主,绿泥石主要为密绿泥石和铁叶绿泥石,长石以正长石和钠长石为主。石榴子石成分剖面显示从核部到边部,石榴子石呈现出钙铝榴石和钙铁榴石交替变化的环带特征,且Fe~(3+)含量的逐渐升高暗示后期成矿流体氧逸度升高,结合黑云母Mg-Fe~(3+)-Fe~(2+)图解,说明富林矽卡岩型铜矿床形成于较强的氧化环境。锆石LA-ICP-MS U-Pb测年结果显示花岗岩形成于~253Ma,花岗斑岩形成于~244Ma,为大兴安岭地区一期新的成矿事件。锆石原位Hf同位素测试结果表明,花岗岩εHf(t)介于-1.60~2.23,花岗斑岩εHf(t)介于-3.53~1.90,二者均具有古老的两阶段模式年龄,结合前人对区域构造背景的研究,认为富林花岗质岩石可能来自于松辽地块和兴安地块后碰撞背景下俯冲板片断离软溜圈上涌导致古老下地壳的部分熔融并卷入少量地幔物质而形成的岩浆。花岗斑岩及与斑岩有关的脉状矿化和蚀变的出现暗示富林地区可能存在印支期的斑岩型矿床,此外结合石榴子石、辉石成分特征以及辉石Mn/Fe比值与世界矽卡岩矿床对比,指出富林矿区外围找矿应综合考虑铜、钼、铁、金、铅、锌等矿化组合。
[Abstract]:The newly discovered Indosinian Fulin skarn copper deposit is located in the east of Xinlin Town, northern Daxing'anling region. Granite directly related to mineralization and granitic porphyry in intrusive granite are developed in the ore area. The orebodies mainly occur in the contact zone between granite and marble of the Paleoproterozoic Xinganqiao formation and the early Ordovician macular ridge mountain formation calcareous siltstone. The mineralization of the Fulin deposit is closely related to skarn. The whole mineralization process can be divided into two stages: skarn stage and quartz-sulfide stage, five stages: early skarn stage, degenerative alteration stage, oxide stage, early sulphide stage and late sulphide stage. The copper mineralization mainly occurs in the early sulfide stage. The sulphide mainly includes chalcopyrite and pyrite, and contains a small amount of sphalerite, galena, porphyrite, etc. The alteration types include garnet diopside skarnization, The results of electron probe analysis (EMPA) show that the pomegranate in the mining area belongs to the calcium aluminum-calcium iron garnet series. Mainly calcium iron garnet, pyroxene is diopside-calcium ferroxene series, mainly diopside, amphibole is mainly tremolite, actinite and a small amount of magnesium green calcium amphibole and iron amphibole, The biotite is mainly magnesia-ferrite biotite and iron leaf mica, chlorite mainly consists of dense chlorite and iron chlorite, feldspar is mainly orthoclase and albite. The composition profile of pomegranate shows from the core to the edge, Pomegranate shows the annular characteristics of alternate change of calcium aluminite and calcium iron garnet, and the increasing of Fe~(3) content indicates that the oxygen fugacity of ore-forming fluid increases in the later stage, which is combined with the diagram of biotite Mg-Fe~(3. The results of zircon LA-ICP-MS U-Pb dating show that granite formed at 253Maand granitic porphyry formed at 244Ma. it is a new metallogenic event in the Daxinganling area. Zircon in-situ HF isochron occurs in the Daxinganling area. The results of prime test show that, Granite 蔚 Hftbetween -1.60 ~ 2.23 and granitic porphyry between -3.53 ~ 1.90. Both of them have an ancient two-stage model age, which is combined with previous studies of regional tectonic setting, and the results show that: (1) the age of granite is between -1.60 and 2.23, and that of granitic porphyry is between -3.53 and 1.90. It is considered that the Fulin granitic rocks may have originated from the magma formed by the upwelling of subduction plate fragments from the soft slip circle in the post-collision background of the Songliao and Xingan massif, which resulted in partial melting of the ancient lower crust and involvement in a small amount of mantle material. The occurrence of porphyry and porphyry related vein mineralization and alteration suggests that Indosinian porphyry deposits may exist in the Fulin area. In addition, combined with the characteristics of pomegranate, pyroxene composition and the ratio of pyroxene Mn/Fe to the world skarn deposit, it is pointed out that the mineralization combination of copper, molybdenum, iron, gold, lead and zinc should be considered comprehensively in the prospecting of the periphery of Fulin ore area.
【作者单位】：中国科学院矿产资源研究重点实验室中国科学院地质与地球物理研究所;中国科学院大学;黑龙江有色地质七0六队;
【基金】：国家自然科学基金重大项目和面上项目(41390444、41272108)资助
【分类号】：P618.41

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