【作者】 朱华平；

【导师】 张德全；

【作者基本信息】 中国地质科学院 ， 矿物学、岩石学、矿床学， 2004， 博士

【摘要】 柞山地区位于南秦岭造山带东段，以发育众多铅锌多金属矿床而闻名于世。多年来，这些铅锌多金属矿床一直被厘定为泥盆纪热水沉积矿床（SEDEX）。近年来的金属找矿勘探实践证明，该地区不仅存在同生热水沉积成矿作用，而且后生成矿作用也非常重要。通过穆家庄铜矿和桐木沟锌矿的地质特征、同位素地球化学、流体包裹体地球化学、成矿年代学研究后提出，穆家庄铜矿床是后生流体交代充填型矿床，桐木沟锌矿为热水沉积-后生流体交代改造矿床。通过对比区域热事件结构提出石炭纪秦岭地块与华北板块的点接触碰撞而使深部形成花岗岩浆，导致浅部地壳出现高热背景场，从而形成后生流体交代成矿作用。通过对南秦岭东段区域岩浆作用、变质作用和成岩成矿年代学数据分析，证明了柞山地区自古生代以来的区域热事件结构与成矿事件的耦合关系，厘定了三个极为重要的热事件和成矿作用事件：360～340Ma热水沉积事件与热水沉积成矿作用；320～280Ma深部岩浆活动和地热活动与后生流体交代成矿作用；190～170Ma发生在地壳水热活动中的脆韧性变形构造活动与构造蚀变和韧性剪切等构造-流体成矿作用。首次确认320～280Ma是柞山地区后生流体交代成矿的重要热事件之一。详细解剖了柞山地区二个典型金属矿床，确定了后生成矿作用的两种情形：流体交代成矿作用和热水沉积-流体交代改造成矿作用。穆家庄铜矿床为后生流体交代矿床，它产于柞山地区红岩寺-黑山复式向斜南翼金井河-胡家沟次级背斜中。该背斜南陡北缓并倒转，南翼近轴部断裂早期表现为滑脱，晚期表现为左行压剪的复合构造带。二个构造阶段均有含铜铁白云石石英脉充填，但矿体主体形成于压剪阶段。矿体赋存于泥盆系青石垭组中上部白云质岩石中，其空间展布严格受背斜陡倾南翼（倒转翼）近轴部的层间断裂．裂隙带构造控制，在缓倾北翼（正常翼）相同层位未发现含矿构造带，且地层岩石含铜低于20×10^-6，低于区域背景值。团块状富矿石和密集网脉带沿构造引张部位即构造扩容带充填。矿体在走向上呈膨大缩小，倾向上呈S形，其规模取决于断裂构造的部位，而矿石类型（团块状富矿、网脉状矿）则取决于围岩性质和构造属性，相对脆性岩石中以网脉状矿石为主，相对软弱岩石以团块状、块状矿石为主。黑云母化蚀变与铜矿成矿关系密切。桐木沟锌矿床为热水沉积-流体交代改造矿床，产于马鹿坪倒转向斜北翼（倒转翼）的层间破碎带中。赋矿地层为中泥盆统青石垭组下部一套粉砂质泥质岩，其中发育数层层纹状细粒．微细粒贫锌矿石。这种矿石与泥质矿物（绢云母）紧密交生、构成细密纹层，残余层理清楚，单侧不对称蚀变，其热水交代蚀变岩包括钠长石岩、方柱石岩等，为典型的同生热水沉积作用形成的。富矿体位于F2断裂带的次级断裂F3构造带中，靠近两断裂交点开始以东矿体厚而富，在倾向上呈雁行排列，闪锌矿多呈胶结物胶结围岩角砾和热水沉积岩角砾。富矿体两侧发育流体交代岩（绿色岩），这些绿色岩石是块状富矿体和角砾状富矿体的主要容矿岩石，这与热水沉积形成的层纹状锌矿（钠长石方柱石板岩）具有显著差异。后生流体交代岩（主要由透闪石、绿帘石、透辉石、黑云母、石英、绿泥石等矿物组成）显著受层间断层控制，它是流体交代原热水沉积层和热水沉积闪锌矿纹层而形成的，该矿床为热水沉积．流体交代改造矿床。穆家庄铜矿矿石铅和近矿围岩岩石铅具有极高的放射性成因铅特点。通过对矿石铅、近矿围岩岩石铅与测定的寒武系碳硅质岩岩石全岩铅进行综合对比，发现它们的组成特征类似，说明穆家庄铜矿铅源来自于寒武系。由于极高的放射性异常铅仅分布在矿体及其近矿围岩中，因而提出异常铅同位素组成可以作为勘查的主要地球化学标志之一。桐木沟矿石铅也是异常铅，反映的铅源和早期热水沉积期的来源于基底的铅源是一致的。综合对比区内几个重要矿床的铅同位素组成特征，反映了三种不同的铅源特征：小河口铜矿反映的是与同期岩浆岩（印支期）具有相同铅源；桐木沟锌矿和银洞子银铅矿的铅源一致，说明和热水沉积期的铅源一致；穆家庄铜矿的铅则是来自于寒武系的极高放射性异常铅源。流体包裹体研究揭示了后生成矿流体的两阶段流体演化过程：第一阶段的成矿流体为中温，中、高盐度岩浆热液含CO₂的NaCl-H₂O流体。均一温度为190～265℃，盐度12.5～35.34wt％NaCl，压力12.8～21.3Mp，在同一寄主矿物中均一温度变化小，而盐度变化极大，是岩浆流体沸腾的产物。第二阶段流体为为中高温，中高盐度岩浆期后热液NaCl-H₂O流体。均一温度为300～350℃，盐度7.4～41.59wt％NaCl，压力10.8～19.3Mp。反映了岩浆期后热液流体的二次沸腾。这两期流体与二个断裂构造阶段相吻合。流体的演化过程为：第一阶段，深部岩浆上侵，岩浆的气液流体上升，混入地层建造水，当到达浅地表构造带时减压，流体迅速沸腾，产生流体不混溶，因而沉淀出金属，形成网脉状矿石。第二阶段的流体为岩浆期后热液NaCl-H₂O流体，随着第二个断裂构造阶段的发生，流体发生二次沸腾并沉淀出金属。桐木沟锌矿后生成矿流体仅发育第一阶段，并未见流体的二次沸腾。应用流体地球化学的综合方法（包裹体流体组成、演化，包裹体稀有气体示踪和包裹体中流体稀土元素示踪）识别出后生交代流体性质，桐木沟为地层水（建造水）加岩浆水，穆家庄铜矿的成矿流体第一阶段为岩浆水，第二阶段的成矿流体为岩浆水加部分地层水（建造水）。氢氧同位素分析也支持上述结论。获得了穆家庄铜矿与黄铜矿共生的黑云母氩氩坪年龄为323.68Ma；桐木沟块状富矿石中后生交代蚀变岩（绿色岩）中透闪石钾氩表面年龄为293Ma。认为柞山地区后生流体交代形成的铜铅锌矿床的主期成矿年龄在293～323Ma间，这个成矿年龄刚好和区域热事件结构中的320～280Ma热事件相吻合。确定的石炭纪（300Ma左右）的流体交代成矿作用，可能是南秦岭地区又一次非常重要的成矿作用。本文根据穆家庄铜矿、桐木沟锌矿等地质地球化学特征，建立了后生流体交代矿床的成矿作用模型，为南秦岭地区找矿勘查提供了新的方向。更多还原

【Abstract】 Zhashan polymetallic concentration area,is located in the East part of South Qinling Orogenic belts,is famous for Lead-Zinc polymetallic ore deposits.Most of them are regarded as SEDEX deposits formed during Devonian. Recently, some advancement of exploration approves there is not only hydrothermal exhalation-sedimentary mineralization but also epigenetic mineralization, which is very important. It is very clear that the Mujiazhuang copper deposit,located in the Zhashan polymetallic concentration area, is an epigenetic one formed by fluid metasomatism during Carboniferous and the Tongmugou zinc deposit, located in the Zhashan polymetallic concentration area, is fluid matomatism reformed ore deposit based on hydrothermal exhalation-sedimentary ores or rocks on basis of researching on gological characteristics of isotopes geochemistry, fluid inclusions geochemistry, mineralization dating and event geology both the Mujiazhuang copper deposit and the Tongmugou zinc deposit in the Zhashan area. By comparing of regional geothermal events, it is put forward that the point-to-point collision between the Qinling Block Mass and the North China Plate during Carboniferous begin forming the granite in the deep interior of the Zhashan area to make this area forming high geothermal background, and forming fluid metasomatic metallogenics.It is established three more key construct-magma-geothermal events and matched mineralizationat events based on researching regional magmatism, metamorphism and chronology: the hydrothermal sedimentary event during 360～340Ma, the structurally magmatic reformation mineralization formed by the deep-derived magma activity and the geothermal activity during 320～280Ma,and the alteration .i.e the retrometamorphism happening at the fragile-ductile deforming zone within the later-stage crust water hydrothermal activity during 190～170Ma. It is discovered firstly that fluid matomatism event during 320～280Ma（Carboniferous） is very important among regional hydrothermal events.It is clear that there are two kinds of epigenetic mineralization based on researching two typical ore deposits in the Zhashan polymetallic concentration area: fluid metasomatism and fluid matomatism reformed mineralization based on hydrothermal exhalation-sedimentary ores or rocks. The Mujiazhuang copper deposit is a fluid metasomatic ore deposit which is located nearly in axialplane fracture of Jinjinghe-hujiamiao inverted anticline which is in south limb of Hongyansi-heishan composite syncline in the Zhashan area. The axialplane fracture, is a complicated structure, forms in inverted limb, has two stages construct activities: detachment early and left-lateral strike-slip fault lately. They are filled by Cu-bearing ankerite-quartz veins, but main ore bodies are located the later stage fractures. Most of ores, filled in dilatant zone of fracture, are mass and network mineralization. The scale of ore bodies depends on the property of embracing rocks: network veins ore body in fragile rocks and mass ore body in soft rocks. Biotite alteration is relation to copper mineralization. The Tongmugou zinc deposit, is located in North lamb（inverted lamb） interlays fracture of Maluping inverted syncline, is a rich zinc deposit of fluid matomatic reformed. The main ore-bearing rock is Qingshiya group of Devonian （albite slate or albite-scapolite slate）, in which there are multiplayer lamellar and minutiness sphaleritite low-grade ores that it is intergrows with pelite, composes minutia lamellar and shows remains layering. Wall-rock alteration（aibite,silication, scapolite et, al） is single side nonsymmetry, It is clear that they are formed by hydrothermal exhalation-sedimentary during Devonian. Ore shoots, are located in subsidiary fracture（F3） derived from structure F2, are larger and thickness near point of intersection between F2 and F3, and are enchelon arrangement in dip. Wall-rock alteration（green color stone, mainly composed of hoepfnerite, epidote, diopside, biotite, quartz, and chlorite etc.） is around ore shoots to be distribute with symmetry, that show the block and brecciated ores of the Tongmugou zinc deposit are fluid metasomatic reformed deposit.It is discovered that ore mineral lead isotopes of the Mujiazhuang are sky-high radioactivity lead abnormal, and alteration rocks nearly ore body are also. On the contrast of both the Mujiazhuang and Cambrian ores and rocks lead isotopes composition, they are homoplasy, and it is suggested that the lead abnormal isotopes resource of the Mujiazhuang are from Cambrian.It is put forword that lead of the Tongmugou zinc deposit are also abnormal lead isotopes which are from the basis rocks like hydrothermal deposit rocks.It is approved with regional contrast research.On the basis of fluid inclusions for the Mujiazhuang copper deposit, it is showed that there were two stages of fluid evolution: the first stage is magma hydrothermal with middle temperature, middle and high salinity （CO₂）-H₂O+NaC1 fluid, its homogenization temperature are 190²65℃and salinity 12.5～35.34wt%NaCl,preture 12.8～21.3Mp, Meanwhile, a large of three faces fluid inclusions with a salty crystal coexistence to vapour face inclusions are discovered in the high and middle high temperature steps of homotemperature of fluid inclusions for the Mujiazhuang copper deposit, it is suggested that the mineralization fluid is over-saturation and occurring boilization and supposed that there is magma chamber in deep of mining area. The second stage is behind hydrothermal of magma with middle-high temperature, middle and high salinityH₂O+NaCl fluid, its homogenization temperature are 300～350℃and salinity 7.4～41.59wt%NaCl,preture 10.8～19.3Mp. On the basis of fluid inclusions for the Tongmugou zinc deposit, it shows that there is only first stage of fluid evolution, a large of three faces fluid inclusions with a salty crystal coexistence to vapour face inclusions are discovered in the high and middle high temperature steps of homotemperature of fluid inclusions for the Tongmugou zinc deposit, it is suggested that the mineralization fluid is occurred boilization. Boilization is an important mechanism of mineral matters precipitation. The process of fluid evolution is: first, with magma invasion in deeper area, hydrothermal fluid of magma mixied with strata-formed water transports up to near surface and quickly are boiling and form nonintermingle fluid, then mineral matters deposit form strangle lode ores; second, The late hydrothermal fluid of magma are boiling again to form main ores. The evolution of fluid is going along with two stages tectonic movement.On the basis of Geochemistry of fluid inclusion（fluid composition, fluid evolution, the fluid resource judged from the tracing of indifferent gas and REE）, it is approved that the mineralization fluid is from the formational water（water in the strata）and magma water in the Tongmugou, and is from the magma water in the Mujiazhuang（the first stage）, and is from the formational water and the deep-derived magma in the Mujiazhuang （the second stage）. In addition, the hydrogen and oxygen isotopic data of the Mujiazhuang copper deposit supports the results.The biotite associated with chalcopyrite in the Mujiazhuang copper deposit, its Ar-Ar age is 323.68Ma, which represents the age of mineralization. The forming age of hoepfnerite mineral was close to the forming time of Pb-Zn deposit, and the K-Ar surface age is 293Ma. The main ore-forming age of Cu-Pb-Zn deposits in the Zhashan area is about 323～293Ma.It is supposed that Carboniferous mineralization maybe was a very important metallogenesis period in the Zhashan area. The mineralization model of epigenetic fluid matomatism, is founded according to geological and geochemistry characteristics, and suggests a new direction for ore deposits exploration.更多还原