本文選題：疊合成礦作用 + 年代學(xué)��； 參考：《中國(guó)地質(zhì)大學(xué)》2017年博士論文

【摘要】：內(nèi)蒙古雙尖子山銀多金屬礦床位于大興安嶺南段黃崗-甘珠爾廟成礦帶,為超大型熱液脈型礦床,在時(shí)空分布上與中-晚侏羅世構(gòu)造-巖漿活動(dòng)關(guān)系密切。雙尖子山銀多金屬礦化產(chǎn)出在下二疊統(tǒng)大石寨組火山-沉積巖內(nèi),并且構(gòu)成似層狀、(長(zhǎng))扁豆?fàn)�、透鏡狀和囊狀等脈型礦體,且被中侏羅世火山巖所覆蓋。礦區(qū)內(nèi)三種主要礦化類型被認(rèn)知:主要賦存在蝕變圍巖中的浸染-細(xì)脈狀礦化、寄宿在北西向和北東向的脈和斷層中的角礫狀礦化。根據(jù)不同礦化類型的切割關(guān)系,雙尖子山銀多金屬礦化系統(tǒng)可能是相對(duì)較早的石英-細(xì)脈狀礦化被相對(duì)后期的脈型和角礫狀礦化所疊加。鋯石LA-ICP-MS U-Pb測(cè)年結(jié)果基本厘定了雙尖子山礦區(qū)及外圍侵入-火山巖的年代學(xué)格架,確定巖漿活動(dòng)主要分三個(gè)階段,分別為262~238 Ma、169~159 Ma和142~131 Ma,主要集中在晚二疊世-早三疊世、中-晚侏羅世和早白堊世三個(gè)階段。此外,北西向含礦石英脈的白云母Ar-Ar坪年齡為147±2 Ma和硫化物(毒砂、黃鐵礦)的Re-Os等時(shí)線年齡為159±6 Ma,以及含礦石英脈的鋯石U-Pb加權(quán)平均年齡給出了三組年齡值,分別為263±2 Ma,177±2 Ma和148±1 Ma。其中最年輕的一組數(shù)據(jù)(148±1 Ma)指示著巖漿熱液鋯石的年齡或石英脈形成的最晚時(shí)限。這些數(shù)據(jù)均顯示了雙尖子山脈型礦化可能與中晚侏羅世熱事件有關(guān)。礦床穩(wěn)定和放射性同位素地球化學(xué)指示,石英脈和角礫巖型礦石的成礦流體主要由巖漿水和高度演化的大氣降水組成,流體緩沖作用和成礦流體的混合是重要的成礦機(jī)理。C和S同位素均指示成礦流體中的碳和硫主要源于巖漿,并混染了部分圍巖。鉛同位素同樣證實(shí)了成礦流體的混合模式,成礦系統(tǒng)(浸染-細(xì)脈狀、脈型和角礫狀礦石)的鉛同位素呈現(xiàn)線性分布,主要分布在殼源鉛和地幔鉛之間,同樣也指示了成礦流體中的鉛源自深源,并混入了殼源鉛。根據(jù)礦石組合和礦石地球化學(xué),雙尖子山礦床是一個(gè)中溫中硫的銀多金屬礦床,其氧逸度和硫逸度分別是-35.1~-30.5和-17.2~-13.1,主成礦溫度為250~240℃,成礦物質(zhì)的沉淀主要是在流體混合和沸騰作用下由混合流體沉淀而成。與雙尖子山銀多金屬主礦化有關(guān)的中-晚侏羅世巖漿活動(dòng)可能是蒙古-鄂霍茨克洋閉合后的后造山伸展及古太平洋板塊俯沖共同作用的結(jié)果。這種聯(lián)合的動(dòng)力機(jī)制,引起構(gòu)造體制從擠壓到拉張的轉(zhuǎn)變,隨后引發(fā)大規(guī)模加厚下地殼和巖石圈地幔拆沉。巖石圈拆沉及隨后上涌的軟流圈地幔誘發(fā)大量巖漿的侵入,這些巖漿從深部帶來了大量的硫和其他金屬成礦元素,為后期大規(guī)模的熱液成礦提供了充足的物質(zhì)準(zhǔn)備,雙尖子山熱液脈型礦化就形成于這樣的構(gòu)造背景之下。
[Abstract]:The Shuangjianzishan silver polymetallic deposit in Inner Mongolia is located in the Huanggang-Ganjuermiao metallogenic belt in the southern section of the Daxinganling Mountains. It is a very large hydrothermal vein type deposit and is closely related to the tectonic-magmatic activity of the Middle-Late Jurassic in time and space. Shuangjianzishan silver polymetallic mineralization occurred in volcanic-sedimentary rocks of the Lower Permian Dashizhai formation, and formed a lamellar (long) lentil, lenticular and cystic vein orebody, which was covered by the volcanic rocks of the Middle Jurassic. Three main types of mineralization are recognized in the mining area: leaching and veinlike mineralization in altered surrounding rocks, and breccia mineralization in veins and faults in NW and NE directions. According to the cutting relationship of different mineralization types, the bangjianzishan silver polymetallic mineralization system may be superimposed by the relatively late vein type and breccia mineralization in the relatively early quartz-veinlike mineralization system. The zircon LA-ICP-MS U-Pb dating results have basically determined the geochronological framework of the intrusion-volcanic rocks in the Shuangjianzishan ore area and its periphery, and determined that magmatic activity is mainly divided into three stages, namely, 262an238Ma-169159Ma and 142Pn-131Ma, mainly concentrated in the late Permian-early Triassic. Middle-late Jurassic and early Cretaceous. In addition, the Ar-Ar plateau age of Muscovite and Re-Os isochron of sulfide (arsenopyrite, pyrite) in NW direction is 147 鹵2 Ma and 159 鹵6 Ma.The zircon U-Pb weighted mean age of ore-bearing vein gives three sets of age values. It is 263 鹵2 Ma 177 鹵2 Ma and 148 鹵1 Ma respectively. The youngest set of data (148 鹵1 Ma) indicates the age of magmatic hydrothermal zircon or the latest time limit for the formation of quartz veins. All these data suggest that the bipine-type mineralization may be related to the middle and late Jurassic thermal events. The deposit stability and radioisotope geochemistry indicate that the ore-forming fluid of quartz vein and breccia type ore is mainly composed of magmatic water and highly evolved atmospheric precipitation. The mixing of fluid buffer and ore-forming fluid is an important metallogenic mechanism. Both C and S isotopes indicate that the carbon and sulfur in the ore-forming fluid are mainly derived from magma and mixed with part of the surrounding rock. The lead isotopes also confirmed the mixed model of ore-forming fluids. The lead isotopes of the ore-forming systems (leaching-vein-vein, vein-type and breccia ores) showed a linear distribution, mainly between crust-derived lead and mantle lead. It also indicates that the lead in the ore-forming fluid originates from the deep source and mixed with the shell source lead. According to ore assemblage and ore geochemistry, Shuangjianzishan deposit is a medium temperature medium sulfur silver polymetallic deposit with oxygen fugacity and sulfur fugacity of -35.1 ~ 30.5 and -17.2 ~ (-2) ~ (-1), respectively. The main ore-forming temperature is 250 ~ 240 鈩，

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