本文選題：印支期造山型金成礦系統(tǒng)　切入點：多樣性與連續(xù)性　出處：《中國地質(zhì)大學(xué)(北京)》2016年博士論文

【摘要】：西秦嶺金礦帶內(nèi)印支期造山型金礦床分布地域廣泛、產(chǎn)出空間各異、礦化類型多樣,但其成礦時代、成礦地球動力學(xué)背景和成礦流體性質(zhì)等特征一致。論文選擇了位于南亞帶內(nèi)的陽山、鏵廠溝與馬腦殼三個造山型金礦床作為研究對象,聚焦于區(qū)域及礦區(qū)尺度三個礦床地質(zhì)特征的異同與其成因,通過系統(tǒng)的礦床地質(zhì)與礦床地球化學(xué)工作,獲得了如下主要成果。(1)區(qū)域尺度上,礦床的地質(zhì)特征顯示出連續(xù)性:金成礦事件發(fā)生于221~200 Ma,與區(qū)域變質(zhì)作用峰期同時或略滯后,成礦作用發(fā)生于后碰撞伸展環(huán)境;受控于勉略構(gòu)造帶及其二、三級斷裂構(gòu)造系統(tǒng),賦存于(低)綠片巖相變質(zhì)地體,礦化樣式有浸染型和石英脈型兩種,金礦化與硫化、硅化、碳酸鹽化蝕變密切相關(guān);初始成礦流體為中低溫、低鹽度的變質(zhì)流體。(2)礦區(qū)尺度上,礦床的地質(zhì)特征顯示出多樣性:鏵廠溝、陽山、馬腦殼分別為大型、超大型與大型金礦床,主要賦礦圍巖依次為細碧巖、千枚巖、板巖等;礦石礦物共生組合依次為黃鐵礦,黃鐵礦、毒砂、輝銻礦與黃鐵礦、毒砂、輝銻礦、雄(雌)黃等。(3)LA-ICP-MS微區(qū)原位分析顯示,三個礦床成礦早、主階段黃鐵礦、毒砂強烈富集Au、As和Te,不同程度富集Sb、Bi和Ag,不富集Cu和Zn,Pb、Co和Ni接近背景值;陽山及馬腦殼金礦床中輝銻礦呈略微富集Au、較強富集Ag的特征。這些特征表明成礦流體可能是來自區(qū)域變質(zhì)作用過程中變質(zhì)脫揮發(fā)分形成的含金變質(zhì)流體。礦床尺度硫化物微量元素的差異,是在不同成礦深度/環(huán)境下,成礦流體對元素運移的差異及不同的沉淀機制所致。(4)Sr-Nd-Pb同位素研究表明,深部中下地殼結(jié)晶基底與淺部就位環(huán)境中賦礦圍巖共同為金成礦提供了成礦物質(zhì)。(5)構(gòu)建了區(qū)域金成礦模式:晚三疊世后碰撞伸展環(huán)境下,區(qū)域大范圍的殼幔作用及廣泛的巖漿活動,引起巖石圈尺度地?zé)崽荻壬仙?驅(qū)動中下地殼物質(zhì)變質(zhì)脫揮發(fā)分形成的含金流體進入地殼尺度的斷裂系統(tǒng),在不同成礦深度/環(huán)境通過圍巖硫化、相分離或流體混合等,形成了一系列造山型金礦床。
[Abstract]:The Indosinian orogenic gold deposits in the West Qinling gold belt are widely distributed, have different occurrence space and various types of mineralization, but their metallogenic geodynamic background and ore-forming fluid properties are consistent in the metallogenic age.In this paper, three orogenic gold deposits, Yangshan, Huachanggou and Manaokou, which are located in the South Asian belt, are selected as the research objects, focusing on the similarities and differences of the geological characteristics and the genesis of the three ore deposits in the regional and mining scale.Based on the systematic geological and geochemical work of ore deposits, the following main achievements have been obtained: on the regional scale, the geological characteristics of the deposits show continuity: the gold mineralization event occurred at 221 ~ 200 Ma and was at the same or slightly behind the peak stage of regional metamorphism.Mineralization occurred in the post-collision extensional environment, controlled by the Mianluo tectonic belt and its secondary and tertiary fault systems, and occurred in the (low) greenschist phase change textures, with mineralization patterns of disseminated and quartz vein types, gold mineralization and sulfidation, silicification,Carbonate alteration is closely related; the initial ore-forming fluid is metamorphic fluid with medium and low temperature and low salinity. On the scale of the ore area, the geological characteristics of the deposit show diversity: the Huachanggou, Yangshan and Manaohou are large, super large and large gold deposits, respectively.The main ore-bearing rocks are in turn acrylite, phyllite, slate, etc. The ore mineral symbiotic assemblages are pyrite, pyrite, arsenopyrite, stibnite and pyrite, arsenopyrite, stibnite, male (female) yellow, etc. The in-situ analysis shows that the ore mineral symbiotic assemblage is pyrite, pyrite, arsenopyrite, stibnite, androgenite, etc.The three deposits are characterized by early mineralization, major stage pyrite and arsenopyrite, enrichment of SB, Bi and Ag to varying degrees, and no enrichment of Cu and ZnPbPb Co and Ni close to the background value, while in Yangshan and Manaoheng gold deposits, stibnite is slightly enriched in Auand strongly enriched in Ag.These characteristics suggest that the ore-forming fluid may be derived from the gold metamorphic fluid formed by metamorphic devolatilization during the regional metamorphism.The difference of trace elements in the scale of the deposit is due to the difference of the migration of elements in the ore-forming fluid and the different precipitation mechanism under different ore-forming depth / environment.The crystalline basement of the deep middle and lower crust and the ore-bearing surrounding rock in the shallow emplacement environment together provide the ore-forming material. 5) the regional gold metallogenic model is constructed: in the late Triassic post-collision extensional environment.The extensive crust and mantle action and extensive magmatic activity in the region cause the lithospheric geothermal gradient to rise, driving the gold-bearing fluid formed by metamorphic and devolatilized matter in the middle and lower crust into the crustal scale fracture system.A series of orogenic gold deposits were formed in different ore-forming depth / environment by surrounding rock vulcanization, phase separation or fluid mixing.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)(北京)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：P618.51

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