【摘要】：河南嵩縣七畝地溝金礦床位于華北克拉通南緣的熊耳山地區(qū)。礦床賦存在中元古代熊耳群中酸性火山巖中,礦體嚴(yán)格受構(gòu)造斷裂帶控制,主要呈脈狀產(chǎn)出,礦石以石英脈型占主導(dǎo),少量蝕變巖型;主要礦石礦物為黃鐵礦、少量方鉛礦、閃鋅礦、黃銅礦等。圍巖蝕變以硅化、絹云母化、綠泥石化和碳酸鹽化為主。成礦過(guò)程從早到晚可分為3個(gè)階段:石英-黃鐵礦階段、黃鐵礦-石英-多金屬硫化物階段和石英-方解石階段。不同成礦階段的石英和/或方解石中廣泛發(fā)育流體包裹體。早階段和中階段石英中CO_2型流體包裹體、NaCl-H_2O型流體包裹體、含子礦物流體包裹體均有發(fā)育,晚階段方解石中主要發(fā)育NaCl-H_2O型流體包裹體。從早階段到晚階段,流體包裹體均一溫度分別為254℃-397℃、221℃-397℃、162℃-237℃,鹽度從早階段雙峰鹽度值3.52-21.88wt.%NaCl.eqv和34.95-45.33wt.%NaCl.eqv,經(jīng)中階段雙峰鹽度值0.42-13.83wt.%NaCl.eqv和29.11-42.48wt.%NaCl.eqv,到晚階段鹽度為0.35-5.86wt.%NaCl.eqv。早階段和中階段CO_2型包裹體估算的捕獲壓力為93-199MPa、47-169MPa,晚階段W型包裹體估算的捕獲壓力為28-64MPa,相應(yīng)的成礦深度為3.4-7.2km、1.7-6.2km和2.9-6.5km,指示成礦發(fā)生在地殼隆升過(guò)程中,區(qū)域應(yīng)力場(chǎng)由擠壓向伸展轉(zhuǎn)變。流體沸騰作用是導(dǎo)致硫化物和金等成礦物質(zhì)快速沉淀的主要機(jī)制,通過(guò)沸騰和大氣降水的混合,成礦流體系統(tǒng)由富CO_2向貧CO_2演化,由變質(zhì)流體向大氣降水演化。本研究在不同中段內(nèi)系統(tǒng)采集了不同成礦階段的蝕變巖型和石英脈型礦石樣品,利用電感耦合等離子體質(zhì)譜(ICP-MS)方法分析樣品內(nèi)黃鐵礦、全巖微量元素和稀土元素,以此反映成礦流體演化。與碳質(zhì)球粒隕石相比,各階段黃鐵礦的LREE比HREE更富集,Hf/Sm和Th/La值總體小于1,表明成礦流體中富Cl-,F-含量低。與大陸上地殼相比,黃鐵礦微量元素特征表明成礦流體富集親硫元素Cu、Pb和鐵族元素Co、Ni。各階段黃鐵礦Ce異常較弱(δCe值0.60-1.08),表明在成礦過(guò)程中物理化學(xué)條件為還原環(huán)境。Eu~(2+)易于在高溫條件下存在,形成正異常,黃鐵礦內(nèi)Eu無(wú)異常,早階段δEu值0.71-1.29,變化范圍較大,個(gè)別樣品δEu值大于1,中階段δEu值0.89-0.92,變化范圍減小,分布在0.90左右,晚階段δEu值為1.13,δEu值變化特征表明成礦前期流體溫度總體較低,成礦后期流體溫度較低,可能有較高溫度的熱液混入。同一熱液體系中Y/Ho和Zr/Hf比較穩(wěn)定,七畝地溝金礦床各成礦階段Y/Ho和Zr/Hf值變化范圍較大,表明成礦各階段熱液體系可能受到干擾,發(fā)生了交代作用或有外來(lái)熱液加入。δ~(18)O水的平均值從早階段的5.8‰,經(jīng)中階段的3.5‰,到晚階段的-4.4‰,δD值介于-79‰和-96‰之間。成礦流體中的δ13CCO_2值介于-0.9‰和-22.2‰之間,平均為-13.0‰。C、H、O同位素研究表明七畝地溝金礦床的成礦流體可能最初來(lái)自變質(zhì)熱液作用,隨著時(shí)間的推移,逐漸與大氣降水混合。
[Abstract]:The Qimu Digou gold deposit in Songxian, Henan Province is located in Xiong'er Mountain area on the southern margin of North China Craton. The ore body is strictly controlled by tectonic fault zone and mainly occurs in vein shape. The ore is dominated by quartz vein type with a small amount of altered rock type, and the main ore mineral is pyrite, a small amount of galena, the ore body is mainly controlled by tectonic fault zone, and the ore body is dominated by quartz vein type with a small amount of altered rock, and the main ore mineral is pyrite with a small amount of galena. Sphalerite, chalcopyrite, etc. The main alteration of surrounding rock is silicification, sericite, green mud petrifaction and carbonization. The metallogenic process can be divided into three stages from early to late: quartz-pyrite stage, pyrite-quartz-polymetallic sulfide stage and quartz-calcite stage. Fluid inclusions are widely developed in quartz and / or calcite at different metallogenic stages. The CO_2 fluid inclusions of CO_2 type and the submineral fluid inclusions of CO_2 type are developed in the early and middle stages of quartz, and the NaCl-H_2O type fluid inclusions are mainly developed in the late stage of calcite. From early stage to late stage, the homogenization temperature of fluid inclusions was 254 鈩，

本文編號(hào)：2250180