安徽铜陵狮子山矿田铜、金共生与分离的热力学研究
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摘要
狮子山矿田是安徽铜陵矿集区内最具代表性的大型铜金多金属矿田。矿田内铜、金矿床或矿体既各自独立产出,又相互共生或伴生,铜矿化和金矿化在时间上和空间上存在既共生又分离的现象。本文选择矿田内代表性铜矿床和金矿床开展系统的流体包裹体地球化学研究,并进行成矿流体中铜、金溶解度的热力学理论计算和分析,探索铜、金共生与分离的机制和制约因素。研究认为,狮子山矿田成矿热液流体中的铜主要以CuCl2-和CuCl0络合物形式迁移,铜的溶解度受热液中的Cl-浓度影响,铜的卸载沉淀主要受温度、pH值、fO2和fS2等因素控制;金主要以Au(HS)2-和Au2S(HS)22-络合物形式迁移,金的溶解度受热液中的总硫浓度影响,金的卸载沉淀同样受温度、pH值、fO2和fS2等因素控制。共存于同一成矿流体中的铜和金由于其络合物类型和溶解度的差异及其对物理化学条件变化作出的响应不同,铜在较高温度及偏酸性条件下即开始沉淀,而金则在较低温度和弱碱性条件下开始沉淀,因而导致铜和金的时空分离,进而分别形成铜矿床和金矿床。
Shizishan orefield is the most representative large-scale copper-gold orefield in the Tongling ore-intensive district,Anhui Province.Copper deposits and gold deposits in the district exist individually or paragenetically.Copper and gold mineralization occurs in paragenesis or separation both temporally and spatially.This study carried out systematic geochemical research on fluid inclusions from typical Cu-Ag deposits in the orefield and calculated and analyzed the solubility of Cu and Au in the ore-forming fluids so as to probe the mechanism of separation and paragenesis of copper and gold and controlling factors.The research indicates that copper in the ore-forming fluids of the Shizishan orefield occurred mainly as Cu complexes CuCl-2 and CuCl0 which migrated.Copper solubility was affected by the Cl- concentration and unloading and precipitation of copper were affected by temperature,pH,fO2 and fS2.While gold occurred as the complexes Au(HS)-2 and Au2S(HS)2-2 to migrate and gold solubility was always influenced by the total sulfur concentration.The unloading and precipitation of gold was controlled by temperature,pH,fO2 and fS2.Due to the complex types and solubility difference,copper and gold in the same ore-forming fluid responded very differently to the physicochemical conditions.Copper precipitates in relatively acid condition at high temperature while gold in a weak alkaline condition at relatively low temperature,thus resulting in temporal-spatial separation and mineralization of copper and gold.
Shizishan orefield is the most representative large-scale copper-gold orefield in the Tongling ore-intensive district,Anhui Province.Copper deposits and gold deposits in the district exist individually or paragenetically.Copper and gold mineralization occurs in paragenesis or separation both temporally and spatially.This study carried out systematic geochemical research on fluid inclusions from typical Cu-Ag deposits in the orefield and calculated and analyzed the solubility of Cu and Au in the ore-forming fluids so as to probe the mechanism of separation and paragenesis of copper and gold and controlling factors.The research indicates that copper in the ore-forming fluids of the Shizishan orefield occurred mainly as Cu complexes CuCl-2 and CuCl0 which migrated.Copper solubility was affected by the Cl- concentration and unloading and precipitation of copper were affected by temperature,pH,fO2 and fS2.While gold occurred as the complexes Au(HS)-2 and Au2S(HS)2-2 to migrate and gold solubility was always influenced by the total sulfur concentration.The unloading and precipitation of gold was controlled by temperature,pH,fO2 and fS2.Due to the complex types and solubility difference,copper and gold in the same ore-forming fluid responded very differently to the physicochemical conditions.Copper precipitates in relatively acid condition at high temperature while gold in a weak alkaline condition at relatively low temperature,thus resulting in temporal-spatial separation and mineralization of copper and gold.
引文
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储国正,2003.铜陵狮子山矿田成矿系统及其找矿意义.博士学位论文.北京:中国地质大学,1~163.
邓晋福,戴圣潜,赵海玲,杜建国.2002.铜陵Cu-Au(Ag)成矿区岩浆-流体-成矿系统和亚系统的识别.矿床地质,21(4):317~322.
邓晋福,吴宗絮.2001.下扬子克拉通岩石圈减薄事件与长江中下游Cu、Fe成矿带.安徽地质,11(2):86~95.
黄许陈,储国正.1993.铜陵狮子山矿田多位一体(多层楼)模式.矿床地质,12(3):221~229.
胡受奚,陈武,华仁民.1992.气化-热液矿床的侧向分带及其成因机制.矿床地质,11(4):291~300.
林传仙,白正华,张哲儒.1985.矿物及有关化合物热力学数据手册.北京:科学出版社.1~355.
刘斌,沈昆.1999.流体包裹体热力学.北京:地质出版社.1~290
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卢焕章.1997.成矿流体.北京:北京科学技术出版社,35~80.
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陆三明.2007.安徽铜陵狮子山铜金矿田岩浆作用和流体成矿.合肥合肥工业大学博士学位论文,1~158.
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毛景文,邵拥军,谢桂清,张建东,陈毓川.2009.长江中下游成矿带铜陵矿集区铜多金属矿床模型.矿床地质,28(2):109~119.
孟祥金,侯增谦,高永丰,曲晓明,黄卫.2004.碰撞造山型斑岩铜矿蚀变分带模式——以西藏冈底斯斑岩铜矿带为例.地学前缘,11(1):201~214.
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唐永成,吴言昌,储国正,邢凤鸣,王永敏,曹奋扬,常印佛.1998.安徽沿江地区铜金多金属矿床地质.北京:地质出版社,1~351.
王登红.1998.地幔柱及其成矿作用.北京:地震出版社,1~160.
王莉娟.1998.流体包裹体成分分析研究.地质论评,44(5):496~501.
王彦斌,刘敦一,曾普胜,杨竹森,田世洪.2004.安徽铜陵地区幔源岩浆底侵作用的时代——朝山辉石闪长岩锆石SHRI MP定年.地球学报,25(4):423~27.
吴才来,周若,黄许陈,张成火,黄文明.1996.铜陵地区中酸性侵入岩年代学研究.岩石矿物学杂志,15(4):299~306.
吴才来,董树文,国和平,郭祥焱,高前明,刘良根,陈其龙,雷敏,Wooden J L,Mazadab F K,Mattinson C.2008.铜陵狮子山地区中酸性侵入岩锆石SHRI MP U-Pb定年及岩浆作用的深部过程.岩石学报,24(8):1801~1812.
涂光炽.1988.中国层控矿床地球化学.北京:科学出版社.
徐德义,於崇文,鲍征宇.2005.热液成矿分带的径向对称性.地学前缘,12(2):303~308.
徐克勤,朱金初.1978.我国东南部几个断裂凹陷带中沉积(或火山沉积)?热液叠加类铁铜矿床成因探讨.福建地质科学情报,(4):1~68.
徐晓春,陆三明,谢巧勤,柏林,储国正.2008a.铜陵狮子山矿田岩浆岩锆石SHRI MP定年及其成因意义.地质学报,82(4):500~509.
徐晓春,陆三明,谢巧勤,楼金伟,褚平利.2008b.安徽铜陵冬瓜山铜金矿床流体包裹体微量元素地球化学特征及其地质意义.岩石学报,24(8):1865~1874.
徐晓春,尹滔,楼金伟,陆三明,谢巧勤,褚平利.2010.铜陵冬瓜山层控矽卡岩型铜金矿床的成因机制:硫同位素制约.岩石学报,26(9):2739~2750.
徐晓春,赵丽丽,谢巧勤,褚平利,房海波,王文俊.2009.铜陵狮子山矿田金矿床和铜矿床矿石稀土元素地球化学.高校地质学报,15(1):35~47.
曾贻善.1993.热水溶液中化学元素的迁移形式.北京:地质出版社,50~90.
翟裕生,林新多,姚书振.1992.长江中下游地区铁铜(金)成矿规律.北京:地质出版社,1~235.
张德会.1997.成矿流体中金的沉淀机理研究综述.矿物岩石.7(4):122~129.
朱和平,王莉娟,刘建明.2003.不同成矿阶段流体包裹体气相成分的四极质谱测定.岩石学报,19(2):314~318.
ВИ西尼雅科夫.1987.内生矿床的一般矿石成因模式.江胜璧译,1991.安徽省地矿局科技情报室,矿床模式译文专辑,1~13.
Benedetti M,Bouleque J.1991.Mechanism of gold transfer anddeposition in a supergene environment:Geochi mica etCosmochi mica Acta,55:1539~1547.
Benning L G,Seward T W.1996.Hydrosulphide complex of Au(I)in hydrothermal solutions from150?400℃and5001500bar:Geochi mica et Cosmochi mica Acta,60:500~1000.
Bodnar B J.1993.Revised equation and table for determining thefreezing point depression of H2O-NaCl solution.Geochemicaet Cosmochemica Acta,57:683~684.
Cox D P,Singer D A.1986.Mineral deposit models.United StatesGeological Survey Bulletin,1693.
Du Y S,Tian S H,Li X J.2003.Contrast in fluid metallogeny between the Tianmashan Au-S deposit and Datuanshan Cudeposit in Tongling,Anhui province.Acta geologica Sinica,77(1):116~124.
Hall D L,Sterner S M,Bodnar R J.1988.Freezing pointdepression of NaCl-KCl-H2O solution.Economic Geology,83:197~202.
Helgeson H C.1969.Thermodynamics of hydrothermal systems atelevated temperatures and pressures:American JournalScinece,267:729~804.
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