青海东昆仑莫河下拉银多金属矿区晚泥盆世花岗斑岩锆石U-Pb年代学及地球化学特征
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摘要
莫河下拉银多金属矿床是青海省东昆仑成矿带上近些年新发现的矿床。笔者对矿区平硐口花岗斑岩进行了LA-ICP-MS锆石U--Pb测年和岩石地球化学特征研究,以期揭示岩体的成岩时代、岩浆源区和形成的构造背景。锆石测年结果显示岩体形成于古生代晚泥盆世(371. 6±2. 9 Ma)。元素地球化学特征表现为高硅、高碱、富铁铝、相对富钾和贫钙镁的特征;微量元素表现为明显富集Rb、Th、La、Ce、Nd、Zr、Sm和Gd等元素,强烈亏损Ba、Sr、P、Ti等元素、相对亏损Nb和Ta的特征;稀土元素表现为轻稀土元素(LREE)明显富集和Eu的强烈负异常。综合研究认为,矿区平硐口花岗斑岩的成因类型为A2型花岗岩,形成物质来源主要为部分熔融的长英质地壳,形成的大地构造背景为晚泥盆世万宝沟大洋玄武岩高原和苦海古陆拼贴到柴达木地块南缘后的后碰撞伸展环境。
Mohexiala silver polymetallic deposit is a newly discovered deposit in the East Kunlun metallogenic belt of Qinghai in recent years. The zircon LA-ICP-MS U-Pb dating and geochemical characteristics of granite porphyry in Pingdongkou mine area are studied to reveal the diagenetic age,magma source area and tectonic setting. Zircon dating results show that it was formed in the Late Devonian( 371. 6 ± 2. 9 Ma) of Paleozoic. Elemental geochemistry is characterized by high Si,high alkali,rich in Fe and Al,relatively rich in K and poorin Ca and Mg. The trace elements are characterized by the enrichment of Rb,Th,La,Ce,Nd,Zr,Sm and Gd,but strong loss of Ba,Sr,P,Ti,etc.,and relatively poor in Nb and Ta. Rare earth elements are characterized by obvious enrichment of light rare earth elements( LREE) and strong negative Eu anomalies. Comprehensive studies show that the genetic type of Pingdongkou granite porphyry in the mining area is A type of granite,with the forming material mainly from partial melting of felsic crust. The geotectonic setting of its formation is the post-collision extensional environment resulted from the collaging of Wanbaogou oceanic basalt plateau and Kuhai ancient land to the southern margin of Qaidam block in Late Devonian.
Mohexiala silver polymetallic deposit is a newly discovered deposit in the East Kunlun metallogenic belt of Qinghai in recent years. The zircon LA-ICP-MS U-Pb dating and geochemical characteristics of granite porphyry in Pingdongkou mine area are studied to reveal the diagenetic age,magma source area and tectonic setting. Zircon dating results show that it was formed in the Late Devonian( 371. 6 ± 2. 9 Ma) of Paleozoic. Elemental geochemistry is characterized by high Si,high alkali,rich in Fe and Al,relatively rich in K and poorin Ca and Mg. The trace elements are characterized by the enrichment of Rb,Th,La,Ce,Nd,Zr,Sm and Gd,but strong loss of Ba,Sr,P,Ti,etc.,and relatively poor in Nb and Ta. Rare earth elements are characterized by obvious enrichment of light rare earth elements( LREE) and strong negative Eu anomalies. Comprehensive studies show that the genetic type of Pingdongkou granite porphyry in the mining area is A type of granite,with the forming material mainly from partial melting of felsic crust. The geotectonic setting of its formation is the post-collision extensional environment resulted from the collaging of Wanbaogou oceanic basalt plateau and Kuhai ancient land to the southern margin of Qaidam block in Late Devonian.
引文
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[2]佘宏全,张德全,景向阳,等.青海省乌兰乌珠尔斑岩铜矿床地质特征与成因[J].中国地质,2007,34(2):306-314.SHE Hong-quan,ZHANG De-quan,JING Xiang-yang,et al.Geological characteristics and genesis of the Ulan Uzhur porphyry copper deposit in Qinghai[J].Geology in China,2007,34(2):306-314.
[3]李世金,孙丰月,王力,等.青海东昆仑卡尔却卡多金属矿区斑岩型铜矿的流体包裹体研究[J].矿床地质,2008,27(3):399-406.LI Shi-jin,SUN Feng-yue,WANG Li,et al.Fluid inclusion studies of porphyry copper mineralization in Kaerqueka polymetallic ore district,East Kunlun Mountains,Qinghai province[J].Mineral Deposits,2008,27(3):399-406.
[4]何书跃,李东生,李良林,等.青海东昆仑鸭子沟斑岩型铜(钼)矿区辉钼矿铼-锇同位素年龄及地质意义[J].大地构造与成矿学,2009,33(2):236-242.HE Shu-yue,LI Dong-sheng,LI Liang-lin,et al.Re-Os age of molybdenite from the Yazigou copper(molybdenum)mineralized area in Eastern Kunlun of Qinghai province,and its geological significance[J].Geotectonica et Metallogenia,2009,33(2):236-242.
[5]丰成友,李东生,吴正寿,等.青海东昆仑成矿带斑岩型矿床的确认及找矿前景分析[J].矿物学报,2009,29(增刊1),171-172.FENG Cheng-you,LI Dong-sheng,WU Zheng-shou,et al.Confirmation of porphyry deposits in the East Kunlun metallogenic belt of Qinghai province and analysis of prospecting prospects[J].Acta Mineralogica Sinica,2009,29(Suppl.1):171-172.
[6]李碧乐,孙丰月,于晓飞,等.青海东昆仑卡尔却卡地区野拉塞铜矿床成因类型及成矿机制[J].岩石学报,2010,26(12):3796-3708.LI Bi-le,SUN Feng-yue,YU Xiao-fei,et al.Genetic type and mineralizing mechanism of the Yelasai copper deposit in Kaerqueka area,eastern Kunlun,Qinghai province[J].Acta Petrologica Sinica,2010,26(12):3796-3708.
[7]向鹏,熊索菲.青海省共和县加当根铜(钼)矿矿床类型探讨[J].矿床地质,2010,29(增刊1):303-304.XIANG Peng,XIONG Suo-fei.Discussion on the types of Jiadanggen Cu(Mo)deposit in Gonghe county,Qinghai province[J].Mineral Deposits,2010,29(Suppl.1):303-304.
[8]刘建楠,丰成友,亓锋,等.青海都兰县下得波利铜钼矿区锆石U-Pb测年及流体包裹体研究[J].岩石学报,2011,28(2):679-690.LIU Jian-nan,FENG Cheng-you,QI Feng,et al.SIMSzircon U-Pb dating and fluid inclusion studies of Xiadeboli Cu-Mo ore district in Dulan county,Qinghai province,China[J].Acta Petrologica Sinica,2011,28(2):679-690.
[9]李洪普.东昆仑祁漫塔格铁多金属矿成矿地质特征与成矿预测:博士学位论文[D].北京:中国地质大学,2010.LI Hong-pu.Metallogenic geological characteristics and metallogenic prediction of Qimantage iron and polymetallic deposit of East Kunlun Mountains:doctor's degree thesis[D].Beijing:China University of Geosciences,2010.
[10]许庆林,孙丰月,李碧乐,等.东昆仑莫河下拉银多金属矿床花岗斑岩年代学、地球化学特征及其构造背景[J].大地构造与成矿学,2014,38(2):421-433.XU Qing-lin,SUN Feng-yue,LI Bi-le,et al.Geochronological dating,geochemical characteristics and tectonic setting of the granite-porphyry in the Mohexiala silver polymetallic deposit,Eastern Kunlun orogenic belt[J].Geotectonica et Metallogenia,2014,38(2):421-433.
[11]古凤宝.东昆仑地质特征及晚古生代-中生代构造演化[J].青海地质,1994(1):4-14.GU Feng-bao.Geological characteristics of east Kunlun and tectonic evolution in Late Palaezoic-Mesozoic era[J].Qinghai Geology,1994(1):4-14.
[12]许志琴,姜枚,杨经绥.青藏高原北部隆升的深部构造物理作用:以“格尔木-唐古拉山”地质及地球物理综合剖面为例[J].地质学报,1996(3):195-206.XU Zhi-qin,JIANG Mei,YANG Jing-sui.Tectono physical process at depth for the uplift of the northern part of the Qinghai-Tibet plateau:illustrated by the geological and geophysical comprehensive profile from golmud to the tanggula mountains,Qinghai province,China[J].Acta Geolocica Sinica,1996(3):195-206.
[13]张双全,莫宣学,郭铁鹰,等.西冈底斯中段中、新生代火山岩的大地构造意义[J].地学前缘,1998(3):85.ZHANG Shuang-quan,MO Xuan-xue,GUO Tie-ying,et al.Tectonic significance of Mesozoic and Cenozoic era volcanic rocks in the middle part of west Gangdese[J].Earth Science Frontiers,1998(3):85.
[14]孙丰月,陈国华,迟效国,等.东昆仑成矿带成矿规律和找矿方向综合研究调查报告[R].长春:吉林大学,2003.SUN Feng-yue,CHEN Guo-hua,CHI Xiao-guo,et al.Investigation report on metallogenic law and prospecting direction of East Kunlun metallogenic belt[R].Changchun:Jilin University,2003.
[15]Andersen T.Correction of common lead in U-Pb analyses that do not report204Pb[J].Chemical Geology,2002,192(1):59-79.
[16]Pupin J P.Zircon and granite petrology[J].Contributions to Mineralogy&Petrology,1980,73(3):207-220.
[17]Koschek G.Origin and significance of the SEM cathode luminescence from zircon[J].Journal of Microscopy,1993,171(3):10.
[18]Belousova E,Griffin W,O'Reilly S Y,et al.Igneous zircon:trace element composition as an indicator of source rock type[J].Contributions to Mineralogy&Petrology,2002,143(5):602-622.
[19]Wilson M.Igneous petrogenesis[M].London:Unwin Hyman Ltd,1989:1-466.
[20]Rickwood P C.Boundary lines within petrologic diagrams which use oxides of major and minor elements[J].Lithos,1989,22:247-263.
[21]Maniar P D,Piccoli P M.Tectonic discrimination of granitoids[J].Geological Society of America Bulletin,1989,10:635-643.
[22]Whalen J B,Currie K L,Chappell B W.A-type granites:geochemical characteristics,discrimination and petrogenesis[J].Contributions to Mineralogy and Petrology,1987,95(4):407-419.
[23]贾小辉,王强,唐功建.A型花岗岩的研究进展及意义[J].大地构造与成矿学,2009,33(3):465-480.JIA Xiao-hui,WANG Qiang,TANG Gong-jian.A-type granites:research progress and implications[J].Geotectonica et Metallogenia,2009,33(3):465-480.
[24]Frost C D,Frost B R.On ferroan(A-type)granitoids:their compositional variability and modes of origin[J].Journal of Petrology,2011,52(1):39-53.
[25]王德滋,刘昌实,沈渭洲,等.桐庐I型和相山S型两类碎斑熔岩对比[J].岩石学报,1993,9(1):44-54.WANG De-zi,LIU Chang-shi,SHEN Wei-zhou,et al.The contrast between Tonglu I-type and Xiangshan S-type clasto porphyritic lava[J].Acta Petrologica Sinica,1993,9(1):44-54.
[26]高阳,张招崇,杨铁铮.黑龙江宝山一带海西晚期强过铝花岗岩地质地球化学及岩石成因[J].岩石矿物学杂志,2009,28(5):433-449.GAO Yang,ZHANG Zhao-chong,YANG Tie-zheng.Geology-geochemistry and petrogenesis of Late Hercynian granites in Baoshan area,Heilongjiang province[J].Acta Petrologica et Mineralogica,2009,28(5):433-449.
[27]Taylor S R,Mclennan S M.The chemical composition of the Archaean crust[J].Geological Society London Special Publications,1986,24:173-178.
[28]Altherr R,Holl A,Hegner E,et al.High-potassium,calc-alkaline I-type plutonism in the European variscides:northern Vosges(France)and northern Schwarzwald(Germany)[J].Lithos,2000,50(1):51-73.
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