安徽铜陵狮子山矿田岩浆岩锆石U-Pb年龄意义
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摘要
铜陵地区中酸性侵入岩与广泛分布的铜、金矿床有着密切成因关系。为有效限定狮子山矿田内岩浆活动时代,对其中岩性由辉石闪长质、石英闪长质至花岗闪长质的侵入岩体进行系统的锆石LA-ICPMS定年研究,获得南洪冲花岗闪长岩的206Pb/238U年龄为141.2±1.6Ma。在辉石闪长岩和石英闪长岩中发现继承锆石(继承锆石构成的核部),为揭示分散复杂的年龄中包含的地质意义,通过综合相关研究成果,做207Pb/235U-206Pb/238U图解,发现年龄介于太古宙到古元古代和年龄介于中元古代到早白垩世的投影点分别构成了不一致直线(下交点年龄分别为1785-+6649Ma,141.9±8.1Ma;上交点年龄分别是2795+-9801Ma,1290±12Ma,其中,141.9±8.1Ma与燕山期岩浆活动时代相一致,而三个较为古老的交点年龄与年轻地壳中锆石的统计峰值年龄(2.7Ga、1.9Ga、1.2Ga)较为接近,暗示了壳源物质加入的可能性;通过把已发表的岩浆成分数据代入由锆石结晶实验获得的公式,得到Zr饱和温度,辉石闪长岩为650~700℃,石英闪长岩为750~790℃,花岗闪长岩为750~760℃。饱和温度、Zr-SiO2图解和继承锆石出现的事实,共同表明狮子山矿田内岩浆温度偏低。
The Yanshanian plutons that occur extensively in Tongling,Anhui Province are essential to the genesis of world-class strata-bound ore deposits.We have sampled plutons ranging from gabbroic diorite to granodiorite in the Shizishan orefield to conduct systematical studies on geochronology with LA ICPMS.The magmatic zircons from the Nanhongchong granodiorite yield an age of 141.2±1.6 Ma.A number of inherited zircons(or inherited cores)have been found in Baimangshan gabbroic diorite as well as Qingshanjiao quartz diorite.In order to reveal geological significance of complicated ages,the age data for these zircons and age data for adjacent quartz diorites are plotted on the 207Pb/235U and 206Pb/238U diagram,from which two groups of age data(one group ranging from Archean to paleo Proterozoic,and the other from middle Paleozoic to Early Cretaceous),do not constitute a straight line,with lower intercepts at 1785+64__-69 and 141.9±8.1 Ma and upper intercepts at 2795+91__-80Ma,1290±12 Ma respectively.Of the four ages,the second(141.9±8.1 Ma)is consistent to the times of Yanshanian magma activity and the other three are the old intercept age,close to the three statistical age peaks(2.7Ga,1.9Ga and 1.2Ga)for juvenile continental crust,implying a possibility of supplement of crustral materials.ZrSiO_2 correlation diagram,and the presence of inherited zircons indicate that zirconium reached to saturation in the magma;consequently,the dominant magmatic temperatures were close to the calculated temperatures for saturated zirconium(for gabbroic diorite:650~700℃,quartz diorite:750~790℃ and granodiorite:750~760℃),indicating that the magma temperature in Shizishan was relatively lower.
The Yanshanian plutons that occur extensively in Tongling,Anhui Province are essential to the genesis of world-class strata-bound ore deposits.We have sampled plutons ranging from gabbroic diorite to granodiorite in the Shizishan orefield to conduct systematical studies on geochronology with LA ICPMS.The magmatic zircons from the Nanhongchong granodiorite yield an age of 141.2±1.6 Ma.A number of inherited zircons(or inherited cores)have been found in Baimangshan gabbroic diorite as well as Qingshanjiao quartz diorite.In order to reveal geological significance of complicated ages,the age data for these zircons and age data for adjacent quartz diorites are plotted on the 207Pb/235U and 206Pb/238U diagram,from which two groups of age data(one group ranging from Archean to paleo Proterozoic,and the other from middle Paleozoic to Early Cretaceous),do not constitute a straight line,with lower intercepts at 1785+64__-69 and 141.9±8.1 Ma and upper intercepts at 2795+91__-80Ma,1290±12 Ma respectively.Of the four ages,the second(141.9±8.1 Ma)is consistent to the times of Yanshanian magma activity and the other three are the old intercept age,close to the three statistical age peaks(2.7Ga,1.9Ga and 1.2Ga)for juvenile continental crust,implying a possibility of supplement of crustral materials.ZrSiO_2 correlation diagram,and the presence of inherited zircons indicate that zirconium reached to saturation in the magma;consequently,the dominant magmatic temperatures were close to the calculated temperatures for saturated zirconium(for gabbroic diorite:650~700℃,quartz diorite:750~790℃ and granodiorite:750~760℃),indicating that the magma temperature in Shizishan was relatively lower.
引文
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杜杨松,李顺庭,曹毅,秦新龙,楼亚儿.2007.安徽铜陵铜官山矿区中生代侵入岩的形成过程——岩浆底侵、同化混染和分离结晶,现代地质,2007,21(1):71～77.
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高庚,徐兆文,杨小男,王云健,张军,蒋少涌,凌洪飞.2006.安徽铜陵白芒山岩体的成因:Sr-Nd-Pb-O同位素制约,南京大学学报,42(3):269～279.
高山,Qiu Yumin,凌文黎,McNaughton NJ,Groves DI.2001.崆岭高级变质地体单颗粒锆石SHRI MPU-Pb年代学研究——扬子克拉通>3.2Ga陆壳物质的发现.中国科学(D辑),31(1):27～35.
黄顺生,徐兆文,顾连兴,华明,陆现彩,际建军,聂桂平,朱士鹏.2004.安徽铜陵狮子山矿田岩浆岩地球化学特征及成因机制探讨.高校地质学报,10(2):217～226.
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.
王彦斌,刘敦一,曾普胜,杨竹森,田世洪.2004a.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):423～427.
王彦斌,刘敦一,曾普胜,杨竹森,蒙义峰,田世洪.2004b.铜陵地区小铜官山石英闪长岩锆石SHRI MP的U-Pb年龄及其成因指示.岩石矿物学杂志,23(4):298～304.
王彦斌,刘敦一,蒙义峰,曾普胜,杨竹森,田世洪.2004c.安徽铜陵新桥铜-硫-铁-金矿床中石英闪长岩和辉绿岩锆石SHRI MP年代学及其意义,中国地质,31(2):169～173.
王元龙,王焰,张旗,贾秀琴,韩松.2004.铜陵地区中生代中酸性侵入岩的地球化学特征及其成矿-地球动力学意义,岩石学报,20(2):325～338.
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,周若,黄许陈,张成火.1994.铜陵地区中酸性侵入岩锆石群结晶特征及成因.岩石矿物学杂志,13(3):239～247.
邢凤鸣.1999.安徽沿江地区岩浆成矿带.安徽地质,9(4):272～279.
邢凤鸣,徐祥.1995.安徽沿江地区中生代岩浆岩的基本特点.岩石学报,11(4):409～422.
徐夕生,范钦成,O’Reilly S Y,蒋少涌,Griffn WL,王汝成,邱检生.2004.安徽铜官山石英闪长岩及其包体锆石U-Pb定年与成因探讨.科学通报,49(18):1883～1890.
杨小男,徐兆文,张军,王云健,徐夕生,蒋少涌,凌洪飞,刘良根,陈达源.2007.安徽狮子山矿田南洪冲岩体形成时代及成因机制研究.岩石学报,23(6):1543～1551.
翟裕生,姚书振,林新多,周若,万天丰,全福全,周宗桂.1992.长江中下游地区铁铜(金)成矿规律.北京:地质出版社.
张达,吴淦国,狄永军,臧文拴,邵拥军,余心起,张祥信,汪群峰.2006.铜陵凤凰山岩体SHRI MP锆石U-Pb年龄与构造变形及其对岩体侵位动力学背景的制约.地球科学,31(6):823～829.
Andersen T.2002.Correction of common Pbin U-Pb analyses thatdo not report204Pb.Chem Geology,192:59～79.
Chappell B W,Bryant C J,Wyborn D,White AJ R,Williams I S.1998.High-and low-temperature I-type granites.ResourceGeology,48:225～236.
Condie K C.1998.Episodic continental growth andsupercontinents:a mantle avalanche connection Earth andPlanetary Science Letters,163:97～108.
Condie K C.1995.Episodic ages of greenstones:a key to mantledynamics Geophys Res Lett,22:2215～2218.
Di Yongjun,Wu Ganguo,Zhang Da,Song Biao,Zhang Wenshuan,Zhang Zhongyi,Li Jinwen.2005.SHRI MP U-Pb ZirconGeochronology of the Xiaotongguanshan and Shatanjiaointrustions and its petrological i mplications in the Tonglingarea,Anhui.Acta Geologica Sinica,79(6):795～802.
Griffin WL,Belousva E A,Shee S R,Pearson NJ,O'Reilly SY.2004.Archean crustal evolutionin the northern Yilgrn Craton:U-Pb and Hf-isotope evidence from detrital zircons.Precambrian Research,131(3-4):231～282.
Jackson S E,Pearson NJ,Griffin WL,Belousova E A.2004.Theapplication of laser ablation-inductively coupled plasma-massspectrometry to in situ U-Pb zircon geochronology.ChemicalGeology,211:47～69.
Ludwig K R.2000.Isoplot a geochronological toolkit for MicrosoftExcel.Berkeley Geochronoly Center Special Publication,No1a.
Stein M,Hoff mann A W.1994.Mantle plumes and episodic crustalgrowth,Nature,372:63～68.
Wang Qiang,Xu Jifeng,Zhao Zhenhua,Xiong Xiaolin,Bao Zhi wei.2003.Petrogenesis of the Mesozoic intrusive rocks in theTongling area,Anhui Province,China and their constraint ongeodynamic process.Science in China(Ser.D)46(8):801～805.
Watson B E,Harrison M T.1983.Zircon saturation revisited:temperature and composition effects in a variety of crustalmagma types.Earth and Planetary Science Letters,64:295～304.
Wetherill G W.1956.An interpretation of the Phodesia andWitwatersrand age patterns.Geochi mica et Cosmochi micaActa,9:290～292.
Xing Fengming,Xu Xiang,Li Zhichang.1994.Discovery of theearly Proterozoic basement in the Middle-Lower reaches ofYangtze River andits significance.Chinese Science Bulletin,39(2):135～139.
Xu Zhaowen,Lu Xiancai,Ling Hongfei,Lu Jianjun,JiangShaoyong,Nie Guiping,Huang Shunsheng,Hua Ming.2005.Metallogenetic mechanism and ti ming of late superi mposingfluid mineraliztion in the Dongguashan diplogenetic stratifiedcopper deposit,Anhui province.Acta Geologica Sinica,79(3):405～413.
常印佛,刘湘培,吴言昌.1991.长江中下游铜铁成矿带.北京:地质出版社.
陈江峰.1991.简单混合,AFC混合和花岗岩同位素数据解释,安徽地质,1(1):19～27.
杜杨松,李顺庭,曹毅,秦新龙,楼亚儿.2007.安徽铜陵铜官山矿区中生代侵入岩的形成过程——岩浆底侵、同化混染和分离结晶,现代地质,2007,21(1):71～77.
杜杨松,李铉具.2004.安徽铜陵岩浆岩中辉长质岩石包体的发现及其地质意义.高校地质学报,10(3):332～342.
高庚,徐兆文,杨小男,王云健,张军,蒋少涌,凌洪飞.2006.安徽铜陵白芒山岩体的成因:Sr-Nd-Pb-O同位素制约,南京大学学报,42(3):269～279.
高山,Qiu Yumin,凌文黎,McNaughton NJ,Groves DI.2001.崆岭高级变质地体单颗粒锆石SHRI MPU-Pb年代学研究——扬子克拉通>3.2Ga陆壳物质的发现.中国科学(D辑),31(1):27～35.
黄顺生,徐兆文,顾连兴,华明,陆现彩,际建军,聂桂平,朱士鹏.2004.安徽铜陵狮子山矿田岩浆岩地球化学特征及成因机制探讨.高校地质学报,10(2):217～226.
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.
王彦斌,刘敦一,曾普胜,杨竹森,田世洪.2004a.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):423～427.
王彦斌,刘敦一,曾普胜,杨竹森,蒙义峰,田世洪.2004b.铜陵地区小铜官山石英闪长岩锆石SHRI MP的U-Pb年龄及其成因指示.岩石矿物学杂志,23(4):298～304.
王彦斌,刘敦一,蒙义峰,曾普胜,杨竹森,田世洪.2004c.安徽铜陵新桥铜-硫-铁-金矿床中石英闪长岩和辉绿岩锆石SHRI MP年代学及其意义,中国地质,31(2):169～173.
王元龙,王焰,张旗,贾秀琴,韩松.2004.铜陵地区中生代中酸性侵入岩的地球化学特征及其成矿-地球动力学意义,岩石学报,20(2):325～338.
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,周若,黄许陈,张成火.1994.铜陵地区中酸性侵入岩锆石群结晶特征及成因.岩石矿物学杂志,13(3):239～247.
邢凤鸣.1999.安徽沿江地区岩浆成矿带.安徽地质,9(4):272～279.
邢凤鸣,徐祥.1995.安徽沿江地区中生代岩浆岩的基本特点.岩石学报,11(4):409～422.
徐夕生,范钦成,O’Reilly S Y,蒋少涌,Griffn WL,王汝成,邱检生.2004.安徽铜官山石英闪长岩及其包体锆石U-Pb定年与成因探讨.科学通报,49(18):1883～1890.
杨小男,徐兆文,张军,王云健,徐夕生,蒋少涌,凌洪飞,刘良根,陈达源.2007.安徽狮子山矿田南洪冲岩体形成时代及成因机制研究.岩石学报,23(6):1543～1551.
翟裕生,姚书振,林新多,周若,万天丰,全福全,周宗桂.1992.长江中下游地区铁铜(金)成矿规律.北京:地质出版社.
张达,吴淦国,狄永军,臧文拴,邵拥军,余心起,张祥信,汪群峰.2006.铜陵凤凰山岩体SHRI MP锆石U-Pb年龄与构造变形及其对岩体侵位动力学背景的制约.地球科学,31(6):823～829.
Andersen T.2002.Correction of common Pbin U-Pb analyses thatdo not report204Pb.Chem Geology,192:59～79.
Chappell B W,Bryant C J,Wyborn D,White AJ R,Williams I S.1998.High-and low-temperature I-type granites.ResourceGeology,48:225～236.
Condie K C.1998.Episodic continental growth andsupercontinents:a mantle avalanche connection Earth andPlanetary Science Letters,163:97～108.
Condie K C.1995.Episodic ages of greenstones:a key to mantledynamics Geophys Res Lett,22:2215～2218.
Di Yongjun,Wu Ganguo,Zhang Da,Song Biao,Zhang Wenshuan,Zhang Zhongyi,Li Jinwen.2005.SHRI MP U-Pb ZirconGeochronology of the Xiaotongguanshan and Shatanjiaointrustions and its petrological i mplications in the Tonglingarea,Anhui.Acta Geologica Sinica,79(6):795～802.
Griffin WL,Belousva E A,Shee S R,Pearson NJ,O'Reilly SY.2004.Archean crustal evolutionin the northern Yilgrn Craton:U-Pb and Hf-isotope evidence from detrital zircons.Precambrian Research,131(3-4):231～282.
Jackson S E,Pearson NJ,Griffin WL,Belousova E A.2004.Theapplication of laser ablation-inductively coupled plasma-massspectrometry to in situ U-Pb zircon geochronology.ChemicalGeology,211:47～69.
Ludwig K R.2000.Isoplot a geochronological toolkit for MicrosoftExcel.Berkeley Geochronoly Center Special Publication,No1a.
Stein M,Hoff mann A W.1994.Mantle plumes and episodic crustalgrowth,Nature,372:63～68.
Wang Qiang,Xu Jifeng,Zhao Zhenhua,Xiong Xiaolin,Bao Zhi wei.2003.Petrogenesis of the Mesozoic intrusive rocks in theTongling area,Anhui Province,China and their constraint ongeodynamic process.Science in China(Ser.D)46(8):801～805.
Watson B E,Harrison M T.1983.Zircon saturation revisited:temperature and composition effects in a variety of crustalmagma types.Earth and Planetary Science Letters,64:295～304.
Wetherill G W.1956.An interpretation of the Phodesia andWitwatersrand age patterns.Geochi mica et Cosmochi micaActa,9:290～292.
Xing Fengming,Xu Xiang,Li Zhichang.1994.Discovery of theearly Proterozoic basement in the Middle-Lower reaches ofYangtze River andits significance.Chinese Science Bulletin,39(2):135～139.
Xu Zhaowen,Lu Xiancai,Ling Hongfei,Lu Jianjun,JiangShaoyong,Nie Guiping,Huang Shunsheng,Hua Ming.2005.Metallogenetic mechanism and ti ming of late superi mposingfluid mineraliztion in the Dongguashan diplogenetic stratifiedcopper deposit,Anhui province.Acta Geologica Sinica,79(3):405～413.
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