安徽滁州地区闪长质岩锆石U-Pb年龄与地球化学:岩石成因和动力学意义
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摘要
用LA-ICP-MS测得安徽滁州2个闪长玢岩样品中锆石~(206)Pb/~(238)U年龄为126.19±0.44Ma和126.4±0.7Ma,结合前人研究,得出滁州地区岩体的侵位时代应为120~130Ma之间,为早白垩世。岩石地球化学研究显示,Si O_2含量变化范围为56.75%~60.90%,具有高Al_2O_3(14.82%~15.77%)、Mg O(>4%)、Sr(>750×10~(-6))、Sr/Y(62~110)、La/Yb(20~36),低Y、Yb的特征,同时富集轻稀土元素和大离子亲石元素,亏损高场强元素,Eu异常不明显,属于典型的埃达克质岩。Mg~#值为39~45,K_2O/Na_2O值为0.57~0.96,平均值为0.75,明显低于大别造山带加厚下地壳埃达克岩,Ce/Pb值较低,大多集中在3~5之间,类似于陆壳而明显低于洋壳。研究认为,安徽滁州地区埃达克质岩由拆沉下地壳部分熔融形成,埃达克质岩浆在上升过程中与地幔橄榄岩发生反应,导致熔体Mg O、Cr、Ni等含量增加。早白垩世中国东部地壳伸展减薄导致下地壳拆沉,地幔物质的参与带来铜、金等成矿物质,埃达克质岩可作为该地区重要的找矿标志。
LA-ICP-MS zircon~(206)Pb/~(238)U ages of two diorite porphyrite samples from Chuzhou area of Anhui Province are 126.19±0.44Ma and 126.4±0.7Ma,respectively.Previous study shows that the emplacement age of dioritic rocks should be 120~130Ma,suggesting early Cretaceous.Geochemical study shows the values of Si O_2vary from 56.75%to 60.90%,with the characteristics of high Al_2O_3(14.82%~15.77%),Mg O(>4%),Sr(>750×10~(-6)),Sr/Y(62~110),and La/Yb(20~36)but low Y,Yb,LREE as well as enrichment of LREE and LILE but depletion of HREE,with indistinct Eu anomaly,indicating typical adakitic rocks.Mg~#values range from 39to 45,K_2O/Na_2O vary from 0.57 to 0.96,0.75 on average,significantly lower than the values of the adakitic rocks in the thickened crustal of Dabie orogenic belt;Ce/Pb ratios are low,mostly concentrated in the range of 3~5,similar to the values of the continental crust but significantly lower than those of the oceanic crust.The authors hold that the adakitic rocks in Chuzhou area of Anhui was formed by partial melting of delaminated lower crust,and the reaction of upward migrating adakitic magmas and mantle peridotite led to the increase of Mg O,Cr and Ni melt content.In Early Cretaceous,eastern China crustal extension thinning resulted in lower crust delamination,and mantle material was involved in bringing Cu,Au and other ore-forming elements;hence adakitic rocks can be used as an important prospecting indicator in this area.
LA-ICP-MS zircon~(206)Pb/~(238)U ages of two diorite porphyrite samples from Chuzhou area of Anhui Province are 126.19±0.44Ma and 126.4±0.7Ma,respectively.Previous study shows that the emplacement age of dioritic rocks should be 120~130Ma,suggesting early Cretaceous.Geochemical study shows the values of Si O_2vary from 56.75%to 60.90%,with the characteristics of high Al_2O_3(14.82%~15.77%),Mg O(>4%),Sr(>750×10~(-6)),Sr/Y(62~110),and La/Yb(20~36)but low Y,Yb,LREE as well as enrichment of LREE and LILE but depletion of HREE,with indistinct Eu anomaly,indicating typical adakitic rocks.Mg~#values range from 39to 45,K_2O/Na_2O vary from 0.57 to 0.96,0.75 on average,significantly lower than the values of the adakitic rocks in the thickened crustal of Dabie orogenic belt;Ce/Pb ratios are low,mostly concentrated in the range of 3~5,similar to the values of the continental crust but significantly lower than those of the oceanic crust.The authors hold that the adakitic rocks in Chuzhou area of Anhui was formed by partial melting of delaminated lower crust,and the reaction of upward migrating adakitic magmas and mantle peridotite led to the increase of Mg O,Cr and Ni melt content.In Early Cretaceous,eastern China crustal extension thinning resulted in lower crust delamination,and mantle material was involved in bringing Cu,Au and other ore-forming elements;hence adakitic rocks can be used as an important prospecting indicator in this area.
引文
[1]周力,张均,王健,等.安徽张八岭地区管店岩体成因及其与上成金矿床的关系[J].地质科技情报,2014,33(1):32-40.
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[4]张旗,王元龙,王焰.燕山期中国东部高原下地壳组成初探:埃达克质岩Sr,Nd同位素制约[J].岩石学报,2001,4:505-513.
[5]王元龙,王焰,张旗,等.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[J].岩石学报,2004,2:325-338.
[6]汪洋,邓晋福,姬广义.长江中下游地区早白垩世埃达克质岩的大地构造背景及其成矿意义[J].岩石学报,2004,2:297-314.
[7]王强,许继峰,赵振华,等.安徽铜陵地区燕山期侵入岩的成因及其对深部动力学过程的制约[J].中国科学(D辑),2003,4:323-334.
[8]王强,赵振华,许继峰,等.鄂东南铜山口、殷祖埃达克质(adakitic)侵入岩的地球化学特征对比:(拆沉)下地壳熔融与斑岩铜矿的成因[J].岩石学报,2004,2:351-360.
[9]Wang Q,Xu J F,Zhao Z H,et al.Cretaceous high potassium intrusive rocks in the Yueshan-Hongzhen area of east China:adakites inan extension al tectonic regime within a continent[J].Geochemical Journal,2004,38:417-434.
[10]Wang Q,Zhao Z H,Bao Z W,et al.Geochemistry and petrogenesis of the Tongshankou and Yinzu adakitic intrusive rocksand the associated porphyry copper-molybdenum mineralization in southeast Hubei,east China[J].Resource Geology,2004,54:137-152.
[11]Wang Q,Wyman D A,Xu J F,et al.Petrogenesis of Cretaceous adakitic and shoshonitic igneous rocks in the Luzong area,Anhui Province(eastern China):implications for geodynamics and Cu-Au mineralization[J].Lithos,2006,89:424-446.
[12]Wang Q,Xu J F,Jian P,et al.Petrogenesis of adakitic porphyries in an extensional tectonic setting,Dexing,South China:implications for the genesis of porphyry copper mineralization[J].Journal of Petrology 2006,47:119-144.
[13]Wang Q,Wyman D A,Xu J F,et al.Early Cretaceous adakitic granites in the Northern Dabie Complex,central China:implications for partial melting and delamination of thickened lower crust[J].Geochemical Cosmochimica Acta,2007,71:2609-2636.
[14]Wang Q,Wyman D A,Xu J F,et al.Partial melting of thickened or delaminated lower crust in the middle of Eastern China:implications for Cu-Au mineralization[J].Journal of Geology,2007,115:149-161.
[15]Xu J F,Shinjo R,Defant M J,et al.Origin of Mesozoic adakitic intrusive rocks in the Ningzhen area of eastern China:partial melting of delaminated lower continental crust?[J]Geology,2002,30:1111-1114.
[16]谢成龙,朱光,牛漫兰,等.滁州中生代火山岩LA-ICP-MS锆石U-Pb年龄及其地质意义[J].地质论评,2007,53(5):642-655.
[17]Xie G Q,Mao J W,Li L R,et al.Geochemistry and Nd-Sr isotopic studies of Late Mesozoic granitoids in the southeastern Hubei province,Middle-Lower Yangtze River belt,Eastern China:petrogenesis and tectonic setting[J].Lithos,2008,104:216-230.
[18]Ling M X,Wang F Y,Ding X,et al.Cretaceous ridge subduction along the lower Yangtze river belt,eastern China[J].Economic Geology,2009,104:303-321.
[19]Ling M X,Wang F Y,Ding X,et al.Different origins of adakitesfrom the Dabie Mountains and the Lower Yangtze River belt in eastern China:geochemical constraints[J].International Geology Review,2011,53:727-740.
[20]Li J W,Zhao X F,Zhou M F,et al.Late Mesozoic magmatism from the Daye region,eastern China:U-Pb ages,petrogenesis,and geodynamics implications[J].Contribution to Mineralogy and Petrology,2009,157:383-409.
[21]Liu S A,Li S G,He Y S,et al.Geochemical contrasts between early Cretaceous ore-bearing and ore-barren high-Mg adakites in central-eastern China:implications for petrogenesis and Cu-Au mineralization[J].Geochimica et Cosmochimica Acta,2010,74:7160-7178.
[22]孙卫东,凌明星,杨晓勇,等.洋脊俯冲与斑岩铜金矿成矿[J].中国科学(D辑),2010,2:127-137.
[23]Sun W D,Zhang H,Ling M X,et al.The genetic association of adakites and Cu-Au ore deposits[J].International Geology Review,2011,53:691-703.
[24]Sun W D,Ling M X,Chung S L,et al.Geochemical constraints on adakites of different origins and copper mineralization[J].Journal of Geology,2012,120:105-120.
[25]谢建成,陈思,孙卫东,等.安徽铜陵早白垩世埃达克质岩地球化学:成岩成矿制约[J].岩石学报,2012,10:3181-3196.
[26]Chen B,Jahn B M,Suzuki K.Petrological and Nd-Sr-Os isotopic constraints onthe origin of high-Mg adakitic rocks from the North China Craton:tectonic implications[J].Geology,2013,41:91-94.
[27]Yang Y Z,Chen F K,Siebel W,et al.Age and composition of CuAu related rocks from the lower Yangtze River belt:Constraints on paleo-Pacific slab roll-back beneath eastern China[J].Lithos,2014,200/203:331-346.
[28]Defant M J,Drummond M S.Derivation of some modern arc magmas by meltingof young subducted lithosphere[J].Nature,1990,347:662-665.
[29]Defant M J,Kepezhinskas P.Evidence suggests slab melting in arc magmas[J].Eos Transactions,2001,82:62-65.
[30]Mungall J E.Roasting the mantle:slab melting and the genesis of major Au and Aurich Cu deposits[J].Geology,2002,30:915-918.
[31]Oyarzun R,Márquez A,Lillo J,et al.Giant versus small porphyrycopper deposits of Cenozoic age in northern Chile:adakitic versus normal calcalkaline magmatism[J].Mineralium Deposita,2001,36:794-798.
[32]Sajona F G,Maury R C.Association of adakites with gold and copper mineralization in the Philippines.Comptes Rendus de l'Académie des Sciences-Series IIA[J].Earth and Planetary Science,1998,326:27-34.
[33]Thieblemont D,Stein G,Lescuyer J L.Gisementsepithermaux et porphyriques:laconnexionadakite.Comptes Rendus de l’Academie des Science-Series[J].Earth and Planetary Science,1997,325:103-109.
[34]Liu Y S,Gao S,Hu Z C,et al.Continental and oceanic crust recycling-induced melt-peridotite interactions in the Trans-North China Orogen:U-Pb dating,Hf isotopes and trace elements in zircons from mantle xenoliths[J].Journal of Petrology,20009,51(1/2):537-571.
[35]Sun S S,Mc Donough W F.Chemical and isotopic systematics ofoceanic basalts:Implications for mantle composition and processes[C]//Saunders A D,Norry M J.Magmatism in OceanicBasins.Geological Society,London,Special Publication,1989,42(1):313-345.
[36]李学明,李彬贤,张巽,等.安徽管店岩体的同位素地质年龄和郯庐断裂带的动力学变质作用[J].中国科学技术大学学报,1985,15(增刊):254-261.
[37]牛漫兰.张八岭地区中生代岩体中黑云母的40Ar-39Ar年龄及其地质意义[J].地质科学,2006,41(2):217-225.
[38]资锋,王强,唐功建,等.皖中管店岩体的锆石年代学与地球化学:岩石成因和动力学意义[J].地球化学,2008,37(5),462-480.
[39]Wang Q,Wyman D A,Xu J F,et al.Early Cretaceous adakitic granites in the Northern Dabie Complex,central China:implications for partial melting and delamination of thickened lower crust[J].Geochemical Cosmochimica Acta,2007,71:2609-2636.
[40]Huang F,Li S G,Dong F,et al.High-Mg adakiticrocks in the Dabie orogeny,Central China:Implications for foundering mechanism of lower continental crust[J].Chemical Geology,2008,255(1/2):1-13.
[41]Sen C,Dunn T.Dehydration melting of a basaltic compositionamphibolite at 1.5 and 2.0GPa:Implications for the origin of adakite[J].Contributions to Mineralogy and Petrology,1994,117(4):394-409.
[42]Taylor S R,Mc Lennan S M.The Continental Crust:Its Composition and Evolution[M].Oxford:Blackwell Scientific Publications,1985:1-100.
[43]Rudnick R L,Gao S.Composition of the continental crust[C]//Rudnick R L,Holland H D,Turekian K K.The Crust Vol.3 Treatiseon Geochemistry.Oxford:Elsevier-Pergamon,2003:1-64.
[44]Zhu G,Xie C L,Xiang B W,et al.Genesis of the Hongzhen metamorphic core complex and its tectonic implications[J].Science in China(D),2007,50:649-659.
[45]Sun W D,Ding X,Hu Y H,et al.The golden transformation of the Cretaceous plate subduction in the west Pacific[J].Earth and Planetary Science Letters,2007,262(3/4):533-542.
[2]胡子龙.皖东滁州地区燕山期岩浆岩地球化学特征与铜金成矿[D].中国科学技术大学硕士学位论文,2015:6-16.
[3]张旗,王焰,钱青,等.中国东部燕山期埃达克岩的特征及其构造成矿意义[J].岩石学报,2001(2):236-244.
[4]张旗,王元龙,王焰.燕山期中国东部高原下地壳组成初探:埃达克质岩Sr,Nd同位素制约[J].岩石学报,2001,4:505-513.
[5]王元龙,王焰,张旗,等.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[J].岩石学报,2004,2:325-338.
[6]汪洋,邓晋福,姬广义.长江中下游地区早白垩世埃达克质岩的大地构造背景及其成矿意义[J].岩石学报,2004,2:297-314.
[7]王强,许继峰,赵振华,等.安徽铜陵地区燕山期侵入岩的成因及其对深部动力学过程的制约[J].中国科学(D辑),2003,4:323-334.
[8]王强,赵振华,许继峰,等.鄂东南铜山口、殷祖埃达克质(adakitic)侵入岩的地球化学特征对比:(拆沉)下地壳熔融与斑岩铜矿的成因[J].岩石学报,2004,2:351-360.
[9]Wang Q,Xu J F,Zhao Z H,et al.Cretaceous high potassium intrusive rocks in the Yueshan-Hongzhen area of east China:adakites inan extension al tectonic regime within a continent[J].Geochemical Journal,2004,38:417-434.
[10]Wang Q,Zhao Z H,Bao Z W,et al.Geochemistry and petrogenesis of the Tongshankou and Yinzu adakitic intrusive rocksand the associated porphyry copper-molybdenum mineralization in southeast Hubei,east China[J].Resource Geology,2004,54:137-152.
[11]Wang Q,Wyman D A,Xu J F,et al.Petrogenesis of Cretaceous adakitic and shoshonitic igneous rocks in the Luzong area,Anhui Province(eastern China):implications for geodynamics and Cu-Au mineralization[J].Lithos,2006,89:424-446.
[12]Wang Q,Xu J F,Jian P,et al.Petrogenesis of adakitic porphyries in an extensional tectonic setting,Dexing,South China:implications for the genesis of porphyry copper mineralization[J].Journal of Petrology 2006,47:119-144.
[13]Wang Q,Wyman D A,Xu J F,et al.Early Cretaceous adakitic granites in the Northern Dabie Complex,central China:implications for partial melting and delamination of thickened lower crust[J].Geochemical Cosmochimica Acta,2007,71:2609-2636.
[14]Wang Q,Wyman D A,Xu J F,et al.Partial melting of thickened or delaminated lower crust in the middle of Eastern China:implications for Cu-Au mineralization[J].Journal of Geology,2007,115:149-161.
[15]Xu J F,Shinjo R,Defant M J,et al.Origin of Mesozoic adakitic intrusive rocks in the Ningzhen area of eastern China:partial melting of delaminated lower continental crust?[J]Geology,2002,30:1111-1114.
[16]谢成龙,朱光,牛漫兰,等.滁州中生代火山岩LA-ICP-MS锆石U-Pb年龄及其地质意义[J].地质论评,2007,53(5):642-655.
[17]Xie G Q,Mao J W,Li L R,et al.Geochemistry and Nd-Sr isotopic studies of Late Mesozoic granitoids in the southeastern Hubei province,Middle-Lower Yangtze River belt,Eastern China:petrogenesis and tectonic setting[J].Lithos,2008,104:216-230.
[18]Ling M X,Wang F Y,Ding X,et al.Cretaceous ridge subduction along the lower Yangtze river belt,eastern China[J].Economic Geology,2009,104:303-321.
[19]Ling M X,Wang F Y,Ding X,et al.Different origins of adakitesfrom the Dabie Mountains and the Lower Yangtze River belt in eastern China:geochemical constraints[J].International Geology Review,2011,53:727-740.
[20]Li J W,Zhao X F,Zhou M F,et al.Late Mesozoic magmatism from the Daye region,eastern China:U-Pb ages,petrogenesis,and geodynamics implications[J].Contribution to Mineralogy and Petrology,2009,157:383-409.
[21]Liu S A,Li S G,He Y S,et al.Geochemical contrasts between early Cretaceous ore-bearing and ore-barren high-Mg adakites in central-eastern China:implications for petrogenesis and Cu-Au mineralization[J].Geochimica et Cosmochimica Acta,2010,74:7160-7178.
[22]孙卫东,凌明星,杨晓勇,等.洋脊俯冲与斑岩铜金矿成矿[J].中国科学(D辑),2010,2:127-137.
[23]Sun W D,Zhang H,Ling M X,et al.The genetic association of adakites and Cu-Au ore deposits[J].International Geology Review,2011,53:691-703.
[24]Sun W D,Ling M X,Chung S L,et al.Geochemical constraints on adakites of different origins and copper mineralization[J].Journal of Geology,2012,120:105-120.
[25]谢建成,陈思,孙卫东,等.安徽铜陵早白垩世埃达克质岩地球化学:成岩成矿制约[J].岩石学报,2012,10:3181-3196.
[26]Chen B,Jahn B M,Suzuki K.Petrological and Nd-Sr-Os isotopic constraints onthe origin of high-Mg adakitic rocks from the North China Craton:tectonic implications[J].Geology,2013,41:91-94.
[27]Yang Y Z,Chen F K,Siebel W,et al.Age and composition of CuAu related rocks from the lower Yangtze River belt:Constraints on paleo-Pacific slab roll-back beneath eastern China[J].Lithos,2014,200/203:331-346.
[28]Defant M J,Drummond M S.Derivation of some modern arc magmas by meltingof young subducted lithosphere[J].Nature,1990,347:662-665.
[29]Defant M J,Kepezhinskas P.Evidence suggests slab melting in arc magmas[J].Eos Transactions,2001,82:62-65.
[30]Mungall J E.Roasting the mantle:slab melting and the genesis of major Au and Aurich Cu deposits[J].Geology,2002,30:915-918.
[31]Oyarzun R,Márquez A,Lillo J,et al.Giant versus small porphyrycopper deposits of Cenozoic age in northern Chile:adakitic versus normal calcalkaline magmatism[J].Mineralium Deposita,2001,36:794-798.
[32]Sajona F G,Maury R C.Association of adakites with gold and copper mineralization in the Philippines.Comptes Rendus de l'Académie des Sciences-Series IIA[J].Earth and Planetary Science,1998,326:27-34.
[33]Thieblemont D,Stein G,Lescuyer J L.Gisementsepithermaux et porphyriques:laconnexionadakite.Comptes Rendus de l’Academie des Science-Series[J].Earth and Planetary Science,1997,325:103-109.
[34]Liu Y S,Gao S,Hu Z C,et al.Continental and oceanic crust recycling-induced melt-peridotite interactions in the Trans-North China Orogen:U-Pb dating,Hf isotopes and trace elements in zircons from mantle xenoliths[J].Journal of Petrology,20009,51(1/2):537-571.
[35]Sun S S,Mc Donough W F.Chemical and isotopic systematics ofoceanic basalts:Implications for mantle composition and processes[C]//Saunders A D,Norry M J.Magmatism in OceanicBasins.Geological Society,London,Special Publication,1989,42(1):313-345.
[36]李学明,李彬贤,张巽,等.安徽管店岩体的同位素地质年龄和郯庐断裂带的动力学变质作用[J].中国科学技术大学学报,1985,15(增刊):254-261.
[37]牛漫兰.张八岭地区中生代岩体中黑云母的40Ar-39Ar年龄及其地质意义[J].地质科学,2006,41(2):217-225.
[38]资锋,王强,唐功建,等.皖中管店岩体的锆石年代学与地球化学:岩石成因和动力学意义[J].地球化学,2008,37(5),462-480.
[39]Wang Q,Wyman D A,Xu J F,et al.Early Cretaceous adakitic granites in the Northern Dabie Complex,central China:implications for partial melting and delamination of thickened lower crust[J].Geochemical Cosmochimica Acta,2007,71:2609-2636.
[40]Huang F,Li S G,Dong F,et al.High-Mg adakiticrocks in the Dabie orogeny,Central China:Implications for foundering mechanism of lower continental crust[J].Chemical Geology,2008,255(1/2):1-13.
[41]Sen C,Dunn T.Dehydration melting of a basaltic compositionamphibolite at 1.5 and 2.0GPa:Implications for the origin of adakite[J].Contributions to Mineralogy and Petrology,1994,117(4):394-409.
[42]Taylor S R,Mc Lennan S M.The Continental Crust:Its Composition and Evolution[M].Oxford:Blackwell Scientific Publications,1985:1-100.
[43]Rudnick R L,Gao S.Composition of the continental crust[C]//Rudnick R L,Holland H D,Turekian K K.The Crust Vol.3 Treatiseon Geochemistry.Oxford:Elsevier-Pergamon,2003:1-64.
[44]Zhu G,Xie C L,Xiang B W,et al.Genesis of the Hongzhen metamorphic core complex and its tectonic implications[J].Science in China(D),2007,50:649-659.
[45]Sun W D,Ding X,Hu Y H,et al.The golden transformation of the Cretaceous plate subduction in the west Pacific[J].Earth and Planetary Science Letters,2007,262(3/4):533-542.