北祁连甘肃毛藏寺铜-钼矿床花岗质岩石锆石U-Pb年龄、地球化学特征及其地质意义
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摘要
甘肃毛藏寺铜钼矿是与花岗质岩石有关的斑岩型矿床,矿区内花岗质岩石类型主要为似斑状二长花岗岩和花岗闪长岩。对矿区岩体进行年龄、地球化学研究,以约束其形成时代,并探讨岩石成因及其与成矿的关系。LA-ICP-MS锆石UPb测年分别获得似斑状二长花岗岩与花岗闪长岩谐和年龄为455.8±3.1Ma和425.0±2.8Ma,属于晚奥陶世和晚志留世岩浆活动的产物。地球化学数据显示,似斑状二长花岗岩属于过铝质钙碱性岩浆系列,花岗闪长岩属于准铝质高钾钙碱性岩浆系列,二者均富集大离子亲石元素,亏损高场强元素,稀土元素配分曲线呈右倾型,轻、重稀土元素分馏明显。似斑状二长花岗岩具有弱正Eu异常(δEu=1.18～1.24),显示埃达克岩的地球化学特征,形成于北祁连洋俯冲消减阶段,由俯冲洋壳(含海洋沉积物)部分熔融形成,源区主要残留物为石榴子石。花岗闪长岩显示弱负Eu异常,形成于碰撞后伸展环境,是洋壳板片断离后软流圈上涌诱发的下地壳玄武质岩石部分熔融的产物。似斑状二长花岗岩符合成矿期埃达克岩特征,具有较好的成矿条件。结合前人资料,在北祁连东段寻找和勘查与埃达克岩有关的铜-钼-金矿可能是一个新的方向。
The Maozangsi Cu-Mo deposit in Gansu is a porphyry type deposit related to granitoids. Maozangsi granitoids are composed of porphyritoid monzogranite and granodiorite. In this paper, zircon U-Pb dating and geochemical study of the Maozangsi granitoids were conducted to constrain its geochronology and discuss petrogenesis and its relationship with mineralization. Zircon LA-ICP-MS dating yielded concordant ages of 455.8±3.1 Ma and 425.0±2.8 Ma respectively, indicating that the two plutons were formed in Late Ordovician and late Silurian respectively. Geochemical data show that porphyritoid monzogranite is a peraluminous granite and belongs to the calc-alkaline series, whereas granodiorite is a aluminous granite and belongs to the high-K calc-alkaline series. They are characterized by enrichment of LILEs and depletion of HFSEs, with REE patterns exhibiting the right-deviation type and strong fractionation with LREE enrichment. The porphyritoid monzogranite show weak positive Eu anomalies(δEu=1.18～1.24) and geochemical affinity to adakite, probably resulting from the slab melting(including marine sediments) of the subduction of North Qilian Ocean with the residual minerals of garnet in the source. The granodiorite shows weak negative Eu anomalies and was generated in a post-collisional extension setting and derived from partial melting of basaltic rocks in the lower crust induced by asthenosphere after the breakup of previously subducted North Qilian oceanic slab. The features of porphyritoid monzogranite are in accordance with the characteristics of ore-forming period adakitic rocks and thus suggest good mineralization conditions. In combination with data obtained from previous studies, the authors hold that it is possible to find Cu-Mo-Au deposits related to adakites in the eastern section of the Northern Qilian Mountain.
The Maozangsi Cu-Mo deposit in Gansu is a porphyry type deposit related to granitoids. Maozangsi granitoids are composed of porphyritoid monzogranite and granodiorite. In this paper, zircon U-Pb dating and geochemical study of the Maozangsi granitoids were conducted to constrain its geochronology and discuss petrogenesis and its relationship with mineralization. Zircon LA-ICP-MS dating yielded concordant ages of 455.8±3.1 Ma and 425.0±2.8 Ma respectively, indicating that the two plutons were formed in Late Ordovician and late Silurian respectively. Geochemical data show that porphyritoid monzogranite is a peraluminous granite and belongs to the calc-alkaline series, whereas granodiorite is a aluminous granite and belongs to the high-K calc-alkaline series. They are characterized by enrichment of LILEs and depletion of HFSEs, with REE patterns exhibiting the right-deviation type and strong fractionation with LREE enrichment. The porphyritoid monzogranite show weak positive Eu anomalies(δEu=1.18～1.24) and geochemical affinity to adakite, probably resulting from the slab melting(including marine sediments) of the subduction of North Qilian Ocean with the residual minerals of garnet in the source. The granodiorite shows weak negative Eu anomalies and was generated in a post-collisional extension setting and derived from partial melting of basaltic rocks in the lower crust induced by asthenosphere after the breakup of previously subducted North Qilian oceanic slab. The features of porphyritoid monzogranite are in accordance with the characteristics of ore-forming period adakitic rocks and thus suggest good mineralization conditions. In combination with data obtained from previous studies, the authors hold that it is possible to find Cu-Mo-Au deposits related to adakites in the eastern section of the Northern Qilian Mountain.
引文
[1]吴才来,姚尚志,杨经绥,等.北祁连洋早古生代双向俯冲的花岗岩证据[J].中国地质,2006,33(6):1197-1208.
[2]吴才来,徐学义,高前明,等.北祁连早古生代花岗质岩浆作用及构造演化[J].岩石学报,2010,26(4):1027-1044.
[3]王金荣,郭原生,付善明,等.甘肃黑石山早古生代埃达克质岩的发现及其构造动力学意义[J].岩石学报,2005,21(3):977-985.
[4]王金荣,吴春俊,蔡郑红.北祁连山东段银硐梁早古生代高镁埃达克岩:地球动力学及成矿意义[J].岩石学报,2006,22(11):2655-2664.
[5]王金荣,吴继承,贾志磊.北祁连山东段苏家山高Mg埃达克岩地球动力学意义[J].兰州大学学报:自然科学版,2009,44(3):16-24.
[6]Tseng C,Yang H,Yang H.Continuity of the North Qilian and North Qinling orogenic belts,Central Orogenic System of China:Evidence from newly discovered Paleozoic adakitic rocks[J].Gondwana Research,2009,(16):285-293.
[7]熊子良,张宏飞,张杰.北祁连东段冷龙岭地区毛藏寺岩体和黄羊河岩体的岩石成因及其构造意义[J].地学前缘,2012,19(3):214-227.
[8]Sillitoe R.A plate tectonic model for the origin of porphyry copper deposits[J].Economic Geology,1972,67:184-197.
[9]Burnham C W.Magmas and hydrothermal fluids[C]//Barnes H L.Geochemistry of Hydrothermal Ore Deposits,2nd edition.John Wiley and Sons,New York,1979:71-13.
[10]Tatsumi Y.Formation of the volcanic front in subduction zones[J].Geophysical Research Letters,1986,17:717-720.
[11]Peacock S M.Large-scale hydration of the lithosphere above subducting slabs[J].Chemical Geology,1993,108:49-59.
[12]Schmidt M W,Poli S.Experimentally based water budgets for dehydrating slabs and consequences for arc magma generation[J].Earth and Planetary Science Letters,1998,163:361-379.
[13]Grove T L,Chatterjee N,Parman S W,et al.The influence of H2O on mantle wedge melting[J].Earth and Planetary Science Letters,2006,249:74-89.
[14]Grove T L,Till C B,Krawczynski M J.The role of H2O in subduction zone magmatism[J].Annual Review of Earth and Planetary Sciences,2012,40:413-439.
[15]侯增谦,莫宣学,高永丰,等.埃达克岩:斑岩铜矿的一种可能的重要含矿母岩——以西藏和智利斑岩铜矿为例[J].矿床地质,2003,22(1):1-12.
[16]冯益民,何世平.祁连山大地构造与造山作用[M].北京:地质出版社,1996:1-135.
[17]夏林圻,李向民,余吉远,等.祁连山新元古代中—晚期至早古生代火山作用与构造演化[J].中国地质,2016,43(4):1087-1138.
[18]李文渊,郭周平,王伟.北祁连山加里东期聚敛作用的构造转换及其成矿响应[J].地质论评,2005,51(2):120-127.
[19]Hoskin P W O,Black L P.Metamorphic zircon formation by solidstate recrystallization of protolith igneous zircon[J].J.Metamorph.Geol.,2000,18:423-439.
[20]Rickwood PC.Boundary lines within petrologic diagrams which use oxides major and minor elements[J].Lithos,1999,22:247-263.
[21]Preccerillo R,Taylor S R.Geochemistry of Eocene calakaline volcanic rocks from the Kastamonu area,northern Turkey[J].Contrib.Mineral.Petrol.,1976,58:63-81.
[22]Sun S S,Mc Donough W F.Chemical and isotopic systematics of oceanic basalt:Implications for mantle composition and process[C]//Saunders A D,Norry M J.Magmatism in the Ocean Basins[J].Spc.Publ.Geol.Soc.Lond.,1989,42:313-345.
[23]Defant M J,Drummond M S.Derivation of some modern arc magmas by melting of young subducted lithosphere[J].Nature,1990,347(6294):662-665.
[24]Oyarzun R,Marquez A,Lillo J,et al.Giant versus small porphy copper deposits of Cenozoic age in northern Chile:Adakite versus normal calc Kalkaline magmatism[J].Mineralium Deposita,2001,36:794.
[25]Mungall J E.Roasting the mantle:Slab melting and the genesis of major Au and Au-rich Cu deposits[J].Geology,2002,30(10):915-918.
[26]Atherton M P,Petford N.Generation of sodium-rich magmas from newly underplated basaltic crust[J].Nature,1993,362:144-146.
[27]张旗,王焰,钱青,等.中国东部中生代埃达克岩的特征及其构造-成矿意义[J].岩石学报,2001,17(2):236-244.
[28]王强,赵振华,熊小林,等.底侵玄武质下地壳的熔融:来自沙溪adakite质富钠石英闪长玢岩的证据[J].地球化学,2001,30(4):353-362.
[29]Chung S L,Chu M F,Zhang Y Q,et al.Tibetan tectonic evolution inferred from spatial and temporal variations in post-collisional magmatism[J].Earth Science Reviews,2005,68(3/4):173-196.
[30]Xu J F,Shinjo R,Defant M J,et al.Origin of Mesozoic adakitic intrusive rocks in the Ningzhen area of east China:partial melting of delaminated lower continental crust?[J].Geology,2002,30(12):1111-1114.
[31]Gao S,Rudnick R L,Yuan H L,et al.Recycling lower continental crust in the North China craton[J].Nature,2004,432:892-897.
[32]Wang Q,Xu J F,Jian P,et al.Petrogenesis of adakitic porphyriesin an extensional tectonic setting,dexing,South China:Implications for the genesis of porphyry copper mineralization[J].Journal of Petrology,2006,47(1):119-144.
[33]Shirey S B,Hanson G N.Mantle-derived Archaean monozodiorites and trachyandesites[J].Nature,1984,310(5974):222-224
[34]Stern R A,Hanson G N.Archean high-Mg granodiorite:A derivative of light rare earth element-enriched monozodiorite of mantle origin[J].Journal of Petrology,1991,32(1):201-238.
[35]Hirose K.Melting experiments on lherzolite KLB-1under hydrous conditions and generation of high-magnesian andesitic melts[J].Geology,1997,25(1):42-44.
[36]Kay R W,Kay S M.Delamination and delamination magmatism[J].Tectonophysics,1993,19:177-189.
[37]Rapp R P,Shimizu N,Norman M D,et al.Reaction between slab-derived melts and peridotite in the mantle wedge:Experimental constraints at 3.8Ga[J].Chem.Geol.,1999,160:335-356.
[38]Martin H,Smithies R,Rapp R,et al.An overview of adakite,tonalite-trondhjemite-granodiorite(TTG),and sanukitoid:Relationships and some implications for crustal evolution[J].Lithos,2005,79(1):1-24.
[39]Hawkesworth C,Turner S,Peate D,et al.Elemental U and Th variations in island arc rocks:Implications for U-series isotopes[J].Chem.Geol.,1997,139:207-221.
[40]Plank T,Langmuir C H.The chemical composition of subducting sediment and its consequences for the crust and mantle[J].Chem.Geol.,1998,145:325-394.
[41]Green T H.Experimental studies of trace-element portioning applicable to igneous petrogenesisi-Sedona 16 years later[J].Chem.Geol.,1994,117:1-36.
[42]Foley S F,Jackson S E,Fryer B J,et al.Trace element artition coefficients for clinopyroxene and phlogopite in an alkaline lamprophyre from Newfoundland by LA-ICP-MS[J].Geochim.Cosmochim.Acta,1996,60:629-638.
[43]Pitcher W S.The nature and origin of granite(2nd edition)[M].Chapman and Hall,Landon,1997.
[44]Pearce J A.Sources and setting of granitic rocks[J].Episodes,1996,19:120-125.
[45]Kay S M,Mpodozis C.Central Andean ore deposits linked to evolving shallow subduction systems and thickening crust[J].GSA Today,2001,11(3):4-9.
[2]吴才来,徐学义,高前明,等.北祁连早古生代花岗质岩浆作用及构造演化[J].岩石学报,2010,26(4):1027-1044.
[3]王金荣,郭原生,付善明,等.甘肃黑石山早古生代埃达克质岩的发现及其构造动力学意义[J].岩石学报,2005,21(3):977-985.
[4]王金荣,吴春俊,蔡郑红.北祁连山东段银硐梁早古生代高镁埃达克岩:地球动力学及成矿意义[J].岩石学报,2006,22(11):2655-2664.
[5]王金荣,吴继承,贾志磊.北祁连山东段苏家山高Mg埃达克岩地球动力学意义[J].兰州大学学报:自然科学版,2009,44(3):16-24.
[6]Tseng C,Yang H,Yang H.Continuity of the North Qilian and North Qinling orogenic belts,Central Orogenic System of China:Evidence from newly discovered Paleozoic adakitic rocks[J].Gondwana Research,2009,(16):285-293.
[7]熊子良,张宏飞,张杰.北祁连东段冷龙岭地区毛藏寺岩体和黄羊河岩体的岩石成因及其构造意义[J].地学前缘,2012,19(3):214-227.
[8]Sillitoe R.A plate tectonic model for the origin of porphyry copper deposits[J].Economic Geology,1972,67:184-197.
[9]Burnham C W.Magmas and hydrothermal fluids[C]//Barnes H L.Geochemistry of Hydrothermal Ore Deposits,2nd edition.John Wiley and Sons,New York,1979:71-13.
[10]Tatsumi Y.Formation of the volcanic front in subduction zones[J].Geophysical Research Letters,1986,17:717-720.
[11]Peacock S M.Large-scale hydration of the lithosphere above subducting slabs[J].Chemical Geology,1993,108:49-59.
[12]Schmidt M W,Poli S.Experimentally based water budgets for dehydrating slabs and consequences for arc magma generation[J].Earth and Planetary Science Letters,1998,163:361-379.
[13]Grove T L,Chatterjee N,Parman S W,et al.The influence of H2O on mantle wedge melting[J].Earth and Planetary Science Letters,2006,249:74-89.
[14]Grove T L,Till C B,Krawczynski M J.The role of H2O in subduction zone magmatism[J].Annual Review of Earth and Planetary Sciences,2012,40:413-439.
[15]侯增谦,莫宣学,高永丰,等.埃达克岩:斑岩铜矿的一种可能的重要含矿母岩——以西藏和智利斑岩铜矿为例[J].矿床地质,2003,22(1):1-12.
[16]冯益民,何世平.祁连山大地构造与造山作用[M].北京:地质出版社,1996:1-135.
[17]夏林圻,李向民,余吉远,等.祁连山新元古代中—晚期至早古生代火山作用与构造演化[J].中国地质,2016,43(4):1087-1138.
[18]李文渊,郭周平,王伟.北祁连山加里东期聚敛作用的构造转换及其成矿响应[J].地质论评,2005,51(2):120-127.
[19]Hoskin P W O,Black L P.Metamorphic zircon formation by solidstate recrystallization of protolith igneous zircon[J].J.Metamorph.Geol.,2000,18:423-439.
[20]Rickwood PC.Boundary lines within petrologic diagrams which use oxides major and minor elements[J].Lithos,1999,22:247-263.
[21]Preccerillo R,Taylor S R.Geochemistry of Eocene calakaline volcanic rocks from the Kastamonu area,northern Turkey[J].Contrib.Mineral.Petrol.,1976,58:63-81.
[22]Sun S S,Mc Donough W F.Chemical and isotopic systematics of oceanic basalt:Implications for mantle composition and process[C]//Saunders A D,Norry M J.Magmatism in the Ocean Basins[J].Spc.Publ.Geol.Soc.Lond.,1989,42:313-345.
[23]Defant M J,Drummond M S.Derivation of some modern arc magmas by melting of young subducted lithosphere[J].Nature,1990,347(6294):662-665.
[24]Oyarzun R,Marquez A,Lillo J,et al.Giant versus small porphy copper deposits of Cenozoic age in northern Chile:Adakite versus normal calc Kalkaline magmatism[J].Mineralium Deposita,2001,36:794.
[25]Mungall J E.Roasting the mantle:Slab melting and the genesis of major Au and Au-rich Cu deposits[J].Geology,2002,30(10):915-918.
[26]Atherton M P,Petford N.Generation of sodium-rich magmas from newly underplated basaltic crust[J].Nature,1993,362:144-146.
[27]张旗,王焰,钱青,等.中国东部中生代埃达克岩的特征及其构造-成矿意义[J].岩石学报,2001,17(2):236-244.
[28]王强,赵振华,熊小林,等.底侵玄武质下地壳的熔融:来自沙溪adakite质富钠石英闪长玢岩的证据[J].地球化学,2001,30(4):353-362.
[29]Chung S L,Chu M F,Zhang Y Q,et al.Tibetan tectonic evolution inferred from spatial and temporal variations in post-collisional magmatism[J].Earth Science Reviews,2005,68(3/4):173-196.
[30]Xu J F,Shinjo R,Defant M J,et al.Origin of Mesozoic adakitic intrusive rocks in the Ningzhen area of east China:partial melting of delaminated lower continental crust?[J].Geology,2002,30(12):1111-1114.
[31]Gao S,Rudnick R L,Yuan H L,et al.Recycling lower continental crust in the North China craton[J].Nature,2004,432:892-897.
[32]Wang Q,Xu J F,Jian P,et al.Petrogenesis of adakitic porphyriesin an extensional tectonic setting,dexing,South China:Implications for the genesis of porphyry copper mineralization[J].Journal of Petrology,2006,47(1):119-144.
[33]Shirey S B,Hanson G N.Mantle-derived Archaean monozodiorites and trachyandesites[J].Nature,1984,310(5974):222-224
[34]Stern R A,Hanson G N.Archean high-Mg granodiorite:A derivative of light rare earth element-enriched monozodiorite of mantle origin[J].Journal of Petrology,1991,32(1):201-238.
[35]Hirose K.Melting experiments on lherzolite KLB-1under hydrous conditions and generation of high-magnesian andesitic melts[J].Geology,1997,25(1):42-44.
[36]Kay R W,Kay S M.Delamination and delamination magmatism[J].Tectonophysics,1993,19:177-189.
[37]Rapp R P,Shimizu N,Norman M D,et al.Reaction between slab-derived melts and peridotite in the mantle wedge:Experimental constraints at 3.8Ga[J].Chem.Geol.,1999,160:335-356.
[38]Martin H,Smithies R,Rapp R,et al.An overview of adakite,tonalite-trondhjemite-granodiorite(TTG),and sanukitoid:Relationships and some implications for crustal evolution[J].Lithos,2005,79(1):1-24.
[39]Hawkesworth C,Turner S,Peate D,et al.Elemental U and Th variations in island arc rocks:Implications for U-series isotopes[J].Chem.Geol.,1997,139:207-221.
[40]Plank T,Langmuir C H.The chemical composition of subducting sediment and its consequences for the crust and mantle[J].Chem.Geol.,1998,145:325-394.
[41]Green T H.Experimental studies of trace-element portioning applicable to igneous petrogenesisi-Sedona 16 years later[J].Chem.Geol.,1994,117:1-36.
[42]Foley S F,Jackson S E,Fryer B J,et al.Trace element artition coefficients for clinopyroxene and phlogopite in an alkaline lamprophyre from Newfoundland by LA-ICP-MS[J].Geochim.Cosmochim.Acta,1996,60:629-638.
[43]Pitcher W S.The nature and origin of granite(2nd edition)[M].Chapman and Hall,Landon,1997.
[44]Pearce J A.Sources and setting of granitic rocks[J].Episodes,1996,19:120-125.
[45]Kay S M,Mpodozis C.Central Andean ore deposits linked to evolving shallow subduction systems and thickening crust[J].GSA Today,2001,11(3):4-9.