云南二叠纪白马寨铜镍硫化物矿床的成因:地壳混染与矿化的关系
|
摘要
云南金平白马寨-营盘街一带的奥陶纪变砂岩和板岩中出露大量小型约260Ma的镁铁-超镁铁质岩体,其中白马寨地区三个岩体具明显铜-镍硫化物矿化:三号岩体有一个中型铜镍硫化物矿床,一号和二号岩体可见微弱矿化。一号岩体的Ni/Cu值为0.7~2.2,二号岩体的Ni/Cu值为1.4~4.0,与三号岩体的比值(Ni/Cu=0.5~6.7)相近,说明他们的母岩浆成分接近,为富Mg的镁铁质或苦橄质岩浆。三个岩体遭受不同程度的地壳混染,表现为强烈的Nb(Ta)异常,很低的Nb/La值(0.5~0.7)和很负的εNd(t)值(-5.1~-9.0)。根据全岩的Th/Yb和Nb/Th值估算,一号岩体的地壳混染程度为5%~20%,二号岩体的地壳混染程度为5%~10%,而三号岩体的地壳混染程度高达35%。三个岩体的地壳混染程度与岩体中硫化物的含量呈正相关关系,表明地壳混染是导致白马寨岩体硫化物饱和的主要因素。
A number of small ~260 Ma-mafic-ultramafic intrusions intruded Ordovician meta-sandstone and slate in the Baimazhai-Yingpanjie region,Jinping,southern Yunnan.Three of them at Baimazhai have been explored to contain Ni-Cu-(PGE)sulfide mineralization.No.3 intrusion at Baimazhai hosts a medium-sized Ni-Cu-(PGE)deposit whereas No.1 and no.2 intrusions are weakly mineralized.However,similar low Ni/Cu ratios of the three intrusions(No.1 intrusion:0.7 to 2.2;No.2 intrusion:1.4 to 4.0;No.3 intrusion:0.5 to 6.7)indicate that they all may have derived from Mg-rich mafic magmas or picritic magmas.The three intrusions have assimilated by crustal material which resulted in negative Nb(Ta)anomaly in the primitive-mantle normalized trace elemental patterns,and low Nb/La ratios(0.5 to 0.7)and very negative εNd(t)values(-5.1 to-9.0).It is estimated from whole-rock Th/Yb and Nb/Th ratios that the degree of crustal contamination is 5%-20% for No.1 intrusion,5%-10% for No.2 intrusion and 35% for No.3 intrusion.Sulfide contents of the three intrusions vary positively with the degrees of crustal contamination,indicating that the crustal contamination is a major trigger for the formation of immiscible sulfide melts from the magmas.
A number of small ~260 Ma-mafic-ultramafic intrusions intruded Ordovician meta-sandstone and slate in the Baimazhai-Yingpanjie region,Jinping,southern Yunnan.Three of them at Baimazhai have been explored to contain Ni-Cu-(PGE)sulfide mineralization.No.3 intrusion at Baimazhai hosts a medium-sized Ni-Cu-(PGE)deposit whereas No.1 and no.2 intrusions are weakly mineralized.However,similar low Ni/Cu ratios of the three intrusions(No.1 intrusion:0.7 to 2.2;No.2 intrusion:1.4 to 4.0;No.3 intrusion:0.5 to 6.7)indicate that they all may have derived from Mg-rich mafic magmas or picritic magmas.The three intrusions have assimilated by crustal material which resulted in negative Nb(Ta)anomaly in the primitive-mantle normalized trace elemental patterns,and low Nb/La ratios(0.5 to 0.7)and very negative εNd(t)values(-5.1 to-9.0).It is estimated from whole-rock Th/Yb and Nb/Th ratios that the degree of crustal contamination is 5%-20% for No.1 intrusion,5%-10% for No.2 intrusion and 35% for No.3 intrusion.Sulfide contents of the three intrusions vary positively with the degrees of crustal contamination,indicating that the crustal contamination is a major trigger for the formation of immiscible sulfide melts from the magmas.
引文
[1]Tang Z L.Genetic model of the Jinchuan nickel-copper deposit[A].Kirkham R V,Sinclair W D,Thorpe R I,Duke J M.Mineral deposit modeling[C].Geological Association of Cana-da,Special Publication,1993,40:389-401.
[2]Zhou MF,Yang Z X,Song X Y,Lesher C M,Keays R R.Magmatic Ni-Cu-(PGE)sulfide deposits in China[A].Cabri L J.The geology,geochemistry,mineralogy,mineral beneficia-tion of the platinum-group elements[C].Canadian Institute of Mineralogy Metallurgy Petroleum Special Volume,2002,54:619-636.
[3]汤中立,李文渊.金川铜镍硫化物(含铂)矿床成矿模式及地质对比[M].北京:地质出版社,1995:61-66.(in Chinese)Tang Zhongli,Li Wenyuan.Mineralisation model and geology of the Jinchuan Ni-Cu sulphide deposit bearing PGE[M].Bei-jing:Geological Publishing House,1995:61-66.(in Chinese)
[4]Wang C Y,Zhou M F.Genesis of the Permian Baimazhai magmatic Ni-Cu-(PGE)sulfide deposit,Yunnan,SW China[J].Mineralium Deposita,2006,41:771-783.
[5]Wang C Y,Zhou M F,Keays R R.Geochemical constraints on the origin of the Permian Baimazhaimafic-ultramafic intru-sion,SWChina[J].Contributions to Mineralogy and Petrolo-gy,2006,152:309-321.
[6]云南地矿局.云南省区域地质报告[R].北京:地质出版社,1990:554.Yunnan Bureau of Geology and Mineral Resources.Regional geology of Yunnan Province[R].Beijing:Geological Publish-ing House,1990:554.(in Chinese)
[7]Yan D P,Zhou MF,Song H L,Wang X W,Malpas J.Ori-gin and tectonic significance of a Mesozoic multi-layer over-thrust system within the Yangtze Block(South China)[J].Tectonophysics,2003,361:239-254.
[8]Xu Y G,Chung S L,Jahn B M,Wu G Y.Petrologic and geo-chemical constraints on the petrogenesis of Permian-Triassic Emeishan flood basalts in southwestern China[J].Lithos,2001,58:145-168.
[9]Xiao L,Xu Y G,Mei HJ,Zheng Y F,He B,Pirajno F.Dis-tinct mantle sources of low-Ti and high-Ti basalts from the western Emeishanlargeigneous province,SWChina:Implica-tions for plume-lithosphereinteraction[J].Earth and Planetary Science Letter,2004,228:525-546.
[10]Wang C Y,Zhou MF,Qi L.Permianflood basalts and mafic intrusions in the Jinping(SWChina)-Song Da(northern Vi-etnam)district:Mantle sources,crustal contamination and sulfide segregation[J].Chemical Geology,2007,243:317-343.
[11]Qi L,Hu J,Gregoire D C.Determination of trace elements in granites by inductively coupled plasma mass spectrometry[J].Talanta,2001,51:507-513.
[12]Song X Y,Zhou MF,Wang Y L,Zhang C J,Cao Z M,Li Y.Geochemical constrains on the mantle source of the Upper Permian Emeishan continental flood basalts,SW China[J].International Geology Review,2001,43:213-225.
[13]Zhou MF,Malpas J,Song X Y,Kennedy A K,Robinson P T,Sun M,Lesher C M,Keays R R.A temporal link be-tween the Emeishan large igneous province(SW China)and the end-Guadalupian mass extinction[J].Earth and Planetary Science Letter,2002,196:113-122.
[14]Qi L,Zhou MF,Wang C Y,Sun M.Evaluation of the de-termination of Re and PGEs abundance of geological samples by ICP-MS coupled with a modified Carius tube digestion at different temperatures[J].Geochemical Journal,2007,41:407-414.
[15]Zhang HF,Sun M,Lu F X,Zhou X M,Zhou MF,Liu Y S,Zhang G H.Moderately depleted lithospheric mantle un-derneath the Yangtze Block:Evidence from a garnet lherzo-lite xenolith in the Dahongshan kimberlite[J].Geochemical Journal,2001,35:315-331.
[16]Sun S S,McDonough WF.Chemical andisotopic systematics of oceanic basalts:Implications for mantle composition and processes[A].Saunders A D,Norry MJ.Magmatismin the ocean basins[J].Geological Society of London Special Publi-cation,1989,42:313-345.
[17]Lesher C M,Arndt N T,Groves DI.Genesis of komatiite-associated nickel sulfide deposits at Kambalda,Western Aus-tralia:Adistal volcanic model[A].Buchanan D L,Jone MJ.Sulfide deposits in mafic and ultramafic rocks[M].Institute of Mineralogy Metallurgy London,1984:70-80.
[18]Naldrett AJ.Magamtic sulfide deposit:Geology,geochemis-try and exploration[J].Springer,Germany,2004:137-277.
[19]Anders E,Grevesse N.Abundances of the elements:Mete-oritic and solar[J].Geochimica et Cosmochimica Acta,1989,53:197-214.
[20]Beswick A E.Some geochemical aspects of alteration and ge-netic relations in komatiitic suites[A].Arndt N T,Nisbet E G.Komatiities.George Allen&Unwin,London,1982:283-308
[21]Staudigel H,Hart S R.Alteration of basaltic glass:Mecha-nisms and significance for the oceanic crust-seawater budget[J].Geochimica et Cosmochimica Acta,1983,47:337-350.
[22]Barnes S J,Naldrett A J,Gorton M P.The origin of the fractionation of platinum-group elements in terrestrial mag-mas[J].Chemical Geology,1985,53:303-323.
[23]Ely J C,Neal C R.Using platinum-group elements toinvesti-gate the origin of the Ontong Java Plateau,SW Pacific[J].Chemical Geology,2003,196:235-257.
[24]Francis R D.Sulfide globules in mid-ocean ridge basalts(MORB),and the effect of oxygen abundance in Fe-S-Oliq-uids on the ability of those liquids to partition metals from MORB and komatiite magmas[J].Chemical Geology,1990,85:199-213.
[25]Lightfoot P C,Keays R R.Siderophile and chalcophile metal variations in flood basalts from the Siberian Trap,Noril'sk Region:Implications for the origin of the Ni-Cu-PGE sulfide ores[J].Econ.Geol.,2005,100:439-462.
[26]Li C,Naldrett A J.Geology and petrology of the Voisey’s Bay intrusion:Reaction of olivine with sulfide and silicateliq-uids[J].Lithos,1999,47:1-31.
[27]Peck D C,Keays R R.Insightsintothe behaviour of precious metals in primitive,S-undersaturated magmas:Evidence fromthe Heazlewood River complex,Tasmania[J].Canadian Mineralogist,1990,28:553-577.
[28]Zhou M F,Yan D P,Kennedy A K,Li Y Q,Ding J.SHRI MP U-Pb zircon geochronological and geochemical evi-dence for Neoproterozoic arc-magmatism along the western margin of the Yangtze Block,South China[J].Earth and Planetary Science Letter,2002,196:51-67.
[29]Zhang Z C,Mahoney J,Mao J W,Wang F S.Geochemistry of picritic and associated basalt flows of the Western Emeis-han Flood Basalt Province,China[J].Journal of Petrology,2006,47:1997-2019.
[30]Taylor S R,Mclennan S M.The continental crust:Its com-position and evolution,an examination of the geochemical re-cord preservedin sedimentary rocks[J].Blackwell Sci.Publ.Oxford,UK,1985:312.
[31]Irvine T N,Keith D W,Todd S G.The J Mplatinum-palla-dium Reef of the Still water Complex,Montana,II:Origin by double-diffusive convective magma mixing and implications for the Bushveld Complex[J].Economic Geology,1983,78:1287-1334.
[32]Haughton D R,Roeder P L,Skinner B J.Solubility of sul-phur in mafic magmas[J].Economic Geology,1974,69:451-467.
[33]Gain S B,Mostert A B.The Geological setting of the plati-noid and base metal sulfide mineralization in the Platreef of the Bushveld Complexin Drenthe,north of Potgietersrus[J].Economic Geology1982,77:1395-l404.
[34]De Waal S A.Carbon dioxide and water from metamorphicreactions as agents for sulphide and spine1precipitation in mafrc magmas[J].Transactions Geological Society South Af-rica,1977,80:193-196.
[35]Gauert C.Sulphide and oxide mineralisation in the Uitkomst Complex,South Africa:Originin a magma conduit[J].Jour-nal of African Earth Sciences,2001,32:149-161.
[36]Naldrett A J.Key factors in the genesis of Noril’sk,Sud-bury,Jinchuan,Voisey’s Bay and other world-class Ni-Cu-PGE deposits:Implications for exploration[J].Australian Journal Earth Sciences,1997,44:283-315.
[2]Zhou MF,Yang Z X,Song X Y,Lesher C M,Keays R R.Magmatic Ni-Cu-(PGE)sulfide deposits in China[A].Cabri L J.The geology,geochemistry,mineralogy,mineral beneficia-tion of the platinum-group elements[C].Canadian Institute of Mineralogy Metallurgy Petroleum Special Volume,2002,54:619-636.
[3]汤中立,李文渊.金川铜镍硫化物(含铂)矿床成矿模式及地质对比[M].北京:地质出版社,1995:61-66.(in Chinese)Tang Zhongli,Li Wenyuan.Mineralisation model and geology of the Jinchuan Ni-Cu sulphide deposit bearing PGE[M].Bei-jing:Geological Publishing House,1995:61-66.(in Chinese)
[4]Wang C Y,Zhou M F.Genesis of the Permian Baimazhai magmatic Ni-Cu-(PGE)sulfide deposit,Yunnan,SW China[J].Mineralium Deposita,2006,41:771-783.
[5]Wang C Y,Zhou M F,Keays R R.Geochemical constraints on the origin of the Permian Baimazhaimafic-ultramafic intru-sion,SWChina[J].Contributions to Mineralogy and Petrolo-gy,2006,152:309-321.
[6]云南地矿局.云南省区域地质报告[R].北京:地质出版社,1990:554.Yunnan Bureau of Geology and Mineral Resources.Regional geology of Yunnan Province[R].Beijing:Geological Publish-ing House,1990:554.(in Chinese)
[7]Yan D P,Zhou MF,Song H L,Wang X W,Malpas J.Ori-gin and tectonic significance of a Mesozoic multi-layer over-thrust system within the Yangtze Block(South China)[J].Tectonophysics,2003,361:239-254.
[8]Xu Y G,Chung S L,Jahn B M,Wu G Y.Petrologic and geo-chemical constraints on the petrogenesis of Permian-Triassic Emeishan flood basalts in southwestern China[J].Lithos,2001,58:145-168.
[9]Xiao L,Xu Y G,Mei HJ,Zheng Y F,He B,Pirajno F.Dis-tinct mantle sources of low-Ti and high-Ti basalts from the western Emeishanlargeigneous province,SWChina:Implica-tions for plume-lithosphereinteraction[J].Earth and Planetary Science Letter,2004,228:525-546.
[10]Wang C Y,Zhou MF,Qi L.Permianflood basalts and mafic intrusions in the Jinping(SWChina)-Song Da(northern Vi-etnam)district:Mantle sources,crustal contamination and sulfide segregation[J].Chemical Geology,2007,243:317-343.
[11]Qi L,Hu J,Gregoire D C.Determination of trace elements in granites by inductively coupled plasma mass spectrometry[J].Talanta,2001,51:507-513.
[12]Song X Y,Zhou MF,Wang Y L,Zhang C J,Cao Z M,Li Y.Geochemical constrains on the mantle source of the Upper Permian Emeishan continental flood basalts,SW China[J].International Geology Review,2001,43:213-225.
[13]Zhou MF,Malpas J,Song X Y,Kennedy A K,Robinson P T,Sun M,Lesher C M,Keays R R.A temporal link be-tween the Emeishan large igneous province(SW China)and the end-Guadalupian mass extinction[J].Earth and Planetary Science Letter,2002,196:113-122.
[14]Qi L,Zhou MF,Wang C Y,Sun M.Evaluation of the de-termination of Re and PGEs abundance of geological samples by ICP-MS coupled with a modified Carius tube digestion at different temperatures[J].Geochemical Journal,2007,41:407-414.
[15]Zhang HF,Sun M,Lu F X,Zhou X M,Zhou MF,Liu Y S,Zhang G H.Moderately depleted lithospheric mantle un-derneath the Yangtze Block:Evidence from a garnet lherzo-lite xenolith in the Dahongshan kimberlite[J].Geochemical Journal,2001,35:315-331.
[16]Sun S S,McDonough WF.Chemical andisotopic systematics of oceanic basalts:Implications for mantle composition and processes[A].Saunders A D,Norry MJ.Magmatismin the ocean basins[J].Geological Society of London Special Publi-cation,1989,42:313-345.
[17]Lesher C M,Arndt N T,Groves DI.Genesis of komatiite-associated nickel sulfide deposits at Kambalda,Western Aus-tralia:Adistal volcanic model[A].Buchanan D L,Jone MJ.Sulfide deposits in mafic and ultramafic rocks[M].Institute of Mineralogy Metallurgy London,1984:70-80.
[18]Naldrett AJ.Magamtic sulfide deposit:Geology,geochemis-try and exploration[J].Springer,Germany,2004:137-277.
[19]Anders E,Grevesse N.Abundances of the elements:Mete-oritic and solar[J].Geochimica et Cosmochimica Acta,1989,53:197-214.
[20]Beswick A E.Some geochemical aspects of alteration and ge-netic relations in komatiitic suites[A].Arndt N T,Nisbet E G.Komatiities.George Allen&Unwin,London,1982:283-308
[21]Staudigel H,Hart S R.Alteration of basaltic glass:Mecha-nisms and significance for the oceanic crust-seawater budget[J].Geochimica et Cosmochimica Acta,1983,47:337-350.
[22]Barnes S J,Naldrett A J,Gorton M P.The origin of the fractionation of platinum-group elements in terrestrial mag-mas[J].Chemical Geology,1985,53:303-323.
[23]Ely J C,Neal C R.Using platinum-group elements toinvesti-gate the origin of the Ontong Java Plateau,SW Pacific[J].Chemical Geology,2003,196:235-257.
[24]Francis R D.Sulfide globules in mid-ocean ridge basalts(MORB),and the effect of oxygen abundance in Fe-S-Oliq-uids on the ability of those liquids to partition metals from MORB and komatiite magmas[J].Chemical Geology,1990,85:199-213.
[25]Lightfoot P C,Keays R R.Siderophile and chalcophile metal variations in flood basalts from the Siberian Trap,Noril'sk Region:Implications for the origin of the Ni-Cu-PGE sulfide ores[J].Econ.Geol.,2005,100:439-462.
[26]Li C,Naldrett A J.Geology and petrology of the Voisey’s Bay intrusion:Reaction of olivine with sulfide and silicateliq-uids[J].Lithos,1999,47:1-31.
[27]Peck D C,Keays R R.Insightsintothe behaviour of precious metals in primitive,S-undersaturated magmas:Evidence fromthe Heazlewood River complex,Tasmania[J].Canadian Mineralogist,1990,28:553-577.
[28]Zhou M F,Yan D P,Kennedy A K,Li Y Q,Ding J.SHRI MP U-Pb zircon geochronological and geochemical evi-dence for Neoproterozoic arc-magmatism along the western margin of the Yangtze Block,South China[J].Earth and Planetary Science Letter,2002,196:51-67.
[29]Zhang Z C,Mahoney J,Mao J W,Wang F S.Geochemistry of picritic and associated basalt flows of the Western Emeis-han Flood Basalt Province,China[J].Journal of Petrology,2006,47:1997-2019.
[30]Taylor S R,Mclennan S M.The continental crust:Its com-position and evolution,an examination of the geochemical re-cord preservedin sedimentary rocks[J].Blackwell Sci.Publ.Oxford,UK,1985:312.
[31]Irvine T N,Keith D W,Todd S G.The J Mplatinum-palla-dium Reef of the Still water Complex,Montana,II:Origin by double-diffusive convective magma mixing and implications for the Bushveld Complex[J].Economic Geology,1983,78:1287-1334.
[32]Haughton D R,Roeder P L,Skinner B J.Solubility of sul-phur in mafic magmas[J].Economic Geology,1974,69:451-467.
[33]Gain S B,Mostert A B.The Geological setting of the plati-noid and base metal sulfide mineralization in the Platreef of the Bushveld Complexin Drenthe,north of Potgietersrus[J].Economic Geology1982,77:1395-l404.
[34]De Waal S A.Carbon dioxide and water from metamorphicreactions as agents for sulphide and spine1precipitation in mafrc magmas[J].Transactions Geological Society South Af-rica,1977,80:193-196.
[35]Gauert C.Sulphide and oxide mineralisation in the Uitkomst Complex,South Africa:Originin a magma conduit[J].Jour-nal of African Earth Sciences,2001,32:149-161.
[36]Naldrett A J.Key factors in the genesis of Noril’sk,Sud-bury,Jinchuan,Voisey’s Bay and other world-class Ni-Cu-PGE deposits:Implications for exploration[J].Australian Journal Earth Sciences,1997,44:283-315.
目录