川西拉拉Fe-Cu矿区含矿镁铁质层状岩席的首次发现及其成岩成矿意义
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摘要
尽管镁铁质层状侵入体得到了广泛关注,与其相关的成岩和成矿过程仍然存在很多疑问。文中首次报道了在川西拉拉Fe-Cu矿区发现的一种含矿镁铁质岩席,它的深入研究可能有助于理解拉拉Fe-Cu矿床的成因,以及层状侵入体的组装过程与成矿作用。野外观察表明,该岩席共由9个岩相带组成,相邻岩相带为侵入接触关系,上半部分和下半部分的岩性呈镜像对应。对该岩席上半部分的5个岩相带分别进行了显微镜观察、粉晶X-射线衍射分析和CSD分析,表明相邻岩相带的矿物组成和结构参数具有明显区别,揭示该岩席由4、5次岩浆脉动组装而成。各岩相带均具有显微斑状结构,其中1～4岩相带的斑晶矿物主要为角闪石、云母和Ti-Fe氧化物,第5岩相带的斑晶为白云母、钾长石和石英。此外,第3岩相带还含有大颗粒单斜辉石斑晶,第4岩相带含有方解石大斑晶。含水矿物呈斑晶产出表明所有岩相带都是挥发分(H2O+CO2)饱和或过饱和岩浆固结的产物,但各岩相带的岩浆具有不同的来源。根据斑晶(循环晶)矿物组合、定量化结构参数和参数变异趋势,推测拉拉岩席之下曾经存在3～5个位于不同深部水平上的岩浆房。这些岩浆房有不同成分的进化岩浆充填,可能富集了相应的成矿金属。当深部含矿流体输入该岩浆系统时,有可能引起骨牌效应,导致各种含矿流体大规模释放。拉拉矿区的这类岩席可能对成矿物质起到了屏蔽作用,使其大规模聚集形成超大型矿床。需要注意的是,拉拉岩席的富矿岩相带侵位时间最晚,类似于攀枝花铁矿。因此,拉拉岩席的成岩成矿模式有可能也适应于攀枝花式铁矿。
The layered intrusion has received much attention,however,its petrogenensis and metallogenic model are still debatable.Here,we report for the first time the mafic ore-bearing layered intrusions in the Lala Fe-Cu ore district.This discovery will aid metallogenic research on the Fe-Cu ore,Lala district for a better understanding of the intrusion and metallogenic processes of layered intrusion.Field observation showed that the layered intrusion was composed of nine lithofacies zones,with intrusive contacts between adjacent zones and mirror imaging between the upper and lower halves of the facies.Microscopic observations,X-ray diffraction and CDC analyses of the upper five lithofacies zones indicated that the mineral composition and structural parameters of the adjacent facies zones were markedly different,which may suggest that the intrusion was formed by 4-5 pulsed invasions.Each lithofacies zone has the porphyritic texture.Phenocrysts in the 1 st-4 th facies zones were mainly hornblende,mica and Ti-Fe oxide,while muscovite,potash feldspar and tquartz mainly in the 5 h,and big clinopyroxene and calcite phenocrysts made up the 3 rd and 4 th facies zones,respectively.The hydrous mineral in phenocryst implied that all ore-forming magmas contained saturated or supersaturated H2 O + CO2 volatiles,but had different origin for each facies zone.Based on the phenocryst mineral assemblage,quantitative structural parameters and parameter variation trend,one can speculate that 3-5 magma chambers of different depths existed under the Lala sill.These magma chambers were packed with evolved magmas of varied compositions,possibly enriching the corresponding ore-forming metals.As the deep metallogenetic fluid entered this magmatic system,ensuing domino effect might lead to mass release of all kinds of metallogenetic fluids.The Lala-type sill might act as shield for the ore-forming materials to aggregate at a large scale and form super-size deposits.It is worth noting that the rich ore lithofacies zone experienced the latest emplacement,similar to that of the Panzhihua-type iron deposit.Therefore,the petro-metallogenetic model of the Lala sill may be applicable to the Panzhihua-type iron deposit.
The layered intrusion has received much attention,however,its petrogenensis and metallogenic model are still debatable.Here,we report for the first time the mafic ore-bearing layered intrusions in the Lala Fe-Cu ore district.This discovery will aid metallogenic research on the Fe-Cu ore,Lala district for a better understanding of the intrusion and metallogenic processes of layered intrusion.Field observation showed that the layered intrusion was composed of nine lithofacies zones,with intrusive contacts between adjacent zones and mirror imaging between the upper and lower halves of the facies.Microscopic observations,X-ray diffraction and CDC analyses of the upper five lithofacies zones indicated that the mineral composition and structural parameters of the adjacent facies zones were markedly different,which may suggest that the intrusion was formed by 4-5 pulsed invasions.Each lithofacies zone has the porphyritic texture.Phenocrysts in the 1 st-4 th facies zones were mainly hornblende,mica and Ti-Fe oxide,while muscovite,potash feldspar and tquartz mainly in the 5 h,and big clinopyroxene and calcite phenocrysts made up the 3 rd and 4 th facies zones,respectively.The hydrous mineral in phenocryst implied that all ore-forming magmas contained saturated or supersaturated H2 O + CO2 volatiles,but had different origin for each facies zone.Based on the phenocryst mineral assemblage,quantitative structural parameters and parameter variation trend,one can speculate that 3-5 magma chambers of different depths existed under the Lala sill.These magma chambers were packed with evolved magmas of varied compositions,possibly enriching the corresponding ore-forming metals.As the deep metallogenetic fluid entered this magmatic system,ensuing domino effect might lead to mass release of all kinds of metallogenetic fluids.The Lala-type sill might act as shield for the ore-forming materials to aggregate at a large scale and form super-size deposits.It is worth noting that the rich ore lithofacies zone experienced the latest emplacement,similar to that of the Panzhihua-type iron deposit.Therefore,the petro-metallogenetic model of the Lala sill may be applicable to the Panzhihua-type iron deposit.
引文
[1] WAGER L R,BROWN G M.Layered igneous rocks[M].San Francisco:WH Freeman,1967:20-35.
[2] MCBIRNEY A.The Skaergaard intrusion[J].Developments in Petrology,1996,15:147-180.
[3] MARSH B D.Solidification fronts and magmatic evolution[J].Mineralogical Magazine,1996,60(1):5-40.
[4] BOORMAN S L,MCGUIRE J B,BOUDREAU A E,et al.Fluid overpressure in layered intrusions:formation of a breccia pipe in the Eastern Bushveld Complex,Republic of South Africa[J].Mineralium Deposita,2003,38(3):356-369.
[5] ZHOU M F,ROBINSON P T,LESHER C M,et al.Geochemistry,petrogenesis and metallogenesis of the Panzhihua gabbroic layered intrusion and associated Fe-Ti-V oxide deposits,Sichuan Province,SW China[J].Journal of Petrology,2005,46(11):2253-2280.
[6] GUTIERREZ F,PARADA M A.Numerical modeling of time-dependent fluid dynamics and differentiation of a shal-low basaltic magma chamber[J].Journal of Petrology,2010,51(3):731-762.
[7] LATYPOV R,HANSKI E,LAVRENCHUK A,et al.A‘three-increase model’for the origin of the marginal reversal of the Koitelainen layered intrusion,Finland[J].Journal of Petrology,2011,52(4):733-764.
[8] CHENG L,ZENG L,REN Z,et al.Timescale of emplacement of the Panzhihua gabbroic layered intrusion recorded in giant plagioclase at Sichuan Province,SW China[J].Lithos,2014,204:203-219.
[9] SPANDLER C,MAVROGENES J,ARCULUS R.Origin of chromitites in layered intrusions:evidence from chromite-hosted melt inclusions from the Stillwater Complex[J].Geology,2005,33(11):893-896.
[10] BARLING J,WEIS D,DEMAIFFE D.A Sr-,Nd-and Pbisotopic investigation of the transition between two megacyclic units of the Bjerkreim-Sokndal layered intrusion,South Norway[J].Chemical Geology,2000,165(1):47-65.
[11] NORTON D,TAYLOR H.Quantitative simulation of the hydrothermal systems of crystallizing magmas on the basis of transport theory and oxygen isotope data:an analysis of the Skaergaard intrusion[J].Journal of Petrology,1979,20(3):421-486.
[12] EGOROVA V,LATYPOV R.Mafic-ultramafic sills:new insights from M-and S-shaped mineral and whole-rock compositional profiles[J].Journal of Petrology,2013,54(10):2155-2191.
[13] ZIEG M,MARSH B.Multiple reinjections and crystal-mush compaction in the Beacon Sill,McMurdo Dry Valleys,Antarctica[J].Journal of Petrology,2012,53(12):2567-2591.
[14] BARNES S,LATYPOV R.‘From Igneous Petrology to Ore Genesis':an introduction to this thematic issue of Journal of Petrology[J].Journal of Petrology,2015,56(12):2295-2296.
[15] FERRE E C,MARSH B D.Special issue:physical and chemical processes in layered mafic intrusions[J].Lithos,2009,111(1):7-8.
[16] PANG K N,ZHOU M F,QI L,et al.Petrology and geochemistry at the Lower zone-Middle zone transition of the Panzhihua intrusion,SW China:implications for differentiation and oxide ore genesis[J].Geoscience Frontiers,2013,4(5):517-533.
[17]邱一冉,罗照华,杨宗锋,等.四川米易青皮村镁铁质侵入体的固结过程[J].地学前缘,2016,23(4):241-254.
[18]李解,罗照华,杨宗锋,等.攀枝花铁矿朱家包包矿段层状铁矿体的成因:来自矿物结构定量化分析的证据[J].地学前缘,2016,23(3):210-220.
[19]陈根文,夏斌.四川拉拉铜矿床成因研究[J].矿物岩石地球化学通报,2001,20(1):42-44.
[20]李泽琴,胡瑞忠,王奖臻,等.中国首例铁氧化物铜金铀稀土型矿床的厘定及其成矿演化[J].矿物岩石地球化学通报,2002,21(4):258-260.
[21]杨宗锋,罗照华,卢欣祥.定量化火成岩结构分析与岩浆固结的动力学过程[J].地学前缘,2010,17(1):246-266.
[22] YANG Z F.Combining quantitative textural and geochemical studies to understand the solidification processes of a granite porphyry:Shanggusi,East Qinling,China[J].Journal of Petrology,2012,53(9):1807-1835.
[23] YANG Z F,LUO Z H,LU X X,et al.The role of external fluid in the Shanggusi dynamic granitic magma system,East Qinling,China:quantitative integration of textural and chemical data[J].Lithos,2014,208:339-360.
[24] MARSH B D.Crystallization of silicate magmas deciphered using crystal size distributions[J].Journal of the American Ceramic Society,2007,90(3):746-757.
[25] MARSH B D.Crystal size distribution(CSD)in rocks and the kinetics and dynamics of crystallization[J].Contributions to Mineralogy and Petrology,1988,99(3):277-291.
[26] HIGGINS M D.Quantitative textural measurements in igneous and metamorphic petrology[M].Cambridge:Cambridge University Press,2006,70(4):459-460.
[27] MARSH B D.On the interpretation of crystal size distributions in magmatic systems[J].Journal of Petrology,1998,39(4):553-599.
[28] ZIEG M,MARSH B.Crystal size distributions and scaling laws in the quantification of igneous textures[J].Journal of Petrology,2002,43(1):85-101.
[29]罗照华,莫宣学,卢欣祥,等.透岩浆流体成矿作用理论分析与野外证据[J].地学前缘,2007,14(3):165-183.
[30]罗照华,刘翠,苏尚国.理解岩浆系统的物理过程[J].岩石学报,2014,30(11):3113-3119.
[31] MILLER C F,WARK D A.Supervolcanoes and their explosive supereruptions[J].Elements,2008,4(1):11-15.
[32]罗照华,杨宗锋,代耕,等.火成岩的晶体群与成因矿物学展望[J].中国地质,2013,40(1):176-181.
[33] CLAESON D T,MEURER W P.Fractional crystallization of hydrous basaltic“arc-type”magmas and the formation of amphibole-bearing gabbroic cumulates[J].Contributions to Mineralogy and Petrology,2004,147(3):288-304.
[34] FEIG S T,KOEPKE J,SNOW J E.Effect of water on tholeiitic basalt phase equilibria:an experimental study under oxidizing conditions[J].Contributions to Mineralogy and Petrology,2006,152(5):611-638.
[35]李德东,罗照华,周久龙,等.岩墙厚度对成矿作用的约束:以石湖金矿为例[J].地学前缘,2011,18(1):166-178.
[2] MCBIRNEY A.The Skaergaard intrusion[J].Developments in Petrology,1996,15:147-180.
[3] MARSH B D.Solidification fronts and magmatic evolution[J].Mineralogical Magazine,1996,60(1):5-40.
[4] BOORMAN S L,MCGUIRE J B,BOUDREAU A E,et al.Fluid overpressure in layered intrusions:formation of a breccia pipe in the Eastern Bushveld Complex,Republic of South Africa[J].Mineralium Deposita,2003,38(3):356-369.
[5] ZHOU M F,ROBINSON P T,LESHER C M,et al.Geochemistry,petrogenesis and metallogenesis of the Panzhihua gabbroic layered intrusion and associated Fe-Ti-V oxide deposits,Sichuan Province,SW China[J].Journal of Petrology,2005,46(11):2253-2280.
[6] GUTIERREZ F,PARADA M A.Numerical modeling of time-dependent fluid dynamics and differentiation of a shal-low basaltic magma chamber[J].Journal of Petrology,2010,51(3):731-762.
[7] LATYPOV R,HANSKI E,LAVRENCHUK A,et al.A‘three-increase model’for the origin of the marginal reversal of the Koitelainen layered intrusion,Finland[J].Journal of Petrology,2011,52(4):733-764.
[8] CHENG L,ZENG L,REN Z,et al.Timescale of emplacement of the Panzhihua gabbroic layered intrusion recorded in giant plagioclase at Sichuan Province,SW China[J].Lithos,2014,204:203-219.
[9] SPANDLER C,MAVROGENES J,ARCULUS R.Origin of chromitites in layered intrusions:evidence from chromite-hosted melt inclusions from the Stillwater Complex[J].Geology,2005,33(11):893-896.
[10] BARLING J,WEIS D,DEMAIFFE D.A Sr-,Nd-and Pbisotopic investigation of the transition between two megacyclic units of the Bjerkreim-Sokndal layered intrusion,South Norway[J].Chemical Geology,2000,165(1):47-65.
[11] NORTON D,TAYLOR H.Quantitative simulation of the hydrothermal systems of crystallizing magmas on the basis of transport theory and oxygen isotope data:an analysis of the Skaergaard intrusion[J].Journal of Petrology,1979,20(3):421-486.
[12] EGOROVA V,LATYPOV R.Mafic-ultramafic sills:new insights from M-and S-shaped mineral and whole-rock compositional profiles[J].Journal of Petrology,2013,54(10):2155-2191.
[13] ZIEG M,MARSH B.Multiple reinjections and crystal-mush compaction in the Beacon Sill,McMurdo Dry Valleys,Antarctica[J].Journal of Petrology,2012,53(12):2567-2591.
[14] BARNES S,LATYPOV R.‘From Igneous Petrology to Ore Genesis':an introduction to this thematic issue of Journal of Petrology[J].Journal of Petrology,2015,56(12):2295-2296.
[15] FERRE E C,MARSH B D.Special issue:physical and chemical processes in layered mafic intrusions[J].Lithos,2009,111(1):7-8.
[16] PANG K N,ZHOU M F,QI L,et al.Petrology and geochemistry at the Lower zone-Middle zone transition of the Panzhihua intrusion,SW China:implications for differentiation and oxide ore genesis[J].Geoscience Frontiers,2013,4(5):517-533.
[17]邱一冉,罗照华,杨宗锋,等.四川米易青皮村镁铁质侵入体的固结过程[J].地学前缘,2016,23(4):241-254.
[18]李解,罗照华,杨宗锋,等.攀枝花铁矿朱家包包矿段层状铁矿体的成因:来自矿物结构定量化分析的证据[J].地学前缘,2016,23(3):210-220.
[19]陈根文,夏斌.四川拉拉铜矿床成因研究[J].矿物岩石地球化学通报,2001,20(1):42-44.
[20]李泽琴,胡瑞忠,王奖臻,等.中国首例铁氧化物铜金铀稀土型矿床的厘定及其成矿演化[J].矿物岩石地球化学通报,2002,21(4):258-260.
[21]杨宗锋,罗照华,卢欣祥.定量化火成岩结构分析与岩浆固结的动力学过程[J].地学前缘,2010,17(1):246-266.
[22] YANG Z F.Combining quantitative textural and geochemical studies to understand the solidification processes of a granite porphyry:Shanggusi,East Qinling,China[J].Journal of Petrology,2012,53(9):1807-1835.
[23] YANG Z F,LUO Z H,LU X X,et al.The role of external fluid in the Shanggusi dynamic granitic magma system,East Qinling,China:quantitative integration of textural and chemical data[J].Lithos,2014,208:339-360.
[24] MARSH B D.Crystallization of silicate magmas deciphered using crystal size distributions[J].Journal of the American Ceramic Society,2007,90(3):746-757.
[25] MARSH B D.Crystal size distribution(CSD)in rocks and the kinetics and dynamics of crystallization[J].Contributions to Mineralogy and Petrology,1988,99(3):277-291.
[26] HIGGINS M D.Quantitative textural measurements in igneous and metamorphic petrology[M].Cambridge:Cambridge University Press,2006,70(4):459-460.
[27] MARSH B D.On the interpretation of crystal size distributions in magmatic systems[J].Journal of Petrology,1998,39(4):553-599.
[28] ZIEG M,MARSH B.Crystal size distributions and scaling laws in the quantification of igneous textures[J].Journal of Petrology,2002,43(1):85-101.
[29]罗照华,莫宣学,卢欣祥,等.透岩浆流体成矿作用理论分析与野外证据[J].地学前缘,2007,14(3):165-183.
[30]罗照华,刘翠,苏尚国.理解岩浆系统的物理过程[J].岩石学报,2014,30(11):3113-3119.
[31] MILLER C F,WARK D A.Supervolcanoes and their explosive supereruptions[J].Elements,2008,4(1):11-15.
[32]罗照华,杨宗锋,代耕,等.火成岩的晶体群与成因矿物学展望[J].中国地质,2013,40(1):176-181.
[33] CLAESON D T,MEURER W P.Fractional crystallization of hydrous basaltic“arc-type”magmas and the formation of amphibole-bearing gabbroic cumulates[J].Contributions to Mineralogy and Petrology,2004,147(3):288-304.
[34] FEIG S T,KOEPKE J,SNOW J E.Effect of water on tholeiitic basalt phase equilibria:an experimental study under oxidizing conditions[J].Contributions to Mineralogy and Petrology,2006,152(5):611-638.
[35]李德东,罗照华,周久龙,等.岩墙厚度对成矿作用的约束:以石湖金矿为例[J].地学前缘,2011,18(1):166-178.