条带状铁建造(banded iron formation,BIF)是地球早期演化历史中形成的重要铁矿类型。那西郭勒BIF型矿床位于东昆仑造山带西段,赋存于新元古代金水口群中-高级变质斜长角闪岩组合中,呈层状-透镜状产出。该矿床资源量达75 Mt,铁品位介于1...条带状铁建造(banded iron formation,BIF)是地球早期演化历史中形成的重要铁矿类型。那西郭勒BIF型矿床位于东昆仑造山带西段,赋存于新元古代金水口群中-高级变质斜长角闪岩组合中,呈层状-透镜状产出。该矿床资源量达75 Mt,铁品位介于15%~28.83%,矿石主体为具典型条带状构造的磁铁石英岩。为深入理解该矿床成因并为区域找矿提供依据,基于系统的野外地质调查,结合磁铁矿电子探针微区分析及全岩主、微量元素地球化学研究,系统阐明了矿床的地质特征、成矿物质来源及成因类型。电子探针分析表明,磁铁矿具有高TFeO(90.01%~92.98%)和极低的TiO_(2)、MgO、MnO、CaO、Al_(2)O_(3)等质量分数(均<0.4%),符合典型BIF型磁铁矿的成分特征。全岩地球化学数据揭示矿石具有变化的w(TFeO)(15.45%~74.74%)和w(Al_(2)O_(3))(1.84%~17.04%),并具显著的Eu正异常(Eu/Eu_(PAAS)^(*)=1.38~2.12)、Y正异常(Y/Y_(PAAS)^(*)=0.98~1.42)、较低的Eu/Sm比值(0.30~0.51)以及较高的Sm/Yb(0.69~2.17)和Y/Ho(26.55~40.73)比值。综合上述地球化学特征,指示成矿物质主要来源于海水与极少量(约0.1%)海底高温热液的混合。矿石中缺乏显著的Ce负异常,结合赋矿围岩属性,暗示矿床形成于还原性边缘海环境。综合其严格受层位控制的地质产状、典型的磁铁石英岩矿物组合以及上述特征性地球化学证据,确定那西郭勒铁矿为典型的苏必利尔型(Superior-type)BIF矿床。展开更多
为了从遥感角度对西澳大利亚哈默斯利盆地的沉积变质条带状含铁建造(banded iron formation,BIF)型铁矿进行深入研究,利用ETM图像对皮尔巴拉地块进行地质矿产解译,采用ASTER图像对目标区域进行矿化蚀变信息提取;结合传统地质矿产理论及...为了从遥感角度对西澳大利亚哈默斯利盆地的沉积变质条带状含铁建造(banded iron formation,BIF)型铁矿进行深入研究,利用ETM图像对皮尔巴拉地块进行地质矿产解译,采用ASTER图像对目标区域进行矿化蚀变信息提取;结合传统地质矿产理论及相关文献,对区内BIF型铁矿的遥感地质特征及其成矿机理进行深入解剖、对比和研究,在此基础上建立了BIF型铁矿的遥感地质找矿模型;并圈定了找矿远景区,以期能在BIF型铁矿找矿(前期)技术方面取得突破,为寻找BIF型铁矿提供技术支持与帮助。具有现实验证意义的是,在所圈定的找矿远景区进行野外调查时发现,澳大利亚力拓集团已经在纽曼—必和必拓C区远景区内筹建一处大型铁矿,前期平地工作已基本完成。展开更多
The Shilu Fe-polymetallic ore deposit,a famous hematite-rich Fe-ore deposit,is situated at the western Hainan Province of south China.The deposit characterizes the upper Fe ores and the lower Co-Cu ores,which are main...The Shilu Fe-polymetallic ore deposit,a famous hematite-rich Fe-ore deposit,is situated at the western Hainan Province of south China.The deposit characterizes the upper Fe ores and the lower Co-Cu ores,which are mainly hosted within a low-grade to medium-grade,dominantly submarine metamorphosed siliciclastic and carbonate sedimentary succession of the Neoproterozoic Shilu Group.Three facies types of metamorphosed BIFs,i.e.the oxide facies,the silicate-oxide facies and the sulfide-carbonate facies BIFs,are identified within the sixth sequence of the Shilu Group.The oxide facies BIF(i.e.the Fe-rich itabirites or ores)consists of alternating hematite-rich microbands with quartz-rich microbands;the silicate-oxide facies BIF(i.e.the Fe-poor itabirites or ores)comprises alternating millimeter-to a few tens meter-scale,magnetite-hematite-rich bands with calcsilicate-rich(garnet+actinolite+diopside+epidote+quartz)meso-to microbands;and the sulfide-carbonate facies BIF(i.e.the Co-Cu ores)contains alternating macro-to mesobands of Co-bearing pyrite and pyrrhotite,and chalcopyrite with mesobands of dolomite+calcite+diopside+quartz and/or chlorite+sericite+quartz.The blastooolitic,blastopelletoid blastocolloidal and blastopsammitic textures,and blasobedding structures which most likely represent primary sedimentation are often observed in these BIF facies.The interbedded host rocks with the BIFs mainly are the pyroxene-amphibole rocks and the banded or impure dolostones,and also contain banded or laminated structures,and lepido-gra-noblastic,nematoblastic and/or blastoclastic textures.Compositionally,the main host rocks,the pyroxene-amphibole rocks contain basic-intermediate SiO_2(~54.00 wt.%),CaO(~14.19 wt.%),MgO(~9.68 wt.%)and Al_2O_3(~8.49 wt.%)with a positive correlation between Al_2O_3 and TiO_2.The UCC-like Zr and Hf abundances,high Ba content andεNd(t)value(^-5.99)as well as the ratios of La/YbPAAS(0.17~1.00),δEuPAAS(0.88~1.12)andδCePAAS(0.93~1.13)commonly reveal that the protoliths to this type rocks are hydrogenic with a large contribution of terrigenous sediments and minor hydrothermal input.The high CaO+MgO+LOI contents and the extremely low trace element and REEconcentrations as well as the ratios of Y/Ho(44~45),δEuPAAS(1.13~1.57)andδCePAAS(0.69~0.98)reflect a marine origin with minor terrigenous materials for the banded or impure dolostones.Moreover,this type rocks also account for a negativeεNd(t)value(^-7.49).The oxide facies BIF is dominated by Fe_2O_3+FeO(~75.59wt.%)and SiO_2(~20.47 wt.%)with aεNd(t)value of^-6.10.The variable contents in Al_2O_3,TiO 2,K2O,Na2O,Zr,Hf and∑REE,and variable ratios of Y/Ho(24~39)andδEuPAAS(0.86~11.07)suggest the precursor sediments to this facies BIF are admixtures of sea-floor hydrothermal fluids and seawaters with minor involvement of detrital components.Compared to the oxide facies BIF,the silicate-oxide facies BIF is lower in Fe_2O_3+Fe O(~39.81wt.%)and Ba but higher in SiO_2(~42.54 wt.%),Al2O3(~3.60 wt.%),TiO_2(~0.19 wt.%),MgO(~1.12 wt.%),CaO(~9.06 wt.%),K_2O(~0.98 wt.%),Mn and Zr.The ratios of Y/Ho(25~34),La/YbPAAS(0.14-0.74)andδEuPAAS(0.91~1.12)most likely are linked to higher degree of detrital contamintants.While the sulfide-caronate facies BIF is main but variable in Fe_2O_3+Fe O(15.79~57.91 wt.%),SiO 2(0.54~61.52 wt.%),MgO(0.12~16.09wt.%),CaO(0.17~23.41 wt.%)and LOI(8.28-30.06 wt.%).The generally low contents in trace elements(including REE)except for an obvious enrichment in Pb,and the positive Ce anomalies(δCePAAS=1.04~1.95)and negative Pr anomalies(δPrPAAS=0.67~0.93),as well as the variable ratios ofδEuPAAS(0.72~1.71),La/YbPAAS(0.26~1.60)and Y/Ho(26~57)suggest that the precursors to the sulfide-carbonate facies BIF mainly are metalliferious sediments from deep-marine hydrotheral source with minor detrital components.The T2DM ages(ca.2.0 Ga)imply that the Shilu BIFs and interbedded host rocks contain a component with Paleoproterozoic crustal residence age due to a significant crustal accretion event at ca.2.0 Ga in Hainan Island.In connection with the petrographical and mineralogical relationship,we conclude that the precursor precipitates to the Shilu BIFs are variable degree of admixtures of the Fe-Co-Cu-(Si)-rich hydrothermal fluids and detrital components from seawater and fresh water carring continental landmass;whereas the protolith to the main interbedded host rocks,i.e.the pyroxene-amphibole rocks,most likely was terrigenous,fine-grained clastic-sediments but with significant input of hydrothermal fluids in a seawater environment.As a result,a continent marginal marine basin is proposed for deposition of the Shilu BIFs and interbedded host rocks.Sea-level fluctuations caused by marine transgression–regressions possibly contributed to changes in the composition and varied input of the terrigenous sediments.展开更多
文摘条带状铁建造(banded iron formation,BIF)是地球早期演化历史中形成的重要铁矿类型。那西郭勒BIF型矿床位于东昆仑造山带西段,赋存于新元古代金水口群中-高级变质斜长角闪岩组合中,呈层状-透镜状产出。该矿床资源量达75 Mt,铁品位介于15%~28.83%,矿石主体为具典型条带状构造的磁铁石英岩。为深入理解该矿床成因并为区域找矿提供依据,基于系统的野外地质调查,结合磁铁矿电子探针微区分析及全岩主、微量元素地球化学研究,系统阐明了矿床的地质特征、成矿物质来源及成因类型。电子探针分析表明,磁铁矿具有高TFeO(90.01%~92.98%)和极低的TiO_(2)、MgO、MnO、CaO、Al_(2)O_(3)等质量分数(均<0.4%),符合典型BIF型磁铁矿的成分特征。全岩地球化学数据揭示矿石具有变化的w(TFeO)(15.45%~74.74%)和w(Al_(2)O_(3))(1.84%~17.04%),并具显著的Eu正异常(Eu/Eu_(PAAS)^(*)=1.38~2.12)、Y正异常(Y/Y_(PAAS)^(*)=0.98~1.42)、较低的Eu/Sm比值(0.30~0.51)以及较高的Sm/Yb(0.69~2.17)和Y/Ho(26.55~40.73)比值。综合上述地球化学特征,指示成矿物质主要来源于海水与极少量(约0.1%)海底高温热液的混合。矿石中缺乏显著的Ce负异常,结合赋矿围岩属性,暗示矿床形成于还原性边缘海环境。综合其严格受层位控制的地质产状、典型的磁铁石英岩矿物组合以及上述特征性地球化学证据,确定那西郭勒铁矿为典型的苏必利尔型(Superior-type)BIF矿床。
文摘为了从遥感角度对西澳大利亚哈默斯利盆地的沉积变质条带状含铁建造(banded iron formation,BIF)型铁矿进行深入研究,利用ETM图像对皮尔巴拉地块进行地质矿产解译,采用ASTER图像对目标区域进行矿化蚀变信息提取;结合传统地质矿产理论及相关文献,对区内BIF型铁矿的遥感地质特征及其成矿机理进行深入解剖、对比和研究,在此基础上建立了BIF型铁矿的遥感地质找矿模型;并圈定了找矿远景区,以期能在BIF型铁矿找矿(前期)技术方面取得突破,为寻找BIF型铁矿提供技术支持与帮助。具有现实验证意义的是,在所圈定的找矿远景区进行野外调查时发现,澳大利亚力拓集团已经在纽曼—必和必拓C区远景区内筹建一处大型铁矿,前期平地工作已基本完成。
文摘The Shilu Fe-polymetallic ore deposit,a famous hematite-rich Fe-ore deposit,is situated at the western Hainan Province of south China.The deposit characterizes the upper Fe ores and the lower Co-Cu ores,which are mainly hosted within a low-grade to medium-grade,dominantly submarine metamorphosed siliciclastic and carbonate sedimentary succession of the Neoproterozoic Shilu Group.Three facies types of metamorphosed BIFs,i.e.the oxide facies,the silicate-oxide facies and the sulfide-carbonate facies BIFs,are identified within the sixth sequence of the Shilu Group.The oxide facies BIF(i.e.the Fe-rich itabirites or ores)consists of alternating hematite-rich microbands with quartz-rich microbands;the silicate-oxide facies BIF(i.e.the Fe-poor itabirites or ores)comprises alternating millimeter-to a few tens meter-scale,magnetite-hematite-rich bands with calcsilicate-rich(garnet+actinolite+diopside+epidote+quartz)meso-to microbands;and the sulfide-carbonate facies BIF(i.e.the Co-Cu ores)contains alternating macro-to mesobands of Co-bearing pyrite and pyrrhotite,and chalcopyrite with mesobands of dolomite+calcite+diopside+quartz and/or chlorite+sericite+quartz.The blastooolitic,blastopelletoid blastocolloidal and blastopsammitic textures,and blasobedding structures which most likely represent primary sedimentation are often observed in these BIF facies.The interbedded host rocks with the BIFs mainly are the pyroxene-amphibole rocks and the banded or impure dolostones,and also contain banded or laminated structures,and lepido-gra-noblastic,nematoblastic and/or blastoclastic textures.Compositionally,the main host rocks,the pyroxene-amphibole rocks contain basic-intermediate SiO_2(~54.00 wt.%),CaO(~14.19 wt.%),MgO(~9.68 wt.%)and Al_2O_3(~8.49 wt.%)with a positive correlation between Al_2O_3 and TiO_2.The UCC-like Zr and Hf abundances,high Ba content andεNd(t)value(^-5.99)as well as the ratios of La/YbPAAS(0.17~1.00),δEuPAAS(0.88~1.12)andδCePAAS(0.93~1.13)commonly reveal that the protoliths to this type rocks are hydrogenic with a large contribution of terrigenous sediments and minor hydrothermal input.The high CaO+MgO+LOI contents and the extremely low trace element and REEconcentrations as well as the ratios of Y/Ho(44~45),δEuPAAS(1.13~1.57)andδCePAAS(0.69~0.98)reflect a marine origin with minor terrigenous materials for the banded or impure dolostones.Moreover,this type rocks also account for a negativeεNd(t)value(^-7.49).The oxide facies BIF is dominated by Fe_2O_3+FeO(~75.59wt.%)and SiO_2(~20.47 wt.%)with aεNd(t)value of^-6.10.The variable contents in Al_2O_3,TiO 2,K2O,Na2O,Zr,Hf and∑REE,and variable ratios of Y/Ho(24~39)andδEuPAAS(0.86~11.07)suggest the precursor sediments to this facies BIF are admixtures of sea-floor hydrothermal fluids and seawaters with minor involvement of detrital components.Compared to the oxide facies BIF,the silicate-oxide facies BIF is lower in Fe_2O_3+Fe O(~39.81wt.%)and Ba but higher in SiO_2(~42.54 wt.%),Al2O3(~3.60 wt.%),TiO_2(~0.19 wt.%),MgO(~1.12 wt.%),CaO(~9.06 wt.%),K_2O(~0.98 wt.%),Mn and Zr.The ratios of Y/Ho(25~34),La/YbPAAS(0.14-0.74)andδEuPAAS(0.91~1.12)most likely are linked to higher degree of detrital contamintants.While the sulfide-caronate facies BIF is main but variable in Fe_2O_3+Fe O(15.79~57.91 wt.%),SiO 2(0.54~61.52 wt.%),MgO(0.12~16.09wt.%),CaO(0.17~23.41 wt.%)and LOI(8.28-30.06 wt.%).The generally low contents in trace elements(including REE)except for an obvious enrichment in Pb,and the positive Ce anomalies(δCePAAS=1.04~1.95)and negative Pr anomalies(δPrPAAS=0.67~0.93),as well as the variable ratios ofδEuPAAS(0.72~1.71),La/YbPAAS(0.26~1.60)and Y/Ho(26~57)suggest that the precursors to the sulfide-carbonate facies BIF mainly are metalliferious sediments from deep-marine hydrotheral source with minor detrital components.The T2DM ages(ca.2.0 Ga)imply that the Shilu BIFs and interbedded host rocks contain a component with Paleoproterozoic crustal residence age due to a significant crustal accretion event at ca.2.0 Ga in Hainan Island.In connection with the petrographical and mineralogical relationship,we conclude that the precursor precipitates to the Shilu BIFs are variable degree of admixtures of the Fe-Co-Cu-(Si)-rich hydrothermal fluids and detrital components from seawater and fresh water carring continental landmass;whereas the protolith to the main interbedded host rocks,i.e.the pyroxene-amphibole rocks,most likely was terrigenous,fine-grained clastic-sediments but with significant input of hydrothermal fluids in a seawater environment.As a result,a continent marginal marine basin is proposed for deposition of the Shilu BIFs and interbedded host rocks.Sea-level fluctuations caused by marine transgression–regressions possibly contributed to changes in the composition and varied input of the terrigenous sediments.
