江西赣中铁矿“红绸带”式铁矿体形态成因及其找矿预测
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摘要
江西赣中新余铁矿是我国重要的铁矿类型之一,产于震旦纪火山-沉积浅变质岩系硅铁建造中。铁矿体普遍呈现"红绸带"式形态,前人认为是多期次褶皱叠加的结果。本文通过野外调查,在整个铁矿区发现,区域透入性的拉伸线理、A型褶曲十分发育,局部地段甚至出现鞘褶皱;系统测量表明,区域拉伸线理、A型褶皱的脊线走向稳定在295°~320°之间,倾角一般小于25°。推测赣中铁矿经历了强烈的塑性流变,"红绸带"式铁矿体是塑性流变,而非多期褶皱叠加变形的结果;整个铁矿区的原始形态应是一个鼻端向南封闭的巨形鞘褶皱,但变形期后不均匀的构造抬升和剥蚀,导致了不同铁矿区现今地表出露了原始形态的不同部位。结合褶皱构造对铁成矿物质的控制作用和矿区的地层出露状态分析,认为大陂-陂头、寨口-太平山-良山一带皆处于鞘褶皱的前缘部位,具有寻找富大厚矿体的找矿前景,松山-杨家桥处于鞘褶皱的西翼,平剖面上都发育小型鞘褶皱和红绸带式重叠矿体,因而也具有良好的找矿前景。
The Xinyu iron deposit, located in central Jiangxi province, is one of the most important BIFs-type deposits in China. It is hosted in the Late Proterozoic volcanic-sedimentary rocks. Ore-bearing layers, especially quartz veins or bands in hosting rocks in most mining areas, are strongly deformed, showing complex Z-, S-type folds, and folded lens. As a result, the "red-ribbon" style folded iron-bodies are common. Multi-phases of deformation and folding were proposed to interpret the origin of the "red-ribbon" style ore-bodies, which suggests that they were produced by fold superimposition. Our field investigation revealed that regional penetrative mineral stretching lineation and A-type folds were well developed throughout the entire Xinyu iron deposit. Sheath folds were identified abundantly in the Yangjiaqiao, Pitou mining areas in the southern part of the Xinyu deposits. Systematic measurements indicated that the mineral stretching lineation and hinge lines of A-type fold varied from NW295° to NW320°, with plunging angles of less than 25°. The quartz-feldspar pebble, the so-called pseudo-pebble in metamorphic pebble-bearing siltstones was strongly elongated in the lineation direction. Thus, it is suggested that the Xinyu iron-ore deposits have experienced strongly regional plastic deformation subsequent to the sedimentation and metamorphism of BIFs. The ductile fabrics such as regional mineral stretching lineation, A-type folds and sheath folds, as well as the "red-ribbon" style of folded iron-ore-bodies, are regarded as the products of plastic deformation. It was also suggested that the original form of the Xinyu iron-ore deposit area could be a giant sheath fold, generated from differential southward viscous flow. Regional non-uniform tectonic uplifting and erosion after the plastic deformation resulted in varied preservation of the regional sheath fold, exhibiting various structure patterns in different mining areas at the surface. The Dapi-Pitou and Zhaikou-Taipingshan-Liangshan areas, both located in the front of the regional giant sheath fold, are favorable locus for ore-forming material(iron) to be settled through differential flow, forming large, thick, and high-grade ore bodies. And thus, they are the most favorable areas for ore prospecting. The Songshan-Yangjiaqiao mining area, which is located in the west limb of the large sheath fold with abundant ptygmatic folds and small sheath folds, is also a favorable ore prospecting area.
The Xinyu iron deposit, located in central Jiangxi province, is one of the most important BIFs-type deposits in China. It is hosted in the Late Proterozoic volcanic-sedimentary rocks. Ore-bearing layers, especially quartz veins or bands in hosting rocks in most mining areas, are strongly deformed, showing complex Z-, S-type folds, and folded lens. As a result, the "red-ribbon" style folded iron-bodies are common. Multi-phases of deformation and folding were proposed to interpret the origin of the "red-ribbon" style ore-bodies, which suggests that they were produced by fold superimposition. Our field investigation revealed that regional penetrative mineral stretching lineation and A-type folds were well developed throughout the entire Xinyu iron deposit. Sheath folds were identified abundantly in the Yangjiaqiao, Pitou mining areas in the southern part of the Xinyu deposits. Systematic measurements indicated that the mineral stretching lineation and hinge lines of A-type fold varied from NW295° to NW320°, with plunging angles of less than 25°. The quartz-feldspar pebble, the so-called pseudo-pebble in metamorphic pebble-bearing siltstones was strongly elongated in the lineation direction. Thus, it is suggested that the Xinyu iron-ore deposits have experienced strongly regional plastic deformation subsequent to the sedimentation and metamorphism of BIFs. The ductile fabrics such as regional mineral stretching lineation, A-type folds and sheath folds, as well as the "red-ribbon" style of folded iron-ore-bodies, are regarded as the products of plastic deformation. It was also suggested that the original form of the Xinyu iron-ore deposit area could be a giant sheath fold, generated from differential southward viscous flow. Regional non-uniform tectonic uplifting and erosion after the plastic deformation resulted in varied preservation of the regional sheath fold, exhibiting various structure patterns in different mining areas at the surface. The Dapi-Pitou and Zhaikou-Taipingshan-Liangshan areas, both located in the front of the regional giant sheath fold, are favorable locus for ore-forming material(iron) to be settled through differential flow, forming large, thick, and high-grade ore bodies. And thus, they are the most favorable areas for ore prospecting. The Songshan-Yangjiaqiao mining area, which is located in the west limb of the large sheath fold with abundant ptygmatic folds and small sheath folds, is also a favorable ore prospecting area.
引文
戴元裕.1986.江西省新余太平山铁矿区叠加褶皱构造解析并论恢复复杂褶皱系的包络面的意义.地质找矿论丛,1(2):13-21.
戴元裕.1989.变质岩层构造形变的野外调查与研究.地质与勘探,25(11):31-37.
胡立,曾超,周敏娟,张昊.2013.赣中铁矿田“新余式”铁矿成矿模式探讨.现代矿业,(3):70-72.
吉磊.1995.江西武功山东区大型韧性剪切带的显微构造特征.地质科学,30(1):95-103.
江西地质矿产局.1964.1∶20万地质调查报告(宜春幅).北京:地质出版社:8-12.
江西地质矿产局.1984.江西省区域地质志.北京:地质出版社:766-767.
林伟,王军,刘飞,冀文斌,褚杨,王清晨.2013.华北克拉通及邻区晚中生代伸展构造及其动力学背景的讨论.岩石学报,29(5):1791-1810.
刘珺,毛景文,叶会寿,谢桂青,杨国强,章伟.2008.江西省武功山地区浒坑花岗岩的锆石U-Pb定年及元素地球化学特征.岩石学报,24(8):1813-1822.
刘细元,衷存堤.2003.关于赣西武功山地区构造问题的讨论.华东地质学院学报,26(3):249-253.
楼法生,沈渭洲,王德滋,舒良树,吴富江,张芳荣,于津海.2005.江西武功山弯隆复式花岗岩的锆石U-Pb年代学研究.地质学报,79(5):636-644.
舒良树,孙岩,王德滋,Faure M,Charvet J,Monie P.1998.华南武功山中生代伸展构造.中国科学(D辑),28:431-438.
宋志瑞.1996.江西省震旦系大沙江组、朝阳组和外观组的建立.江西地质科技,23(2):71-75.
孙岩,舒良树,Faure M,Charvet J.1994.赣北武功山花岗岩穹窿伸展构造--中法合作考察研究新进展.南京大学学报(自然科学版),30(4):633-637.
汤加富.1983.褶皱包络面的研究与运用.中国区域地质,7:97-104.
汤加富.1985.武功山区变质岩层形变特征与构造演化.华东地质学院学报,(2):1-9.
汤加富,符鹤琴,余志庆.1987.华南晚前寒武纪硅铁建造的层位、类型与形成条件.矿床地质,(1):1-10.
汤加富,王希明,刘芳宇,唐春花.1991.武功山变质岩区构造变形与地质填图.北京:中国地质大学出版社:1-122.
王晓颖,周建廷,李婷.2013.江西新余式铁矿田变质作用基本特征.资源调查与环境,(3):159-164.
肖光荣,姚琪.2013.江西省新余式铁矿中深部铁矿勘查探讨.地学前缘,20(4):1-7.
谢自谷,梅才湘,王建国,付清东.1986.关于赣中新余式铁矿多层次(位)的讨论.矿床地质,(1):88-95.
许温复,王仁根.1983.赣中新余式变质铁矿勘查过程中的小构造研究.江西地质科技,58:18-29.
姚琪,胡立,徐力千.2012.江西省新余铁矿田区域成矿控矿地质条件与找矿思路.四川有色金属,(4):16-25.
余志庆,汤家富,符鹤琴.1989.“新余式”铁矿地质特征及其成因.矿床地质,8(4):1-10.
曾书明,周建廷,王学平,刘川.2010.新余铁矿田铁矿成矿地质特征与成因分析.东华理工大学学报(自然科学版),33(3):231-240.
曾书明,周建廷,王学平,刘川,董国臣.2011.江西新余铁矿田铁矿成矿地质特征与成因分析.地质与勘探,47(2):187-196.
周建廷,王学平,刘川.2007.新余铁矿田中的地质系统律和地质全息律.东华理工大学学报,30(3):211-216.
周永贵,陈正乐,陈柏林,韩凤彬.2012.河北迁安杏山富大铁矿体成因初析.吉林大学学报(地球科学版),42(S3):81-93.
BerthéD and Brun J P.1980.Evolution of folds during progressive shear in the South Armorican Shear Zone,France.Journal of Structural Geology,2:127-133.
Carreras J,Druguet E and Griera A.2005.Shear zone-related folds.Journal of Structural Geology,27:1229-1251.
Cobbold P R and Quinquis H.1980.Development of sheath folds in shear regimes.Journal of Structural Geology,2:119-126.
Faure M,Sun Y,Shu L S and Charvet J.1996.Extensional tectonics within a subduction-type orogen:The case study of the Wugongshan dome(Jiangxi Province,Southeastern China).Tectonophysics,263:77-106.
Hudleston P J.1989.The association of folds and veins in shear zones.Journal of Structural Geology,11:949-957.
Hudleston P J and Lan L.1993.Information from fold shapes.Journal of Structural Geology,15:253-264.
Mueller K and Talling P.1997.Geomorphic evidence for tear faults accommodating lateral propagation of an active fault-bend fold,Wheeler Ridge,California.Journal of Structural Geology,19:397-411.
Ramsay D M.1979.Analysis of rotation of folds during progressive deformation.Geological Society of America Bulletin,90:732-738.
Rich J L.1934.Mechanics of low-angle overthrust faulting as illustrated by Cumberland thrust block,Virginia,Kentucky and Tennessee.AAPG Bulletin,18:1584-1596.
Shu L S and Charvet J.1996.Kinematics and geochronology of the Proterozoic Dongxiang-Shexian ductile shear zone:With HP metamorphism and ophiolitic mélange(Jiangnan Region,South China).Tectonophysics,267:291-302.
戴元裕.1989.变质岩层构造形变的野外调查与研究.地质与勘探,25(11):31-37.
胡立,曾超,周敏娟,张昊.2013.赣中铁矿田“新余式”铁矿成矿模式探讨.现代矿业,(3):70-72.
吉磊.1995.江西武功山东区大型韧性剪切带的显微构造特征.地质科学,30(1):95-103.
江西地质矿产局.1964.1∶20万地质调查报告(宜春幅).北京:地质出版社:8-12.
江西地质矿产局.1984.江西省区域地质志.北京:地质出版社:766-767.
林伟,王军,刘飞,冀文斌,褚杨,王清晨.2013.华北克拉通及邻区晚中生代伸展构造及其动力学背景的讨论.岩石学报,29(5):1791-1810.
刘珺,毛景文,叶会寿,谢桂青,杨国强,章伟.2008.江西省武功山地区浒坑花岗岩的锆石U-Pb定年及元素地球化学特征.岩石学报,24(8):1813-1822.
刘细元,衷存堤.2003.关于赣西武功山地区构造问题的讨论.华东地质学院学报,26(3):249-253.
楼法生,沈渭洲,王德滋,舒良树,吴富江,张芳荣,于津海.2005.江西武功山弯隆复式花岗岩的锆石U-Pb年代学研究.地质学报,79(5):636-644.
舒良树,孙岩,王德滋,Faure M,Charvet J,Monie P.1998.华南武功山中生代伸展构造.中国科学(D辑),28:431-438.
宋志瑞.1996.江西省震旦系大沙江组、朝阳组和外观组的建立.江西地质科技,23(2):71-75.
孙岩,舒良树,Faure M,Charvet J.1994.赣北武功山花岗岩穹窿伸展构造--中法合作考察研究新进展.南京大学学报(自然科学版),30(4):633-637.
汤加富.1983.褶皱包络面的研究与运用.中国区域地质,7:97-104.
汤加富.1985.武功山区变质岩层形变特征与构造演化.华东地质学院学报,(2):1-9.
汤加富,符鹤琴,余志庆.1987.华南晚前寒武纪硅铁建造的层位、类型与形成条件.矿床地质,(1):1-10.
汤加富,王希明,刘芳宇,唐春花.1991.武功山变质岩区构造变形与地质填图.北京:中国地质大学出版社:1-122.
王晓颖,周建廷,李婷.2013.江西新余式铁矿田变质作用基本特征.资源调查与环境,(3):159-164.
肖光荣,姚琪.2013.江西省新余式铁矿中深部铁矿勘查探讨.地学前缘,20(4):1-7.
谢自谷,梅才湘,王建国,付清东.1986.关于赣中新余式铁矿多层次(位)的讨论.矿床地质,(1):88-95.
许温复,王仁根.1983.赣中新余式变质铁矿勘查过程中的小构造研究.江西地质科技,58:18-29.
姚琪,胡立,徐力千.2012.江西省新余铁矿田区域成矿控矿地质条件与找矿思路.四川有色金属,(4):16-25.
余志庆,汤家富,符鹤琴.1989.“新余式”铁矿地质特征及其成因.矿床地质,8(4):1-10.
曾书明,周建廷,王学平,刘川.2010.新余铁矿田铁矿成矿地质特征与成因分析.东华理工大学学报(自然科学版),33(3):231-240.
曾书明,周建廷,王学平,刘川,董国臣.2011.江西新余铁矿田铁矿成矿地质特征与成因分析.地质与勘探,47(2):187-196.
周建廷,王学平,刘川.2007.新余铁矿田中的地质系统律和地质全息律.东华理工大学学报,30(3):211-216.
周永贵,陈正乐,陈柏林,韩凤彬.2012.河北迁安杏山富大铁矿体成因初析.吉林大学学报(地球科学版),42(S3):81-93.
BerthéD and Brun J P.1980.Evolution of folds during progressive shear in the South Armorican Shear Zone,France.Journal of Structural Geology,2:127-133.
Carreras J,Druguet E and Griera A.2005.Shear zone-related folds.Journal of Structural Geology,27:1229-1251.
Cobbold P R and Quinquis H.1980.Development of sheath folds in shear regimes.Journal of Structural Geology,2:119-126.
Faure M,Sun Y,Shu L S and Charvet J.1996.Extensional tectonics within a subduction-type orogen:The case study of the Wugongshan dome(Jiangxi Province,Southeastern China).Tectonophysics,263:77-106.
Hudleston P J.1989.The association of folds and veins in shear zones.Journal of Structural Geology,11:949-957.
Hudleston P J and Lan L.1993.Information from fold shapes.Journal of Structural Geology,15:253-264.
Mueller K and Talling P.1997.Geomorphic evidence for tear faults accommodating lateral propagation of an active fault-bend fold,Wheeler Ridge,California.Journal of Structural Geology,19:397-411.
Ramsay D M.1979.Analysis of rotation of folds during progressive deformation.Geological Society of America Bulletin,90:732-738.
Rich J L.1934.Mechanics of low-angle overthrust faulting as illustrated by Cumberland thrust block,Virginia,Kentucky and Tennessee.AAPG Bulletin,18:1584-1596.
Shu L S and Charvet J.1996.Kinematics and geochronology of the Proterozoic Dongxiang-Shexian ductile shear zone:With HP metamorphism and ophiolitic mélange(Jiangnan Region,South China).Tectonophysics,267:291-302.