弓长岭铁矿二矿区蚀变岩中锆石SHRIMP U-Pb年龄及地质意义
SHRIMP U-Pb geochronology of zircons from the garnet-rich altered rocks in the mining area Ⅱ of the Gongchangling iron deposit：Constraints on the ages of the high-grade iron deposit
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摘要: 国外的富铁矿（TFe含量超过50%）主要来自长期稳定的古老克拉通上早前寒武纪铁建造（BIF）经过后期风化淋滤作用形成的赤铁矿石。虽然我国的华北克拉通等古老地块也发育早前寒武纪BIF，并经历了强烈的变质变形改造，但是由于地块活动性强导致缺乏充分风化淋滤作用的条件，因而赤铁富矿很少，铁矿石以TFe含量30%左右的沉积变质型磁铁贫矿为主。辽宁弓长岭铁矿床位于华北克拉通东北部，是一个大型沉积变质型铁矿床，总体以磁铁矿贫矿石为主，但其二矿区的磁铁富矿（TFe含量大于50%）达大型规模，是我国唯一的大型沉积变质型磁铁富矿。弓长岭二矿区富铁矿是条带状铁建造沉积后受后期叠加改造作用形成的，富矿体成矿时发生了强烈的围岩蚀变，形成以石榴石和镁铁闪石为特征矿物的蚀变岩，这种富含石榴石的蚀变岩在区域上乃至全国的沉积变质型磁铁矿矿床中都是独一无二的，表明其与磁铁矿富矿有密切的成因联系。该蚀变岩中与镁铁闪石、绿泥石、石英、钛铁矿共生有热液锆石。本文从该蚀变岩中分选出了锆石，锆石呈他形至半自形粒状，在阴极发光（CL）图像上呈多孔状、斑块状、补丁状，明暗极不均匀，可见不明显的环带；锆石内包体在背散射图像上呈暗色，长条状或片状自形晶，主要由MgO、FeO、SiO2、Al2O3组成，为绿泥石、铝直闪石和镁铁闪石；锆石LA-ICP-MS原位微量元素分析表明，Hf含量为10672×10-6~11822×10-6，Y为12.58×10-6~19.41×10-6，Th为0.32×10-6~1.48×10-6，U为425×10-6~663×10-6，Th/U为0.001~0.003，Ti为1.63×10-6~3.7×10-6，∑REE为10.37×10-6~20.15×10-6，球粒陨石标准化的稀土配分曲线上轻稀土强烈亏损，中、重稀土富集，重稀土较平坦，有弱的铕正异常，这些特点表明该锆石为与蚀变岩和富铁矿同时形成的热液成因锆石。利用SHRIMP U-Pb定年方法对该热液锆石进行了年龄测定，获得的上交点年龄为1850±16Ma，MSWD=2.1；10个测点加权平均年龄为1840±7Ma，MSWD=1.6。该年龄代表了富含石榴石的蚀变岩的成岩年龄，因而也可能代表了富铁矿石的形成年龄，因此推测磁铁富铁矿的形成是条带状磁铁石英岩在1.9~1.8Ga时华北克拉通基底隆升与裂谷-非造山岩浆事件所产生的热液交代作用的结果。Abstract: Global occurrence of BIF-related iron resources are typically represented by high-grade hematite ores (TFe>50%) formed by supergene leaching. Most of the BIF-related iron deposits in China are low-grade iron ores with TFe grade approximately of 30%. The BIFs in China have experienced intense metamorphism and deformation, which led to the majority of iron oxides transforming into coarse-grained magnetites. Though their ores generally contain only 30% TFe, the BIFs are favorable for industrial exploitation by using magnetic beneficiation. The mining area II of the Gongchangling high-grade iron deposit, the largest high-grade magnetite deposit in China, is referred to a kind of sedimentary metamorphosed deposit. The high-grade iron ores were formed by the superimposition and reformation of banded iron formation (BIF). During the process of the high-grade iron mineralization, the country rocks of the ore bodies were intensely altered into garnet-rich rocks. In BSE images, zircons are observed to be in close association with quartz, ilmenite, cummingtonite and chlorite. The mineral assemblage is distributed along fractures in garnet, indicating that the zircons were formed during the process of retrograde alteration of garnet. Zircons separated from the garnet-rich altered rocks are hypautomorphic-allotriomorphic granular, and display different bright and dark patches in the cathodoluminescence (CL) images and back-scattered electron images and vaguely oscillatory zones in CL images. The inclusions inside the zircons display dark color; long strip and flake shaped euhedral crystal, and are determined as chlorite, gedrite and cummingtonite. In-situ trace element analyses of the zircons by LA-ICP-MS gives Hf from 10672×10-6 to 11822×10-6, Y from 12.58×10-6 to 19.41×10-6, Ti from 1.63×10-6 to 9.48×10-6, Th from 0.32×10-6 to 1.48×10-6,U from 365×10-6 to 663×10-6, Th/U from 0.001 to 0.003, ∑REE from 7.18×10-6 to 20.45×10-6. Chondrite-normalized REE patterns are MREE and HREE rich and show flat HREE curves and slightly positive Eu anomaly. All of the above suggest that the zircons from the garnet-rich altered rocks are of hydrothermal origin and formed at the same time as the high-grade iron ore and altered rocks. SHRIMP U-Pb dating of the zircons yield an upper intercept age of 1850±16Ma (MSWD=2.1) and a weighted mean age of 1840±7Ma (MSWD=1.6). This age represents the metallogenetic age of the high-grade iron deposit, and matches with the uplift of the early metamorphic basement and rift-anorogenic magmatism in North China Craton at ~1.8Ga. This high-grade magnetite deposit is transformed from BIF by the tectonic thermal event at 1.9~1.8Ga.
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[1] Chen HJ and Xu GR. 1984. Characteristics of genetic mineralogy of magnetite in the II mining area of the Gongchangling iron deposit and its signification. Jilin Geology, (1): 22-30 (in Chinese with English abstract)
[2] Chen JF, Yang YL, Li P, Cheng WJ, Zhou TX and Liu YP. 1985. Sulfur isotopic study of the high-grade iron deposits in the Anshan-Benxi area in Liaoning Province, China. Geology and Prospecting, 21(1): 32-37 (in Chinese)
[3] Cheng YQ. 1957. Problems on the genesis of the high-grade ore in the Pre-Sinian (Pre-Cambrian) banded iron ore deposits of the Anshan-type of Liaoning and Shantung provinces. Acta Geologica Sinica, 37(2): 153-180 (in Chinese with English abstract)
[4] Cheng YQ and Zhang SG. 1982. Notes on the metamorphic series and metamorphic belts of various metamorphic epochs of China and related problems. Regional Geology of China, (2): 1-14 (in Chinese with English abstract)
[5] Compston W, Williams SI, Kirschvink JL, Zhang Z and Ma G. 1992. Zircon U-Pb ages for the Early Cambrian time scale. Journal of the Geological Society, London, 149(2): 171-184
[6] Cong F, Lin SL, Zou GF et al. 2011. Magma mixing of granites at Lianghe: In-situ zircon analysis for trace elements, U-Pb ages and Hf isotopes. Scientia Sinica (Terrae), 41(4): 468-481 (in Chinese)
[7] Duan C, Li YH, Mao JW, Hou KJ and Yuan SD. 2012. Zircon trace element characteristics of intrusions in the Washan iron deposit of Ningwu volcanic basin and their geological significance. Geology in China, 39(6): 1874-1884 (in Chinese with English abstract)
[8] Hou ZH, Li SG, Chen NS, Li QL and Li XM. 2005. Sm-Nd and zircon SHRIMP U-Pb dating of Huilanshan mafic granulite in the Dabie Mountains and its zircon trace element geochemistry. Science in China (Series D), 48(12): 2081-2091
[9] Li BL, Li XM, Cui XF, Wang ZL and Liu YM. 1977. Genesis and prospecting criteria of the high-grade ores in the mining II of the Gongchangling iron deposit: Evidence from fluid inclusion study. Geology and Prospecting, 13(6): 3-11 (in Chinese)
[10] Li CM. 2009. A review on the minerageny and situ microanalytical dating techniques of zircons. Geological Survey and Research, 32(3): 161-174 (in Chinese with English abstract)
[11] Li GL, Hua RM, Hu DQ, Huang XE, Zhang WL and Wang XD. 2010. Petrogenesis of Shilei quartz diorite in southern Jiangxi: Constraints from petrochemistry, trace elements of accessory minerals, zircon U-Pb dating, and Sr-Nd-Hf isotopes. Acta Petrologica Sinica, 26(3): 903-918 (in Chinese with English abstract)
[12] Li HM, Liu MJ, Li LX, Yang XQ, Chen J, Yao LD, Hong XK and Yao T. 2012. Geology and geochemistry of the marble in the Gongchangling iron deposit in Liaoning Province and their metallogenic significance. Acta Petrologica Sinica, 28(11): 3497-3512 (in Chinese with English abstract)
[13] Li HM, Zhang ZJ, Li LX, Zhang ZC, Chen J and Yao T. 2014a. Types and general characteristics of the BIF-related iron deposits in China. Ore Geology Reviews, 57: 264-287
[14] Li P, Xu XY, Wang HL, Zhu T and Wan XM. 2012. Petrogenesis of Nalati alkali granites in South Central Tianshan Mountains: Evidence from zircon trace elements and Hf isotope. Geological Bulletin of China, 31(12): 1949-1964 (in Chinese with English abstract)
[15] Li QL, Li SG, Hou ZH, Hong JA and Yang W. 2005. A combined study of SHRIMP U-Pb dating, trace element and mineral inclusions on high-pressure metamorphic overgrowth zircon in eclogite from Qinglongshan in the Sulu terrane. Chinese Science Bulletin, 50(5): 459-465
[16] Li SB. 1979. A contribution to the genesis of rich magnetite deposit of the Gongchangling type: In the light of graphite discovered in it. Geochimica, (2): 170-177 (in Chinese with English abstract)
[17] Li SG. 1982. Geochemical model for the genesis of Gongchangling rich magnetite deposit in China. Geochimica, (2): 113-121 (in Chinese with English abstract)
[18] Li SG, Zhi XC, Chen JF, Wang JX and Deng YY. 1983. Origin of graphites in Early Precambrian banded iron formation in Anshan, China. Geochimica, (2): 162-169 (in Chinese with English abstract)
[19] Li YH, Hou KJ, Wan DF, Zhang ZJ and Yue GL. 2014b. Precambrian banded iron formations in the North China Craton: Silicon and oxygen isotopes and genetic implications. Ore Geology Reviews, 57: 299-307
[20] Liu J and Jin SY. 2010. Genesis study of magnetite-rich ore in Gongchangling iron deposit, Liaoning. Geoscience, 24(1): 80-88 (in Chinese with English abstract)
[21] Liu MJ, Li HM, Li LX, Yang XQ, Yao LD, Hong XK and Cheng J. 2012. Petrological and mineralogical characteristics of the skarnoid in No.2 mining area of the Gongchangling iron deposit, Liaoning, China. Rock and Mineral Analysis, 31(6): 1067-1076 (in Chinese with English abstract)
[22] Lu XP, Wu FY, Lin JQ, Sun DY, Zhang YB and Guo CL. 2004. Geochronological successions of the Early Precambrian granitic magmatism in southern Liaodong Peninsula and its constaints on tectonic evolution of the North China Craton. Chinese Journal of Geology, 39(1): 123-138 (in Chinese with English abstract)
[23] Qian Y, Sun FY, Li BL, Huo L and Zhang YJ. 2013. Trace element geochemical and U-Pb geochronology of metamorphic recrystallization zircon: Taking gneiss from Hongtoushan copper-zinc deposit as an example. Journal of Central South University (Science and Technology), 44(4): 1500-1509 (in Chinese with English abstract)
[24] Shen QH. 1992. Early Precambrian granulites of China. Advances in Earth Science, 7(1): 95-96 (in Chinese)
[25] Shi JX and Li BC. 1980. Origin of rich magnetite ores in the Gongchangling area as evidenced by fluid inclusion studies from the Anshan-Benxi region, Northeast China. Geochimica, (1): 43-53 (in Chinese with English abstract)
[26] Song B, Zhao DM and Wan YS. 1992. Geochronology research of the iron formation of Gongchangling, Liaoning Province. Acta Petrologica et Mineralogica, 11(4): 317-323 (in Chinese with English abstract)
[27] Song B, Zhang YH and Liu DY. 2002. Introduction to the naissance of SHRIMP and its contribution to isotope geology. Journal of Chinese Mass Spectrometry Society, 23(1): 58-62 (in Chinese with English abstract)
[28] Sun XH, Zhu XQ, Tang HS, Zhang Q and Luo TY. 2014. The Gongchangling BIFs from the Anshan-Benxi area, NE China: Petrological-geochemical characteristics and genesis of high-grade iron ores. Ore Geology Reviews, 60: 112-125
[29] Tang Y, Zhang H and Lü ZH. 2012. Characteristics of zircon cathodoluminescence and trace elements of granite and pegmatite from Altai Mountains, Northwest China. Journal of Mineralogy and Petrology, 32(1): 8-15 (in Chinese with English abstract)
[30] Wan YS and Liu DY. 1993. Ages of zircons from mid-archaean gnessic granite and fuchsite quartzite in the Gongchangling area, Liaoning. Geological Review, 39(2): 124-129 (in Chinese with English abstract)
[31] Wang ED, Xia JM, Zhao CF, Fu JF and Hou GQ. 2012. Forming mechanism of high-grade magnetite bodies in Gongchangling, Liaoning Province. Acta Geologica Sinica, 86(11): 1761-1772 (in Chinese with English abstract)
[32] Wang ED, Xia JM, Fu JF, Jia SS and Men YK. 2014. Formation mechanism of Gongchangling high-grade magnetite deposit hosted in Archean BIF, Anshan-Benxi area, northeastern China. Ore Geology Reviews, 57: 308-321
[33] Wang SL. 1986. The genetic types of rich iron deposits of Anshan Group in Anshan-Benxi area. Mineral Deposits, 5(4): 14-23 (in Chinese with English abstract)
[34] Williams IS. 1998. U-Th-Pb Geochronology by iron microprobe. In: McKibben MA, Shanks III WC and Ridley WI (eds.). Applications of Microanalytical Techniques to Understanding Mineraling Processes. Reviews in Economic Geology, 7: 1-35
[35] Wu YB, Chen DG, Xia QK, Tu XL and Cheng H. 2002. In-situ trace element analyses of zircons from Dabieshan Huangzhen eclogite: Trace element characteristics of eclogite-facies metamorphic zircon. Chinese Science Bulletin, 47(16): 1398-1401
[36] Wu YB, Chen DG, Xia QK and Tu XL. 2004a. Trace element analysis of zircon and associated minerals in the Huangtuling granulite, Dabieshan and its geological implication. Geochimica, 33(4): 334-342 (in Chinese with English abstract)
[37] Wu YB. Chen DG, Zheng YF, Xia QK and Tu XL. 2004b. Trace element geochemistry of zircons in migmatitic gneiss at Manshuihe, North Dahieshan and its geological implications. Acta Petrologica Sinica, 20(5): 1141-1150 (in Chinese with English abstract)
[38] Xia JM, Wang ED, Zhao CF and Men YK. 2011. The formation mechanism of the redox environment in the rich iron deposits of Gongchangling. Journal of Northeastern University (Natural Science), 32(11): 1643-1646 (in Chinese with English abstract)
[39] Yang XQ, Li HM, Li LX, Liu MJ, Chen J and Bai Y. 2012. Characteristics of rare earth elements and the geological significance of magnetite from Gongchangling iron deposit in Liaoning Province. Rock and Mineral Analysis, 31(6): 1058-1066 (in Chinese with English abstract)
[40] Zhai MG. 2008. Lower crust and lithospheric mantle beneath the North China Craton before the Mesozoic lithospheric disruption. Acta Petrologica Sinica, 24(10): 2185-2204 (in Chinese with English abstract)
[41] Zhai MG. 2010. Tectonic evolution and metallogenesis of North China Craton. Mineral Deposits, 29(1): 32-46 (in Chinese with English abstract)
[42] Zhang XW, Xiang H, Zhong ZQ, Zhou HW, Zhang L, Yang N and Wang J. 2009. U-Pb dating and trace elements composition of hyydrothermal zircons from Jianfengling granite, Hainan: Restriction on the age of hydrothermal event and mineralization of Baolun gold deposit. Earth Science, 34(6): 921-930 (in Chinese with English abstract)
[43] Zhang ZC, Hou T, Santosh M, Li HM, Li JW, Zhang ZH, Song XY and Wang M. 2014. Spatio-temporal distribution and tectonic settings of the major iron deposits in China: An overview. Ore Geology Reviews, 57: 247-263
[44] Zhao B and Li TJ. 1980. A preliminary study on the mechanism and physico-chemical conditions of formation of Gongchangling rich iron deposit. Geochimica, (4): 333-344 (in Chinese with English abstract)
[45] Zheng JP, Lu FX, Yu CM and Tang HY. 2004. An in situ zircon Hf isotopic, U-Pb age and trace element study of banded granulite xenolith from Hannuoba basalt: Tracking the early evolution of the lower crust in the North China craton. Chinese Science Bulletin, 49(3): 277-285
[46] Zhou ST. 1994. Geology of Banded Iron Deposits in Anshan-Benxi Area. Beijing: Geological Publishing House, 1-276 (in Chinese)
[47] 陈洪江, 徐光荣. 1984. 弓长岭铁矿二矿区磁铁矿的成因矿物学特征及其意义. 吉林地质, (1): 22-30
[48] 陈江峰, 杨延龄, 李平, 程伟基, 周泰禧, 刘燕平. 1985. 辽宁鞍山-本溪地区富磁铁矿床硫同位素地质研究. 地质与勘探, 21(1): 32-37
[49] 程裕淇. 1957. 中国东北部辽宁山东等省前震旦纪鞍山式条带状铁矿中富矿的成因问题. 地质学报, 37(2): 153-180
[50] 程裕淇, 张寿广. 1982. 略论我国不同变质时期的变质岩系、变质带和若干有关问题. 中国区域地质, (2): 1-14
[51] 丛峰, 林仕良, 邹光富等. 2011. 梁河花岗岩岩浆混合作用: 锆石微量元素、U-Pb和Hf同位素示踪. 中国科学(地球科学), 41(4): 468-481
[52] 段超, 李延河, 毛景文, 侯可军, 袁顺达. 2012. 宁芜火山岩盆地凹山铁矿床侵入岩锆石微量元素特征及其地质意义. 中国地质, 39(6): 1874-1884
[53] 李秉伦, 李学明, 崔贤富, 汪芝兰, 刘有梅. 1977. 根据矿物包体研究试论弓长岭二矿区磁铁富矿的成因及找矿标志. 地质与勘探, 13(6): 3-11
[54] 李长民. 2009. 锆石成因矿物学与锆石微区定年综述. 地质调查与研究, 32(3): 161-174
[55] 李光来, 华仁民, 胡东泉, 黄小娥, 张文兰, 王旭东. 2010. 赣南地区石雷石英闪长岩的成因:岩石化学、副矿物微量元素、锆石U-Pb年代学与Sr-Nd-Hf同位素制约. 岩石学报, 26(3): 903-918
[56] 李厚民, 刘明军, 李立兴, 杨秀清, 陈靖, 姚良德, 洪学宽, 姚通. 2012. 辽宁弓长岭铁矿区大理岩地质地球化学特征及其成矿意义. 岩石学报, 28(11): 3497-3512
[57] 李平, 徐学义, 王洪亮, 朱涛, 万晓明. 2012. 中天山南缘那拉提碱性花岗岩岩石成因——来自锆石微量元素和Hf同位素的证据. 地质通报, 31(12): 1949-1964
[58] 李绍柄. 1979. 我国铁矿床的一种新类型——弓长岭式含石墨的富磁铁矿矿床及其成因. 地球化学, (2): 170-177
[59] 李曙光. 1982. 弓长岭富磁铁矿床成因的地球化学模型. 地球化学, (2): 113-121
[60] 李曙光, 支霞臣, 陈江峰, 王俊新, 邓衍尧. 1983. 鞍山前寒武纪条带状含铁建造中石墨的成因. 地球化学, (2): 162-169
[61] 刘军, 靳淑韵. 2010. 辽宁弓长岭铁矿磁铁富矿的成因研究. 现代地质, 24(1): 80-88
[62] 刘明军, 李厚民, 李立兴, 杨秀清, 姚良德, 洪学宽, 陈靖. 2012. 辽宁弓长岭铁矿床二矿区类矽卡岩的岩石矿物学特征. 岩矿测试, 31(6): 1067-1076
[63] 路孝平, 吴福元, 林景仟, 孙德有, 张艳斌, 郭春丽. 2004. 辽东半岛南部早前寒武纪花岗质岩浆作用的年代学格架. 地质科学, 39(1): 123-138
[64] 钱烨, 孙丰月, 李碧乐, 霍亮, 张雅静. 2013. 变质重结晶锆石微量元素地球化学与U-Pb年代学: 以辽宁红透山铜锌矿床赋矿片麻岩为例. 中南大学学报(自然科学版), 44(4): 1500-1509
[65] 沈其韩. 1992. 中国早前寒武纪麻粒岩. 地球科学进展, 7(1): 95-96
[66] 施继锡, 李本超. 1980. 根据鞍本地区包裹体研究试论弓长岭磁铁富矿的成因. 地球化学, (1): 43-53
[67] 宋彪, 赵敦敏, 万渝生. 1992. 辽宁弓长岭含铁建造年代学研究. 岩石矿物学杂志, 11(4): 317-323
[68] 宋彪, 张玉海, 刘敦一. 2002. 微量原位分析仪器SHRIMP的产生与锆石同位素地质年代学. 质谱学报, 23(1): 58-62
[69] 唐勇, 张辉, 吕正航. 2012. 不同成因锆石阴极发光及微量元素特征:以新疆阿尔泰地区花岗岩和伟晶岩为例. 矿物岩石, 32(1): 8-15
[70] 万渝生, 刘敦一. 1993. 辽宁弓长岭中太古代片麻状花岗岩和铬云母石英岩的锆石年龄. 地质论评, 39(2): 124-129
[71] 王恩德, 夏建明, 赵纯福, 付建飞, 侯根群. 2012. 弓长岭铁矿床磁铁富矿形成机制探讨. 地质学报, 86(11): 1761-1772
[72] 王守伦. 1986. 鞍本地区鞍山群富铁矿成因类型的讨论. 矿床地质, 5(4): 14-23
[73] 吴元保, 陈道公, 夏群科, 涂湘林. 2004a. 大别山黄土岭麻粒岩锆石和共生矿物的微量元素分析及其地质意义. 地球化学, 33(4): 334-342
[74] 吴元保, 陈道公, 郑永飞, 夏群科, 涂湘林. 2004b. 北大别漫水河混合岩化片麻岩中锆石微区微量元素特征及其地质意义. 岩石学报, 20(5): 1141-1150
[75] 夏建明, 王恩德, 赵纯福, 门业凯. 2011. 弓长岭富铁矿氧化还原环境的形成机制. 东北大学学报(自然科学版), 32(11): 1643-1646
[76] 杨秀清, 李厚民, 李立兴, 刘明军, 陈靖, 白云. 2012. 辽宁弓长岭铁矿床磁铁矿稀土元素特征及其地质意义. 岩矿测试, 31(6): 1058-1066
[77] 翟明国. 2008. 华北克拉通中生代破坏前的岩石圈地幔与下地壳. 岩石学报, 24(10): 2185-2204
[78] 翟明国. 2010. 华北克拉通的形成演化与成矿作用. 矿床地质, 29(1): 32-46
[79] 张小文, 向华, 钟增球, 周汉文, 张利, 杨念, 王婧. 2009. 海南尖峰岭岩体热液锆石U-Pb定年及微量元素研究: 对热液作用及抱伦金矿成矿时代的限定. 地球科学, 34(6): 921-930
[80] 赵斌, 李统锦. 1980. 鞍山弓长岭富磁铁矿床的形成机制和物理化学条件研究. 地球化学, (4): 333-344
[81] 周世泰. 1994. 鞍山-本溪地区条带状铁矿地质. 北京: 地质出版社, 1-276
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