内蒙古东珺铅锌银矿床质量平衡计算与围岩蚀变特征
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摘要
为研究内蒙古东珺铅锌银矿床围岩蚀变类型与蚀变分带地球化学特征,将近矿、远矿蚀变围岩与紫红色安山岩进行对比,以Al_2O_3为惰性组分,利用标准化Isocon图解法对围岩蚀变过程中物质组分带入、带出进行质量平衡计算;分析微量元素的迁移机制。研究结果表明:蚀变的空间位置关系自内向外可以划分为3个蚀变带即钾硅化-绢云母化带、绢英岩化带、青磐岩化带,其中与矿床成矿关系最为密切的是绢英岩化带;岩浆热液沿裂隙侵位交代围岩,近矿蚀变围岩中各组分质量变化都非常明显,Mg O,P2O5,TFe2O3,Ca O和Na2O组分都在蚀变时随热液大量迁出,而SiO_2和K2O则在热液对围岩进行交代过程中保留下来;近矿蚀变围岩多发生硅化、钾化、绢云母化、黑云母化蚀变;近矿蚀变围岩中明显减少的组分TFe2O3,Mg O和P2O5在远矿蚀变围岩中都略有增加,Ca O质量分数显著上升,SiO_2质量分数减少;远矿蚀变多发生绿帘石化、绿泥石化、碳酸盐化;近矿蚀变围岩轻重稀土分馏最强,远矿蚀变围岩轻重稀土分馏减弱;近矿蚀变围岩主要富集U和Th等高场强元素,多强烈亏损Ba和Sr等大离子亲石元素,其中La,Ce,Sr,Nd,Zr,Sm和Y元素从近矿围岩中组分流失而在远矿围岩处相对富集,具备火山—次火山热液矿床地球化学与围岩蚀变特征。
To study the types and geochemical characteristics of wallrock alternation in Dongjun Pb-Zn-Ag deposit, Inner Mongolia, altered near-ore or far-ore wallrock and purplish red andesite were compared. Al_2O_3 was used as the inert component, and mass transfer in the process of wallrock alteration was calculated by normalized Isocon diagram method. In addition, migration mechanism of trace elements was analyzed. The results show that there exist three alteration zones from the inside to the outside, i.e., K-silication-sericitization zone, phyllic alteration zone and propylitization zone. The phyllic alternation zone displays the closest relationships with mineralization. The components in the altered near-ore wallrock fluctuate obviously. A great amount of Mg O, P2 O5, TFe2 O3, Ca O and Na2 O move out along with hydrotherm during alternation, while SiO_2 and K2 O are preserved in the process of metasomatism of magmatic hydrothermal along fracture emplacement. Potassic, silicified, sericite and biotite alterations are common in the altered near-ore wallrock. Contents of TFe2 O3, Mg O and P2 O5 increase slightly in altered far-ore wallrock, which all reduce dramatically in altered near-ore wallrock. There is an obvious increase in Ca O mass fraction, but a decrease in SiO_2 mass fraction in far-ore alternation zone in which epidotization, chloritization and carbonatization are easy to be found. Rare earth elements(REE) fractionation of altered near-ore wallrock is the strongest, and REE fractionation of altered far-ore wallrock is weakened. High field strength elements(e.g. U, Th) are enriched in altered near-ore wall rock, while large ion lithophile elements(e.g. Ba, Sr) are depleted. Elements(e.g. La, Ce, Sr, Nd, Zr, Sm, Y) run from near-ore wallrock and relatively enrich in far-ore wallrock, which shows the geochemical and wallrock alternation characteristics of volcanic-subvolcanic hydrothermal deposit.
To study the types and geochemical characteristics of wallrock alternation in Dongjun Pb-Zn-Ag deposit, Inner Mongolia, altered near-ore or far-ore wallrock and purplish red andesite were compared. Al_2O_3 was used as the inert component, and mass transfer in the process of wallrock alteration was calculated by normalized Isocon diagram method. In addition, migration mechanism of trace elements was analyzed. The results show that there exist three alteration zones from the inside to the outside, i.e., K-silication-sericitization zone, phyllic alteration zone and propylitization zone. The phyllic alternation zone displays the closest relationships with mineralization. The components in the altered near-ore wallrock fluctuate obviously. A great amount of Mg O, P2 O5, TFe2 O3, Ca O and Na2 O move out along with hydrotherm during alternation, while SiO_2 and K2 O are preserved in the process of metasomatism of magmatic hydrothermal along fracture emplacement. Potassic, silicified, sericite and biotite alterations are common in the altered near-ore wallrock. Contents of TFe2 O3, Mg O and P2 O5 increase slightly in altered far-ore wallrock, which all reduce dramatically in altered near-ore wallrock. There is an obvious increase in Ca O mass fraction, but a decrease in SiO_2 mass fraction in far-ore alternation zone in which epidotization, chloritization and carbonatization are easy to be found. Rare earth elements(REE) fractionation of altered near-ore wallrock is the strongest, and REE fractionation of altered far-ore wallrock is weakened. High field strength elements(e.g. U, Th) are enriched in altered near-ore wall rock, while large ion lithophile elements(e.g. Ba, Sr) are depleted. Elements(e.g. La, Ce, Sr, Nd, Zr, Sm, Y) run from near-ore wallrock and relatively enrich in far-ore wallrock, which shows the geochemical and wallrock alternation characteristics of volcanic-subvolcanic hydrothermal deposit.
引文
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[14]GRANT J A.The isocon diagram-a simple solution to Gresens’equation for metasomatic alteration[J].Economic Geology,1986,81(8):1976-1982.
[15]郭顺,叶凯,陈意,等.开放地质体系中物质迁移质量平衡计算方法介绍[J].岩石学报,2013,29(5):1486-1498.GUO Shun,YE Kai,CHEN Yi,et al.Introduction of mass-balance calculation method for component transfer during the opening of a geological system[J].Acta Petrologica Sinica,2013,29(5):1486-1498.
[16]GUO Shun,YE Kai,CHEN Yi,et al.Fluid-rock interaction and element mobilization in UHP metabasalt:constraints from an omphacite-epidote vein and host eclogites in the Dabie Orogen[J].Lithos,2013,s136/139(4):145-167.
[17]张婷.湘西合仁坪钠长石-石英脉型金矿床围岩蚀变及其与成矿关系研究[D].湖南:中南大学地球科学与信息物理学院,2014:36-37.ZHANG Ting.Wallrock alteration and its relation with gold mineralization in the Herenping albite-quartz lode gold deposit in western Hunan[D].Hunan:Central South University.School of Earth Science and Information Physics,2014:36-37.
[18]陈随海,韩润生,申屠良义,等.滇东北矿集区昭通铅锌矿区蚀变岩分带及元素迁移特征[J].吉林大学学报(地球科学版),2016,46(3):711-721.CHEN Suihai,HAN Runsheng,SHENTU Liangyi,et al.Alteration zoning and geochemical element migration in alteration rock of Zhaotong lead-zinc deposit in northeastern Yunnan mineralization concentration area[J].Journal of Jilin University(Earth Science Edition),2016,46(3):711-721.
[19]周永章,涂光炽,CHOWN E H,等.热液围岩蚀变过程中数学不变量的寻找及元素迁移的定量估计——以广东河台金矿田为例[J].科学通报,1994,39(11):1026-1028.ZHOU Yongzhang,TU Guangchi,CHOWN E H,et al.The search for mathematical invariants and quantitative estimation of element migration in the process of hydrothermal wall rock alteration:taking Guangdong Hetai gold deposit as an example[J].Chinese Science Bulletin,1994,39(11):1026-1028.
[20]BOYNTON W V.Cosmochemistry of the rare earth elements:meteorite studies.In:P Henderson(ed.),Rare Earth Element Geochemistry[M].Amsterdam,Netherlands:Elsevier,1983:63-114.
[2]龚庆杰,周连壮,胡杨,等.胶东玲珑金矿田煌斑岩蚀变过程元素迁移行为及其意义[J].现代地质,2012,26(5):1065-1077.GONG Qingjie,ZHOU Lianzhuang,HU Yang,et al.Element transfer behaviors and its application during lamprophyre alteration in the Linglong gold deposit,Jiaodong Peninsula,China[J].Geoscience,2012,26(5):1065-1077.
[3]GUO Shun,YE Kai,CHEN Yi,et al.A normalization solution to mass illustration of multiple progressively altered samples using the isocon diagram[J].Economic Geology,2009,104(6):881-886.
[4]张荣庆.内蒙古东珺铅锌银矿综合找矿模型[J].西部探矿工程,2014(6):79-82.ZHANG Rongqing.Integrated ore prospecting model for Donjun Pb-Zn-Ag deposit in Inner Mongolia[J].West-china Exploration Engineering,2014(6):79-82.
[5]佘宏全,李红红,李进文,等.内蒙古大兴安岭中北段铜铅锌金银多金属矿床成矿规律与找矿方向[J].地质学报,2009,83(10):1456-1472.SHE Hongquan,LI Honghong,LI Jinwen,et al.The metallogenetical characteristics and prospecting direction of the copper-lead-zinc polymetal deposits in the northern-central Daxing’anling mountain,Inner Mongolia[J].Acta Geologica Sinica,2009,83(10):1456-1472.
[6]张斌.内蒙古东珺铅锌银矿矿床地质特征及其成因研究[D].北京:中国地质科学院矿产资源研究所,2011:1-6.ZHANG Bin.The geological features and genesis of the Dongjun lead-zinc-sliver deposit in Inner Mongolia[D].Beijing:Chinese Academy of Geological Sciences.Institute of Mineral Resources,2011:1-6.
[7]张光亮.额尔古纳东珺地区火山岩岩石地球化学特征研究[D].沈阳:东北大学资源与土木工程学院,2013:1-10.ZHANG Guangliang.Study on geochemical characteristics of volcanic rocks from Dongjun region in Ergun[D].Shenyang:Northeastern University.School of Resources and Civil Engineering,2013:1-10.
[8]唐克东,王莹,何国琦,等.中国东北及邻区大陆边缘构造[J].地质学报,1995,69(1):16-30.TANG Kedong,WANG Ying,HE Guoqi,et al.Continental-margin structure of northeast China and its adjacent areas[J].Acta Geologica Sinica,1995,69(1):16-30.
[9]周鹏,朱恩静.内蒙古东珺地区火山岩喷发期次探讨[J].矿物学报,2015,35(增刊):190-191.ZHOU Peng,ZHU Enjing.Discussion on volcanic eruption period in Dongjun,Inner Mongolia[J].Acta Mineralogica Sinica,2015,35(Suppl):190-191.
[10]梁玉伟,张斌,田京,等.内蒙古东珺铅锌银矿床地质特征及成因探讨[J].现代地质,2014,28(6):1112-1121.LIANG Yuwei,ZHANG Bin,TIAN Jing,et al.Geological characteristics and genesis of the Dongjun Pb-Zn-Ag deposit in Inner Mongolia[J].Geoscience,2014,28(6):1112-1121.
[11]BOHLKE J K.Comparison of metasomatic reactions between a common CO2-rich vein fluid and diverse wall rocks:intensive variables,mass transfers,and Au mineralization at Alleghany,California[J].Economic Geology,1989,84(2):291-327.
[12]张婷,彭建堂.湘西合仁坪钠长石-石英脉型金矿床围岩蚀变及质量平衡[J].地球科学与环境学报,2014,36(4):32-44.ZHANG Ting,PENG Jiantang.Wall-rock alteration and mass balance of Herenping albite-quartz vein-type gold deposit in the western Hunan[J].Journal of Earth Sciences and Environment,2014,36(4):32-44.
[13]GRESENS R L.Composition-volume relationships of metasomatism[J].Chemical Geology,1967,2(1):47-65.
[14]GRANT J A.The isocon diagram-a simple solution to Gresens’equation for metasomatic alteration[J].Economic Geology,1986,81(8):1976-1982.
[15]郭顺,叶凯,陈意,等.开放地质体系中物质迁移质量平衡计算方法介绍[J].岩石学报,2013,29(5):1486-1498.GUO Shun,YE Kai,CHEN Yi,et al.Introduction of mass-balance calculation method for component transfer during the opening of a geological system[J].Acta Petrologica Sinica,2013,29(5):1486-1498.
[16]GUO Shun,YE Kai,CHEN Yi,et al.Fluid-rock interaction and element mobilization in UHP metabasalt:constraints from an omphacite-epidote vein and host eclogites in the Dabie Orogen[J].Lithos,2013,s136/139(4):145-167.
[17]张婷.湘西合仁坪钠长石-石英脉型金矿床围岩蚀变及其与成矿关系研究[D].湖南:中南大学地球科学与信息物理学院,2014:36-37.ZHANG Ting.Wallrock alteration and its relation with gold mineralization in the Herenping albite-quartz lode gold deposit in western Hunan[D].Hunan:Central South University.School of Earth Science and Information Physics,2014:36-37.
[18]陈随海,韩润生,申屠良义,等.滇东北矿集区昭通铅锌矿区蚀变岩分带及元素迁移特征[J].吉林大学学报(地球科学版),2016,46(3):711-721.CHEN Suihai,HAN Runsheng,SHENTU Liangyi,et al.Alteration zoning and geochemical element migration in alteration rock of Zhaotong lead-zinc deposit in northeastern Yunnan mineralization concentration area[J].Journal of Jilin University(Earth Science Edition),2016,46(3):711-721.
[19]周永章,涂光炽,CHOWN E H,等.热液围岩蚀变过程中数学不变量的寻找及元素迁移的定量估计——以广东河台金矿田为例[J].科学通报,1994,39(11):1026-1028.ZHOU Yongzhang,TU Guangchi,CHOWN E H,et al.The search for mathematical invariants and quantitative estimation of element migration in the process of hydrothermal wall rock alteration:taking Guangdong Hetai gold deposit as an example[J].Chinese Science Bulletin,1994,39(11):1026-1028.
[20]BOYNTON W V.Cosmochemistry of the rare earth elements:meteorite studies.In:P Henderson(ed.),Rare Earth Element Geochemistry[M].Amsterdam,Netherlands:Elsevier,1983:63-114.