Lead Isotopic Composition and Genesis of Phanerozoic Metal Deposits in China

来源 :Geochemistry(English Language Edition) | 被引量 : 0次 | 上传用户:tomzhang155
下载到本地 , 更方便阅读
声明 : 本文档内容版权归属内容提供方 , 如果您对本文有版权争议 , 可与客服联系进行内容授权或下架
论文部分内容阅读
Lead isotopic compositions of more than 130 galena specimens from Phanerozoic metaldeposits in China have been analyzed with a standard deviation of less than 0.5%.The rangesof isotopic composition are from 17.8 to 19.3 for Pb~(206)/Pb~(204),15.2 to 16.0 for Pb~(207)/Pb~(204)and37 to 40.8 for Pb~(208)/Pb~(204).These values overlap those of MORB,pelagic chemical sedimentsand intra-oceanic ares of western Pacific in plots of Pb~(207)/Pb~(204)vs.Pb~(206)/Pb~(204)and Pb~(208)/Pb~(204)vs.Pb~(206)/Pb~(204).This indicates that mixing between mantle and crustal materials due topartial melting of the Pacific subduction slab is the principal mechanism for ore genesis.Onthe basis of global Precambrian conformable leads,together with that of Guanmenshan,Peng-jiapu and Baiyun deposits in China,it is suggested that mantle lead was developed in asingle stage with a(U~(238)/Pb~(204))value of 7.8.If the ages of igneous rocks associated withthese deposits are adopted as formation ages,the mean Th/U of the second stage of crust-mantle evolution can be calculated with a lead mixing model.The mean μ value of Chinacontinent is 9.98±0.78,which is in agreement with that of global conformable leads,9.81±0.58.The mean Th/U ratio of 4.27 is distinctly larger than the global value(3.81),indicat-ing that the China continent is rich in Th.Simultaneously,mean formation ages have also-been obtained of the continental crusts in various regions,ranging from 3,000 to 3,800 m.y-and from 2,500 to 2,700 m.y.which are comparable with the age distribution of global Ar-chaean cratons. Lead isotopic compositions of more than 130 galena specimens from Phanerozoic metal deposits in China have been analyzed with a standard deviation of less than 0.5%. The ranges of isotopic compositions are from 17.8 to 19.3 for Pb ~ (206) / Pb ~ (204), 15.2 to 17.0 for Pb ~ (207) / Pb ~ (204) and 37 to 40.8 for Pb ~ (208) / Pb ~ (204). The se values ​​overlap those of MORB, pelagic chemical sediments and intra-oceanic ares of western Pacific in plots of Pb 207 Pb / 204 vs. Pb 206 / Pb 204 and Pb 208 / Pb 204 vs. Pb 206 / Pb 204. This indicates that mixing between mantle and crustal materials due topartial melting of the Pacific subduction slab is the principal mechanism for ore genesis. Onthe basis of global Precambrian conformable leads, together with that of Guanmenshan, Peng-jiapu and Baiyun deposits in China, it is suggested that mantle lead was developed in asingle stage with a (U ~ (238) / Pb ~ (204)) value of 7.8.If the ages of igneous rocks associated with the deposits are formed as formation ages, the mean Th / U of t he second stage of crust-mantle evolution can be calculated with a lead mixing model. The mean μ value of Chinacontinent is 9.98 ± 0.78, which is in agreement with that of global conformable leads, 9.81 ± 0.58. The mean Th / U ratio of 4.27 is distinctly larger than the global value (3.81), indicat-ing that the China continent is rich in Th. Simultaneously, mean formation ages have also-been obtained of the continental crusts in various regions, ranging from 3,000 to 3,800 my-and from 2,500 to 2,700 mywhich are comparable with the age distribution of global Ar-chaean cratons.
其他文献
惠东行政督导处,是抗战时期,中共为了加强惠东地区党、政、军各项工作的统一领导而建立起来的军政合一的县级政权,是东江地区较早建立的民主政权之一。它的建立为东纵东进部
目的研究ATP结合盒转运蛋白B1(ABCB1)基因C1236T多态性在皖南地区汉族自然人群中的频率分布及与血脂异常者各项血脂指标的相关性。方法根据血清总胆固醇(TC)、甘油三酯(TG)、
从自然区域来划分,中国已知产锑之区域,计有十三省一百数十县。属於珠江流域者,有粤桂滇黔四省,属於长江流域者,有康川鄂湘赣皖七省,属於黄河流域者,仅有甘肃一省,属於松遼
地幔是成矿物质的最初来源,地幔在地球的最初发展阶段形成了地壳,主要由玄武岩构成。在基性岩石和暗色铁镁质矿物中不仅含有较高的亲铁元素(铁、钛、钒)含量,而且含有亲铜元
钙和镁的测定一般采用络合滴定法,但终点不甚清晰,而且钙镁比例只允许为1:10-10:1,有的方法虽然提高比例到30倍,但不简便,干扰因素颇多。高鸿等对大量镁存在下钙的交流示波
测定硫酸盐法制浆蒸煮液、黑液中的S~(2-)、Sx~(2-)含量,对于选择合理的蒸煮条件,减少造纸蒸煮黑液对环境的污染,都有重要意义。国外Swartz和Lenz等研究了使用Ag/Ag_2S电极
光测弹性力学作为实验应力分析的一个分支,近半个世纪已经成熟,并在生产中得到广泛的应用,如:重型机械、动力机械、火力发电、交通运输、航空与空间技术等的结构与强度研究
图10表示瓣鳃类化石变形前后的形态。它不具备两侧对称性,若能知道变形前后三条直线之间的夹角α1、α2、α′_1、α′_2,根据公式(21)、(22)、(23) Fig. 10 shows the mor
柏林是一座脸上留着伤疤的城市。作为欧盟最大国家一一德国的首都,柏林没有巴黎的精美,没有伦敦的厚重,没有罗马的华贵……这座城市最大的特点似乎是浓缩了德意志民族历史的
1982年,我们在对南汀河断裂的地震地质考察中,于云县盆地西南缘朱家村附近发现了古地震遗迹。该遗迹保留于晚更新世至全新世初期的地层中,并发现为多次强震活动。此遗迹的发