今天是2019年04月19日

北秦岭寨根地区富铌辉长岩地球化学特征及其构造意义

DOI:10.3799/dqkx.2018.340

作者:赵利刚,李承东,许雅雯,武志宇,常青松,许腾,滕雪明

联系地址:中国地质调查局天津地质调查中心,天津 300170

摘要:富铌辉长岩往往与高镁闪长岩、埃达克岩共生,被认为是具有指相意义的岩石构造组合,但豫西地区北秦岭造山带南侧该类岩浆活动却很少被发现.对寨根地区秦岭岩群中的斜长角闪岩类进行岩石学、地球化学、同位素地球化学和年代学研究,在该深成杂岩中发现了富铌辉长岩,并且测得富铌辉长岩的变质锆石U-Pb年龄为484.3±1.8 Ma,与区内超高压榴辉岩变质峰值年龄相近.富铌辉长岩地球化学特征表现为富集Rb、Th等大离子亲石元素,亏损Nb、Ta、P等高场强元素,εNd(t)介于 -1.61~ +0.49,相应的(87Sr/86Sr)i范围为0.714 273~0.723 936.推测其成因与秦岭古陆壳深俯冲过程中部分熔融的板片熔体交代地幔楔橄榄岩再熔融有关,经受深俯冲时有大量陆壳物质的加入,该发现为秦岭造山带早古生代早期存在多个微陆块提供了证据.

关键字:富铌辉长岩;地球化学;寨根;秦岭造山带

Geochemistry of Nd-enriched Gabbros in Zhaigen Area in Northern Qinling and Their Tectonic Significance

Author:Zhao Ligang , Li Chengdong , Xu Yawen , Wu Zhiyu , Chang Qingsong , Xu Teng , Teng Xueming

Author Address:Tianjin Center of China Geological Survey, Tianjin 300170, China

Abstract:Nb-enriched gabbros are often associated with high-Mg diorite and adakite, which is considered to be a petrotectonic association of facies significance. However, this kind of magmatic activity has seldom been found in the southern side of the North Qinling orogenic belt in western Henan. Based on the method of petrology, geochemistry, isotope geochemistry and chronology for amphibolites from the Qinling Group in Zhaigen area, the Nb-enriched gabbros were separated from the deep plutonic complex in this study. The results show that the U-Pb age of metamorphic zircons from Nb-enriched gabbros is 484.3±1.8 Ma, which is similar to the peak of metamorphic ages of the UHP eclogites in this area. Nb-enriched gabbros are characterized by enrichment of Rb, Th and other heavy ion lithophilic elements and depletion of Nb, Ta, P and other high field strength elements. εNd(t) values range from -1.61 to +0.49, and (87Sr/86Sr)i values range from 0.714273 to 0.723936. We speculate that their formation was related to the remelting of mantle wedge peridotite by partially melted plate melts during the deep subduction of the Qinling paleocontinental crust. And a large amount of continental crust was added to the deep subduction. The discovery of Nbenriched gabbros provides evidence for the existence of multiple small continental blocks in the Early Paleozoic of the Qinling orogen.

Keyword:Nd-enriched gabbros; geochemistry; Zhaigen; the Qinling orogenic belt

 

【点击数:130【下载数:83】【PDF预览】


作者简介:赵利刚(1981-),男,助理研究员,主要从事区域成矿规律研究.ORCID: 0000-0003-1550-6293. E-mail: zhaoligang981@126.com

参考文献