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引用本文:赵利刚,李承东,武志宇,高学生,许雅雯,张阔,常青松. 豫西五里川—寨根一带秦岭岩群碎屑锆石U-Pb年龄研究[J]. 中国地质, 2018, 45(4): 753-766.
ZHAO Ligang,LI Chengdong,WU Zhiyu,GAO Xuesheng,XU Yawen,ZHANG Kuo,CHANG Qingsong. Detrital zircon U-Pb geochronology of the Qinling Group in WulichuanZhaigen area, West Henan[J]. Geology in China, 2018, 45(4): 753-766(in Chinese with English abstract).
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豫西五里川—寨根一带秦岭岩群碎屑锆石U-Pb年龄研究
赵利刚1, 李承东1, 武志宇2, 高学生1, 许雅雯1, 张阔1, 常青松1
1.中国地质调查局天津地质调查中心, 天津市 300170;2.长庆实业集团, 陕西 西安 710016
摘要:
秦岭岩群为北秦岭微陆块的主要组成部分,其时代的准确厘定对秦岭造山带构造演化研究具有重要的地质意义。本次工作对五里川-寨根一带秦岭岩群雁岭沟岩组钠长二云片岩和郭庄岩组矽线二云二长片麻岩进行碎屑锆石LA-ICP-MS U-Pb同位素年代学研究。钠长二云片岩具有岩浆成因特征的碎屑锆石核部年龄主要存在545~551 Ma、754~778 Ma、900~1000 Ma、1340~1830 Ma和2300~2500 Ma 5个年龄段,并以900~1000 Ma段碎屑锆石的峰最明显;部分数据点在锆石U-Pb谐和图上拟合成一条上交点年龄为(2478 ±25)Ma的不一致线。矽线二云二长片麻岩年龄主要集中于1400~1800 Ma,另有4颗锆石年龄为1134~1243 Ma,其中最年轻的1颗碎屑岩浆锆石年龄为(1134±17)Ma。根据分析结果,推断本地区雁岭沟岩组的形成时代应晚于900 Ma,早于438 Ma的五垛山岩体。郭庄岩组的主体形成于中元古代晚期,时代应该晚于1122 Ma,老于962 Ma的新元古代花岗岩类。雁岭沟岩组最主要的物质来源为新元古代花岗岩,其次为新太古代-古元古代陆壳,少部分来源于郭庄岩组;郭庄岩组物质来源主要为的古元古代晚期至中元古代早期的花岗岩陆壳。雁岭沟岩组与郭庄岩组形成时代不同,二者之间存在沉积间断,主要物源区也不相同,雁岭沟岩组中甚至有少量郭庄岩组剥蚀后再沉积的物质。因此,二者是不同的构造岩片,本地区雁岭沟岩组应从秦岭岩群中解体出来。
关键词:  豫西  秦岭造山带  秦岭岩群  雁岭沟组  郭庄岩组  碎屑锆石U-Pb  LA-ICP-MS
DOI:10.12029/gc20180408
分类号:P597+.3
基金项目:国家自然科学基金(41272065)和中国地质调查局地质大调查项目(DD20160043)联合资助。
Detrital zircon U-Pb geochronology of the Qinling Group in WulichuanZhaigen area, West Henan
ZHAO Ligang1, LI Chengdong1, WU Zhiyu2, GAO Xuesheng1, XU Yawen1, ZHANG Kuo1, CHANG Qingsong1
1.Tianjin Center of Geological Survey, CGS, Tianjin 300170, China;2.Changqing Industry and Commerce Group, Xi'an 710016, Sichuan, China
Abstract:
The Qinling Group is the main component of the Qinling microcontinent, and the accurate determination of its age is of great significance for the study of the tectonic evolution of the Qinling orogenic belt. This paper presents zircon LA-MC-ICPMS U-Pb geochronologic data of the albite two-mica schist from Yanlinggou Formation and the sillimanite two-mica monzo-gneiss from Guozhuang Formation of Qinling Group in Wulichuan-Zhaigen area. The dating results of the magmatic core of detrital zircons from albite two-mica schist show 5 age groups mainly, i.e., 545-551 Ma, 754-778 Ma, 900-1000 Ma, 1340-1830 Ma and 2300-2500 Ma, in which the 900-1000 Ma group exhibits most obvious peaks of detrital zircons, and an inconsistent line of the upper intersection point of (2478 ±25) Ma can be fitted to a part of data points. The sillimanite two-mica monzo-gneiss ages are mainly concentrated in 1400-1800 Ma, with only four data points being in the range of 1134-1243 Ma, and the youngest magmatic core of detrital zircons is (1103 ±6) Ma. According to the data, the authors hold that the age of Yanlinggou Formation was younger than 900 Ma, and older than 438 Ma pluton of Wuduoshan. Guozhuang Formation is mainly formed during late Mesoproterozoic, younger than 1122 Ma, and older than 962 Ma Neoproterozoic granitic rocks. The sedimentary material of Yanlinggou Formation complex was mainly from Neoproterozoic granitic rocks and Proterozoic continental crust, with a little from Guozhuang Formation. Most sources of Guozhuang Formation were from the late Paleoproterozoic to Mesoproterozoic granitic continental crust. Yanlinggou Formation and Guozhuang Formation were formed in different periods, and there was a discontinuity between them. Their sedimentary materials were also different, and even a small amount of material of Yanlinggou Formation was postredeposition material from Guozhuang Formation. The two formations are different tectonic sheets. Therefore, the Yanlinggou Formation should be separated from the Qinling Group.
Key words:  west Henan  Qinling orogenic belt  Qinling Group  Yanlinggou Formation  Gaungzhou Formation  detrital zircon U-Pb  LA-ICP-MS