辽东半岛南辽河群锆石U-Pb年代学及其地质意义

CORC > 北京大学 > 地球与空间科学学院

	辽东半岛南辽河群锆石U-Pb年代学及其地质意义; Zircon U-Pb ages and their implications for the South Liaohe Group in the Liaodong Peninsula, Northeast China
	李壮 ; 陈斌 ; 刘经纬 ; 张璐 ; 杨川
刊名	岩石学报
	2015
关键词	辽东半岛南辽河群年代学火山-沉积-变质华北克拉通 Liaodong Peninsula South Liaohe Group Geochronology volcanism-sedimentary-metamorphism North China Craton LA-ICP-MS PALEOPROTEROZOIC CRUSTAL EVOLUTION EASTERN BLOCK JI BELT ISOTOPIC COMPOSITIONS TECTONIC SIGNIFICANCE LIAONING-PROVINCE METAMORPHIC ROCKS DETRITAL ZIRCONS TRACE-ELEMENTS
英文摘要	本文报道了辽东半岛古元古代胶-辽-吉活动带南辽河群中变质火山岩和沉积岩的锆石U-Pb年代学数据。变质流纹岩的锆石具典型的岩浆振荡环带结构和较高的Th/U比值(>0.3),锆石U-Pb年龄为~2.2Ga,该年龄可代表其原岩形成年龄,在误差范围内与古元古代辽吉花岗岩年龄一致,表明辽吉花岗岩并不是辽河群的基底。变质玄武岩的锆石阴极发光强度较弱、弱分带或无分带,同时具较低的Th/U比值(<0.1),为典型的变质成因锆石,锆石U-Pb年龄为~1.9Ga,代表其变质时代。变质沉积岩的碎屑锆石年龄主要介于1981~3520Ma之间:峰期年龄为2033Ma和2092Ma的锆石年龄信息暗示辽东半岛至少存在一期2...; Liaodong Peninsula is located in the southeastern part of Liaoning Province, the basement rocks of which consist mainly of the Archean Anshan-Fushun Complex in the north (Liaobei-Jinan Block), Archean Jinzhou Complex in the south (Liaonan Block), and the Paleoproterozoic Liaohe Group and granitoid intrusions (Jiao-Liao-Ji Belt) in between. The Paleoproterozoic Liaohe Group is divided by the Qinglongshan-Zaoerling shear zone into two parts, the South Liaohe Group and North Liaohe Group, with more volcanic rocks in the former and more elastic and carbonate rocks in the latter. The South Liaohe Group consists of three rock units, with a volcanic-rich sequence in the lower part (the Lieryu and Gaojiayu formations), a carbonate-rich sequence in the middle (the Dashiqiao Formation), and a pelitic sequence in the upper part (the Gaixian Formation). We report in the paper the zircon U-Pb age data for two meta-volcanic rocks from the Lieryu Formation and three meta-sedimentary rocks from the Gaixian Formation of the Paleoproterozoic South Liaohe Group in the Liaodong Peninsula. Zircon analyses on the meta-rhyolite (LZ3) yield Pb-207/Pb-206 ages of ca. 2. 2Ga, with the range of 2178 similar to 2226Ma. These zircons show oscillatory and sector-zoning, and high Th/U ratios (>0. 3), typical of magmatic origin; thus the age probably represents the formation age of the protolith of the meta-volcanic rocks, which are regionally comparable to those of the Paleoproterozoic Liaoji granitoids, indicating that the Liaoji granitoids are not the basement of the Liaohe Group sedimentary-volcanic rocks as previously thought. Zircon analyses on the meta-basalt (LZ12) yield Pb-207/Pb-206 ages of ca. 1. 9Ga, with the range of 1850 similar to 1949 Ma. Zircon grains from the meta-basalt show relatively dark CL images, with patchy zoning or irregular structures and low Th/U ratios (<0. 1). These features suggest that they should be formed during the process of fluid-present metamorphism, and their U-Pb ages of ca. 1. 9Ga represent the metamorphic age. The dating result of the detrital zircons from the meta-sedimentary rocks (LC3, LC5 and LB3) shows that the Pb-207/Pb-206 ages vary from 1981Ma to 3520Ma, with characteristic age probability peaks at ca. 2033Ma, 2092Ma, 2155Ma, 2446Ma, 2509Ma, 2594Ma, 2668Ma, 2790Ma, 3356Ma, 3467Ma and 3520Ma. The characteristic age probability peaks of 2033 Ma and 2092Ma indicate that more than one magmatic event occurred at 2000 similar to 2100Ma in the Liaodong Peninsula seldom recognized before, and.that 2000 similar to 2100Ma acid rocks are an important contributor to the provenance for the South Liaohe Group. The characteristic age probability peaks of 2155 similar to 3520 Ma are mainly consistent with the formation of regionally distributed Liaoji granitoids and coeval volcanic rocks in the Jiao-Liao-Ji Belt and the granitoids of the Archean basement, suggesting that these rocks provided the major component of the provenance for the South Liaohe Group. The deposition time of the meta-sedimentary rocks is later than ca. 2. 0 Ga as limited by the youngest detrital zircons. These new zircon ages for the South Liaohe Group reveal that the volcanism-deposition-metamorphism events of the South Liaohe Group occurred at 2. 2 similar to 1. 9 Ga, and lasted for at least 300Myr. Integration of our new data with recent studies on lithology,, metamorphism, geochemistry and geochronology of Archean-Paleoproterozoic basement rocks is inconsistent with the rifting model, but rather, supports the Paleoproterozoic arc-continent collision model, as follows: (1) The detrital zircon spectra of the South Liaohe Group are similar to that of back-arc basin; (2) There is a lack of rock associations that are typical of the rift, such as OIB, phonolite and carbonatite; (3) The Paleoproterozoic metamorphic volcanic rocks and Liaoji granitoids show geochemical characteristics typical of arc magmas; (4) The South Liaohe and North Liaohe groups have different rock associations and metamorphic histories (P-T-t paths); (5) The Liaobei-Jinan and Liaonan blocks show considerable differences in terms of lithological units, geochronology and metamorphic features. Therefore, we propose that the Paleoproterozoic Jiao-Liao-Ji Belt formed in the arc-continental collision setting, rather than in a continental rifling setting as previously thought by most workers.; 科技部973项目; SCI(E); 中文核心期刊要目总览(PKU); 中国科技核心期刊(ISTIC); 中国科学引文数据库(CSCD); lizhuangcc@pku.edu.cn; binchen@pku.edu.cn; 06; 1589-1605; 31
语种	中文
内容类型	期刊论文
源URL	[http://ir.pku.edu.cn/handle/20.500.11897/454967]
专题	地球与空间科学学院
推荐引用方式 GB/T 7714	李壮,陈斌,刘经纬,等. 辽东半岛南辽河群锆石U-Pb年代学及其地质意义, Zircon U-Pb ages and their implications for the South Liaohe Group in the Liaodong Peninsula, Northeast China[J]. 岩石学报,2015.
APA	李壮,陈斌,刘经纬,张璐,&杨川.(2015).辽东半岛南辽河群锆石U-Pb年代学及其地质意义.岩石学报.
MLA	李壮,et al."辽东半岛南辽河群锆石U-Pb年代学及其地质意义".岩石学报 (2015).