Geochemical characteristics and Ar-40-Ar-39 ages of the amphibolites and gabbros in Tarlang area: implications for tectonic evolution of the Chinese Altai

	Geochemical characteristics and Ar-40-Ar-39 ages of the amphibolites and gabbros in Tarlang area: implications for tectonic evolution of the Chinese Altai
	Cai KeDa ; Yuan Chao ; Sun Min ; Xiao WenJiao ; Chen HanLin ; Long XiaoPing ; Zhao YongJiu ; Li JiLiang
刊名	ACTA PETROLOGICA SINICA
	2007-05-01
卷号	23 期号:5 页码:877-888
关键词	amphibolite gabbro Ar-40-Ar-39 age subduction Altai tectonic transition Paleo-Asian ocean
ISSN号	1000-0569
文献子类	Article
英文摘要	Amphibolitic and gabbroic rocks occur in Tarlang area in Chinese Altay. Amphibolites are metamorphosed products of mafic magmatic rocks (SiO2 = 45.42% similar to 52.96%) and contain high Al2O3(13.14% similar to 17.92%), Fe2O3T (9.08% similar to 16.88%) and TiO2 (0.82% similar to 3.23%) contents. The amphibolite samples show relatively flat REE patterns, without significant fractionations of REEs (La/Yb-N = 1.53 similar to 1.79). These samples are depleted in HFSEs slightly, with slightly Ti-Nb-Ta negative anomalies, which suggest a subtle relation to subduction-related environment. The gabbroic samples (SiO2 = 46.96% similar to 49.86%) have intermediate TiO2 (0.38% similar to 1.89%) and relatively low K2O contents (K2O = 0.34% similar to 1.03%), belonging to subalkali rocks (Na2O > K2O). They have relatively high Al2O3 (15.0% similar to 20.81%), CaO (10.13% similar to 11.60%) and moderate MgO (7.3% similar to 8.3%) contents. The gabbroic samples show two types of REE patterns. One is characterized by slight fractionation of REEs (La/Yb-N = 1.10 similar to 1.67) and weak Eu anomalies (delta Eu = 1.03 similar to 1.10), while the other is enriched in LREEs (La/Yb-N = 5.97 similar to 6.39), with significantly positive Eu anomalies (delta Eu = 1.31 similar to 1.44), which may reflect accumulation of plagioclase in the magma chamber. These gabbroic rocks all exhibit Ti-Nb-Ta troughs and Pb-Sr spikes, also implying a subduction-related origin. The Ar-40/Ar-39 spectrum of the gabbroic sample is simple and flat (plateau age of 266.9 +/- 4.2Ma; isochron age of 261 +/- 23Ma), indicating that its K-Ar isotopic system was not seriously disturbed by subsequent thermal events and may reflect the intrusion time of the gabbro. However, Ar-40-Ar-39 analysis of the amphibolite give rise to a saddle-like spectrum, and its youngest plateau (297.3 +/ 6.1Ma) probably reflects the last metamorphic event. The difference on age and geochemistry between the amphibolitic and gabbroic rocks implies that they probably represent different mafic magma. The protolith of amphibolites probably formed in a seamount near a subduction zone and subsequently accreated to the Altai. The gabbro exhibits subduction-releted characteristics and was coeval with transtensional movement in the Chinese Altai, probably reflecting a tectonic transition in the Permian.
WOS关键词	CENTRAL-ASIA ; NW CHINA ; GEOCHRONOLOGICAL DATA ; NORTHWEST CHINA ; CRUSTAL GROWTH ; OROGENIC BELT ; MANTLE ; ROCKS ; ACCRETIONARY ; SUBDUCTION
WOS研究方向	Geology
语种	英语
出版者	SCIENCE PRESS
WOS记录号	WOS:000248135100002
内容类型	期刊论文
源URL	[http://ir.iggcas.ac.cn/handle/132A11/67914]
专题	中国科学院地质与地球物理研究所
通讯作者	Cai KeDa
作者单位	1.Chinese Acad Sci, Guangzhou Inst Geochem, Guangzhou 510640, Peoples R China 2.Grad Univ Chinese Acad Sci, Beijing 100039, Peoples R China 3.Univ Hong Kong, Dept Earth Sci, Hong Kong, Hong Kong, Peoples R China 4.Chinese Acad Sci, Inst Geol & Geophys, State Key Lab Lithospher Evolut, Beijing 100029, Peoples R China 5.Zhejiang Univ, Dept Earth Sci, Hangzhou 310027, Peoples R China
推荐引用方式 GB/T 7714	Cai KeDa,Yuan Chao,Sun Min,et al. Geochemical characteristics and Ar-40-Ar-39 ages of the amphibolites and gabbros in Tarlang area: implications for tectonic evolution of the Chinese Altai[J]. ACTA PETROLOGICA SINICA,2007,23(5):877-888.
APA	Cai KeDa.,Yuan Chao.,Sun Min.,Xiao WenJiao.,Chen HanLin.,...&Li JiLiang.(2007).Geochemical characteristics and Ar-40-Ar-39 ages of the amphibolites and gabbros in Tarlang area: implications for tectonic evolution of the Chinese Altai.ACTA PETROLOGICA SINICA,23(5),877-888.
MLA	Cai KeDa,et al."Geochemical characteristics and Ar-40-Ar-39 ages of the amphibolites and gabbros in Tarlang area: implications for tectonic evolution of the Chinese Altai".ACTA PETROLOGICA SINICA 23.5(2007):877-888.