Geochemical and Nd isotopic compositions of 3.8 Ga meta-quartz dioritic;and trondhjemitic rocks from the Anshan area and their geological;significance

doi:10.1016/j.jseaes.2004.02.009

	Geochemical and Nd isotopic compositions of 3.8 Ga meta-quartz dioritic;and trondhjemitic rocks from the Anshan area and their geological;significance
	Wan, YS 3; Liu, DY ; Song, B ; Wu, JS ; Yang, CH ; Zhang, ZQ ; Geng, YS
刊名	JOURNAL OF ASIAN EARTH SCIENCES
	2005
卷号	24 期号:5 页码:563-575
关键词	Nd isotopes early Archean TTG rocks Anshan area North China Craton
ISSN号	1367-9120
DOI	10.1016/j.jseaes.2004.02.009
英文摘要	The 3.8 Ga meta-quartz dioritic rocks discovered recently in the Anshan area show relatively high Sigma REE contents and low (La/Yb)(n) ratios, with t(DM) of 3.50-4.16 Ga and epsilon(Nd) (3.8 Ga) of -1.24 to 4.51. Slightly older 3.8 Ga trondhjemitic rocks have been found in two locations in the Anshan area. One is the Baijiafen gneiss, which crops out near Baijiafen village and is characterized by relatively high SiO2 and Na2O, low MgO, Sigma FeO and CaO, rather low Sigma REE contents and low (La/Yb)(n) ratios. The other is the Dongshan banded gneiss located in the Dongshan Scenic Park in Anshan City, which has a similar chemical composition to the Baijiafen gneiss, except for slightly higher MgO, Sigma FeO, CaO and Sigma REE concentrations. All the 3.8 Ga trondhjemitic rocks exhibit large variations in Nd isotopic compositions, with t(DM) and epsilon(Nd) (3.8 Ga) of 3.07-3.87 Ga and 0.82-12.23 for the Baijiafen gneiss, and 2.82 to 3.40 Ga and 7.37-12.44 for the Dongshan banded gneiss, respectively. It is suggested that the 3.8 Ga trondhjemitic rocks from the Anshan area were formed by partial melting of intermediate to acidic continental material, and not basaltic material. TTG rocks of early Archean age are generally low in Sigma REE contents and (La/Yb)(n) ratios compared with those of late Archean age. The regular variations of REE patterns with time may reflect thermal evolution of the primitive Earth. In the early stages, the Earth had higher geothermal gradients (> 30 degrees C/km). After about 3.5-3.6 Ga, its geothermal gradient dropped into the garnet stability field. (c) 2004 Elsevier Ltd. All rights reserved.
学科主题	火成岩岩石学
WOS关键词	SOUTHERN WEST GREENLAND ; ARCHEAN GRANITOIDS ; CRUSTAL EVOLUTION ; NORTHERN ; CANADA ; CASE-HISTORIES ; CRATON ; CONSTRAINTS ; HETEROGENEITY ; TONALITES ; GNEISSES
WOS研究方向	Geology
语种	英语
出版者	PERGAMON-ELSEVIER SCIENCE LTD
WOS记录号	WOS:000228247800004
内容类型	期刊论文
源URL	[http://119.78.100.197/handle/2HKVOGP0/38077]
专题	中国地质科学院地质研究所
作者单位	1.Chinese Acad Geol Sci, Inst Geol, Beijing 100037, Peoples R China. 2.Beijing SHRIMP Ctr, Beijing 100037, Peoples R China. 3.中国地质科学院地质研究所
推荐引用方式 GB/T 7714	Wan, YS,Liu, DY,Song, B,et al. Geochemical and Nd isotopic compositions of 3.8 Ga meta-quartz dioritic;and trondhjemitic rocks from the Anshan area and their geological;significance[J]. JOURNAL OF ASIAN EARTH SCIENCES,2005,24(5):563-575.
APA	Wan, YS.,Liu, DY.,Song, B.,Wu, JS.,Yang, CH.,...&Geng, YS.(2005).Geochemical and Nd isotopic compositions of 3.8 Ga meta-quartz dioritic;and trondhjemitic rocks from the Anshan area and their geological;significance.JOURNAL OF ASIAN EARTH SCIENCES,24(5),563-575.
MLA	Wan, YS,et al."Geochemical and Nd isotopic compositions of 3.8 Ga meta-quartz dioritic;and trondhjemitic rocks from the Anshan area and their geological;significance".JOURNAL OF ASIAN EARTH SCIENCES 24.5(2005):563-575.