辽东辽河群大石桥组碳酸盐岩稀土元素地球化学及其对Lomagundi事件的指示

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	辽东辽河群大石桥组碳酸盐岩稀土元素地球化学及其对Lomagundi事件的指示; Rare earth element geochemistry of carbonates of Dashiqiao Formation, Liaohe Group, eastern Liaoning province: Implications for Lomagundi Event.
	汤好书 ; 陈衍景 ; 武广 ; 杨涛
刊名	岩石学报
	2009
关键词	Lomagundi事件辽河群化学沉积物海水组成大气氧化 REY Lomagundi Event Liaohe Group chemical sediments REY seawater composition atmosphetic oxygenation
英文摘要	2.33～2.06Ga期间发生了全球性大气圈充氧作用及其相关的δ~(13)C_(carb)正异常,被称为Lomagundi事件。2.2～2.174Ga的辽河群大石桥菱镁矿及其围岩显示了δ~(13)C_(carh)正异常,是运用REY(REE+Y)指纹技术研究Lomagundi事件的良好对象。本文研究表明,6件白云岩围岩样品∑REE为0.988×10~(-6)～2.744×10~(-6);Y/Ho比值为37.9～49.4(平均42.5±4.7);(La/La~)_(SN)为1.075±0.317,(Gd/Gd~)_(SN)为1.390±0.166,均为正异常;HREE富集(Nd_(SN)/Y...; The worldwide 2.33 similar to 2.06Ga Positive delta(13) C(carb) excursion is related to the Great Oxidation Event (GOE) of the atmosphere and called as Lomagundi Event. The Dashiqiao magnesite ore-bed and its dolomite hostrocks of the Dashiqiao Fro., Liaohe Group, are characterized by positive delta(13) C(carb) excursion and suitable for the study of the Lomagundi Event using REY (rare earth element and yttrium, REE + Y) chemical fingerprints. Our results show that the PAAS (Post-Archean Average Shale) normalized REY patterns of six dolomite samples, whose Sigma REE range from 0.988 x 10(-6) similar to 2.744 x 10(-6) and Y/Ho ratios range from 37.9 similar to 49.4 with average of 42.5 +/- 4.7, show uniform positive (La/La)(SN) (1.075 +/- 0.317) and (Gd/Gd)(SN) (1.390 +/- 0.166) anomalies and notable HREE enrichment indicated by (Nd/Yb) 0. 38 0. 78 (average 0. 49 0. 15). These features are consistent with the geochemistry of well-oxygenated, shallow ambient seawater, and suggest that these samples substantially record the primary REY signatures of seawater during the Lomagundi Event era. The Sigma REE of six magnesite samples, in average of 4.549 x 10(-6) +/- 2.239 x 10(-6), are higher than those of dolomite hostrocks; and the Y/Ho ratios, averaging 40.2 +/- 3.2, are slightly lower than the dolomites. The magnesites show slight depletion in HREE (Nd(SN)/Yb(SN) = 1.141 +/- 0.265), and positive (La/La)(SN) (average 0.919 +/- 0.203) and (Gd/Gd)(SN) (average 1.036 +/- 0.081) anomalies which are weaker than those of dolomites and still originated from seawater. The mega-cylindrical tale-bearing dolomite in the hanging-wall shows highest Sigma REE, (10.758 x 10(-6)) content and a flat PAAS-nomalised REY pattern, with positive (Eu/Eu) anomaly up to 1.97, the lowest positive (Gd/Gd) and Y anomalies, and the lowest Y/Ho (31.3) and (Nd/Yb)(SN) (0.89). This unique talc-bearing dolomite was reworked by hydrothermal. The (SM/Yb)(CN) values of magnesites average 2.61 +/- 0.45, higher than those of dolomites (1.19 +/- 0.27 in average), which indicates that the seawater depth became shallower during sedimentation of the Dashiqiao Formation, and that the dominant factor controlling the REY geochemical characteristics of the Dashiqiao Formation was the atmosphere-hydrosphere system's nature such as f(o2) and P(co2). The REY in the magnesite and dolomite were mainly sourced from fluxes of solutes from terrestrial weathering, whereas the contribution from marine hydrothermal processes was negligible. The (Ce/Ce)(SN) of dolomites and magnesits range 0.95 similar to 1.25 and 0.94 similar to 1.16, with averages of 1.11 +/- 0.13 and 1.04 +/- 0.08, respectively. This suggests that weathering of continental crust was strong during 2.2 similar to 2.174 Ga, and seawater might be alkaline with pH value above 8.2. Considering that the pre-2.3 Ga and post-2.06 Ga chemical sediments have (Eu/Eu)(SN) values higher and lower than 1.53, respectively, the (Eu/Eu )(SN) values of the Dashiqiao dolomites (1.44 +/- 0.11) and magnestes (1.58 +/- 0.20) indicate that the (Eu/Eu)(SN) approximate to 1.53 can be used as one of criteria for 2.2 similar to 2.174 Ga marine chemical sediments; and that the 2.33 similar to 2. 06 Ga period was a critical turnpoint that the Earth's atmosphere-hydrosphere system sharply changed from reduction to xygenation.; http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000273455000034&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701 ; 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); 15; 11; 3075-3093; 25
语种	中文
内容类型	期刊论文
源URL	[http://ir.pku.edu.cn/handle/20.500.11897/179784]
专题	地球与空间科学学院
推荐引用方式 GB/T 7714	汤好书,陈衍景,武广,等. 辽东辽河群大石桥组碳酸盐岩稀土元素地球化学及其对Lomagundi事件的指示, Rare earth element geochemistry of carbonates of Dashiqiao Formation, Liaohe Group, eastern Liaoning province: Implications for Lomagundi Event.[J]. 岩石学报,2009.
APA	汤好书,陈衍景,武广,&杨涛.(2009).辽东辽河群大石桥组碳酸盐岩稀土元素地球化学及其对Lomagundi事件的指示.岩石学报.
MLA	汤好书,et al."辽东辽河群大石桥组碳酸盐岩稀土元素地球化学及其对Lomagundi事件的指示".岩石学报 (2009).