李曙光
地球化学
个性化签名
- 姓名:李曙光
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学术头衔:
博士生导师, 中国科学院院士
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学科领域:
地球化学
- 研究兴趣:地球化学
李曙光教授,地球化学家,1941年生于陕西咸阳。1960年毕业于天津第17中学。1965年毕业于中国科学技术大学化学系地球化学专业并留校任教。1983年至1986年,在美国麻省理工学院地球与行星科学系进修。先后多次赴德国马普化学所、香港大学作访问学者。现任中国科学技术大学教授。2003年当选为中国科学院院士,2005年荣获何梁何利基金科技进步奖。
李曙光教授在以下领域做出了系统研究,并取得一系列创新性成果。
1. 他在超高压变质作用中同位素体系及变质年代学理论做出许多开拓性工作:较早发现并证明造山带榴辉岩中的白云母含大量过剩氩;证明了超高压变质矿物与退变质矿物之间存在Nd,Sr同位素不平衡;较早发现了基性火山岩在低级变质条件下稀土元素可活动并使其Sm-Nd同位素体系重置;计算了蓝片岩的早期绿片岩相及叠加兰片岩相变质作用各自的Sr同位素均一化尺度;在世界上首次精确地测定了榴辉岩中金红石的U-Pb年龄。这些工作为正确进行超高压变质定年作出了决定性贡献。
2. 他对华北和华南陆块的碰撞过程及秦岭-大别造山带演化进行了长期系统研究并取得重要成果:最早测定出大别山含柯石英榴辉岩的Sm-Nd年龄为三叠纪,并证明它们是陆壳俯冲成因,从而获得华北与华南陆块在三叠纪最终碰撞的结论;系统测定了北,南秦岭一系列蛇绿岩及岛弧岩浆岩的同位素年龄及地球化学特征,为秦岭造山带两条地缝合线的厘定及多陆块拼合模型的建立提供了重要依据;此外,还首次在大别山北侧发现古生代岩浆弧和洋壳俯冲成因榴辉岩,系统测定了大别山其它榴辉岩,岩浆岩年龄,研究了碰撞后壳幔相互作用及岩石圈拆离过程。
3. 超高压变质岩的折返机制是大陆深俯冲研究的著名科学问题。他首次测定出大别山超高压岩石具有二次快速冷却的曲线,对多阶段快速抬升历史给出重要制约。结合测定南秦岭同碰撞花岗岩的年龄,查明俯冲陆壳不同构造单元的U-Pb同位素及变质年龄的差异,他提出了俯冲陆壳内可发生多层次挤离,解耦,并导致超高压变质岩呈多岩板、多阶段折返的模型。
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李曙光, LI
SCIENCE IN CHINA(Series B) Vol. 32 No. 11 November 1989,-0001,():
-1年11月30日
Sm-Nd isotopic ages for C-type eclogite(243.9
collision
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李曙光, SHUGUANG
Precambrian Research, 47(1990)191-203,-0001,():
-1年11月30日
Shuguang Li, Hart, S.R. and Tieshan Wu, 1990. Rb-Sr and Sm-Nd isotopic dating of an Early Precambrian spilite-keratophyre sequence in the Wutaishan area, North China: Preliminary evidence for Nd-isotopic homogenization in the mafic and felsic lavas during low-grade metamorphism. Precambrian Res., 47: 191-203. The spilite-keratophyre sequence in the Wutaishan area, North China has been dated by zircon from the quartz-keratophyre and a volcanic crystallization age of 2522 Ma(Liu Dunyi et al., 1985) was obtained. This volcanic rock sequence experienced a low-grade metamorphism of greenschist facies during 1800-2000Ma. However, combined Sm-Nd whold rock data from the volcanic rock sequence, if interpreted in terms of an isochron, gives a younger age of 2250±180Ma. If separately calculated, Sm-Nd isochrons for quartz-keratophyre and spilite yield two consistently younger ages of 1977±385Ma and 1981±178Ma. These Sm-Nd isochron ages are consistent with a Rb-Sr age of 1871±98Ma, and with the time of regional greenschist facies metamorphism. Consequently, we interpret the 2250 Ma alignment on the Sm-Nd diagram as an errorchron. The two Sm-Nd metamorphic ages suggest that partial homogenization of Nd isotopic composition in water-rich spilite-keratophyric meta-volcanics can be achieved during low-grade metamorphism as a result of REE mobility. Using the €Nd values at the time of metamorphism and the average 147Sm/144Nd ratios of the spilite and the quartz-keratophyre, initial €Nd values of 2.6±3.5 and 3.0±6.1, respectively are estimated at the time of volcanic eruption (2522 Ma). Similar positive initial €Nd values for the spilites and quartz-keratophyres suggest that they might have been derived from the same depleted mantle source, or that the quartz-keratophyres are derived from a short-lived mafic source.
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李曙光, 刘德良, 陈移之, 葛宁洁, 张宗清, 叶笑江
科学通报1992年,-0001,():
-1年11月30日
在大别山带及其东延部分(苏北-胶南隆起)发育一条榴辉岩带,它是华北与扬子陆块在这里碰撞产生高压变质作用的有力证据ψ。最近,人们在一部分榴辉岩中发现了柯石英,它以包裹体形式存在于石榴石和绿辉石矿物晶体中[2,3]1)。这是继挪威、西阿尔卑斯之后,世界上第三个发现柯石英的造山带,因而引起了广泛重视。含柯石英榴辉岩均分布在该造山带南翼(岳西以南)大别群的片麻岩和大理岩中。在大别山北翼的榴辉岩中尚未有发现柯石英的报道。近年来我们曾报道了二个产于大别山北翼、桐柏-磨子潭断裂南侧大别群杂岩中不同类型榴辉岩的Sm-Nd同位素年龄,它们均生成于印支期[4,5]。然而大别山南翼含柯石英榴辉岩的形成时代尚属未知。在大别山带是否存在多期榴辉岩,是否存在元古高压变质带仍是一个有争议的问题[2,6,7]。为此,我们对大别山南翼的含柯石英榴辉岩进行了Sm-Nd同位素定年研究,以确定其形成时代。
榴辉岩, Sm-Nd同位素定年, 大别山
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李曙光, Shuguang
Chemical Geology(Isotope Geoscience Section), 112(1994)343-350,-0001,():
-1年11月30日
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李曙光, LI
SCIENCE IN CHINA(Series D) Vol. 39 No. 3 June 1996,-0001,():
-1年11月30日
The metavolcanic rocks of greenschist facies developed at Heigouxia Valley in the Mian-Lue tectonic zone, South Qinling orogenic belt is a bimodal volcanic series. It is composed of K-poor, Na-rich tholeiite and dacite-rhyolite. The trace elements characteristics with flat REE pattern of these tholeiites are similar to those of MORB. The Sm-Nd whole rock isochron age of (242±21) Ma and Rb-Sr whold rock isochron age of (221±13) Ma of this metavolcanic series consistently indicate their metamorphic time. Their relatively high initial εNd value of +6.1 at the metamorphic age (242Ma) suggest that the volcanic rocks were derived from a depleted MORB type mantle source. Their trace elements and Nd isotope compositions suggest an oceanic basin developed from a rift on the continental margin of the Yangtze Block during the late Paleozoic and closed in the Triassic. This is the first case clearly showing the existence of relict of late Palcozoic occanic crust in East Qinling belt. Which provides important evidence for the Mian-Lue tectonic zone as a structure zone.
Qinling
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【期刊论文】南秦岭勉略构造带黑沟峡变质火山岩的年代学和地球化学——古生代洋盆及其闭合时代的证据
李曙光, 孙卫东, 张国伟, 陈家义, 杨永成
中国科学(D辑)第26卷第3期1996年6月/SCIEN IN CHINA(Series D),-0001,():
-1年11月30日
南秦岭勉略构造带黑沟峡变质火山岩(绿泥钠长片岩)的主要元素组成表明,它是一套双峰式火山岩系,由低K富Na拉斑玄武岩及酸性英安岩、流纹岩组成。该玄武岩具有类似MORB的痕量元素特征,扁平的REE模型,但富Th和Pb。已获得该变质岩系的Sm-Nd全岩等时线年龄为242±21Ma,Rb-Sr全岩等时线年齿为221±13Ma,它们在误差范围内一致,并指示该火山岩系的变质时代。变质时代的初始εNd值(+6.1)指示该玄武岩源区为MORB型亏损地幔(εNd值>+6.1)。
秦岭造山带, 印支运动, 双峰式火山岩, 同位素定年, 痕量元素地球化学
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李曙光, SHUGUANG
International Geology Review, Vol. 41. 1999. p. 1114-1124,-0001,():
-1年11月30日
Because of a complicated metamorphic history, the isotopic systematics of the ultrahigh-pressure(UHP) metamorphic rocks in the Dabie-Sulu belt, east China, appear to be rather different from that were expected, Depending on the degree of retrograde metamorphism and on the retentivity of isotopes. The radiogenic isotopic systematics in the UHP metamorphic rocks yielded a wide range of radiometric ages. Some of these ages are geologically meaningful, but others may not be. In some fine-grained UHP metamorphic rocks, Sm/Nd isotopic systematics appear to be in equilibrium among the UHP phases, showing the best estimate for the age of peak metamorphism at 226±3Ma. On the other hand. Retrograde overprinting ofter makes the interpretation of isotopic data more difficult. It is common to find that the Sm/Nd and Rb/Sr isotopic systematics among the UHP phases and retrograde phases are not in equilibrium. Regression of isotopic data involving both UHP and retrograde minerals in isotopic correlation diagrams ofter yields geologically meaningless ages. Although 40Ar/39Ar dating of UHP metarmorphic rocks has been reported not to be very helpful in establishing the thermal history because of the presence of excess argon, a good correlation between excess argon and rock type in the Dabie-Sulu belt would provide a criterion in identifying the possible sources of excess argon. By taking all the possible effects into consideration, a T-t path with two rapid cooling stage in the period from 226 to 219 Ma may have resulted from rapid exhumation of UHP metamorphic rocks immediately after the peak metamorphism. The second rapid cooling stage, from 450℃ to 300℃, may have been caused by the exhumation of the entire terrane, including UHP metamorphic units and their host gneisses, during the period from 180 to 167Ma.
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李曙光, SHUGUANG
Geochimica et Cosmochimica Acta, Vol. 64, No. 6, pp. 1077-1093, 2000,-0001,():
-1年11月30日
Ultrahigh pressure metamorphic (UHPM) rocks at Shuanghe area in the Dabie Mountains occur as a UHPM block within the regional granitic gneiss. A Sm-Nd isochron defined by garnet+omphacite+rutile from coesite-bearing eclogite yield an age of 226.3±3.2 Ma. Another Sm-Nd isochron defined by Garnet+two phengites form UHP gneiss yield a similar age of 226.5±2.3 Ma. The two consistent Sm-Nd ages defined by three UHPM minerals suggest that Nd isotopic equilibrium between UHPM minerals in these rocks during UHP metamorphism has been achieved. This may correspond to the age of peak metamorphism with an average metamorphic temperature of 800°C. It is demonstrated that the retrograde metamorphism of UHPM rocks occurred in an open chemical system, whereas the Nd and Sr isotopic systematics of UHPM minerals may have remained closed. Nd and Sr isotopic disequilibrium between UHPM minerals and retrograde metamorphic minerals has been observed; therefore, the tie line of garnet or phengite and whole rock containing retrograde metamorphic minerals gives an old Sm-Nd age and a young Rb-Sr age, respectively, with no geologic significance. However, a Rb-Sr ages of 219.0±6.6 Ma defined by phengite+garnet from a UHPM gneiss indicates that the UHPM rocks at Shuanghe cooled down to 500°C at that time. It suggests that the UHPM rocks at Shuanghe experienced the first rapid cooling during 226-219 Ma. On the other hand, the Rb-Sr ages of 174±7.8 to 169.2±3.3 Ma defined by retrograde minerals (amphibole or biotite) with closure temperature ranging from 450° to 300°C and intensely retrograded metamorphic rocks reflect a second rapid cooling during this time interval. This is consistent with the “rapid cooling” time of 190-170 Ma of the orthogneiss in the Dabie-Su-Lu UHPM belt obtained by Ar-Ar dating method. In contrast to UHPM rocks, the Nd isotopic composition of the garnet in granitic gneiss has been reset during retrograde metamorphism and is in equilibrium with those of retrograde epidote and biotite, which yields a Sm-Nd isochron age of 213±5 Ma indicating the retrometamorphic time corresponding to amphibolite facies. In addition, the biotites from the granitic gneiss yield Rb-Sr ages of 171-173 Ma similar to those of the UHPM rocks. These data suggest that the country rocks (granitic gneiss) may have a similar cooling history to the UHPM rocks at Shuanghe. Two stages of rapid cooling of UHPM rocks at Shuanghe may correspond two stages of fast uplift: the initial rapid uplifting and cooling of UHPM rocks during 226-219 Ma may be caused by compression tectonics during subducting time of the continental crust; whereas the later rapid cooling may reflect the exhumation of the entire subducted continental crust by extension during the early-middle Jurassic.
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李曙光, S.
Phys. Chem. Earth(A). Vol. 26, No. 9-10, pp. 655-672, 2001,-0001,():
-1年11月30日
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